Development of New Mean of Individual Transport for Application in Underground Coal Mines

energies

Article Development of New Mean of Individual Transport for Application in Underground Coal Mines

Paweł Kami ´nski

Department of Mining Engineering, Faculty of Mining and Geoengineering, AGH University of Science and Technology, 30-059 Krakow, Poland; [email protected]

Abstract: Development of underground coal mines is reﬂected in increasing lengths of transport routes between shafts and workplaces. This is not an issue in terms of transportation of materials or groups of people, because suspended railways are efﬁcient, safe, and fast mean of transport. However, transportation of individual people or small loads is an issue because of the lack of a means of individual transport and the high cost of transport using suspended railways. The development of individual means of transport, based on historical solutions, utilizes existing equipment of mine workings. This paper presents the stages of development of an underground bike, from the original idea to tests and analysis. The development process consists of simulations of different parameters of the bike using Working Model software and real-life tests conducted in an underground mine. The paper also presents analysis of the legal background of this new means of individual transport.

Keywords: underground mine; underground transport; mean of individual transport; bicycle

1. Introduction The constant increase in transportation routes between mine shafts and workplaces is Citation: Kamiński,P. Development of New Mean of Individual Transport a consequence of the development of mines. This situation has been observed for several for Application in Underground Coal decades. Rapid industrial development at the turn of the 19th and 20th centuries caused Mines. Energies 2021, 14, 2022. significant growth in coal demand because coal was the principal energy resource at that https://doi.org/10.3390/en14072022 time. Growing coal production enforced mine expansion and, in turn, lengthening of roadways [1–3]. At present, the main cause of longer distances in coal mines is the need to Academic Editor: Dariusz Prostański develop mining areas that are distant from shafts in exploited deposits [4]. Numerous means of transport have been developed to improve communication Received: 8 March 2021 between distant excavations and mine shafts [5–7]. Due to the many advantages of rail- Accepted: 2 April 2021 way, this form of transport became the most popular in underground mines, particularly Published: 6 April 2021 combustion and electric floor railways. These have now been replaced in most cases by friction-gear-driven suspended railways, on which mine transport systems are based. Sus- Publisher’s Note: MDPI stays neutral pended railways are efficient and relatively fast means of transport. Thus, transportation with regard to jurisdictional claims in of people and materials is safe and easy, even in the case of distant mine areas [5,8]. published maps and institutional affil- However, despite the development of means of mass transport, the problem of in- iations. dividual transport remains unsolved [7]. Furthermore, due to the specific requirements of large groups of mine employees, significant distances are traveled between different mine workings, potentially several times per day. The desire to increase effectiveness and facilitate work has resulted in extensive development of improvised means of transport. Copyright: © 2021 by the author. Mine employees have readily adapted devices used on the surface to the conditions of Licensee MDPI, Basel, Switzerland. underground workings. Due to the popularity of bicycles in urban spaces, their modified This article is an open access article construction is common in underground mines, especially in Germany and Netherlands. distributed under the terms and Initially, underground bicycles were self-made creations, manufactured in mine workshops. conditions of the Creative Commons In 1954, Scharf GmbH from Hamm, Germany introduced and sold the first miners’ bike, Attribution (CC BY) license (https:// named Grubenflitzer [9,10]. During the years of the market presence of Grubenflitzer, creativecommons.org/licenses/by/ numerous models of the bike were constructed. The basic model is presented in Figure1. 4.0/).

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Energies 2021, 14, 2022 2 of 14 named Grubenflitzer [9,10]. During the years of the market presence of Grubenflitzer, numerous models of the bike were constructed. The basic model is presented in Figure 1.

Figure 1. A view of the miners’ bike Grubenflitzer by Scharf GmbH [9]. Figure 1. A view of the miners’ bike Grubenﬂitzer by Scharf GmbH [9].

