DEVELOPMENT OF A

DYNAMIC ICE-SKATE 

Main Report

Marc Bloem 1144383 Graduation Project 2010

Preface

This final report is the result of my graduation project during the master program of Industrial Design Engineering. It shows the development of a new dynamic ice-skate. The so-called new dynamic ice-skate contains a new innovative solution to make the sport more accessible for all audiences. The ultimate goal for this product is to put ice-skating at an higher level and get new World Records.

A dynamic-ice-skate is a new type of ice-skate which maintains optimal contact with the ice. The bend of the skate-blade adapts during skating by pressure changes in the foot so optimal contact is maintained with the ice-surface. In other words, the shape of the ice-skate adapts dynamically due to the movement of the skater.

This graduation project was set-up in a very interesting way. During my search to an interesting subject, the department of Biomechanics (3ME, TU Delft) came along. My mentor, Otto den Braver, was working on several skating projects like the Peakstake. The Peakskate is an ice-skate with a variable rocker. After some interesting brainstorms the idea of a variable bending came around, which resulted in this graduation project.

Enjoy reading!

Development of a dynamic ice-skate

Marc Bloem Graduate Student

Ruud van Heur Chair – Industrial Design TU Delft Leo Wartenbergh Mentor –Industrial Design TU Delft Otto den Braver Company mentor – O’Sports

Summary

Since the introduction of the klapskate it seems there is not much improvement going on in ice-skates. Nothing is further from the truth. This is specifically for the ice-skates used in short track skating which are bend in the direction of the corner to gain more grip. Several researches showed that the process of bending is difficult to master and requires a great deal of knowledge and experience. Nevertheless many benefits can be achieved by implementing a bending into an ice-skate.

The product is called a dynamic ice-skate. The dynamic behaviour of the skate follows and adapts automatically to the trajectory of the skating stoke. This means that the skates have a better grip on the ice during the turns and the straight ends, improving the skaters performance. For this implementation no expensive bending tools and specific knowledge is required. The skate is compatible with current skating products such as skate-shoes and sharpening tools.

The dynamic (bending) behaviour is based on a simple principle. Tilting the shoe ensures that the curved upper-blade deforms the skate-blade into a bend. A ball joint bearing which is incorporated into the tube helps to tilt the upper-tube. This principle is based on a simple sketch-model which is illustrated below.

Introducing the product will be first done for competition skaters. They can use this skate as a fixed skate and it will help to improve their technique even more. If the product is successful in this group (which happened also with the well known klapskate), the implementation towards the elite skating league will be easily made.

Index

1 Introduction ...... 7 1.1 Ice-Skating ...... 8 1.2 Innovation ...... 16 1.3 Design Assignment ...... 18 2 Analysis ...... 21 2.1 Visual product mapping ...... 22 2.2 Online Questionnaire ...... 24 2.3 Video Observation ...... 25 2.4 Projected radius ...... 28 2.5 Target group ...... 28 2.6 Design space ...... 29 2.7 Biomechanics ...... 31 2.8 Program of Requirements ...... 35 3 Design ...... 39 3.1 Concept generation ...... 40 3.2 Proof of concept ...... 43 3.3 Theoretical model ...... 46 3.4 Optimization ...... 50 3.5 Concept details ...... 55 4 Evaluation ...... 63 4.1 Program of requirements...... 63 4.2 Product recommendations ...... 64 4.3 Implementation ...... 66 4.4 Project evaluation ...... 67 5 References ...... 68 5.1 Literature ...... 68 5.2 Internet ...... 68 Acknowledgments ...... 69



Marc Bloem

6 Development of a dynamic ice-skate

1 Introduction

Several aspects will pass by in this section. The first aspect is about ice-skating in general. The second aspect is to show how innovation can improve this sport. The last part of this section will be the design assignment for this project.

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1.1 Ice-Skating

In all branches of sport is it a primary goal to improve yourself (and others) and achieve your personal goals. For professionals this goal is even more wider. They want to achieve the best possible result and set new (world) records. In other words, sport is accessible for everyone no matter what level you perform it.

The official Olympic motto is “Citius, Altius, Fortius”, which is Latin for “Faster, Higher, Stronger”. A more informal but well known motto, is “The most important thing is not to win but to take part!” Both mottos were introduced by Pierre de Coubertin, on the creation of the International Olympic Committee in 1894. This shortly explains why sports is important for all the people.

Disciplines of ice-skating

Ice-skating is moving on ice with ice-skates. It can be done for a variety of reasons, including leisure, travelling, and various sports. The most known ice-skate disciplines are: Figure Skating, Ice Hockey, Short-Track and Long Track Skating. Ice-skating is very popular in the Netherlands. Especially the two speed disciplines are popular, “Speed skating or Long track” and “Short track skating”. There are some major differences between the sport disciplines. Short track skates are high and have a stiff shoe (Figure 1.1). They skate small laps (oval track of 111m) and the first one who finishes wins. Long track skating takes place on a 400m oval with klapskates. The person with the fastest overall time wins.

high cups

Figure 1.1 – From left to right: a traditional long track skate, long track klapskate, and a short track skate with high cups

The construction of a klapskate (Figure 1.2) is more complex and consists of more of parts than a traditional long track skate. The construction is also more fragile and the hinge introduces extra loads on shoe and bridge. Short track skates have higher fixed cups and do have a very stiff shoe.

shoe

hinge

tube blade spring bridge

Figure 1.2 – Klapskate

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Products

Ice-skates have been developed for a long time. The First ice-skates as we known were from the 12th century. Bones of animals (cows, horses, sheeps, etc) were used in West- Europe for transport over ice. Today, ice-skates are still developing. New innovations make the sport faster and creates ultimately new World Records. This section shows several skating products and (unsuccessful) innovations.

Since the 1900’s century the design of ice-skate has been radically changed. Although there is one major similarity with the newer ice-skate. Attached to the blade is an integrated shoe is to increase the skating comfort (Figure 1.3). Appendix 2.1 shows an overview of the development of the ice-skate, which started in the 12th century.

Figure 1.3 – Top: Ice-skate around 1500 Bottom: Norwegian skate, around 1930 Dial Gauges`

Several gauges are on the market available (Figure 1.4). They measure the bending and rocker (curvature) of the skate-blade. See figure 1.13 and 1.14 for more information about the bending and rocker. These gauges are quite accurate, however when a skate-blade is damaged the results are not reliable. All gauges measure on the same principle. Three contact points (inner, outer, center) are required to measure the radius. They all cost around €200.

Figure 1.4 – Skate-blade Gauges – Zandstra, Pennington, Maple

Benders

A bender is required to bend a ice-skate (Figure 1.5). This is done manually after the rocker is set. The tube of the ice-skate is bend and the blade will follow this shape. To examine the bending, a gauge is also required to measure the radius. All benders have the same principle of bending but vary in comfort and therefore the price (€300-2300). At the moment there is only few specific information available about how to bend a skate-blade. See appendix 2.2 for a complete list of bending products and its specifications.

Figure 1.5 – Skate-blade benders – Pennington (2x), Maple

Paragraph 2.3 and appendix 6 show a detailed usage of a bender and gauge during the bending process.

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Patents

Besides to know what products are available on the market, there are also lots of patents around. These can be found in appendix 3. These could also be used for inspiration during idea phase. Next to the inspiration, there is more to mention about the patents.

There are many fields to explore for the new design of the ice-skate. Next to changing the shape it would also recommended to take care of the other fields of the design. These properties will be taken into account for the program of requirements. These are:

• Bending the tube • Shape the tube • Bending the blade • Material under strain/stress • Flexible tube, blade or supports • Adaptable to terrain/conditions • Changeable blades/ different changeable setups.

Skating technique

Skating on ice is a complex movement where everything comes together. It is a very efficient way to move around. In general, forward speed is created if one pushes backward against the environment. In running, for example, the contact between the ground and the shoe can produce enough friction (Figure 1.6), so the runner is able to push off in backward direction and accelerate forward.

Figure 1.6 – Friction between runner and ground creates grip from slipping away

Running on slippery ice would likely result in a fall. In contrast to a shoe, a skate is able to create enough friction with the ice to push off against (Figure 1.7).

Figure 1.7 – Push off force (Fx) should be perpendicular to the sliding direction (y) The skate-blade cuts into the ice, thereby creating sideward grip while maintaining low friction in lengthwise direction of the skate. The combination of very low friction in lengthwise direction, very much grip in sideward direction and maintaining balance on 1 [mm] thin skate-blade, makes skates and skating very hard to master. He who straps on skates for the first time wonders how he will ever be able to stand even still on them, let alone be able to balance on one leg and generate speed.

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Skating on a 400 meter ice rink contains several phases of ice-skating. Different skating techniques are used during start, straights and corners.

Start

The goal of the start is to gain as much as possible speed (Figure 1.8). Starting on ice-skates is a very complex movement. The first phase of starting is moving in forward direction having the skate perpendicular on the movement of the skater. After several strokes this phase transforms smoothly into a normal skate movement used on the straights. Figure 1.8 – Start of a short track race Straights

Usually a movement in forward direction is a result of a backwards push. In speed skating, the movement is achieved by a sideways push. The skate would slip away during a backwards push, not resulting in the desired propulsion. The sideways push force can only be generated perpendicular to the forwards direction of the skate. This force has a component in the forwards direction. During a stroke on the straight, the skate follows an S-shaped, sinusoidal trajectory (Figure 1.9). A stroke at the straight can be divided into three phases, the gliding phase, pushing phase and return phase (Figure 1.10).

Figure 1.9 – S-curve of the skate in the straight

Figure 1.10 – Skating technique of the skate in the straight and different skating phases (in Dutch)

Gliding phase - The skater has all his weight on the gliding leg and steers the skate in outwards direction, when compared with the body center of gravity. The skater uses the outer side of his blade during the gliding phase, which is used to build up pressure in a controlled way for the pushing phase.

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Pushing Phase - This phase starts when the body center of gravity is above the gliding skate. The skater stretches his leg and the angle of the skate with the ice decreases during the push, meanwhile the push off force increases. (Figure 1.11)

Return phase - At the end of his right stroke, the leg of the skater is fully stretched. Just before this moment he places his right leg on the ice and starts with the gliding phase with that leg. The left leg is retuned to its original position and when the pushing phase of the right leg is finished, the gliding phase starts again.

Figure 1.11 – Technique: Pushing phase

Corners

From a biomechanical standpoint there is almost no difference between the movements of a skater in corners and on straights. In both cases, the work is done by a push under a certain angle with the velocity of the skater and perpendicular to the gliding direction. The difference is that strokes have the same direction; both the left and right stoke move in the outwards direction of the corner.

