­^¤åºK­n The purpose of this work is to provide a design procedure of rear suspension mechanisms of mountain bikes by using the concept of engineering design method. First, the conditions and particularities of mountain biking are investigated and the performance specification of rear suspension mechanisms is set by focusing the investigations on the requirements of rear suspension mechanisms. Second, the requirements and constraints of generating different types of rear suspension mechanisms are developed and the systematic process of creative mechanism design is followed. Third, the different types of rear suspension mechanisms resulted from creative mechanism design are analyzed to realize the property of each type of rear suspension mechanisms and the procedure of kinematic design is developed by using the algorithm of heuristic combinatorial optimization method. Finally a computer aided design program written in Visual BASIC 6.0 programming language is developed to be the powerful tool of performance analysis and kinematic design of rear suspension mechanisms.

With the prevalence of leisure sport, riding mountain bikes becomes an enormous vogue today. The mountain bikes undoubtedly have become one of the most popular products in the leisure sport market. Based on its superior standard of operating quality and the demand of comfortableness, the requirement of the outstanding rear suspension mechanism of mountain bikes is one of the crucial components in the design procedure. The purpose of this work is to provide a design procedure of the system of rear suspension mechanisms of mountain bikes by using the concept of engineering design method. First, to investigate the essential requirements of the system of rear suspension mechanisms of mountain bikes is started. Then the design targets of this research are decided further in order to establish the requirement book for the system of rear suspension mechanisms of mountain bikes. Second, the kinematic design of rear suspension mechanisms is proceeding. Computer Aided Tried and Error program is utilized for synthesizing the dimensions of rear suspension mechanisms to meet the requirement of functions. Finally, topology theory is applied to synthesize the frames of mountain bikes. Furthermore, the systematic design procedure is developed to perform the embodiment design of the system of rear suspension mechanisms of mountain bikes.

The aim of master thesis is the design of full suspension mountain bike frame for racing and competition use. The base of the design solution is selection optimal conception of suspension which influence external design of the frame. General benefit of this concept is utilizing specific properties of carbon composite for design of funkcional frame parts and their technical and visual integration. Important part of this work is design of frame details: rear ends, rear shox's link and duct of the bowdens, wires and brake hydraulic housing.

Cross-country (XC) mountain bike (MTB) riding is a new cycling discipline and research examining the physiological demands of MTB racing is limited. The purpose of this study was to comprehensively measure physiological characteristics, to identify the performance demands of XC and time trial (TT) MTB racing and to simulate a field MTB race in the laboratory to measure the physiological responses associated with racing. Twelve male and four female elite MTB cyclists volunteered to take part in this study. Subjects completed maximal aerobic power and, anaerobic power and capacity tests. MTB race data was collected during TT and XC competitions with SRM MTB power cranks fitted to the subjects MTB. Five male MTB cyclists (V . O2max 72.0 +/- 4.6 ml/kg/min-1, maximum power output (MPO) 5.40 +/- 0.30 W/kg-1, maximum heart rate (HRmax) 189 +/- 7 bpm) performed two laps of a MTB course in the field using their race bikes with MTB SRM power cranks fitted. A laboratory MTB race simulation was performed using a wind braked ergometer. Cyclists attempted to match the average and peak power output (W/kg-1) achieved in the field trial in the laboratory. Power output (PO), heart rate (HR) and cadence (revolutions per minute, rpm) were measured during field and laboratory trials, while oxygen uptake (V . O2) was determined only during the laboratory simulation. Results showed TT MTB racing is significantly shorter in duration and distance than XC racing and significantly higher for power output and heart rate, with more time spent above anaerobic threshold (16.0 +/- 2.4 and 22.8 +/- 4.3% time) and MPO (38.4 +/- 5.2 and 26.5 +/- 9.4% time) than XC racing (p<0.05). Mean power output and heart rate between the field and laboratory trials were similar (4.18 +/- 0.55 and 4.17 +/- 0.15 W/kg-1 respectively, 175 +/- 9 and 170 +/- 8 bpm). Time spent below 2 W/kg-1 and above 6 W/kg-1 for the field and laboratory trials accounted for ~32% and ~30% of the total time, respectively. During field and laboratory trials, cyclists utilised 77.8 and 77.3% of MPO, 93 and 90% of HRmax, respectively. There was a significant difference between mean cadence in the field and laboratory trials (60.3 +/- 9.1 and 75.2 +/- 7.0 rpm, respectively, p<0.05). The cadence band of 60-69 rpm showed a significant difference between the time spent in that band from the field (14.6%) to the laboratory (4.6%). The time spent above a cadence of 80 rpm in the field was 29.8% compared to the laboratory at 62.0% of the time. Mean and peak V . O2 for the simulation was 57.5 +/- 3.3 and 69.3 +/- 4.4 ml/kg-1/min-1 respectively, with cyclists sustaining an average of ~80% V . O2max. In summary, MTB competition requires multiple short-high intensity efforts and places high demands on both the aerobic and anaerobic energy systems. The power output and heart rate responses to a MTB field race are similar when simulated in the laboratory, although in the laboratory higher cadences are selected for the higher power outputs than the field.