Miners’Miners’ bikes bikes significantly significantly reduce reduce ineffective ineffective working working time, time, which which is is caused caused by by the the necessitynecessity of of moving moving between between distant distant work work places, places, and and improves improves the the miner’s miner’s work. work. How- How- ever,ever, due due to to the the growing growing amount amount of of machinery machinery in in mine mine workings, workings bike, bike riding riding has has become become dangerous.dangerous. AnotherAnother major issue is is rail rail deformation deformation caused caused by by floor floor heaving. heaving. These These factors, factors,in addition in addition to increasingly to increasingly restrictive restrictive safety safety regulations regulations,, led to led the to abandonment the abandonment of min- of miners’ers’ bikes. bikes. TheThe main main advantage advantage of of miners’ miners’ bikes bikes was, was, first, first, a a possibility possibility of of quick quick transport transport of of peoplepeople and and small small loads loads over over significant significant distances distances in in a a relatively relatively short short time. time This. This increased increased workwork effectiveness effectiveness and and reduced reduced employee’s employee’s tiredness tiredness caused caused by by the the necessity necessity of of transport. transport. AdditionalAdditional advantage advantage of of bicycles bicycles was was the the possibility possibility to to quickly quickly evacuate evacuate accident accident victims. victims. TheThe disadvantages disadvantages leading leading to to the the abandonment abandonment of of bikes bikes were were an an inability inability to to quickly quickly assembleassemble (making (making passingpassing aa complicated operation), the the strong strong influence influence of of floor floor heaving heav- ingon ontrack track condition conditions,s, and and a failure a failure to meet to meet safety safety regulations regulations (because (because of aluminum of aluminum con- constructionstruction and and lack lack of illumination). of illumination). An Anadditional additional factor factor that that contributed contributed to the to thedisappear- disap- pearanceance of bicy of bicyclescles was was the the growth growth in in popularity popularity of of suspended suspended railways, whichwhich ledled toto the the disappearancedisappearance of of typical typical rails rails from from mine mine workings. workings. TheThe current current situation situation of of Polish Polish mining mining industry, industry, particularly particularly the the constantly constantly growing growing distancesdistances between between shafts shafts and and mining mining areas, areas, represents represents a market a market niche, niche,namely, namely, underground under- individualground individual transport. transport. The historic The solutions historic presented solutions abovepresented can provideabove can guidelines provide for guide- the developmentlines for the development of a device to of fill a thisdevice niche. to fill this niche. TheThe introduction introduction of of new new adaptions adaptions of of the the miners’ miners’ bike bike must must be precededbe preceded by conceptual by concep- worktual work and research and research [11–13 [11].– The13]. currentThe current study study presents presents the processthe process of development of development of aof newa new miners’ miners’ bike, bike, comprising comprising five five main main stages: stages: 1. Analysis of historic solutions. 2. Concept of the new construction of the individual means of transport.

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1. Analysis of historic solutions. Energies 2021, 14, 2022 2. Concept of the new construction of the individual means of transport. 3 of 14 3. Simulations to verify the concept. 4. Prototype of the new miners’ bike. 5. 3. Real-lifeSimulations underground to verify tests the concept.of the new means of individual transport. 6. 4. AnalysisPrototype of compliance of the new miners’with existing bike. laws. 5. Real-life underground tests of the new means of individual transport. 2. 6.The NewAnalysis Means of compliance of Individual with Transport existing laws.Concept From a thorough analysis of historic solutions of means of individual transport in underground2. The New mines, Means the of Individualmain characteristics Transport of Concept the designed device can be specified: • simplicityFrom a thoroughof design, analysis of historic solutions of means of individual transport in • undergroundeasy and intuitive mines, theuse, main characteristics of the designed device can be speciﬁed: • • utilizationsimplicity of of existing design, infrastructure of underground workings. • Basedeasy on and the intuitive features use, listed above, the idea of a miners’ bike utilizing suspended railway• utilization was developed. of existing It was infrastructure assumed ofthat underground this new means workings. of individual transport shouldBased be light on enough the features to be assembled listed above, or disassembled the idea of a miners’by one person. bike utilizing It was necessary suspended torailway take into was account developed. safety Itof was user assumed and enviro thatnment. this new The means result of of individual conceptual transport work on should this meansbe light of individual enough to beunderground assembled ortransport disassembled was the by patent one person. PL 418208 It was [14], necessary which was to take a basisinto for account further safety construction of user and development environment. and The necessary result of research conceptual and worktesting. on this means of individualThe specified underground requirements transport were the was basis the fo patentr a number PL 418208 of new [14 miners’], which bike was construc- a basis for tionfurther proposals, construction which developmentdiffer in terms and of necessarydrive solution, research placement and testing. of the drive and seat, and assemblyThe speciﬁed of the requirementselements. Examples were the of basisdifferent for a miners’ number bike of new solutions miners’ are bike shown construc- in Figurestion proposals, 2 and 3. which differ in terms of drive solution, placement of the drive and seat, and assembly of the elements. Examples of different miners’ bike solutions are shown in Figures2 and3.

FigureFigure 2. 2.ConceptConcept of ofthe the miners’ miners’ bike bike construction construction..

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Figure 3. Concept of the miners’ bike construction. Figure 3. Concept of the miners’ bike construction.construction. The model of the proposed miners’ bike concept is presented in Figure 4. It was de- The m modelodel of of the the proposed proposed miners’ miners’ bike bike concept concept is ispresented presented in inFigure Figure 4. 4It. was It was de- scribed in detail in [15]. The main difference between this construction and the one pre- describedscribed in indetail detail in [ in15 [].15 The]. The main main difference difference between between this thisconstruction construction and andthe one the pre- one sented in the patent is two vertical beams instead of one. Before assembling the prototype, presentedsented in the in patent the patent is two is twovertical vertical beam beamss instead instead of one. of Before one. Before assembling assembling the prototype, the pro- numerical simulations were conducted to verify the correction of the concept assumptions totype,numeric numericalal simulations simulations were conducted were conducted to verify the to correction verify the of correction the concept of assumptions the concept [16]. assumptions[16]. [16].

