UNIT2.6-Mechanisms: Eng Notes
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Design of Continuously Variable Bicycle Transmission
Innovative Bicycle Drivetrain Design of continuously variable bicycle transmission Author: Jean Kolb Supervisor: Dr Eng. Slawomir Kedziora Chain drive with derailleur change mechanism . 98.5% efficiency . Relatively low weight . The most common drivetrain . Not innovative NuVinci CVT hub . Continuously variable ratio . Torque transmitted by traction . Ball planets change the contact angle Source: https://www.fallbrooktech.com/nuvinci-technology CVT hub by Hiroyuki Urabe . Used as reference for own design . Upstream planetary gear train and roller train . Estimated efficiency of 90% . Patented, but not developed CVT hub by Hiroyuki Urabe Pros Cons . Different and innovative . Relatively heavy weight . Continuously variable . Lower transmission efficiency . Enhanced e-bike engine . More complex than the efficiency comparable design from . Protected in hub enclosure “NuVinci” . Clean look Presentation and explanation of the developed design CVT hub Developed CVT hub Autodesk Fusion 360 unites every development step Cloud computing Developed CVT hub Developed CVT hub Upstream planetary gear train Input Output Sprocket Input Input torque on ring gear Fixed carrier Developed CVT hub Planetary roller train Output Input Input torque on sun roller Non-rotatable but on axle displaceable carrier Preloaded spring Preloaded spring to guarantee enough traction Wave spring Preloaded spring Spline Radial bearing on slidable sleeve Needle bearings Axial bearing gets pushed Left handed thread Gap between roller and sun Left handed thread Changing -
Mechanical Advantage Use the Equation for Mechanical Advantage to See How Machines Multiply Force
Name Date Class WORKSHEET MATH SKILLS USED Division MATH IN SCIENCE: PHYSICAL SCIENCE 53 Decimals Mechanical Advantage Use the equation for mechanical advantage to see how machines multiply force. The mechanical advantage of a machine is the factor by which the machine multiplies force. The mechanical advantage of a machine can be used to determine how well a ma- chine works and whether it can perform a particular job. output force EQUATION: mechanical advantage (MA) ϭ ᎏᎏ input force SAMPLE PROBLEM: What is the mechanical advantage of a lever that requires an input force of 20 N and lifts an object that weighs 60 N? 60 N mechanical advantage (MA) ϭ ᎏ 20 N MA ϭ 3 Practice Your Skills! Use the equation for mechanical advantage to answer the following questions: 1. Amanda uses a wheelbarrow to lift a load of bricks. The bricks weigh 600 N, which is more than Amanda could normally carry. However, with the wheelbarrow, Amanda can lift the bricks with as little as 120 N. What is the mechanical advantage of the wheelbarrow? 2. Marshall wants to remove a tree stump from the ground. To do this, he puts one end of a long beam under the stump and puts all of his weight on the other end. His weight is just enough to lift the stump. The stump weighs 400 N. Marshall weighs 250 N. What is the mechanical advantage of the lever Marshall is using? 3. A system of pulleys allows a mechanic to lift an 1800 N engine. t and Winston. All rights reserved. -
Chapter 14 Work, Power, and Machines
0161_hsps09_GRSW_Ch14.qxd 7/27/07 3:33 PM Page 157 Name ___________________________ Class ___________________ Date _____________ Chapter 14 Work, Power, and Machines Summary 14.1 Work and Power For a force to do work on an object, some of the force must act in the same direction as the object moves. If there is no movement, no work is done. • Work is the product of force and distance. • Work is done when a force moves an object over a distance. Any part of a force that does not act in the direction of motion does no work on an object. • The joule (J) is the SI unit of work. • When a force of 1 newton moves an object 1 meter in the direction of the force, 1 joule of work is done. Doing work at a faster rate requires more power. To increase power, you can increase the amount of work done in a given time, or you can do a given amount of work in less time. • Power is the rate of doing work. • The SI unit of power is the watt (W), which is equal to one joule per second. • One horsepower (hp) is equal to about 746 watts. 14.2 Work and Machines Machines make work easier to do. They change the size of a force needed, the direction of a force, or the distance over which a force acts. •Amachine is a device that changes a force. Because of friction, the work done by a machine is always less than the work done on the machine. -
Basic Gear Systems
Basic Gear Systems A number of gears connected together is called a “Gear Train”. The gear train is another mechanism for transmitting rotary motion and torque. Unlike a belt and pulley, or chain and sprocket, no linking device (belt or chain) is required. Gears have teeth which interlock (or mesh) directly with one another. Advantages The main advantages of gear train transmission systems are that because the teeth on any gear intermesh with the next gear in the train, the gears can't slip. (An exact ratio is maintained.) Large forces can be transmitted. The number of turns a gear makes can be easily controlled. High ratios between the input and the output are easily possible. Disadvantages The main disadvantage of a gear system is it usually needs a lubrication system to reduce wear to the teeth. Oil or grease is used to reduce friction and heat caused by the teeth rubbing together. Gear systems to increase and decrease rotational velocity Gears are used to increase or decrease the speed or power of rotary motion. The measure of how much the speed or power is changed by a gear train is called the gear ratio (velocity ratio). This is equal to the number of teeth on the driver gear divided by the number of teeth on the driven gear. To decrease the speed of the output the driver gear is smaller than the driven gear. (This will reduce the speed but increase the “torque”.) This diagram shows a small gear (A) driving a larger gear (B). Because there are more teeth on the driven gear there is a reduction in output speed. -