IN ENGLISH The work deals with the history of mountain bike in Vimpersko from 1989 to the present. Major cycling events, prominent racers, organizers and founders of a mountain bike section in Vimpersko should appear in the work. The main aim of this work is to investigate and record the arrival of a mountain bike in Vimpersko from 1989 to the present. Partial objectives include recording the main characters associated with the emergence of mountain bike races and a section in Vimperk and linking the topic with the history of cycling in the Czech Republic. The main method of work is the historical method enriched with interviews with the main actors of mountaine biking in Vimpersko.

A method for tuning the spring rate and damping rate of a mountain bike suspension based on a data-driven procedure is presented. The design and development of a custom data acquisition system, known as the MTB~DAQ, capable of measuring acceleration data at the front and rear axles of a bike are discussed. These data are input into a model that is used to calculate the vertical acceleration and pitching angular acceleration response of the bike and rider. All geometric and dynamic properties of the bike and rider system are measured and built into the model. The model is tested and validated using image processing techniques. A genetic algorithm is implemented with the model and used to calculate the best spring rate and damping rate of the mountain bike suspension such that the vertical and pitching accelerations of the bike and rider are minimized for a given trail. Testing is done on a variety of different courses and the performance of the bike when tuned to the results of the genetic algorithm is discussed. While more fine tuning of the model is possible, the results show that the genetic algorithm and model accurately predict the best suspension settings for each course necessary to minimize the vertical and pitching accelerations of the bike and rider.

In this thesis project, the possibility to make use of a mechanical spring to achieve stiffness adjustability in a shock absorber for mountain bikes is evaluated. A mechanical spring increases the shock absorber’s sensitivity compared to a fully adjustable air spring. Today, there are no mechanical springs available on the market that offer enough stiffness adjustment to suit different riders with large variation in weight. Therefore, a mechanical spring with a wide stiffness adjustment range could be ground-breaking if it is possible to implement in mountain bike shock absorbers. The work has been carried out in accordance with a product- and concept development approach where the final concept design has been optimised analytically and verified numerically. The developed spring has been integrated in a new damper design and the complete damper and spring system has been dimensioned to fit current mountain bike frames. The result is a prototype shock absorber with a spring to suit riders between 70-88kg. An alternative spring for cyclists between 59-75kg has also been proposed. Since these springs have been made to fit current mountain bikes, it was possible to conclude that a mechanical spring witha wide range of adjustable stiffness is feasible for mountain bike application. With available spring steels, it is not possible to accommodate every rider with only one spring. It is however possible to achieve adjustment that is suitable for a rider weight range of roughly 15-16kg. This is between 70-110% more than similar products available on the market can offer. / I detta examensarbete utvärderas möjligheten att använda en mekanisk fjäder för att uppnå justerbar fjäderstyvhet hos en stötdämpare avsedd för terrängcykling. En mekanisk fjäder ökar stötdämparens känslighet jämfört med en fullt justerbar luftfjäder. I dagsläget finns på marknadeningen mekanisk fjäder vilken kan erbjuda tillräcklig justeringsmån för att passa cyklister med stor viktvariation. Därför kan en mekanisk fjäder med ett brett styvhetsspann vara banbrytande om en sådan kan tillämpas på dagens terrängcyklar. Arbetet har utförts som ett produkt- och konceptutvecklingsprojekt där den slutliga konceptdesignen har optimerats analytiskt och verifierats numeriskt. Den fjäder som tagits fram har integrerats i en ny dämparkonstruktion och stötdämparsystemet har dimensionerats för att passa dagens terrängcyklar. Resultatet är en prototyp av en stötdämpare med en fjäder som passar cyklister mellan 70-88kg. En alternativ fjäder passande cyklister mellan 59-75kg har också tagits fram. Eftersom en justerbar fjäder vars design möjliggör användning i en stötdämpare för dagens terrängcyklar har slutsatsen dragits att en justerbar mekanisk fjäder kan fungera inom detta tillämpningsområde. Det är inte möjligt med dagens material att utforma en mekanisk fjäder med tillräckligt justerbar styvhet föratt passa alla åkare. Det är däremot möjligt att använda en fjäder som passar cyklister inom ett viktspann på omkring 15-17kg. Detta är mellan 70–110% mer än vad liknande produkter tillgängliga på marknaden idag kan erbjuda.