Figure 4. Concept of the miners’ bike. Figure 4. Concept of the miners’ bike.bike. 3. Simulations 3. Simulations 3.1.3.1. Methodology Methodology 3.1. Methodology SimulationsSimulations were were conducted conducted to address to address the theissue issue of the of thebike bike ride. ride. A v Airtual virtual model model of of Simulations were conducted to address the issue of the bike ride. A virtual model of the thenew new construction construction of the of the mean meanss of ofindividual individual underground underground transport transport was was built built for for test- testing the new construction of the means of individual underground transport was built for testing usingusing Working Model software. software. The The aim aim of of the the simulations simulations was was to tospecify specify the the technical technical ing using Working Model software. The aim of the simulations was to specify the technical characteristicscharacteristics of the of thebicycle. bicycle. These These characteristics characteristics comprise comprise maximum maximum speed, speed, climbing climbing characteristics of the bicycle. These characteristics comprise maximum speed, climbing abilityability,, and and average average pressure pressure required required on onthe thepedals. pedals. Simulations Simulations were were conducted conducted for fortwo two ability, and average pressure required on the pedals. Simulations were conducted for two bicyclebicycle variants variants—one—one using using steel steel wheels wheels (variant (variant no. no.1) and 1) and the theother other using using rubber rubber-coated-coated bicycle variants—one using steel wheels (variant no. 1) and the other using rubber-coated steelsteel wheels wheels (variant (variant no. no.2). 2). steel wheels (variant no. 2).

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ObservationObservation of the traditionaltraditional bikebikeride ride revealed revealed that that the the pressure pressure on on the the pedals pedals during dur- ingthe the initialObservation initial phase phase of of theof the the ride traditional ride is higheris higher bike than than ride after afterreveal putting puttinged that the the the bike bike pressure into into motion. motion on the .pedals BasedBased dur-on thisthising observation, observation, the initial phase the the relationship relationshipof the ride is was was higher determined determined than after between between putting the thethe pressure pressurebike into onmotion the pedals . Based at on thethethis initial initial observation, moment moment thet0 t0 and andrelationship its its drop drop wast too 50% determined of the initial between value the after pressure putting on the the bike pedals into at motion.motion.the initial A A g graph raphmoment showing showing t0 and this this its relationship relationship drop to 50% is presentedof presented the initial in Figure value 5after5 andand putting itsits implementation the bike into ininmotion. Working Working A Model graph showing software this is shown relationship in Figure is presented6 6.. in Figure 5 and its implementation in Working Model software is shown in Figure 6.

FigureFigure 5. 5. GraphGraph of of the the function function of of pressure pressure on the pedals pedals.. Figure 5. Graph of the function of pressure on the pedals.

Figure 6. Implementation of the function in the Working Model program. Figure 6. Implementation of the function in the Working Model program. Figure 6. Implementation of the function in the Working Model program. Simulations were conducted for a number of variants in which different parameters were changed,Simulations such were as railconducted inclination, for a pressurenumber of on variants pedals, inor which additional different load. parameters The as- sumedwere weight changed, of suchthe bike as railwas inclination,40 kg and the pressure weight onof the pedals user, orwas additional 80 kg. load. The assumed weight of the bike was 40 kg and the weight of the user was 80 kg.

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Energies 2021, 14, x FOR PEER REVIEW Simulations were conducted for a number of variants in which different parameters6 of 15 were changed, such as rail inclination, pressure on pedals, or additional load. The assumed weightSimulations of the bike was were 40 conducted kg and the for weight a rail of of the varying user was inclination, 80 kg. gradually changing Simulations were conducted for a rail of varying inclination, gradually changing from fromSimulations 0 to 8° in 2° wereincrements conducted. Figures for 7 a– 9 rail present of varying different inclination, stages of the gradually simulations changing; sim- 0 to 8◦ in 2◦ increments. Figures7–9 present different stages of the simulations; simulations fromulation 0 tos of 8° the in 2°bike increments ride without. Figures an additional 7–9 present load different on the stagesrail with of theinclination simulations of 0°; sim-(Fig- of the bike ride without an additional load on the rail with inclination of 0◦ (Figure7), ulationure 7), s2° of ( Figurethe bike 8 )ride, and wi 8°thout (Figure an additional9) are shown. load The on thepressure rail with on inclinationthe pedals isof equal0° (Fig- to 2◦ (Figure8), and 8 ◦ (Figure9) are shown. The pressure on the pedals is equal to 200 N. The 200 N. The analyzed bike was equipped with rubber-covered steel wheels with a diameter analyzedure 7), 2° bike (Figure was equipped8), and 8° with(Figure rubber-covered 9) are shown. steel The wheels pressure with on a the diameter pedals of is 113 equal mm. to 200of 113 N. Themm. a nalyzed bike was equipped with rubber-covered steel wheels with a diameter of 113 mm.