In contrast to the straights, the skater also experiences a centrifugal force in a corner. He has to perform extra work to provide the centripetal force to change the direction of his velocity during the corner. A skater needs at least 7 strokes to compete a corner (Figure 1.12). To maintain speed or to accelerate, the push of the skater must have a component in the forwards direction. The trajectory of the skate on the ice compared to the body Center of Gravity is of extreme importance to achieve this. To maintain pressure during a stroke, the skater steers his skate in the inner direction. This allows him to remain in contact with the ice and results in longer strokes.

Figure 1.12 – Corner stroke Steering in the corner can be compared with the last part of the S-curve trajectory on the straights. Finally, only the basics of skating technique are explained above. There are lots more of aspects to mention like, the position of the body, head, movements of the arms, etcetera. More in depth information about skating technique and can found in the next reference: [Handboek wedstrijdschaatsen, Gemser, 2007]

Tuning the skate

Every skater demands an unique behaviour of his skate; this is very personal, and dependent on the weight, size and skating technique of that specific skater. The behaviour can be adjusted by choosing a certain brand of boots or skate; these all respond differently on the ice.

Next to this, the tuning of the skate is a big issue in the behaviour of the skate on the ice. Several terms will pass around in this report. These will be explained in the next section to become more familiar with ice-skating and the designed product. See appendix 4 for more background information about skating performance.

12 Development of a dynamic ice-skate

Each skater has their own optimum, depending on individual parameters (e.g. physical condition and technique), ice conditions and skating equipment (mechanical parameters). Mechanical tuning parameters (e.g. rocker, bend and stiffness) determine the feeling skaters have on the ice. They experiment a lot with these different tuning parameters. Skaters can only feel the reaction forces of the skate, not the parameters. Appendix 11.1, shows a interesting background article about tuning the ice-skate.

Rocker

In order to steer the skate, the blade needs to have a curvature. The curvature is called rocker ( Figure 1.13) and reduces the contact area between the skate and the ice. It also allows the skate to steer and follow an S-shaped trajectory on the ice. A decreasing (rocker) radius means a skate with more rocker. (i.e. little rocker means a big curvature radius)

Radius belonging to Rocker

Side view of skate

Figure 1.13 – Rocker

More rocker in a skate-blade gives more manoeuvrability to an ice-skate but decrease stability. The next table (Table 1.1) shows manoeuvrability and stability for different rockers.

Rocker Manoeuvrability Stability More (i.e. 20 m) + - Less (i.e. 26 m) - + Table 1.1 – Manoeuvrability and stability

The regularly used curvature of roundness lies between 21 and 25 meter for long track speed skating. This rocker is most of the time constant over the length of the blade. For short track lies this curvature between 8 and 16 meter and could be variable.

Bending

Next to the rocker, especially short track skaters use a technique known as bending. A bend is created in the tube seen from top view ( Figure 1.14). The bend increases the contact area of the blade with the ice resulting in more stability in the corners, because the skate follows the track of the corner more easily.

Radius belonging to Bend

Top view of skate

Figure 1.14 – Bending

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However a to strong bend in the blade is undesirable. It creates a two-point contact with the ice and loses all the grip with the ice (Figure 1.15). Appendix 11.1, shows a interesting background article about bending druing the Winter Olymipcs 2002 in Nagano.

Figure 1.15 – Two point contact due to a too strong bending

A combined bending and rocker in a ice-skate create a projected radius when the skate-blade is rolled over towards the ice floor. If the angle between the skate and ice decreases, then the projected radius increases for better contact with the ice floor. (Figure 1.16). (More about the projected radius in paragraph 2.4)

Angle

Radius belonging to Projection

Top view of ice Figure 1.16 – Projected Radius

Maintenance

Skating on slippery ice requires sharp skates (skate-blades). To get the lowest sliding-resistance of the ice is it important that the blade is as smooth and sharp as possible (Figure 1.17). Sharpening ice- skates can be done mechanical or by hand.

Sharpening the skate frequently (for the elite a daily process) does influent the rocker of the skate- blade. Sharpening the skate levels the blade, it will be more flatten. So often should the rocker of the skate be put again in the blade.

Figure 1.17 – left, sharp skate, right a manual sharpening-table

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Market

Ice skating occurs both on specially prepared indoor and outdoor tracks, as well as on naturally occurring bodies of frozen water such as lakes and rivers. The Netherlands is one of the largest ice-skating countries, because it has a large ice-skating history. Many people can skate, however this is not shown in the official numbers, The Dutch Skating association is only the 7th largest in The Neterlands (2007) (Table 1.2). Next to these numbers, in the Netherlands are relatively a lot of skate rinks (Figure 1.18). However it is not easy to survive for many producers of ice-skates and skate- clubs, because of the poor winters last years. To survive, they are mainly dependent on the main consumers (mass).

Figure 1.18 – Ice skating rinks in the Netherlands

Organisatie Totaal 2007 Totaal 2006 Verschil

1 Koninklijke Nederlandse Voetbal Bond 1.129.885 1.089.427 40.458 2 Koninklijke Nederlandse Lawn Tennis Bond 691.441 698.853 -7.412 3 Nederlandse Golf Federatie 291.184 268.730 22.454 4 Koninklijke Nederlandse Gymnastiek Unie 279.948 284.263 -4.315 5 Koninklijke Nederlandse Hockey Bond 197.134 187.275 9.859 6 Koninklijke Nederlandse Hippische 195.526 188.672 6.854 Sportfederatie 7 Koninklijke Nederlandse Schaatsenrijders Bond 149.920 152.384 -2.464

8 Koninklijke Nederlandse Zwembond 146.063 150.004 -3.941 9 Nederlandse Volleybal Bond 127.308 128.089 -781 10 Atletiekunie 126.413 123.408 3.005 Table 1.2 – Size of Dutch sports associations [Recource: NOC*NSF]

Conclusion

• Since the existence of the ice-skate, it is constantly innovated to make the product better. This has resulted in faster skating times and more comfortable equipment. • During a skate lap there are several phases of the stroke to move around. • Tuning the ice-skate depends on lots of factors and is very personal. For tuning the blade itself can the rocker and bending be adjusted. The equipment to do this is expensive and requires specific experience. A proper tuned ice-skate requires clear instructions, however there is not much information available.

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1.2 Innovation

Innovations

Many different innovations have been made trying to improve the sport. Products that may be clear could have a positive contribution to the sport. These products help to make speed skating, faster and safer. Media attention to these innovations should contribute to a broader image of ice-skating, making the sport more accessible and attractive. An overview of skate innovations can be found in the table below (Table 1.3) and appendix 2.3.

Year Innovation 1960 Skate Clothing 1976 Skin Suit 1988 Indoor skating rinks 1996 Klapskate 1998 Strips 1999 Sharkskin suit 2006 Blade thickness 2009 Peak Skate Table 1.3 – Innovations

Innovations will come to generate new world records. Most revolutionary innovation was the klapskate. Klapskates were introduced at the international level during the 1996/97 season and, after some hesitation, all skaters were soon using them. It is interesting to note that the klapskate is not new. It was invented almost a century ago. At that time, the interaction between various factors and components prevented the klapskate from being successful. Even with current skating techniques, the use of the klapskate after its introduction in 1996 required an adapted style of skating. The increase in performance was 2–3%, compared to conventional ice-skates (Figure 1.19).

Figure 1.19 - World records Speed skating until 2000 (long track)

Many people try to find a innovation in the skating market, however some of the have failed completely. It might be interesting to see these innovations to understand what the ‘inventor’ tried to invent. Appendix 3.4 shows these unsuccessful innovations.

Sports

Sports activities are based on physical movement using characteristics such as strength, speed, agility and mind. This means:

• The athlete performance comes first! • Effort inside the rules of the sport • Having a balance between body and mind • The result will reflect the qualities of the athlete (fair play)

16 Development of a dynamic ice-skate

In ice skating there are several parties are involved to innovate (Figure 1.20).

Figure 1.20 – Mindmap innovations in skating [dutch]

Innovation

Innovation means in sport the following:

• Better performance in sports • Adds something extra to the sport • Searching for the potential limits inside the rules • Makes sport even more challenging • Creates new records!

Conclusion

Innovation brings a lot of interesting things inside sports. This results in some guidelines for designing fair sports products.

• Fair Sport; conditions must be equal for each athlete • The athletes performance should be what matters • The equipment should fit the athlete • The equipment should improve the athletes performance • The product must be accessible and understandable for all involved parties. • The product should not affect external factors.

Innovative sport products should be fair to be accepted by all involved parties. Otherwise it would not be sure if the products will be successful inside the sport. Ice-skating will become easier and more accessible. Positive media attention creates a positive image of sport.

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1.3 Design Assignment

Summary

Each discipline in sports has an urge to innovation. This is also applicable in ice-skating where lots of aspects can be improved. Since ice-skating exists, it is constantly innovating.

For the elite, innovation is a need to improve their performance. Innovation has for recreational sports also an advantage, namely making the sport even more accessible, so a wider audience will be interested.

Nowadays an ice-skate has already many fields to adjust, like changing the position of the shoe in relation to the skate-blade, and grind the blade into a rocker (curvature of the blade). Like short track ice-skating the tube of a speed skate is nowadays also slightly bent in the direction of the corner. This increases the thread of the skate-blade causing more grip in (high speed) corners.

There are several products that can change the radius of the bend and rocker of the blade, but much improvement can be achieved by easily and accurately adjusting the bend of the blade. The skate-blade can thus maintain optimal contact with the ice. This contact is on the straights and corners different.

Problem definition

The above shows that there are some complications while skating. A strong bend can make ice- skating uncomfortable on the straights. Also a strong bend can result in a two point contact with the ice during sharp skate angles with the ice. For the user it is very tedious to adjust the behaviour of the bending, it is based on craftsmanship. Moreover the bending of the skate-blade is a non-reversible process. Therefore, mistakes are very difficult to fix. The equipment to do this is expensive and requires specific experience. A proper tuned ice-skate requires clear instructions, however there is not much information available.

For the user it is fundamental to make the bend easily adjustable because different users have personal and unique demands. The skate should be for all audiences easy to understand, making the product widely accepted.

Assignment

Design a new type of ice-skate which maintains optimal contact with the ice. The result of this project is to create a product design and proof its functionality. (See appendix 1 for the original design assignment)

To bend the skate-blade the Center of Pressure of the foot is used. This center of pressure varies during skating strokes (corners or straights) and could be used to dynamically adapt the shape of the skate-blade. (see paragraph 2.5).