The diploma thesis focuses on recreational cycling because it is regarded as one of possibilities how to strengthen tourism in the region of North-East Bohemia. In the theoretical part there are presented basic terms and definitions connected with the recreational cycling, also there are mentioned legislative foundations. Then, the diploma thesis presents selected institutional documents, which prove the importance of the recreational cycling. Also there are included basic facts about important organizations concerning recreational cycling and about the region of North-East Bohemia itself. The practical part focuses on existing cycling and complementary infrastructure of the region. The last chapter analyses the infrastructure and especially it provides suggestions and possible projects that would support further development of recreational cycling in the region of North-East Bohemia.

Mountain biking is a sport where riders bike on trails, varying in slope and difficulty. Mountain bikes are generally equipped with suspension on the front wheel and often also on the rear. Some types of rear shocks use pressurized air for a spring action instead of the traditional metal coil. Air is sealed inside the shock’s air can by means of X-ring seals, providing a spring force on the wheel. It is of great importance that the sealing system performs as intended so the air spring does not quickly lose pressure during use. An experimental plan is conducted in an attempt to estimate the effects of seal dimension, lubrication and surface roughness on air leakage for more robust shocks. Accelerated tests were performed in a dynamometer, believed to repeatedly cause significant wear on the shock’s air seal within 24 hours. Nineteen tests were carried out, for a duration up to 72 hours, with variations to test parameters such as stroke length and frequency. The expected failure modes did not occur in any of them. Eleven tests showed no signs of failure while the other eight failed due to unexpected components breaking or wearing out. The shock’s main seal was found to wear out faster than the air seal, causing leakage within the air spring, between its positive and negative air chambers. This unforeseen failure needs further examination with tests conducted on more shock types. / Mountainbike är en sport där utövare åker på stigar med varierande lutning och svårighet. Terrängcyklar är generellt utrustade med stötdämpare eller fjädrar på framhjulet och ofta också på bakhjulet. Vissa terrängcyklar har stötdämpare bak som använder trycksatt luft för att dämpa istället för att använda traditionella stålfjädrar. Luften är sluten inuti stötdämparen med hjälp av X-rings tätningar, vilket ger en fjäderkraft på hjulet. Det är viktigt att tätningen fungerar så att luftfjädern inte snabbt tappar trycket när den används. En experimentplan skapades i ett försök att uppskatta effekten av tätningsdimension, smörjning och ytjämnhet på luftläckage för mer robusta stötdämpare. Accelererade tester gjordes i en dynamometer, som troddes kunna skapa signifikant slitage på en stötdämpares tätning inom 24 timmar upprepade gånger. 19 test gjordes med en körtid på upp till 72 timmar med variation av testparametrar som slaglängd och frekvens. De förväntade felkällorna uppstod inte i något av testerna. 11 tester visade inga tecken på fel medan 8 tester misslyckades på grund av att oväntade komponenter slets ut eller gick sönder. Stötdämparens huvudtätning visade sig slitas fortare än lufttätningen, vilket resulterade i läckage inuti luftfjädern mellan dess positiva och negativa kammare. Detta oförutsedda fel behöver vidare undersökning med tester på fler olika typer av stötdämpare.