Figure 7. Simulation of the bicycle ride without additional load on the horizontal rail. Figure 7. Simulation of the bicycle ride without additional load on the horizontal rail. Figure 7. Simulation of the bicycle ride without additional load on the horizontal rail.

Figure 8. Simulation of the bicycle ride without additional load on the rail with inclination of 2°. Figure 8. Simulation of the bicycle ride without additional load on the rail with inclination of 2°. Figure 8. Simulation of the bicycle ride without additional load on the rail with inclination of 2◦.

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Figure 9. Simulation of the bicycle ride without additional load on the rail with inclination of 8°. Figure 9. Simulation of the bicycle ride without additional load on the rail with inclination of 8◦. Figure 9. Simulation of the bicycle ride without additional load on the rail with inclination of 8°. FigureFigure 10 10 presents presents thethe simulationsimulation of the bicycle bicycle ride ride with with an an additional additional load load equal equal to to20 20 kg kgFigure on on the the 10 rail railpresents with with inclination the inclination simulation of of8°. 8 ofThe◦. the The assembly bicycle assembly rideof the of with theprototype an prototype additional is presented is presented load equal in Fig- in to Figureure20 kg 11 on11. . the rail with inclination of 8°. The assembly of the prototype is presented in Fig- ure 11.

Figure 10. Simulation of the bicycle ride with additional load on the rail with inclination of 2° . Figure 10. Simulation of the bicycle ride with additional load on the rail with inclination of 2°. Figure 10. Simulation of the bicycle ride with additional load on the rail with inclination of 2◦. 3.2. Results of Simulations Analysis of simulations revealed that pressure on pedals equal to 200 N is sufﬁcient to set the bike into motion on the rail with inclinations of 0 and 2◦. On the rail with an inclination of 8◦, pressure of this value is insufﬁcient, and the bike tends to slide down the inclination. The maximum speed of the bike with an additional load on the rail with an inclination of 2◦ is 3 m/s. Simulations revealed that rubber-coated wheels are a better solution because setting the bike with steel wheels into motion requires 20% higher force. The pressure on the pedals needed to set the unladen bicycle into motion is 280 kN, whereas in the case of the bike with an additional load, it is equal to 375 N with a maximal load equal to 35 kg. The maximum inclination of the rail is 10◦ for the bicycle equipped with rubber-coated wheels. In terms of the existing equipment of mine workings, this value is satisfactory, because most of the rails in roadways have an inclination of up to 8◦. Riding a bike on rails with higher values of inclination is theoretically possible, but requires pressure on pedals over 400 N, which was recognized to be too high.

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Figure 11. Assembly of the prototype. Figure 11. Assembly of the prototype. 4. Prototype 4.1.3.2. Construction Results of Simulations of the Prototype and Underground Tests ConductedAnalysis of simulations simulations allowed revealed verification that pressure of the on assumptions pedals equal of theto 200 selected N is sufficient solution andto set completion the bike into of the motion engineering on the design rail with of theinclination bike. s of 0 and 2°. On the rail with an inclinationThe constructed of 8°, pressure prototype of this was value tested is insufficient in real-life, and conditions the bike totends verify to slide the results down ofthe theinclination. conducted The simulations. maximum Thespeed first of fieldthe bike test waswith carried an additional out in one load of on the the coal rail mines with ofan Jastrz˛ebskaSpinclination of ó2°łka is W˛eglowa(JSW).3 m/s. The tested device was equipped with rubber-coated steel wheels,Simulations two siderevealed guiding that wheels,rubber-coated and transmission wheels are a gears better with solution ratios because of 42/16 setting and 22/16.the bike The with aim steel of the wheels test was into to determinemotion requires the following 20% higher issues: force. The pressure on the •pedalspossibility needed ofto assemblyset the unladen of the bikebicycle by into one motion or two peopleis 280 kN, and where assemblyas in time, the case of the •bikepossibility with an additional of suspension load, ofit is the equal bike to on 375 the N rail with by onea maximal or two load people equal and to its 35 time, kg. The •maximumstability inclination of the bike of and the possibilityrail is 10° for of bikethe bicycle derailment, equipped both with with rubber or without-coated the wheels. use of In termsguiding of the wheels. existing equipment of mine workings, this value is satisfactory, because most of the rails in roadways have an inclination of up to 8°. Riding a bike on rails with During the test, the means of individual underground transport was equipped with higher values of inclination is theoretically possible, but requires pressure on pedals over measuring equipment to determine: 400 N, which was recognized to be too high. • linear and rotational velocity, •4. Prototypespeed, direction, and force of wind, • vibration during ride, 4.1. Construction of the Prototype and Underground Tests • side swing during ride. Conducted simulations allowed verification of the assumptions of the selected solu- The arrangement of the measuring equipment is presented in Figure 12. Figure 13 tion and completion of the engineering design of the bike. presents graphs of the quantities measured during the tests. The constructed prototype was tested in real-life conditions to verify the results of Analysis of graphs allowed interpretation of some elements of the bike ride. Peaks the conducted simulations. The first field test was carried out in one of the coal mines of in the acceleration figures correspond to connections between rails. Values measured by gyroscopesJastrzębska also Spółka correspond Węglowa to ( theJSW lateral). The swingtested anddevice load was change equipped of axles. with Rotational rubber-coated and angularsteel wheels, speed two was measured,side guiding in additionwheels, and to magnetic transmission field, gears which with allowed ratio determinations of 42/16 and of22/16. a height The profile.aim of the test was to determine the following issues:  possibility of assembly of the bike by one or two people and assembly time,  possibility of suspension of the bike on the rail by one or two people and its time,