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2 Analysis

Several aspects about bending will be analysed to gather enough information to develop the dynamic ice-skate. The outcomes of this analysis will result in a program of requirements.

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2.1 Visual product mapping

Visual product mapping is a tool to categorize the same type of products and determine the relation to each other. By choosing different axes product can be grouped into categories. This tool is also very usable to think in which specific category your own product could be placed. For this project two product mappings have been done, Transport and Skates (Figure 2.1 & Figure 2.2).

Transport

This first visual product mapping is done to get an impression of all land transport possibilities. Many different transport ‘units’ have been placed in this transport grid (i.e. different types of ice-skates, racing cars, shoes, boots, etc.) Therefore it is easier to determine on which place in the grid the new designed product should be. The designed product should be tunable and adaptable. However it is not clear yet how these aspects have to be incorporated in the design.

The visual product mapping shows the following:

• There is no much relation between the two axes (tunability and adaptability) • The average of all products is located around C1. • Most products are barely tunable, including ice-skates. • Products are equally divided on an adaptability scale. • Ice-skates are tunable OR Adaptable, but not both.

For the dynamic ice-skate should the product design should fit in Row E, it has to score very high on a adaptability scale. Preferably as much tunable as possible (column 4).

Figure 2.1 – Visual product mapping: Transport

22 Development of a dynamic ice-skate

Skates

The second visual product mapping is to get an idea of almost all types of skates on the market. By placing a skate into the grid it should be clear what the skate is built for. All skates are categorized on a comfort and/or innovative level.

This visual product mapping shows the following:

• Many types of skates are available. • Different groups can be made. (C1 & C4) • Lots of skates are not innovative. • Comfort is a very important aspect because many of the skates are quite comfortable (row- C&D)

For the dynamic ice-skate should the product design be around category E4 (innovative & comfortable)

Figure 2.2 – Visual product mapping: Skates

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2.2 Online Questionnaire

To know more about skate- bending, an questionnaire is put online, specifically on skating forums. This is a method to get very fast response. The questionnaire is about skate-blade bending. This questionnaire is made for the ice-skate audience (short-track, long-track, or marathon). To address the specific audience, this questionnaire has been sent to regional ice-skate clubs and put on specific internet fora. (Figure 2.3)

Figure 2.3 – Schaatsforum.nl Goal

Get insight in skate-blade bending by asking non-beginner ice-skaters about their material, level and bending-experience. The questions of the questionnaire can be found in appendix 5.1

Description

The questionnaire consists of only four pages and takes at most five minutes.

The first page is about to know the user skating level and what kind of ice-skates he or she uses (user profile). In this section different user profiles will be used to see if there are any differences between the skating level and material used.

The second page is about maintenance of ice-skates. In this section it would be clear in which way the user maintenance of his/her ice-skates finds important.

The third page is about to know if users bend their skate and to know what they think about the bending-process.

When all results of the questionnaire are collected, the respondents will be divided in a unique group (profile) to determine the differences between each group.

Results

See Appendix 5.2 for the questions and responses of the online questionnaire. The results are divided into the three profiles which are described next.

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Beginner & recreational ice-skater In general: Practises 1-2 times/week. Do not often maintenance their equipment. Do have relatively cheap ice-skates (<€300).

Competition ice-skater In general: Practises 2-3 times/week. Sharpens its own ice-skates each 2 weeks. Do have ice-skates of €500.

Professional ice-skater In general: Practises at least 3 times/week. They completely maintenance their material by themselves. Sharpens its own ice-skates each 2 weeks. Do have ice-skates of €1000 or more.

Conclusion

• Bending is not popular by long-track speed skaters (70%) • There is few knowledge available about bending • Without experience bending is almost impossible to do • Bending is personal and unique for each skater • Beginners think that bending will not help themselves • Experienced skaters think that bending might be useful • Maintenance and customizing your equipment is preferably done by skaters themselves. • A bent skate gives more grip/control/pressure in corners

2.3 Video Observation

The conclusions from the questionnaire show that not much information about bending is available. There are some bending-machines are available but all these machines do not have good instructions to bend a skate-blade.

The following video observation is done to know more about the bending process. An experienced short track skater shows the ins and outs about bending. This will be recorded on video. The bending process does have several stages. For each of them a storyboard is made (see Appendix 6).

Goal

The goal of the observation is to get insight in the skate-blade bending process by observing an experienced short track skater during the bending process. He will demonstrate how to bend a skate- tube.

Description

The skate-blade bending process does have different kind of stages. For each of them a different story board has been made. These story boards are:

A The principles of a bending and a rocker in a skate-blade B Measuring the bending C Bending the skating-tube (basic principle) D Bending a piece of the skate-tube

Different equipment is required to bend a skate-tube. This equipment is used in the storyboards. Next section gives an overview of the used equipment (Figure 2.4).

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Used Equipment

A. Bender A lever bends stepwise the desired bending curvature into the skating blade. B. Flat piece of steel Used as a reference to simulate a smooth ice-floor. C. Measuring-gauge The local radius and deflection were measured by placing it on the skate-blade. D. Skate-tube and skate-blade This part will be bend in the bender E. Table for values The measured value of the dial indicator and its corresponding curve can be searched inside the table. F. Bright light source The tread of the rocker and bend could be inspected by placing the skate-blade onto the flat piece of steel (B) in front of the light source.

A E

B

C

D

F

B

Figure 2.4 – Bending equipment

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Results

See Appendix 6 for the complete storyboards of the video observation. The observation video’s can be found on the DVD.

Conclusion

A. The principles of a bending and a rocker in a skate-blade

Checking the desired rocker will be done with the gauge and the light source. Using a gauge only is not sufficient because there might be some small bumps in the skate-blade. So also the light source will be used. Using both tools will be necessary to see the variable rocker in the blade. The light source will also be use to see the bending of the skate blade. Buckling the skate in front of the light source shows an increasing thread of the skate-blade

B. Measuring the bending

The rocker of the skate blade must be set into the skate-blade before the bending can be measured. The skate-blade must also be sharp.

Decided is to bend the skate only for the corners, so the disadvantage on the straights will be ‘ignored’. The advantage in the corners is more than the disadvantage during the straights.

In general skaters like the principle of bending a blade, only fine-tuning a skate is very individual en should be found out by yourself. Here comes it out on experience, there are no strict guidelines for this process.

There are several precise and less precise methods to measure the bending, it is personal which method suits yourself the best.

C. Bending the skating-tube (basic principle)

Skate tubes are not 100% perfect straight due to (minor) damages. Before starting the bending process it is essential to check the tube on its state. Bending the tube is an interaction between, measuring, looking, en bending. Al these aspects should be mastered very well. For this interaction is a gauge, light source and sharp skates essential. The skates must have the correct rocker. The bending will be put in the blade after the rocker.

Pushing the handle of the bender consists purely on feeling. The distance of the two nodges where the skate is placed onto, determine the position where the bending is put into. There is no default setting, this setting depends on personal preference. This principle is for all appliances the same. Setting a bending in the skate is about 30 minutes for an experienced bender.

D. Bending a piece of the skae-tube

Some bending devices have the function to level out the bending into the tube. This gives a nicer result because the bending is smoother over the tube.

Several methods can be used to achieve the same goals. Therefore it is essential to think what kind of method and operations should be used. Experience is very important.

It is recommended that the amount of bending in the front of the tube should be more precise than in the back. However this is only based on experience, not on strict guidelines, these are personal.

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Many aspects are involved by bending a skate:

• The interaction with the light source and the straight beam • Having a bending-gauge • You can sharpen a skate • You have the ability to feel your material during skating • You have to control the bending process in detail • In general, it is a complex process!

2.4 Projected radius

As shown in Figure 1.16 the projected radius depends on the push off angle, rocker and bending of the skate. The same projected radii can be achieve by different settings of rocker and bending, the only difference is the contact thread of the blade.

Very strong push off angles will not affect the project radius, but the contract area increases. A too strong bending has a negative influence on the grip. Because skating is based on feeling, it might be very difficult to determine the ideal relation between rocker and bending. this process has everyone to master but takes time. A more detailed research of the projected radius can be found in appendix 7.

Pure the results of the research show some interesting things. A beginning skater, which does not have sharp push off angels, has more advantage of a bending instead of the rocker. An experienced skater has more advantage of the rocker, where the bending gives a bit extra. The results also show that beginning skaters also have an advantage of an bended ice-skate.

Last but not least, the results do not say anything about the ease of skating itself. Skating is based on feeling and experience. Only geometrical is shown that a bending skating could make easier.

2.5 Target group

The results from the online questionnaire shows us three profiles: Beginner & recreational ice-skater, competition ice-skater and Professional ice-skater.

If you begin with ice-skating you regularly start on fixed skates (no klapskates). This is the traditional method to learn ice-skating. A bended ice-skate is not necessary for beginners. But the previous paragraphs showed, it might help them especially during corner strokes. Competition ice-skaters have fixed skates or klapskates. Their technique is sufficient to go with ease through corners. The skates are already quite expensive. Professional ice-skaters have the best material and the best technique.

In general, the ice-skate can directly be designed for all audiences. However the klapskate was implemented in a different way. The product proved it success first by semi-professionals, this group have the most time to try new innovations. Professionals have less time to test new equipment so they use only proven innovations.

This could mean for the new dynamic ice-skate almost the same. The product will placed in the market for the middle group, the competition skaters. They can use this skate as a fixed skate and this helps to improve their technique even more. If the product is successful in this group, the implementation in for professional skaters will be easily made.

28 Development of a dynamic ice-skate

2.6 Design space

Analyzing the dimensions of ice-skates is essential to know the boundaries where the design could be made in. This is be done for the side and front view. The push off angle with the ice during skating is also analysed.

First is to find out what the dimensions of ice-skates are. Long track and Short track skates are not equal so both types have to be compared for what the differences are (Figure 2.5 – long track vs. short track skates).

Long track skates: Short track skates:

• Only Hinge contact between the blade and • High cups (relatively large distance between shoe foot and ice. • High cups but not as high as in short track • No hinges; fixed contact with blade and shoe skating Figure 2.5 – long track vs. short track skates For this project the decision is made to focus on short track skates. Long track skates are much more complicated (due to the klap mechanism) and have less design space. Besides, bending is very essential and already implemented in short track skating, so it is more logical to focus on short track skating.

Side view dimensions

The design space for the mechanism is shown below. The maximum height is 70 mm in the back of the blade and about 60 mm in the front of the blade. However a safety margin of 20 mm is assumable to build the construction within (Figure 2.6).