Chapter 8 Glossary
Technology: Engineering Our World © 2012 Chapter 8: Machines—Glossary friction. A force that acts like a brake on moving objects. gear. A rotating wheel-like object with teeth around its rim used to transmit force to other gears with matching teeth. hydraulics. The study and technology of the characteristics of liquids at rest and in motion. inclined plane. A simple machine in the form of a sloping surface or ramp, used to move a load from one level to another. lever. A simple machine that consists of a bar and fulcrum (pivot point). Levers are used to increase force or decrease the effort needed to move a load. linkage. A system of levers used to transmit motion. lubrication. The application of a smooth or slippery substance between two objects to reduce friction. machine. A device that does some kind of work by changing or transmitting energy. mechanical advantage. In a simple machine, the ability to move a large resistance by applying a small effort. mechanism. A way of changing one kind of effort into another kind of effort. moment. The turning force acting on a lever; effort times the distance of the effort from the fulcrum. pneumatics. The study and technology of the characteristics of gases. power. The rate at which work is done or the rate at which energy is converted from one form to another or transferred from one place to another. pressure. The effort applied to a given area; effort divided by area. pulley. A simple machine in the form of a wheel with a groove around its rim to accept a rope, chain, or belt; it is used to lift heavy objects. -
Levers and Gears: a Lot for a Little
Physics Levers and Gears: A lot for a little A surprising number of the tools and machines we rely on every day – from door handles and cricket bats to clocks and bikes – can be explained in terms of a few simple ideas. The same principles allowed ancient civilizations to build enormous pyramids and the mysterious astronomical device known as the Antikythera Mechanism. In this lesson you will investigate the following: • How do simple machines allow us to achieve a lot with little effort? • What is mechanical advantage and how does it apply to levers, wheels and gears? • How do gear systems work? So gear up for a look at how some of our most useful machines work. This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com Introduction: Levers and Gears A reconstruction of the Antikythera Mechanism. In 1900 a team of divers discovered a 2000-year-old shipwreck near the Greek island of Antikythera. Inside the wreck they found an incredible range of treasures including beautiful bronze statues and glass bowls. They also found a plain-looking lump of bronze no bigger than a shoebox. Closer examination revealed that the object had gear wheels embedded in it – as though it was some kind of ancient clock. It soon became known as the Antikythera Mechanism but its internal structure and purpose remained mysterious for decades. Later investigations using X-rays uncovered thirty interlocking gears and inscriptions of the ancient Greek words for “sphere” and “cosmos”. -
High Efficiency Moped a MQP Proposal Submitted to the Faculty Of
High Efficiency Moped A MQP Proposal Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor of Science in Mechanical Engineering by ___________________________________ Tim Ellsworth Date: 10/11/2012 Approved: Prof. Kenneth Stafford, Major Advisor Prof. Cosme Furlong-Vazquez Table of Contents List of Tables ................................................................................................................................................. 4 List of Figures ................................................................................................................................................ 5 Abstract ......................................................................................................................................................... 7 Executive Summary ....................................................................................................................................... 9 Introduction ................................................................................................................................................ 12 Objective ................................................................................................................................................. 12 History ..................................................................................................................................................... 13 Component Selection ................................................................................................................................. -
Simple Machines Work 5.1 What Is Work?