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 stability of the bike and possibility of bike derailment, both with or without the use of guiding wheels. During the test, the means of individual underground transport was equipped with measuring equipment to determine:  linear and rotational velocity,  speed, direction, and force of wind,  vibration during ride,  side swing during ride. The arrangement of the measuring equipment is presented in Figure 12. Figure 13 presents graphs of the quantities measured during the tests. Energies 2021, 14, 2022 9 of 14

Energies 2021, 14, x FOR PEER REVIEW 10 of 15 Figure 12. Arrangement of the measuring equipment.

Figure 12. Arrangement of the measuring equipment.

Figure 13. Graphs of measured quantities. Figure 13. Graphs of measured quantities.

4.2. ObservationsAnalysis of graphs allowed interpretation of some elements of the bike ride. Peaks in the accelerationThe ﬁrst underground figures correspond tests revealed to connections several defects between of the rails. construction, Values measured some of by which gy- wereroscopes not noticedalso correspond during simulations. to the lateral One swing of the and issues load is thechange transmission of axles. gearRotational ratio.It and was foundangular that speed the 46/16was measured ratio requires, in addition excessive to magnetic effort for field, climbing which uphill, allow anded determin the 22/16ation ratio isof unablea height to profile. provide satisfactory speed. It is thus recommended to use gears with 34 or 36 teeth. 4.2. Observations The first underground tests revealed several defects of the construction, some of which were not noticed during simulations. One of the issues is the transmission gear ratio. It was found that the 46/16 ratio requires excessive effort for climbing uphill, and the 22/16 ratio is unable to provide satisfactory speed. It is thus recommended to use gears with 34 or 36 teeth. Tests revealed that the weight of the bike’s prototype, which was 36 kg, is too high to allow for suspension of the bike on the rail by only one person. Assembly of the bike can be undertaken by one person, but it is easier and more convenient when it is undertaken by two people. Moreover, the application of wing screws should be considered to reduce the number of tools used for assembly. Figure 14 presents a view of the new miners’ bike during the tests in one of the coal mines in JSW.

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Tests revealed that the weight of the bike’s prototype, which was 36 kg, is too high to allow for suspension of the bike on the rail by only one person. Assembly of the bike can be undertaken by one person, but it is easier and more convenient when it is undertaken by two people. Moreover, the application of wing screws should be considered to reduce EnergiesEnergies 2021 2021, 14, 14, x, FORx FOR PEER PEER REVIEW REVIEWthe number of tools used for assembly. Figure 14 presents a view of the new miners’1111 of bike of15 15 during the tests in one of the coal mines in JSW.

Figure 14. A view of the new miners’ bike during the underground tests. FigureFigure 14 14.. AA view view of of the the new new miners’ miners’ bike bike during during the the underground underground tests tests..