Figure 2.6 – Design space side

Front view dimensions

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The position of the blade is not exactly the in middle under the shoe (especially for short track skaters). The blade is more placed to the center of the corner (red arrows). This makes higher angles possible between the leg/foot and the ice floor while skating corners counter clockwise (Figure 2.7).

Figure 2.7 – Design space front Sharp angles could be made because the shoe is relatively high positioned on the blade (Figure 2.8).

Figure 2.8 - Amazing angles between the ice-floor and skate!

Second is to find out what the minimum angle is between the leg/foot and the ice floor (Figure 2.9). This determines the maximum width where the mechanism could be made in. The green area is the design space for mechanism.

Figure 2.9 – Angle with the ice floor

30 Development of a dynamic ice-skate

Figure 2.10 – Angle with the ice floor measured This minimum angle is about 21 degrees (Figure 2.10). Sharper angles are not possible due to the width of the foot and the position of the blade.

Conclusion

The design space where the mechanism could be build in is the following:

• Front view: up to 70 mm in height • Side view: Angle of about 21 degrees and not wider than the width of the skating shoe

Furthermore is decided to focus for this project on a short track ice-skate. Short track skates have more design space, have bending already implemented in the design. Integrating the new mechanism into a klapskate will be recommended for the next generation dynamic ice-skates.

2.7 Biomechanics

There are many fields to explore in biomechanics. For this graduation project two fields will be explored to know the relevant information to design a dynamic ice-skate. The first field is to find out what the center of pressure does during the different phases (start, straight, corner) in a lap. The second field is to find out what kind of behaviour the dynamic ice-skate has to do for the product design.

Center of pressure during a lap

Relevant for this project is the center of pressure of the foot during different skate strokes and its value. This has been figured out in the next reference: [Building the Best skate, Den Braver, 2007]. The results are a very useful input for this project. “The center of pressure (CoP) beneath the foot of the skater will be used to illustrate the control signal used for steering between the skater and the skate.” In other words the CoP of the foot is measured to understand what happens during a skating lap. (Figure 2.11)

Figure 2.11 – The CoP beneath the foot

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Straights = magenta Corners = blue

Figure 2.12 – Results skating stroke CoP

In the figure above (Figure 2.12) are the results shown for a 57 kg female skater during one skating lap. The results left foot are measured. The first graph shows the forces during a skating lap. The second graph shows the forces per stroke. The last graph shows the Center of Pressure (CoP) of the foot during a stroke.

Note: the measured results are slightly less than the weight of the skater. The system to measure the center of pressure cannot measure lateral forces of the skater. So this explains the difference, which lies around 30% of the weight of the skater.

This is also tested for a heavier (85 kg) professional male skater. The force and CoP patterns during the two type of skating strokes show high similarities between the two very different skaters.

Similarities between the patterns of skater 1 and skater 2: a) Corner strokes have higher forces b) The CoP of corner strokes have larger fore – aft excursion along the blade c) The CoP of corner strokes are located on the right of the skate-blade (beneath the grey line) d) The CoP of straight strokes are located on the left of the skate-blade (above the grey line)

Differences between the patterns of skater 1 and skater 2: e) Corner strokes have a much longer duration in skater 2 f) Straight strokes of skater 2 end much stronger compared to straight strokes of skater 1

Dynamic skate behaviour

The skate trajectory during a straight and corner stroke is shown in the next figure. The large blue arrows show the followed path of the skate stroke.

32 Development of a dynamic ice-skate

Figure 2.13 – Skate trajectory Next to the path is the direction of the followed path shown (clockwise or counter clockwise). This shows immediately where the problem lies. Bended ice-skates are always bended in the direction of the corners (counter clockwise) to go easier through corners. On a straight stroke is there no problem with the right skate. However the direction of the left skate during straights is the opposite as in corners, so there is a conflict. Today, skaters accept the disadvantage during straights because the advantage in the corners is more.

For a dynamic ice skate this left-skate-problem should be avoided. The results from Center of Pressure showed us that there is a challenging opportunity to get rid of this problem. Interesting for the design of the dynamic ice-skates are the similarities C & D (see page 30). It shows us that location of the CoP to the skate-blade is for straight and corner strokes different. Combined with the skate trajectory means this the following (Figure 2.14). The trajectory of strokes is shown in blue, and the CoP is shown in green.

Figure 2.14 – Center of Pressure during strokes

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Conclusions

The previous image shows the following conclusions. This is the behaviour the dynamic ice skate must have.

• If the center of pressure is located on the RIGHT of the blade, then the skate should bend to the LEFT (Figure 2.15) :

Figure 2.15 – Conclusion 1

• If the center of pressure is located on the LEFT of the blade, then the skate should bend to the RIGHT (Figure 2.16):

Figure 2.16 – Conclusion 2

The conclusions above show also that a corner in the opposite direction (clockwise) can be skated with this mechanism. This is a major advantage of the universal design. Besides the left-skate-problem as shown above (Figure 2.13) is also eliminated.

34 Development of a dynamic ice-skate

2.8 Program of Requirements

The outcomes of the analysis phase will result in the Program of Requirements (criteria). These criteria are divided in hard criteria (requirements) and soft criteria (preferences). They will be used at the end of the design process to judge the design and to come up with ideas.

The criteria are bundled in several subjects for the Harris model. This Harris model will be used to choose a concept during the concept phase.

Below you will find the list of requirements as well as the list of preferences.

List of requirements

1. The blade of the product must be adaptable due to pressure changes of the foot. (The product must fulfill its main application to be a dynamic ice-skate) 2. The product must fit the target group, competition (short-track) skaters. 3. The behaviour (adaptability) of the bending of the blade must be set easily, with or without a tool. 4. The product may not cause unsafe situations 5. Current sharpening tools must be usable on the product. 6. Measuring the bending must be with current tools (e.g. a bending gauge) 7. The mechanism of the product must fit in the design space of the skate. 8. The product must be accessible and understandable for all involved parties. 9. The equipment must improve the athletes performance in a fair way.

List of preferences

10. The user must be able to set the behaviour of adaptability of the product. 11. The bending of the skate-blade should be precise in the front section (top) of the blade. 12. The constructions appearance should be designed in a smooth and elegant way. 13. It is preferred that the bending of the skate-blade comprises the whole length of the skate-blade. 14. The product must be preferably for short-track skaters. 15. Setting the desired bending-behaviour should be as much as intuitive and user-friendly . 16. It is preferred that the product fits in current skate-products available 17. It is preferred that the product is maintenance free. 18. It is preferred that the product can be easily mounted and dismounted for maintenance. 19. It is preferred that the products maintenance can be done by the user itself. 20. It is preferred that current production technologies of ice-skates are as much as possible incorporated. 21. The product should be producible in (small) series. 22. It is preferred that the product’s design is as less complex as possible. 23. It is preferred that the product is resistant to different kinds of environments (low temperature, water, soil, etc) 24. It is preferred that the product is easily cleanable. 25. It is preferred that the cost price of the product is at the same level as a regular klap-skate products. 26. It is preferable that the product should not weight more than a regular klap-skate. 27. It is preferred that the product is also usable in a klap-skate mechanism

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Harris model

A Harris model (Table 2.1) is used to determine the product concepts (during concept phase) on their performance. The criteria can be found below in order of importance.

1. Functionality The blade of the product must be adaptable due to pressure changes of the foot. It is preferred that the bending of the skate-blade comprises the whole length of the skate-blade 2. Complexibility It is preferred that the product’s components are as simple as possible. (low complexity) 3. Weight It is preferable that the product should be as light as possible and not weight more than a regular klap-skate. 4. Dimensions The mechanism of the product must fit in the green design space 5. Maintenance It is preferred that the product is resistant to different kinds of environments (low temperature, water, soil, etc) It is preferred that the product is maintenance free. It is preferred that the product can be easily mounted and dismounted for maintenance. It is preferred that maintenance can be done by the user itself. 6. Producibility It is preferred that current production technologies of ice-skates are as much as possible incorporated. 7. Klap-skate It is preferred that the product is also usable in a klap-skate mechanism 8. Compatible Current sharpening tools must be usable on the product. 9. Safety The product may not cause unsafe situations It is preferred that the product fits in current skate-products available 10. Price It is preferred that the cost price of the product is at the same level as a regular klap-skate products. 11. Personal Preference Also my personal preference is taken into account. My opinion is mainly based on potential of the design and the inspirational criteria on the next page.

Criteria Concept x -- - + + + 1. Functionality 2. Complexibility 3. Weight 4. Dimensions 5. Maintenance 6. Producibility 7. Klap-skate 8. Compatible 9. Safety 10. Price 11. Personal

Table 2.1 – Criteria in Harris Model

36 Development of a dynamic ice-skate

Personal Design vision

Of course all the criteria should be implemented in the design, however there might be some criteria which are not directly implementable into the design. I think it is important to look a bit further with criteria. For the dynamic ice-skate I have set some extra criteria, they are merely based on feeling of the product and could be used as inspiration of the product. The next mindmap shows these ‘inspiring criteria’ (Figure 2.17).

Clear Simple Smart

Elegant Understandable Reliable

Fast Professional Dynamic Ice-skate

Adjust Low-Maintenance

Tuning Adaptable Safe Performance Accurate

Figure 2.17 - Mindmap inspiring criteria

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38 Development of a dynamic ice-skate

3 Design

This chapter will be about the development of the design such as; the ideas, the bending mechanism, optimization and the finalization of the product.

39 Marc Bloem

3.1 Concept generation

Ideas

The mindmap in previous paragraph shows the inspiring criteria for a dynamic ice-skate. These inspiring criteria will be used to generate ideas. A proven method to create ideas is to use a morphologic chart. (Figure 3.1) Split the whole design problem into smaller parts helps to create lots of (sub) ideas. This morphologic chart consists of six sub sections:

• How to bend a material? • How to make a construction more rigid? • How to transfer compressive stress? • How to cross forces? • How to make bending adjustable? • How to make something adjustable?

Figure 3.1 – Morphologic chart

This morphologic chart is used as an inspirational source to create the first set of ideas on (Figure 3.2). Each subsection in this chart (rows) has different kind of solutions (6-8). These sub ideas will randomly be combined into a total solution (for example: A2, C6, F7). For a impression for more of these total ideas see appendix 8. These ideas give a first impression what kind of solution the final design should be. Lots of aspects should be integrated in the product.