Thesis (MScSportSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The purpose of this qualitative-quantitative study was to describe the exercise intensity and predictors of performance of a multi-stage mountain bike (MTB) race (2014 Absa Cape Epic) lasting 8 days. Twenty-three amateur mountain bikers (age 39 ± 9 years, height 178.8 ± 8.2 cm, body mass 74.7 ± 9.1 kg, VO2max 54 ± 7 ml.kg-1.min-1) who completed the 2014 Absa Cape Epic were involved in the study. The participants were divided into two groups according to their MTB experience. The experienced group included participants who previously completed more than three 3-day multi-stage MTB events and the novices group included those who has completed less than 3-day multi-stage MTB events. Prior to the event the participants completed a maximal aerobic cycling test and a simulated 40 km time trial (TT). The maximal aerobic test was used to determine 3 work intensity zones based on heart rate (HR) corresponding to blood lactate thresholds (LT: increase in blood lactate concentration of 1 mmol.l-1 above baseline values and the onset of blood lactate accumulation (OBLA), a fixed blood lactate concentration of 4 mmol.l-1). There were no statistically significant differences in the physical, physiological and performance variables measured in the laboratory between the two groups. The exercise intensity during the Cape Epic was measured using telemetric HR monitoring sets. RPE values were noted after each stage of the race. The mean HR was 88.1 ± 5.3% (experienced) and 84.2 ± 11.0% (novices) of maximal HR during the race or 88.9 ± 3.5% (experienced) and 85.9 ± 10.6 (novices) of laboratory determined maximum HR. More time was spent in the “low” HR zone (43.1 % vs 58.5 %, respectively), while only a small amount of time was spent in the “hard” HR zone (7.4% and 6.1%, respectively). The experienced group spent statistically significantly more time in the “moderate” HR zone compared to the novices group (49.5 % vs. 35.4 %). The experienced group performed significantly better during the event compared to the novices group in both the total event time (P = 0.004) and the general classification (P = 0.01). Relative and absolute power output (PO) at OBLA (P = 0.01 and 0.02, respectively) were statistically significant predictors of total event time, while relative peak power output was a significant predictor of general classification for the event (P = 0.02) . The total TT time was a significant predictor of average event HR (P = 0.03). This study showed that this MTB stage race is physiologically very demanding and requires cyclists to have excellent endurance capacity, as well as strength and power. The parameters from the maximal aerobic capacity test correlated better with outdoor performance than parameters from the simulated 40 km TT. Therefore the standard maximal aerobic capacity test are sufficient for testing mountain bikers and sport scientists can continue using this test to prescribe exercise intensity zones for training and events. / AFRIKAANSE OPSOMMING: Die doel van hierdie kwalitatiewe-kwantitatiewe studie was om die oefeningsintensiteit en voorspellers van prestasie tydens ‘n multi-dag bergfiets kompetisie (Absa Cape Epic) van 8 dae lank te bepaal. Drie-en-twintig bergfietsryers (ouderdom 39 ± 9 jaar, lengte 178.8 ± 8.2 cm, liggaamsmassa 74.7 ± 9.1 kg, VO2maks 54 ± 7 ml.kg-1.min-1) wat die 2014 Absa Cape Epic voltooi het, het aan die studie deelgeneem. Die deelnemers is in twee groepe verdeel volgens hulle ervaring in multi-dag bergfiets kompetisies. Die ervare groep was al die deelnemers wat meer as drie 3-dae multi-dag bergfiets kompetisies voltooi het. Die onervare groep was al die deelnemers wat minder as drie 3-dag multi-dag bergfiets kompetisies voltooi het. Voor die kompetisie het al die deelnemers ‘n maksimale aërobiese toets en ‘n gesimuleerde 40 km tydtoets in die laboratorium voltooi. Die maksimale aërobiese toets is gebruik om drie werk intensiteit sones volgens die hartspoed te bepaal, naamlik die hartspoed by die laktaatdraaipunt(‘n toename in bloed [laktaat] van 1 mmol.l-1 bo die basislynwaardes) en die hartspoed by die aanvang van bloedlaktaat akkummulasie (‘n vaste bloed [laktaat] waarde van 4 mmol.l-1). Daar was geen statisties betekenisvolle verskille in die fisiese, fisiologiese en prestasie veranderlikes tussen die twee groepe nie. Die oefeningsintensiteit tydens die Cape Epic was gemeet deur gebruik te maak van hartspoedmonitors. Die RPE waardes was aan die einde van elke skof genoteer. Die gemiddelde hartspoed was 88.1 ± 5.3 % (ervare) en 84.2 ± 11.0 % (onervare) van maksimale kompetisie hartspoed, of 88.9 ± 3.5 % (ervare) en 85.9 ± 10.6 % (onervare) van die maksimale hartspoed soos in die laboratorium gemeet. Die fietsryers het meer tyd spandeer in die “lae” hartspoed sone (43.1 % vs 58.5 %, onderskeidelik), in vergelyking met die “moeilike” hartspoed sone (7.4 % vs 6.1 %, onderskeidelik). Die ervare groep het statisties betekenisvol meer tyd in die “matige” hartspoed sone spandeer (49.5 % vs. 35.4 %) in vergelyking met die onervere groep. Die ervare groep het beter presteer tydens die kompetisie vir beide totale kompetisie tyd (P = 0.004) en algehele klassifikasie (P = 0.01). Relatiewe en absolute krag by aanvang van bloed laktaat akkumulasie was statisties betekenisvolle voorspellers van totale kompetisie tyd (P = 0.01 en 0.02, onderskeidelik), terwyl maksimale krag ‘n statisties betekenisvolle voorspeller was van algehele klassifikasie in die kompetisie (P = 0.02). Die totale tydtoets tyd was ‘n statisties betekenisvolle voorspeller van gemiddelde hartspoed tydens die kompetisie. Die studie het gewys dat hierdie multi-dag bergfiets kompetisie fisiologies baie uitdagend is en dat fietsryers uistekende uithouvermoë kapasiteit, sowel as krag en plofkrag moet besit. Die veranderlikes van die maksimale aërobiese toets het beter met prestasie in die veld gekorreleer as die veranderlikes van die gesimuleerde 40 km tydtoets. Daar word dus afgelei dat die standaard maksimale aërobiese toets voldoende is vir die toetsing van bergfietsryers en sportwetenskaplikes kan aanhou om hierdie toets te gebruik om oefeningsintensiteit sones voor te skryf vir oefensessies en kompetisies.