MountingMountingMounting the the the bike bike bike wa was was anos another anotherther issue issue issue observed observed observed during during during tests, tests, tests, especially especially especially in in in cases cases cases when when when thethethe user user user is is isa a persona person person of of of short short short stature stature, stature, or, or or the the the distance distance distance between betweenbetween the thethe floor floorfloor and and and the thethe rail railrail is is islarge large.large. . AddingAddingAdding a a atype type ofof of stirrupstirrup stirrup should should should be be considered,be considered, considered, constructed construct constructed toed allowto to allow allow its lengthits its length length to be to adjustedto be be ad- ad- justandjusted toed and ensureand to to ensure itensure does it notitdoes does collide not not collide withcollide working with with working working equipment. equipment. equipment. ObservationObservationObservation allowed allowed allowed positive positive positive verif verification verificationication of of thethe the simulation’ssimulation’s simulation’s conclusion,conclusion, conclusion, that that that stability stabil- stabil- ityofity theof of the bike the bike withbike with awith user a auser on user the on seaton the the is seat at seat a satisfactoryis isat at a asatisfactory satisfactory level. A level. low level. center A Alow l ofow gravitycenter center of minimizes of gravity gravity minimizespotentialminimizes lateral potential potential swing. lateral lateral In addition,swing. swing. In pedalingIn addition, addition, does pedaling pedaling not induce does does not lateral not induce induce swing. lateral lateral For swing. this swing. reason, For For thisremovingthis reason, reason, theremoving removing side guiding the the side side wheels guiding guiding should wheels wheels be should considered, should be be considered, considered, which would which which help would would to reduce help help tobike’sto reduce reduce mass. bike’s bike’s mass. mass. TestsTestsTests also also revealed revealed revealed an an an issue issue issue with with with the the prototype’sthe prototype’s prototype’s cornering. cornering. cornering. In corners, In In corners, corners, the chainthe the chaintends chain tendstotends slip to offto slip slip because off off because because of the frameof of the the skew.frame frame Differentskew. skew. Different Different solutions solutions tosolutions these to problems to these these problems wereproblems analyzed: were were analyzed:strengtheninganalyzed: strengthening strengthening the frame the with the frame frame side with bars, with side using side bars, bars, a lower using using flange a lowera lower of theflange flange wheels, of of the the application wheels, wheels, ap- ap- of plicationswivelplication wheels, of of swivel swivel or shorteningwheels wheels, or, or shortening the shortening wheelbase. the the wheelbase. wheelbase. ShorteningShorteningShortening the the the frame frame frame and and and wheelbase wheelbase wheelbase was was was chosen chosen chosen as as as the the the most most most convenient convenient convenient and and and efficient efficient efficient meansmeansmeans of of of solving solving solving the the presentedpresented presented problem.problem. problem. Reduction Reduction Reduction of of the of the framethe frame frame length length length from from from 610 610 to 610 250 to to 250 mm 250 mmmovingmm moving moving along along along the curvethe the curve withcurve with a with radius a aradius radius of 2000 of of mm2000 2000 was mm mm modeled. was was modeled. modeled. This simulation This This simulation simulation is shown is is showninshown Figures in in Figures 15Figures and 15 16 15 and. and 16. 16.

FigureFigureFigure 15 15. 15. Comparison.Comparison Comparison of of of610 610 610 and and and 250 250 250 mm mm mm wheelbases wheelbases. wheelbases. .

Real-life tests confirmed concerns about steel wheels, which tend to slide, even on straight and flat routes. It was concluded that one-wheel drive is sufficient, but the braking system should be improved.

FigureFigure 16 16. Graphical. Graphical representation representation of ofthe the wheels’ wheels’ behavior behavior in in the the corner corner with with radius radius of of2000 2000 mm mm. .

RealReal-life-life tests tests confirmed confirmed concerns concerns about about steel steel wheels, wheels, which which tend tend to to slide, slide, even even on on straightstraight and and flat flat routes routes. It. Itwas was concluded concluded that that one one-wheel-wheel drive drive is issufficient, sufficient, but but the the brak- brak- inging system system should should be be improved. improved.

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Figure 14. A view of the new miners’ bike during the underground tests.

Mounting the bike was another issue observed during tests, especially in cases when the user is a person of short stature, or the distance between the floor and the rail is large. Adding a type of stirrup should be considered, constructed to allow its length to be ad- justed and to ensure it does not collide with working equipment. Observation allowed positive verification of the simulation’s conclusion, that stability of the bike with a user on the seat is at a satisfactory level. A low center of gravity minimizes potential lateral swing. In addition, pedaling does not induce lateral swing. For this reason, removing the side guiding wheels should be considered, which would help to reduce bike’s mass. Tests also revealed an issue with the prototype’s cornering. In corners, the chain tends to slip off because of the frame skew. Different solutions to these problems were analyzed: strengthening the frame with side bars, using a lower flange of the wheels, application of swivel wheels, or shortening the wheelbase. Shortening the frame and wheelbase was chosen as the most convenient and efficient means of solving the presented problem. Reduction of the frame length from 610 to 250 mm moving along the curve with a radius of 2000 mm was modeled. This simulation is shown in Figures 15 and 16.

Energies 2021, 14, 2022 11 of 14 Figure 15. Comparison of 610 and 250 mm wheelbases.

FigureFigure 16. 16.Graphical Graphical representation representation of of the the wheels’ wheels’ behavior behavior in in the the corner corner with with radius radius of of 2000 2000 mm. mm.