The morphologic chart shows that there is lots of aspects to think about, however at this stage of the design there is nothing clear Figure 3.2 – Example sketch ideas

40 Development of a dynamic ice-skate about the main function (A - How to bend a material). Concluded from the morphologic chart it is unrealistic to develop all aspects in this amount of time. So for this project (or the first generation dynamic ice-skates) there will be the focus on the main function: how to make the design adaptable. This area has many unexplored fields and therefore it is important to find out if this field is feasible. A result of this project will be a proof of concept and a producible first generation design. Recommended for the second generation of the design is to focus on adjustability. This means: how to make the design adjustable for all audiences. The final chapter of this report shows more about this recommendation and implementation of the first generation design.

Concepts

The main functionality of the dynamic ice-skate is how to bend the skate-blade. The three best and solutions from row A in the morphologic chart have been chosen to continue with. Each of these solutions will bend the skate-blade on a totally different way. Below (Table 3.1) can be found which three ideas have been chosen with a description.

A pressure on the bolts (1) Pushing a object (1) into the A direct pressure (F) sideward generates a moment for a blade (2) bends the blade bends the blade into the desired bending (2) shape Table 3.1 – Three different bending ideas

These three ideas are improved to a first concept made by a CAD program (Solidworks). This gives a three-dimensional impression of the desired shape and shows the rough dimensions (Table 3.2). For each concept also a (cardboard) sketch model is made (Figure 3.3) to get insight in its functionality and simplicity.

Concept 1 Concept 2 Concept 3 ‘Bridge’ ‘Cardboard’ ‘One-Force’

A pressure on the bridge (1) A pressure on the bridge (1) A pressure on the bridge (1) generates a moment (2) and deforms the blade into the generates a moment (2) and bends the tube desired bend. The tube has a bends the tube curvature so this shape is pressed into a bend Table 3.2 – Concept overview

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Figure 3.3 – Three different type of sketch models

Each concept has its own unique properties. This is explored in the next table (Table 3.3). Important of this table are the last three rows, where the strong and weak aspects are described. Most important is the last row, the unique property of each concept.

Concept 1 Concept 2 Concept 3

Name Bridge Cardboard One Force Working principle A pressure on the bridge A pressure on the top bridges A pressure on the front bridge (description) generates a moment and bends deforms the entire blade into the pushes the tube side wards into the tube desired bend the desired bend Bending of the tube By a Moment Deformation Direct (side)force Strong aspects Compatible with current blade. Simple, few parts, lightweight and Less force needed ‘Perfect’ bending due to moment direct deformation. Easy producible Weak aspects Complex construction; Principle not proven yet Principle not proven yet; Lots of parts Lots of precise parts; Complex construction Overall Pure bending in tube Simple principle Less force needed (what is it all about) Table 3.3 – Concept description Summarized, concept one is a solution which creates a perfect bend, but is complex. Concept two is simple and promising, although the principle is not proven yet. Concept three needs less force to achieve its bending, although that principle is not proven yet too.

Concept decision

Within a Harris Profile you judge each concept to a number of criteria. You can grade every idea combined with a criteria with a double plus, single plus, single minus or double minus. A short description of the criteria can be found earlier in this report (paragraph 2.8). These criteria are ordered by importance. Next table (Table 3.4) shows the scores of the criteria. This results in a concept decision.

42 Development of a dynamic ice-skate

Criteria Concept 1 Concept 2 Concept 3 ‘Bridge’ ‘Cardboard’ ‘One force’ -- -++ + + - - -++ + + - - - + + + 1. Simulation 2. Complexity 3. Weight 4. Dimensions 5. Maintenance 6. Producibility 7. Klap-skate 8. Compatible 9. Safety 10. Price 11. Personal

Table 3.4 – Concept scores (Harris Profile)

On almost each criteria does concept 2 has the best score. Especially in the first three criteria, simulation, complexity and weight does it score very high. Concept one scores better than concept three on the first criteria; it is less complex.

So concept two looks very promising to continue with, but there is one major note. The working principle is not proven yet. A cardboard model made shows the working, but this only intuition. So thing to do is to find enough proof for its working. This will be done in the next paragraph.

If there is unfortunately no proof for concept 2 (in other words: it will not work) concept 1 will be chosen, this is a safe solution to create a bending but the solution is not as nice as concept 2.

3.2 Proof of concept

As mentioned earlier concept 2 looks very promising but the major question is, will it work? This will be found out by two simulations. These simulations should be accurate enough to make a definitive decision. The first simulation is a ‘real simulation’ by testing various sketch models. The second simulation is to test it during a simplified computer simulation. If both simulations have positive outcomes there will be enough proof to make a final decision for concept 2. It the simulations fail, the ‘safe’ concept 1 will be chosen.

Simulation by sketch models

Lots of simple models have been created out of different materials (Figure 3.4). However they have all the same meaning. They all do show what happens during a quick simulation. The following images show a three-step description of the simulation (Table 3.5). For this case a piece of ribbon-cardboard is used. The results look promising.

Figure 3.4 – Several test models

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B A

C

1. Front view 2. Side view 3. Side view

One piece of cardboard with a Top section will be Result: a bended piece of cardboard. prefolded curvature (A). On this line bended sidewards (B) Note bending curvature of the ‘blade’ should the model fold, in fact it is a (C) simplified hinge. Table 3.5 – Cardboard simulation

The illustrations above show the mechanism of the skate blade. If the computer simulation will do the same, this principle will be the ‘core’ of the working principle of the dynamic ice-skate.

Computer simulation

For more evidence if the simple cardboard principle works, more challenging is to make a working computer simulation. This simulation has to do what also previously happened with the cardboard. This kind of behaviour should be the working principle of the skate-design, so it should be properly working during simulation. Testing the simulation is done with the CAD program: Solidworks & add-on Simulation (previously Cosmos).

Figure 3.5 – Simple model

44 Development of a dynamic ice-skate

The simulation is a simple model (Figure 3.5) of the ice-skate. The parameters (wall thickness, etc) are at this stage not important yet. Goal is to get a equivalent effect as the piece of cardboard in the simulation. The shape of the blade is a rectangle with a random curved hinge all over the length. The length of the model is equal to a regular skate-blade (450 mm). The wall thickness is 2 mm.

As shown in the close up in the picture, the hinge is just under dimensioned (very thin). This is the weakest place in the model, where it should fold. At the top are two small ridges where the forces should apply. In the middle is a small rib, here is the model fixed, in the axis of symmetry. This fixation is not equal as sliding on ice, but to fix a model on ice is not supported in Solidworks Simulaton. So this solution is the most closet to reality.

The simulation (Figure 3.6) is set up as follows:

Solidworks Simulaton – Study

Material: Standard stainless steel

Fixtures: In axis of symmetry, no freedom (green)

External loads: 2x 30 N, in top ridges, normal to face (magenta)

Meshing: Standard

Figure 3.6 – Set up Solidworks simulation

The results of this simulation look very promising (Figure 3.7). The behaviour of the Solidworks Simulation is the same as expected. There is a bending in the bottom of the model. On this place is (virtually) the location of the skate-blade.

Note: the different colours in the image are the absolute deformation, they don’t say anything about reliability, stress, etc. This will be tested further on.

So the results look very promising to continue with this concept. In this simulation it is very easy to change lots of aspects in this model. Applying different types of materials and dimensions gives very various results in the bending curvature.

However at this stage of the design there is no insight in the relation of the different parameters (wall thickness, curvature of the hinge, etcetera) These will be investigated in the next paragraph.

Figure 3.7 – Results Solidworks simulation

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3.3 Theoretical model

This paragraph will be about knowing more thoroughly about the models its parameters and bending behaviour. In some quick testing simulations is played with several properties of the model (e.g. wall thickness, materials). However it is not clear what happens during this simulations. Therefore a theoretical model is made to explain the bending behaviour. Before this, there is a mock-up model (Figure 3.8 – Mock-up model) made which gives a first real impression of the design.

Figure 3.8 – Mock-up model This mock up model is made out of two 5mm thick plexiglass parts. The upper part has an extra piece of metal attached to make stiffer. This simulates the tube. The dashed red line is the location of the hinge. Three hinge connections is the minimum to simulate a curved hinge. On the image on the right is the result shown, a bended skate-blade. As you might notice, the original skating tube (Maple) is way smaller than the upper tube.

Calculations

The whole construction has several parameters in its dimensions (Figure 3.9). Some of them are known (the length, radius). Others have to be optimized. The parameter ‘h’ has to be found for the dynamic ice-skate. H is the height of the curvature of the hinge. If h is too large, the bending will be too large and not useful. If h is too small, the bending curvature might be too small. The length ‘L’ of the skate-blade is known, 450mm. X is the absolute deformation of the blade. R is the radius of the bending, for short track skating starts this radius at 6 meters. Long track skaters have very small bending, this could be even 60 meters.

Figure 3.9 – Parameters

46 Development of a dynamic ice-skate

So (Table 3.6):

L Length skate-blade (length of the bending) 450 mm R Radius of the bending 6-60 m x Deformation of the skate-blade … mm h Height of the curve … mm Table 3.6 – Parameters x and h have to be found, this situation above can be translated into the next situation (Figure 3.10):

So (picture circle): ͌ͦ Ɣ ʚ͌Ǝͬʛͦ ƍʚ"͆ʛͦ

͌ͦ Ǝʚ"͆ʛͦ Ɣʚ͌Ǝͬʛͦ

ǭ͌ͦ Ǝʚ"͆ʛͦ Ɣ͌Ǝͬ

Results in: x = R - ǭ͌ͦ Ǝʚ"͆ʛͦ

Figure 3.10 – Simplified situation of the parameters

The values of x can be found easily with R (Table 3.7):

Short track (Radius, R) x (height in mm) 6 meter 4.22 8 meter 3.16 10 meter 2.53 20 meter 1.27 Long track (Radius, R) 30 meter 0.84 40 meter 0.63 50 meter 0.51 60 meter 0.42 Table 3.7 – Values of R and x

The maximum deformation of the total length of the skate-blade is about 4 mm. Check this value with a bended short track skate-tube shows that this value is a good approach. Next is to determine the value of h (the maximum height of the curve). The next image (Figure 3.11) shows all the parameters during bending of the tube.

47 Marc Bloem

The height (h) is the distance between The angle of the bending (alpha) has a direct relation with point 1 and 2 in the side view. the absolute bending (x) Figure 3.11 Note: This model is not 100% equal as in the previous simulation. The top element in this model has an infinitive stiffness.