5 Table of Contents 5 Unit 1: Energy and Motion Chapter 5: Work and Machines 5.1: Work 5.2: Using Machines 5.3: Simple Machines Work 5.1 What is work? • To many people, the word work means something they do to earn money. • The word work also means exerting a force with your muscles. Work 5.1 What is work? • Someone might say they have done work when they push as hard as they can against a wall that doesn't move. • However, in science the word work is used in a different way. Work 5.1 Work Makes Something Move • Remember that a force is a push or a pull. In order for work to be done, a force must make something move. • Work is the transfer of energy that occurs when a force makes an object move. • If you push against the desk and nothing moves, then you haven't done any work. Work 5.1 Doing work • There are two conditions that have to be satisfied for work to be done on an object. • One is that the applied force must make the object move, and the other is that the movement must be in the same direction as the applied force. Work 5.1 Doing work • For example, when you lift a stack of books, your arms apply a force upward and the books move upward. Because the force and distance are in the same direction, your arms have done work on the books. Work 5.1 Force and Direction of Motion • When you carry books while walking, you might think that your arms are doing work. -
TEE Final Report
Project Number: AHH – 1171 Pseudo‐Fluid Control Extension System A Major Qualifying Project Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor of Science In Mechanical Engineering by John Dunbar ______________________________ Christopher Farren ______________________________ Mari Freitas ______________________________ Date: April 26, 2012 Approved: Keywords ______________________________ Professor Allen H. Hoffman, Major Advisor 1. Transducer 2. TEE 3. Pseudo‐fluid ______________________________ Professor Holly K. Ault, Co‐Advisor Abstract An interventional cardiologist (IC) performs procedures using a transesophageal echocardiogram transducer (TEE). The TEE is positioned by an echo cardiologist who is present for the entirety of the procedures. The purpose of this project was to redesign the user interface of the TEE in order to minimize the role of the echo cardiologist and give more control to the IC. This was accomplished by creating an extension of the TEE control system that can remotely control the TEE from a distance of five feet. Preliminary designs were created using cable and fluid hydraulic systems; however, both types of systems were problematic. A pseudo‐fluid system consisting of tubes filled with steel balls was developed to capture the positive aspects of the cable and fluid systems. The user interface of the new system consisted of two rotatable knobs that actuate rack and pinion gear sets, which push the pseudo‐ fluid balls through tubes. At the distal ends of the tubes, the balls move the racks of rack and pinion gear sets that in turn rotate shafts in the current TEE. The resulting user interface has similar ergonomic and mechanical properties as the original TEE. -
Energy, Work, and Simple Machines and Finally, Multiply Both Sides of the Equation by 1/2 M
A Not-So- Simple Machine How does a multispeed bicycle let a cyclist ride over any kind of terrain with the least effort? ➥ Look at the text on page 238 for the answer. CHAPTER Energy, Work, and Simple 10 Machines hat is energy? Energy is needed to make cars run, to heat WHAT YOU’LL LEARN or cool our homes, and to make computers hum. Solar • You will recognize that work W energy is required for crops and forests to grow. The energy and power describe how stored in food gives you the energy needed to play sports or walk energy moves through the to the store. Note, however, all these statements indicate that hav- environment. ing energy enables something to perform an action, rather than • You will relate force to work saying directly what energy is. It is hard to give a good definition and explain how machines of energy without examples of how energy is used and the result- make work easier by chang- ing changes. ing forces. In this chapter, you’ll concentrate on one method of changing the energy of a system—work. You’ll need to be careful here. You WHY IT’S IMPORTANT may think you’re doing work when you put forth a physical effort. • A little mental effort in iden- For example, you and a friend may try to move a stalled car, but tifying the right machine for the car doesn’t budge. You feel as though you’ve done work a task can save you much because you’re out of breath and your arms ache. -
Mechanisms of Most Cars
Moments The crane in the image below looks unstable, as though it should topple over. There appears to be too much of the boom on the left-hand side of the tower. It doesn’t fall because of the presence of a counter balance weight on the right-hand side. The boom is therefore balanced. In order to understand this better, we need to understand pivots, moments and equilibrium. The pivot point or fulcrum is the point at which something rotates. The weights on the scales are at equal points from the pivot point. When something is balanced it is said to be in equilibrium. In the example of the see-saw, if one of the people moves backwards or forwards, the balance is tipped one way or the other. The see-saw is no longer in equilibrium. When something is in equilibrium, the moments of a force are balanced. The Moment of a Force is calculated as the force multiplied by the distance from the pivot point. Moment = F x d Distance (d) Pivot Force (F) This can also be represented as illustrated below: The Principal of Moments states that for there to be equilibrium, the clockwise moments must equal the anti-clockwise moments. Clockwise Moments = F2 x d2 Anti-Clockwise Moments = F1 x d1 If F2 x d2 = F1 x d1 there is equilibrium Example Clockwise Moments = 20N x 1m Anti-Clockwise Moments = 10N x 2m 20Nm = 20Nm Therefore, the scales is in equilibrium. Levers A lever is a rigid rod, pivoted about a fixed point or axis, which is known as a fulcrum. -
General Applications of Gears
UNIT - III GEAR MANUFACTURING PROCESS SPRX1008 – PRODUCTION TECHNOLOGY - II Gears are widely used in various mechanisms and devices to transmit power and motion positively (without slip) between parallel, intersecting (axis) and non-intersecting non parallel shafts, •without change in the direction of rotation •with change in the direction of rotation •without change of speed (of rotation) •with change in speed at any desired ratio Often some gearing system (rack – and – pinion) is also used to transform Rotary motion into linear motion and vice-versa. Fig.1 Features of Spur Gear Gears are basically wheels having, on its periphery, equispaced teeth which are so designed that those wheels transmit, without slip, rotary motion smoothly and uniformly with minimum friction and wear at the mating tooth – profiles. To achieve those favorable conditions, most of the gears have their tooth form based on in volute curve, which can simply be defined as Locus of a point on a straight line which is rolled on the periphery of a circle or Locus of the end point of a stretched string while its unwinding over a cylinder as indicated in Fig. General Applications of Gears Gears of various type, size and material are widely used in several machines and systems requiring positive and stepped drive. The major applications are: • Speed gear box, feed gear box and some other kinematic units of machine tools • Speed drives in textile, jute and similar machineries • Gear boxes of automobiles • Speed and / or feed drives of several metal forming machines • Machineries for mining, tea processing etc. • Large and heavy duty gear boxes used in cement industries, sugar industries, cranes, conveyors etc.