4.3. AdditionalReal-life Undergroundtests confirmed Tests concerns about steel wheels, which tend to slide, even on straightAfter and implementing flat routes. It changes was concluded designed that to improveone-wheel assembly drive is andsufficient, turning but in the the brak- con- structioning system of theshould new be miners’ improved. bike, additional tests were conducted in the Lubelski W˛egiel Bogdanka coal mine. The shortened wheelbase improved the bike’s behavior on the corners, eliminating the derailment problem. The stability of the construction was again successfully validated. The suitability of using 34- and 36-tooth gears was not fully verified because of issues with the chain. However, empirical experience showed that it is right direction for development. The presented construction of the means of individual underground transport was considered a promising opportunity for filling the niche of individual transport in coal mines. However, to become a fully marketable device it should be further developed. The braking system requires improvement because it is not yet satisfactory or efficient. The number of inclined workings in Polish coal mines also requires development of a drive. Because manual propulsion is not considered efficient enough, an electric drive should be designed and tested.

5. Legal Background One of the reasons for the abandonment of the historic construction of underground bikes was their failure to comply with existing law. Current safety regulations are stricter than previously, so it is necessary to analyze them in terms of using the new construction of individual underground means of transport in operating mines. Analysis covers both proposed versions of the bike—with manual and electric propulsion. The basis of the analysis was the bike’s status in terms of the EU Machinery Direc- tive [17]. This directive defines a machinery as “an assembly, fitted with or intended to be fitted with, a drive system other than directly applied human or animal effort, consisting of linked parts or components, at least one of which moves, and which are joined together for a specific application”. This means that a manually powered bike is not a machinery. However, the bicycle equipped with electric engine is a machinery. Conformance testing has to be undertaken for the both versions of the presented means of individual underground transport. However, the version without an electric engine does not have to be compliance tested according to the Machinery Directive. Voluntary conformity assessment, e.g., with EN ISO 4210 Standards [18], is recommended. It is also necessary to meet environmental requirements, which encompass the potentially explosive atmosphere in the case of underground coal mines. The means of individual underground transport does not have to be conformance assessed pursuant to Polish Geological and Mining Law [19], because it is not present on the list of products and devices for which such assessment is required. The fact that the miners’ bike is assembled on a suspended rail, which, in terms of Polish Law is an element of an underground railway, does not mean that the bike is also an element. This means that there is no legal basis for the bicycle to be officially approved by the President of the State Mining Authority. Energies 2021, 14, 2022 12 of 14

However, the means of individual underground transport has to be conformance assessed and approved by the head of mining supervision of the mine (Kierownik Ruchu Zakładu Górniczego according to Polish law) on the basis of technical documentation and the protocol of the commission’s approval. The compliance requirements are included in legal regulations [19,20]. The basis for approval for the use of the means of individual underground transport in underground mines is a technical documentation and maintenance manual, which must be delivered to the end user. Basing on the documentation and declaration of conformity, the means of individual underground transport may be used in underground mines. Good practice involves acquiring the opinion of a certification body (such as Certifying Body of KO- MAG Institute of Mining and Technology), which contains independent and substantive assessment of the device. In addition to fulfilling the requirements of the conformity assessment, the underground bicycle must be flame retardant, anti-electrostatic, and non-toxic. Moreover, it must comply with environmental requirements, which means that it also has to meet requirements of Polish mining law. It should be also noted that elements made of synthetic materials have to be assessed in terms of material requirements. In case of version 1 (with manual propulsion), conformity assessment can be undertaken according to PN-EN ISO 80079-36:2016-07 Standard [21], because a risk of ignition is caused by the drive’s moving parts and potential collision with the mine working equipment. Particularly important is that the relative percentage of light metals in construction elements must not exceed 15%. This is due to the properties of these metals, i.e., risk of sparking through friction on external elements. The second version of the bicycle, equipped with an electric engine powered by battery, is a form of machinery and, in the case of its application in a potentially explosive atmosphere, it is necessary to conduct EU testing, including assessment of ignition risk and elements of explosion-proof construction. Taking into account modern technical capabili- ties, the only possible solution is to use an electric engine protected with an explosion-proof casing and battery cells using casing of the same property. Application of these elements would increase the bike’s weight, means the bike cannot be assembled, or the direction of the bike changed, by one person. Lithium-ion technology has many advantages, but its main defect relative other types of batteries is low safety of use. Li-ion battery cells can explode as a result of high temperature caused by incorrect use. To prevent such a situation, different safety systems are implemented in energy supply systems [22]. The following battery cell parameters must be monitored: • discharge current, • charger current, • voltage. Both bicycle constructions do not require compliance with additional restrictions in terms of their use in workings where there is no risk of explosion. In the case of their use in workings where there is a risk of methane or coal dust explosion, both versions have to meet the requirements of the ATEX Directive.