To find out what the ideal height is for The height (h) of the curvature depends on the angle (alpha). However this angle should not exceed 5 degrees because otherwise skate will buckle. On the other hand the value of h should not exceed 45 mm due to the design space under the foot (paragraph 2.5). So the goal is to find the value of alpha (Table 3.8):

Buckling angle … (max 5 degrees) x Deformation of the skate-blade 5 mm max. h Height of the curve max 45 mm

͜Ɣͬ 1', Figure 3.11 ͬ Ɣ1',ͯͥ ͜

ͭƔ͜Ǝǭͦ͜ Ǝͬͦ

Table 3.8 – values of the design parameters The next table shows the relation between the parameters x, h, , and y. The green values are the optimal values for the different bending settings (x). x = 5 mm x = 4 mm x = 3 mm x = 2 mm h y h y h y h y (in °) (in mm) (in mm) (in °) (in mm) (in mm) (in °) (in mm) (in mm) (in °) (in mm) (in mm) 2 143.7 0.087 2 114.6 0.070 2 85.9 0.052 2 57.3 0.035 3 95.5 0.131 3 76.4 0.105 3 57.3 0.079 3 38.2 0.052 4 71.7 0.175 4 57.3 0.140 4 43.0 0.105 4 28.2 0.070 5 57.4 0.218 5 45.8 0.175 5 34.4 0.131 5 22.9 0.087 6 47.8 0.262 6 38.2 0.210 6 28.7 0.157 6 19.1 0.105 7 41.0 0.306 7 32.8 0.245 7 24.6 0.183 7 16.4 0.122 8 35.9 0.350 8 28.7 0.280 8 21.6 0.210 8 14.3 0.140 Table 3.9 – relation between all parameters

48 Development of a dynamic ice-skate

The table above shows some interesting results:

• The value of h decreases drastically with a higher alpha. • A deformation of x=5 mm cannot be realized, the value alpha exceeds 5 degrees

So with a height (h) of 45 mm all required deformations can be reached op to x=4 mm. furthermore interesting to investigate is to know what will happen if the value of L will be shortened. This will give a stronger bending, but requires less design space in h. In other words, the skate-blade can be more compact.

During analysis is shown that the skater does not use his whole blade during a stroke. During corner stokes the bending in the front is more essential. So the curvature could be stronger in the front than in the back. This is dependent on the length of the curve (L).

Figure 3.12 – different curvatures of the skate

The image (Figure 3.12) shows that a stronger Radius of the bending could be realized with a shorter length of curves (L). At the back of the right skate there is almost no curvature (L2). The optimum ratio between L and L2 should depend on the following:

• L, Length of the curvature, especially necessary for corner strokes • L2, 450 mm minus L, especially necessary for straight strokes • The bending should be minimum 6 meters with an alpha smaller than 5 degrees • The length L should be as large as possible to create a bending in the blade

The next table shows (Figure 3.13) for different lengths of the curvature (L) and height (h) the required angle. The optimal value of L should be as high as possible, but 450 mm is not possible due to the required angle. The height is also variable (40 mm) to see the effect in angle.

Length Curve (L) in mm 450 405 405 340 340 265 265 225 225 of total length (450 mm) 100% 90% 90% 75% 75% 60% 60% 50% 50% Height curve (h) in mm 45 45 40 45 40 45 40 45 40 Bending in m: Alpha: 6 5,38 4,36 4,90 3,07 3,45 1,86 2,10 1,34 1,51 8 4,03 3,27 3,67 2,30 2,59 1,40 1,57 1,01 1,13 10 3,22 2,61 2,94 1,84 2,07 1,12 1,26 0,81 0,91 20 1,61 1,31 1,47 0,92 1,03 0,56 0,63 0,40 0,45 30 1,07 0,87 0,98 0,61 0,69 0,37 0,42 0,27 0,30 40 0,81 0,65 0,73 0,46 0,52 0,28 0,31 0,20 0,23 50 0,64 0,52 0,59 0,37 0,41 0,22 0,25 0,16 0,18 60 0,54 0,44 0,49 0,31 0,34 0,19 0,21 0,13 0,15 Figure 3.13 – Different angles for the skate-blade

49 Marc Bloem

Results

So chosen is to give the length of the curve around 75%, this is enough to cover a nice radius of the bending, without having an high angle. The height of the curve is a bit lowered to 40 mm to gain some extra design space.

Next paragraph will be about optimizing the final dimensions of the skate (e.g. wall thickness).

3.4 Optimization

This paragraph will be about finding the optimal dimensions of the skate. This will be achieved by a simplified model optimized in a Solidworks simulation (Table 3.10). The dimensions of the model fit in the design space (paragraph 2.5). The model consists of an upper tube and lower tube connected by a thin walled hinge.

Goal: • finding the optimal dimensions A between the top part (A) and bottom part (B) (tube and blade)

Simulation properties: B • Hinge: thin-wall • Material: std. Stainless steel • Force: 50N Lateral • Dimensions: various (see next cross section)

Desired results: • Alpha: max. 5 degrees • Blade bending, max. 5 mm Table 3.10 – Optimization in Solidworks Simulation

The optimal ratio of the upper and lower part have to be found by adjusting the dimensions of the skate-blade. These are shown in the next cross sections (Figure 3.14). Some of the parameters are already known, others have to be found to get the desired results (alpha: max 5 degrees & bending max 5 mm). Two cross sections of the model (outer and center) show the parameters for the simulation. These parameters are the height (h & h2) and the width of the top and bottom part (t1 & t2).

50 Development of a dynamic ice-skate

Figure 3.14 – Cross sections

The height of all cross sections are already known (green) due to the design space. The thickness of the two parts are not known yet and have to be found by the simulations.

Several simulations have been done to find the wall thickness t1 and t2. The optimum is shown in the next table (Table 3.11). Appendix 8 shows the full test results.

Wall thickness top part t1 10,9 mm

Height top part h2 13,5 mm

Wall thickness bottom part t2 4,18 mm Height bottom part h 40 mm

Bending skate-blade x 2,29 mm Angle 4,26 degrees

Table 3.11 – Simulation results

Next to mention from the optimization is what happens with the results if the parameters change. A change in t1 or t2 has an influence in the bending and angle of the skate. For fine-tuning the ice-skate in future designs (i.e. next generation) is it important to know what happens if the parameters (t1 and t2) change (Table 3.12).

51 Marc Bloem

increases stays equal stays equal decreases If: t 1 + = = –

stays equal increases decreases stays equal and: t 2 = + – = Then:

Bending increases decreases increases decreases (x) + – + –

Angle decreases decreases increases increases () – – + +

Table 3.12 – Parameters t1 and t2

In addition to the table above there is more to mention about the influence of the parameters (t1 and t2) on the bending and angle:

• A change in the upper wall thickness (t1) has the most influence on the angular rotation (alpha). The bending is less affected.

• A change in the lower wall thickness (t2) has the most influence on the bending of the skate-blade (x). The angular rotation is less affected.

These values from Table 3.11 will be used for the final design. However the simulation consists out of square solid tubes and stainless steel. This might not be ideal for the final design. For example, normal ice-skates have a hollow cylindrical tube. Last part of the optimization is to describe the flexural rigidity (E*I) of the top tube design. This is done for the direction of the bending, the normal-axis to the skate.

Due to the design space, the height (h2) of this part is always fixed (13,5 mm). The wall thickness (t1)

has the most influence.

͖ͧ͜ ͜ ͨ ͧ  Ŵ  ͦ ͥ ST ST

Note: E stands for the Young modulus (N/mm2), and describes the material used. I stands for the Moment of Inertia (m4), and describes the geometry of the material.

The next table (Table 3.13) shows the flexural rigidity for the top and bottom part of the ice-skate.

However as shown earlier, the height of the cross section of the bottom part is not constant but variable (Figure 3.14) due to the changing height (h) of the curvature. On every position in the cross section is h different. Therefore it might be complicated to describe the moment of Inertia. So chosen is to describe the moment of Inertia of the lower part as and leave h into the formula:

͖ͧ͜ ͨ͜ ͧ  Ŵ  ͦ ST ST

52 Development of a dynamic ice-skate

Optimum of the simulation Cross section Top part -*'"0#!2 ,%*#Q!-,12 ,2 Thickness (t1) SRQ[++ Height (h2) SUQW++ ʚ$'6#"ʛ ͧ ͦ͜ ͨͥ Moment of inertia (I) Ɣ SVWZ ++V ST Material 2"T2 ',*#1112##* Youngs modulus (E) TQS Ɛ SRͩ 4 ++T Flexural rigidity top (E*I) ̌Q ̊ Ɛ ̊̉̑ 4++T

Cross section Bottom part -*'"0#!2 ,%*#Q4:;!-,12 ,2 Thickness (t2) VQSZ ++ Height (h) 4 0' *# ͨ͜ ͧ Moment of inertia (I) ͦ ʚ++ͨʛ ST Material 2"T2 ',*#1112##* Youngs modulus (E) TQS Ɛ SRͩ 4 ++T #/ w Flexural rigidity bottom (E*I) ̋T ̊ Ɛ ̊̉̎ Ɛ v 4++T ͥͦ Table 3.13 - Flexural rigidity

The Flexural rigidity of the top and bottom parts are related to each other because they determine the bending behaviour of the ice-skate. The last simulation shows the correct bending simulation, so these values (E*I) are very useful. The ratio between these parts together should therefore always be the same (no matter what kind of material is used). This means the following:

͙͕͚͙͕̀ͬͩͦͦ͛ͨͭͣͨͧͩͨͣ͘͜͢͠͠͝͝͝͝͡͠͝ʚ̻ʛ Ɣ ͙͕͚͙͙͕̀ͬͩͦͦ͛ͨͭͣͨͫͧͨͩͨͣ͘͜͢͢͠͠͝͝͝͝͝ʚ̼ʛ

̿ Ɛ̓/*+ ̿ Ɛ̓/*+ Ɣ  ̿ Ɛ̓*//*( ̿ Ɛ̓*//*(

SUQW ͨ ͧ ͬ ̿ Ɛ  ͥ UQS Ɛ SR ̼ ST Ɣ ͜VQSZ ͧ ͜ ͨ ͧ TTS Ɛ SRͩ Ɛ  ̿ Ɛ  ͦ ST ̼ ST

SUQW ͨ ͧ ͬ   ͥ UQS Ɛ SR ST Ɣ ͩ ͧ ͨ ͧ TTS Ɛ SR ƐVQSZ ͦ

ͬ ͧ ST Ɛ UQS Ɛ SR ͨͥ Ɣ ͩ ͧ ͨ ͧ SUQW Ɛ TTS Ɛ SR ƐVQSZ ͦ

w ͨS̼ ǭSYQ[Y Ɣ ͨT̼

U ͨͥ Ɣ ǭSZ Ɛͨͦ

So this means that for a correct bending behaviour, the wall thickness (t1 and t2) should always have the same ratio to each other.

From now on it is not tough to calculate the dimensions for a new material. The optimal flexural rigidity is found, so they have to count for any new situation as well. The new dimensions for different materials are shown in Table 3.14.

53 Marc Bloem

Simulation Aluminum Titanium Steel tube (solid) Tube (solid) Tube (solid) Flexural Rigidity (E*I) top N mm2 3,1E+08 3,1E+08 3,1E+08 Young’s Modulus (E) N/mm2 210000 70000 105000 Moment of Inertia (I) mm4 1458 4374 2916

Height top (h2) mm 13,5 13,5 13,5

Thickness top (t1) mm 10,9 15,7 13,7

Thickness botttom (t2) mm 4,2 6,0 5,3 Table 3.14 – Dimensions for different materials

The relation between the Young’s modulus and wall thickness (t1 or t2) is also clear. A material with a lower Young’s modulus has an increase in the wall thickness. This value is:

w ̿) 2 ǯ Ɵ Ɛͨ0-- )/ Ɣͨ) 2 ̿0-- )/

Note: Ecurrent and tcurrent are the properties of the steel simulation. These are: 2.1 GPa and 10.9 mm

Appendix x shows some more materials and cross sections (different profiles, (hollow) tubes, etcetera) for the ice-skate.

Conclusion

The relation between the material and geometry is explored. It is clear what kind of change in material selection has in the dimensions and vice versa. The previous calculations are simplified however these should be optimized in a future process. For now on the calculations provide insight into the model.

In general can be concluded the following: If the skate will be made out of a type of steel then will be w the wall thickness of t1 and t2 approximately be 10,9 and 4,2 mm. For aluminum this value is :U  Ɩ STVV higher, namely t1 = 15,7 mm & t2 = 6,0 mm.

Next to that the wall thickness (t1 and t2) should always have the same ratio to each other. U This value is: ͨͥ Ɣ :SZ Ɛͨͦ

54 Development of a dynamic ice-skate

3.5 Concept details

Appearance

The product (Figure 3.15) consists of and upper (1) and lower tube (2) connected by a hinge (3). As shown below is this connection is curved. The skate-blade (4) is placed inside the lower tube. Detailed information (e.g. production, hinge, etc) about the product can be found further in this paragraph.

The intention of the shape of the skate was to design it as elegant as possible. Therefore are the cups (5) integrated into the model, for a smoother finishing. Despite the different shape it is still recognizable as a skate. The hinge is integrated inside the upper tube.

5

5 3

1 4 2

Figure 3.15 – Final appearance of the dynamic ice-skate

The lower tube is perforated with several small vertical slots. These are designed to give the whole skate a more open appearance. So these holes do not have a mechanical function, and are kept as small as possible. The influence on the bending behaviour is therefore as small as possible.

The distance between the cups is the same (165 mm) as other short track skates. So current short track skate shoes are compatible on this product (Figure 3.16).

Figure 3.16 – Compatible on current short track shoes

55 Marc Bloem

Dimensions

The outer dimensions are 450x39x86 mm (Figure 3.17). The height of the skate is a slight bit higher (5 mm) than a short track skate. Because of the required curvature there was a minimum amount of space needed. To lose some height in the design, the skate blade is lower dimensioned than in regular short track skates.

Width: 39 mm

Height: 87 mm

Length: 450 mm

Figure 3.17 – Dimensions

For a long track should the design skate have a lower curvature, because the corners are much wider than in short track. Very challenging for a next phase is to integrate the hinge in a klapskate mechanism while maintaining the dimensions of a current klapskate.

Materials & Production

The ice-skate consists out of five parts:

• An upper tube • A lower tube • A skate-blade • And two caps on the upper tube (as a finishing touch)

For this generation is chosen to build the ice-skate out of steel and aluminum. Because of the open structure of the upper tube (Figure 3.18) is chosen for steel. This is much stronger than aluminum. Due to the complex shape and the integrated cups looks casting very promising.

The lower tube will also be cast, but due to weight issues, is aluminum more suitable. Like in every skate is the skate-blade made of (hardened) steel.

To assemble the both tubes into each other ((Figure 3.18) the lower tube is pressed into the upper tube. This is similar as in regular ball bearings. After assembly the parts cannot be separated anymore. Detailed information about this figure will follow in the section ‘hinge’ of this paragraph.

56 Development of a dynamic ice-skate

Figure 3.18 – Simplified cross section of the hinge

The skate-blade will be assembled as in the regular process. It will be glued into the lower tube. However this could not be the same glue as in current ice-skates. Due to dynamic bending of the skate a new type of glue should be developed. This glue should be (a bit) more flexible than the original glue used in ice-skates. For a future generation skate another solution could be to eliminate glue out of the design for changeable (custom) skate-blades.

Weight

The weight of the product is found by multiplying the volume times the density of the material (Table 3.15) The weight is compared with a current aluminum short skate tube.

Dynamic ice-skate Aluminum Steel Skate-tube Skate tube Material Volume Density Weight Weight Weight cm3 g/cm3 grams grams grams Upper tube Steel 65 7,8 507 Lower tube Aluminum 59 2,7 159,3 Blade Steel 10 7,8 78

Total 134 744,3 400* (54%) 700* (94%) Table 3.15 – Weight ( * = estimation)

For a future generation ice-skate could be very promising to look in other material families than only metals. Using fibers is a very promising solution, they are strong and deformable. It might result in more product volume, however it could be much lighter with the same strength.

57 Marc Bloem

Hinge

In previous simulation was the hinge designed as a continuous flexible hinge which can buckle. On this place was material between the upper tube (gold) and lower tube (gray) is located. (Figure 3.19) This hinge is connected all over the length of the tube. Therefore the hinge has to be optimized.

Figure 3.19 – Location of the hinge This hinge does have several aspects to take care of:

• Failure / fatigue During a skate stroke the construction is loaded on the weakest place. So it could fail on this (thin) place. • Stress Because of the small wall thickness in the hinge, it is assumable that the stress is the highest in this hinge. • Vertical forces The load of the skater will go through the hinge. A thin hinge could probably not resist the weight of a skater. • Production The tolerance should be very accurate for thing hinge.

In order to avoid the weaknesses described above, the type of joint/hinge has to be improved. In all earlier simulations a thin continuous hinge is used instead of a proper designed hinge. A continuous hinge might not be an ideal solution to connect the upper tube and lower tube. Instead of a continuous hinge another solution is to connect the tubes on only several points with a ball joint (Figure 3.20).

Figure 3.20 – Ball joint

58 Development of a dynamic ice-skate

Note: The upper and lower tubes will be considered as separate parts. These parts could be produced separate and will be joined together in the hinge.

To determine what has the most potential, a comparison between a continuous hinge (joint) or a ball joint is been made below (Table 3.16). Several factors have been considered to make a decision for which type of joint/hinge should be used in the final design.

Continuous hinge Ball joint(s)

+ + Possible to cast the hinge in Possible to cast the hinge in Production the upper and lower tube the upper and lower tube design design

– + Assemble the upper and lower tube Lots of Pressure needed to Less pressure needed to assembly the two parts into assembly the two parts into the hinge the several joints Movement in direction 1 – hinge

++ ++ No problems No problems

Front view of the tube Movement in direction 2 – bending the tube – ++ Continuous hinge is not No stress in the joints. Ball designed for a moment over joints can move 360 the length of the blade. degrees around.

Top view of the tube Table 3.16 – Continuous hinge vs. ball joint

Continuous hinge vs. ball joint

There are two major differences between the two types of joints. Assemble the upper and lower tube might be more difficult for a continuous hinge than a ball joint. However this could be a design issue, more important is the bending of the tube. Moving the tube in direction 2 (see table above) is not recommended for a continuous hinge. A continuous hinge is only designed to hinge, not to transfer a moment into the tube (bending). Therefore it could fail after a while. A ball joint does not have this problem and can rotate 360 degrees. It fixes the three possible translations (X,Y,Z). So chosen is for a ball joint.

59 Marc Bloem

Hinge design

There are several design solutions to connect the upper and lower tube by a ball joint. These are shown below (Figure 3.21).

#1 #2 #3 #4 Upper tube around Upper tube around Upper tube inside Upper tube inside lower tube lower tube lower tube lower tube (integrated) (separated) (separated) (integrated) Figure 3.21 – Options to connect the upper and lower tube

These solutions will be compared on several aspects. These aspects are: dimensions, production, strength and elegance for the implementation in the final design. For all different design solutions are these aspects compared (Table 3.17 – Comparison of the four design solutions).

#1 #2 #3 #4 Dimensions + o o o Compact Narrow but high Narrow but high Wide Production o o o o Possible to cast Possible to cast Possible to cast Possible to cast Strength – + o – Open structure in Compact, upper upper tube intact, upper tube intact the upper tube tube intact, no weak spot above but very wide and costs strength abrupt changes in the ball relatively thin wall thickness lower tube Elegance ++ + o – Smooth design, Smooth design, Smooth design, Integrated parts, integrated parts, hinge not visible hinge visible hinge visible hinge not visible Table 3.17 – Comparison of the four design solutions

60 Development of a dynamic ice-skate

Decision Hinge

Solution #1 and #2 have the best outcomes. Solution #1 has better scores in elegance and dimensions, #2 in strength.

For the hinge in a next generation ice-skate does Solution #1 have the highest potential. Integrating the hinge in the upper and lower tube gives the nicest shape and saves space. Because of the open shape of the upper tube #1, this design is not that strong as #2 where the upper tube remains intact. However this might be a design issue because there is only few space available for #1. Adding extra material to increase the strength is only a temporary solution. So design #1 is chosen to implement in the ice-skate. Six ball-joints are incorporated in the upper-tube (Figure 3.22). This is because the ball joints are placed with the same space to each other and on the most essential points (top and outside).

Figure 3.22 – Six ball joints

Prototype

A real prototype will also be available of the product. Due to the unique shape this product will be made by Rapid Prototyping. Rapid prototyping is the automatic construction of physical objects using additive manufacturing technology. It will be used to manufacture parts in relatively small numbers, especially to produce complex shapes.

This prototype will be manufactured by Materialize (Belgium), which is one of the largest and most experienced rapid prototyping manufactures worldwide. The method for this prototype will be: Selective Laser Sintering (SLS). This production method is an ideal the solution for [source: Materialize.be]:

• “Show and tell” parts with smooth surfaces and fine details • Visual prototypes for photo shoots, market testing and checking 3D drawings • Prototypes for (limited) functional testing • High level of accuracy and high surface quality

The goal of this model to show the actual product in real dimensions and to show the mechanism (working principle). This model demonstrates the dynamic ice-skate but is unfortunately not applicable to skate on. For the next phase will be recommended to build a model which can be used in real to test the effect on ice.