6. Conclusions The problem of individual transport in Polish underground coal mines remains unsolved. Due to constantly increasing distances and bad conditions of ﬂoors in mine workings, solving this issue requires an unconventional approach. Historic solutions of underground bicycles, which previously were in common use in underground mines, led to the development of a modern solution, utilizing existing mine equipment, namely, the suspended rail. The development of a means of individual underground transport requires a multi- stage process, which comprises simulations, tests, and analysis. Simulations, conducted in Working Model software, allowed a prototype of an underground bicycle to be created. Energies 2021, 14, 2022 13 of 14

Real-life tests of this prototype in underground mines were key elements of the development process. These tests allowed identification of defects of the construction, which were not noticed during the simulations. In particular, these defects were the large mass, wide wheelbase, wrong gear transmission, and inability to easily get on or off the bike. The defects listed above were successfully eliminated, however, some issues remain. One of these is the construction of a braking system, which was satisfactory in terms of the Energies 2021, 14, x FOR PEER REVIEW 14 of 15 prototype, but requires improvements to make the bike marketable. In addition, manual propulsion might be not efficient enough in the steep inclined workings of Silesian coal mines. Thus, the application of an electric engine powered by li-ion battery cells is the most important field ofcoal improvement. mines. Thus, the application of an electric engine powered by li-ion battery cells is Historic constructionthe most important of underground field of improvement. mine bicycles was abandoned because of, Historic construction of underground mine bicycles was abandoned because of, amongst other reasons, their lack of compliance with legal regulations. To ensure this fail- amongst other reasons, their lack of compliance with legal regulations. To ensure this failure is not repeated, it is necessary to analyze the applicability of the bicycle in terms of the ure is not repeated, it is necessary to analyze the applicability of the bicycle in terms of the existing legal regulations in Poland. The conducted analysis showed that the underground existing legal regulations in Poland. The conducted analysis showed that the under- bicycle may be able to be applied in underground coal mines. ground bicycle may be able to be applied in underground coal mines. Simulations, tests, and analysis carried out during the development process of the Simulations, tests, and analysis carried out during the development process of the underground bicycleunderground verified itsbicycle marketable verified features its marketable and identified features newand identified fields of develop- new fields of devel- ment. In favorableopment. conditions, In favor theable bicycle conditions could, the improve bicycle the could work improve of miners the work and help of miners to and help rise miner’s effectiveness.to rise miner’s effectiveness.

Funding: This researchFunding: was This funded research by INNOAGH, was funded asby aINNOAGH, part of Inkubator as a part Innowacyjno´sci of Inkubator Innowacyjnościprogram. program. Projekt “InkubatorProjekt Innowacyjno´sci4.0” “Inkubator Innowacyjności realizowany przez 4.0” realizowany konsorcjum Akademiiprzez konsorcjum Górniczo-Hutniczej Akademii Górniczo-Hut- im. Stanisława Staszicaniczej wim. Krakowie, Stanisława Centrum Staszica Transferu w Krakowie, Technologii Centrum AGH Transferu i Krakowskiego Technologii Centrum AGH i Krakowskiego Innowacyjnych TechnologiiCentrum Innowacyjnych INNOAGH Sp. Technologii z o.o. w ramach INNOAGH ustanowionego Sp. z o.o. w przezramach Ministra ustanowionego Nauki przez Minis- i Szkolnictwa Wyzszego˙tra Nauki programu i Szkolnictwa pod nazwWyższego ˛a“Inkubator programu Innowacyjno´sci2.0” pod nazwą “Inkubator w trybieInnowacyjności projektu 2.0” w trybie pozakonkursowegoproj “Wsparcieektu pozakonkursowego zarz ˛adzaniabadaniami “Wsparcie naukowymi zarządzania i komercjalizacji badaniami naukowymi wyników prac i komercjalizacji B+R w jednostkachwyników naukowych prac B+R i przedsi˛ebiorstwach”realizowane w jednostkach naukowych i przedsiębiorstwach” w ramach POIR realizowane 2014–2020, w ramach POIR Działanie 4.4—Zwi˛ekszeniepotencjału2014–2020, Działanie 4.4 kadrowego—Zwiększenie sektora potencjału B+R. kadrowego sektora B+R.

Institutional ReviewInstitutional Board Statement: Review BoardNot applicable.Statement: Not applicable. Informed ConsentInformed Statement: ConsentNot applicable. Statement: Not applicable. Data AvailabilityData Statement: AvailabilityNot applicable. Statement: Not applicable. Conﬂicts of Interest:ConflictsThe author of Interest: declares The no author conﬂict declare of interest.s no conflict of interest.

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