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Product overview

The dynamic ice-skate has a lot of potential to be a success for the skating sport. The advantage of the dynamic ice-skate product is described next in some key statements:

• The dynamic behaviour of the skate follows and adapts automatically to the trajectory of the skating stoke (adaptable). • Expertise about bending a skate is not required, but bending will more a part of the skate world. • No expensive bending equipment is needed anymore. • This means automatically more grip during corners AND on the straights. The skater can deliver more performance than with current skates. • Product is compatible with current skating products such as skate-shoes and sharpening tools. • Easy to understand for all the audiences, no unfair technologies or features are implemented. • Very cool and elegant product design (Figure 3.13).

Figure 3.23 – Product detail

62 Development of a dynamic ice-skate

4 Evaluation

4.1 Program of requirements

First aspect of the evaluation is to evaluate the program of requirements which was set in paragraph 2.8.

List of requirements

 1. The blade of the product must be adaptable due to pressure changes of the foot. (The product must fulfill its main application to be a dynamic ice-skate)  2. The product must fit the target group, competition (short-track) skaters.  3. The behaviour (adaptability) of the bending of the blade must be set easily (adjustable), with or without a tool.  4. The product may not cause unsafe situations  5. Current sharpening tools must be usable on the product.  6. Measuring the bending must be with current tools (e.g. a bending gauge)  7. The mechanism of the product must fit in the design space of the skate.  8. The product must be accessible and understandable for all involved parties.  9. The equipment must improve the athletes performance in a fair way.

List of preferences

 10. The user must be able to set the behaviour of adaptability of the product.  11. The bending of the skate-blade should be precise in the front section (top) of the blade.  12. The constructions appearance should be designed in a smooth and elegant way.  13. It is preferred that the bending of the skate-blade comprises the whole length of the skate-blade.  14. The product must be preferably for short-track skaters.  15. Setting the desired bending-behaviour should be as much as intuitive and user-friendly.  16. It is preferred that the product fits in current skate-products available  17. It is preferred that the product is maintenance free.  18. It is preferred that the product can be easily mounted and dismounted for maintenance.  19. It is preferred that the products maintenance can be done by the user itself.  20. It is preferred that current production technologies of ice-skates are as much as possible incorporated.  21. The product should be producible in (small) series.  22. It is preferred that the product’s design is as less complex as possible.  23. It is preferred that the product is resistant to different kinds of environments (low temperature, water, soil, etc)  24. It is preferred that the product is easily cleanable.  25. It is preferred that the cost price of the product is at the same level as a regular klap-skate products.  26. It is preferable that the product should not weight more than a regular klap-skate.  27. It is preferred that the product is also usable in a klap-skate mechanism

 The product does comprise several criteria. They are based on three subjects (behaviour, production, and klapskate) which will be discussed in the next paragraph 4.2.

63 Marc Bloem

4.2 Product recommendations

First I want to express the potential of the design. During the process and evaluation of the product some topics came around to improve the design.

Potential of the design

The results of the simulations look promising, the mechanism works and the appearance is pretty cool. The advantage of the dynamic ice-skate are clear:

More grip in the corners and straights during skating. Better contact with the ice means faster and easier skating. Besides there is no need to master the complex bending process.

Even important is what this product means on the market. In the first case it will be designed for competition long and short track skaters. It should cheaper than a regular klapskate because no expensive equipment will be required anymore. Introducing the product will be first for competition skaters. They can use this skate as a fixed skate and this helps to improve their technique even more before they buy a klapskate. If the product is successful in this group (what also happened with the well known klapskate), the implementation towards the elite skating league will be easily made.

Users can experience by using the dynamic ice-skate what advantages bending will have. Because of this, bending has the great potential to be widely accepted for the whole skating audience (not specifically for only the short track audience)

Behaviour & set flexibility of the skate-blade (adjustable)

In this dynamic ice-skate is one essential feature missing (see the program of requirements). It is not possible yet to set or adjust the flexibility of the skate-blade before ice-skating to a personal preference. The adjustability (or dynamic behaviour) should be dependent on various factors such as the skating technique, the build (weight) of the skater, etcetera.

The ambition for this design project was to include this feature in the product design, however developing the current solution was already challenging enough. Therefore during the design project was considered to focus only on the adaptability of the ice-skate.

The next step for the design is to include this extra functionality into the ice-skate (Figure 4.1). This is the most important missing feature and must be first implemented in the product design. Without this feature it is useless to put it into the stores and make it available to all audiences.

Figure 4.1 – Functionality of the final dynamic ice-skate

64 Development of a dynamic ice-skate

Hinge

At this moment the hinge (a ball joint) is integrated inside the skate-tube. This solution looks the most elegant but is not the strongest. Due to the open structure of the tube will it lose some of its rigidity. Therefore is chosen to thicken the tube to increase the rigidity. On the other hand this makes the tube heavier. Now for this generation is chosen for the open structure, this makes production (casting) less complex with the integrated cups.

The next generation of this product should better have a closed tube, however this might be very challenging to find a producible solution, especially with the integrated cups.

Optimization parameters

Another recommendation is to explore the parameters of the design more thoroughly to know the effects on the bending behaviour and rigidity of the design. This might be done by making a Matlab model of the design. The design parameters can be optimized to find the perfect products dimensions in combination with the material used which reduces the weight of the product. Another element to explore are the vertical forces. At this moment the tube is strong enough to hold a skater, however it is unknown what happens with material during skating itself.

In this stage is the volume of the skate relatively high, so reducing weight is essential. As described above, this can be achieved by using other materials, like fibers. Fibers do have a lot of potential in weight reduction, become cheaper and are not tough to handle anymore. This generation does not have fibers integrated, but for future generation should this type of material definitely considers. Applying fibers in the lower tube looks very suitable in this design.

Klap skate integration

The mechanism for this generation is designed for high fixed skates (high cups). It should be amazing when this mechanism can be integrated into a klapskate. This will be quite challenging because the design space in a klapskate is much smaller than for example a short track skate. A promising element is that long track skating rinks are much wider, which requires less for the mechanism design space.

Prototype Model II

A second prototype will be recommended to find out if the product works on ice. Testing the prototype in a real setting on ice should give a lot of feedback. It will be very interesting to know what an ice-skater thinks and feels about a constantly adapting skate-blade.

65 Marc Bloem

4.3 Implementation

Short-term

On the short term it is essential to build a working prototype which can be used on ice. This is to find out if the mechanism really works and to get feedback of the users about the behaviour of the skate. For example is the behaviour of the skate really comfortable as expected? Furthermore will the model be used to find out which weak spots exist in the construction. This will be the first part of the implementation (trial and error).

Next step is to find a solution to set the behaviour of the adaptability, so the skate will be useable for all kinds of users (weight, experience, etcetera).

Also it is important to gather more specific knowledge of the design by using computer simulations. This simulations help to understand and optimize the model.

Long-term

The items in the short-term implementation should be clear first before the introduction on the market can be started. The product will be targeted first for competition skaters. They can use this skate as a fixed skate (with high cups) and it will help them to improve their technique even more before they buy a klapskate. If the product is successful in this group (what also happened with the well known klapskate), the implementation towards the elite skating league will be easily made because the advantage will be clear.

66 Development of a dynamic ice-skate

4.4 Project evaluation

Before this project started, I had set some personal goals to achieve:

• Sports Using my affinity for sport to innovate a product which seemed to out-developed for the mass.

• Industrial Design o Integrating my strong points of industrial design into this project: modeling, calculations, testing and building.

• Graduate o To graduate in a realistic amount of time whereby all involved parties are satisfied.

At this moment (two weeks before the final presentation) I definitely can say that I have achieved all these goals. These three aspects are all equally important for me. During the project none of them kept the overhand.

All these goals were in balance which gave me the fun and motivation to finalize this graduating project with a cool product!

67 Marc Bloem

5 References

5.1 Literature

Design of a winning speed skate Maarten Bach TU Delft, Master Thesis AE 2007 Handboek wedstrijdschaatsen Henk Gemser, G.J. van Ingen Schenau, Jos de Koning Eisma Businessmedia bv, 1998 Een instelbare mal voor een schaatsrondingsmachine Joost Vreugdenhil TU Delft, Afstudeerverslag IDE 2006/2007 Design for sports, The cult of performance Akiko Busch Princeton Architectural Press, 1998 Building the Best Skate Otto den Braver TU Delft, 2007

5.2 Internet

Altijd maar bezig met 'zijn instrument' http://www.volkskrant.nl/sport/article175136.ece/Altijd_maar_bezig_met_zijn_instrument History of the ice-skate http://sport.infonu.nl/overige-sport/6159-de-ontwikkeling-van-de-schaats.html Virtueel schaatsmuseum http://www.schaatsenmuseum.nl/index.htm De finesses van het gebogen ijzer http://www.volkskrant.nl/archief_gratis/article957949.ece/De_finesses_van_het_gebogen_ijzer http://www.sportgeschiedenis.nl/2006/07/04/wetenschappers-kennen-geen-zomer.aspx http://www.intermediair.nl/artikel/de-loopbaan-van/135942/exschaatser-marnix-ten-kortenaar-een- spirituele-chemicus.html Dunne ijzers, op maat gerond en gebogen http://www.volkskrant.nl/sport/article224795.ece/Dunne_ijzers,_op_maat_gerond_en_gebogen Nieuwe klapschaats moet records breken http://www.metaaljournaal.nl/MetaalJournaal.Website/TemplateReport.aspx?RID=148 Olie op mes maakt 'gesmeerde schaats' mogelijk extra snel http://www.volkskrant.nl/sport/article170915.ece/Olie_op_mes_maakt_gesmeerde_schaats_mogelijk_ extra_snel Klapschaats en zwempakken devalueren wereldrecords http://www.elementweb.nl/courant/2008/12/technologische_ontwikkelingen_in_de_sport_zijn_net.php Crisis gaat voorbij aan schaatswereld http://www.z24.nl/bijzaken/artikel_93702.z24/Crisis_gaat_voorbij_aan_schaatswereld.html NOC*NSF - Sportbonden http://www.nocnsf.nl/cms/showpage.aspx?id=243 Materialise - Sterolithography http://www.materialise.com/Stereolithography

68 Development of a dynamic ice-skate

Acknowledgments

I want to thank specifically the next people for their help and positive support: Linda, Gerda, Robert, Mathys, Gijs, Melchior, Otto, Ruud, Leo, Lorraine & Adrie.

My graduation was without them clearly impossible, so many thanks again!

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