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Sports equipment
Published in Paul Grimshaw, Michael Cole, Adrian Burden, Neil Fowler, Instant Notes in Sport and Exercise Biomechanics, 2019
To add to the controversy and confusion, the UCI subsequently decided to ban this “Superman position” and created rules that stated the handlebar must not exceed the front hub by more than 15 cm. In addition, they also added that the distance between the front hub and the bottom bracket (pedal spindle) could now be 75 cm. Considering this distance was only 60 cm for most conventional bikes, this new value of 75 cm appeared to put the specifications at a ridiculous level and only required the front part of the frame to be extended for a rider to adopt the banned “Superman position”. However, despite this possibility, the UCI’s specifications still made it particularly difficult to achieve precisely the position previously adopted by Graeme Obree, Chris Boardman and now many other riders.
Mountain Bike Technology
Published in Franz Konstantin Fuss, Aleksandar Subic, Martin Strangwood, Rabindra Mehta, Routledge Handbook of Sports Technology and Engineering, 2013
The cruiser bikes of Repack were single speed but the first successful bikes built for the rigours of off-road borrowed derailleur shifting from their road counterparts (Brandt 2005). Components of a drive-train include a crankset [pedal-driven crank arms with chainrings (one to three front gears), bottom bracket (crank axle, bearings and housing), chain, cassette (up to ten rear gears) and a front and rear derailleur (Figure 8.4). The bottom bracket is usually threaded into a bottom-bracket shell (an aluminium or maybe composite cylinder) which is welded/bonded into the bike frame at the junction of the seat and down tubes. The cassette is splined to a freehub on the rear wheel that allows coasting without pedalling by a ratchet mechanism. The most complex component, the rear derailleur, is a two-guide pulley, two spring-loaded pivot, slant parallelogram linkage, which was optimised for both road and mountain bike applications in 1985 by a Shimano patent (Jordan 2009); its basic technology has changed little since. Bicycle drive trains are remarkably efficient, approaching 98 percent depending on the gear combination (Wilson 2004).
Instrumentation for Mechanical Vibration Analysis
Published in Redha Taiar, Christiano Bittencourt Machado, Xavier Chiementin, Mario Bernardo-Filho, Whole Body Vibrations, 2019
Thomas Provot, Roger Serra, Samuel Crequy
Another ergometers have been developed with excitations just applied only to the lower limbs and oriented in the vertical (Sperlich and Kleinoeder, 2009) and sagittal direction (Filingeri et al., 2012). For example, on the bench of Sperlich and Kleinoeder, the frame is connected to a rigid frame without any vibration, the ergometer, consists of an aluminum frame, a steel bicycle frame (D), a vibrating platform (B) and a resistance unit (A). The bottom bracket (C) is physically disconnected from the chassis, and connected to which the crankset is in turn connected to a vibrating lower part with frequencies between 20 Hz and 4 mm amplitude.
Multi-body simulation with notch stress analysis of an axle assembly
Published in Mechanics Based Design of Structures and Machines, 2023
Suresh Kumar G., L. A. Kumaraswamidhas
An existing PB welded junction was converted into a bolted joint. Four M16 bolts were utilized on the bottom spring bracket to secure the two PB bracket assemblies (Figure 9). Bolt thread was attached to the spring bottom bracket and bolt head was tied to the PB bracket, and 121 kN preload was applied. As the PB welded junction was removed, the stress was centered on the bottom bracket weld connection of the spring seat, and the damage factors in that welded junction of the bracket at the front and rear sides of the axle became important. The MBS model was used to test all three design approaches on the rear axle to Plummer block junction, and the cumulative damage results were compared.
On the road again! Tricycle adaptation with the design of a universal rig
Published in Assistive Technology, 2023
Elizabeth Hoskin, Michael Fader, Andrew Gowthorpe, Ariana Alvarino, T. Claire Davies
The inner crank arms were welded to the bearing housing and bottom bracket mount for both sides. The cottered pin bottom bracket from the original tricycle was replaced with a modern square tapered bottom bracket. This provided compatibility and replaceability benefits over the cottered pin if any repairs or modifications are required in the future. The new bottom bracket necessitated a new housing shell/frame clamp that was sourced through the tricycle’s manufacturer, Freedom Concepts (“Home Page – Freedom Concepts Inc.,” n.d.). The shell is a bolt-on component on the tricycle and did not require any permanent modifications on the tricycle to be made.
Equations to Prescribe Bicycle Saddle Height based on Desired Joint Kinematics and Bicycle Geometry
Published in European Journal of Sport Science, 2022
Anthony A. Gatti, Peter J. Keir, Michael D. Noseworthy, Marla K. Beauchamp, Monica R. Maly
Participants completed 18 three-minute cycling bouts at the cadence and power derived from the incremental protocol, in a fully-crossed block-wise order. These 18 positions included all combinations of 3 vertical saddle positions (Y), 3 horizontal saddle positions (X), and 2 crank arm lengths. The Y component was the vertical distance from the bottom bracket to the centre of the saddle clamp, and the X component was the horizontal distance from the bottom bracket to the centre of the saddle clamp. One position of each factor was commercial (i.e. as determined by the commercial bike fit), and the others were random deviations. Each random saddle X and Y position was independently randomly sampled within +/- 10% for X and 5% for Y of the commercial position. A shorter range of 5% was used for saddle Y because higher ranges were not anatomically possible. The random crank arm length was either 2.5 mm longer or shorter than commercial (172.5 mm). Randomization of the saddle and crank arm positions are described in Supplemental 2. For every position, effective seat tube angle () was calculated as , and represents a seat tube from the bottom bracket to the X-Y position of the saddle clamp on the fit-bike. Effective seat tube angle takes saddle fore-aft into account, where a steeper effective seat tube is equivalent to a more anterior saddle position. The effective saddle height was calculated by summing the crank arm length, the bottom bracket to saddle clamp distance (), and the saddle clamp to top of saddle distance. The saddle clamp to top of saddle distance was calculated along the line of the effective seat tube as: where the saddle vertical depth was the vertical height from the centre of the saddle rails to the top of the saddle. The effective saddle height was equivalent to the distance from the top of the saddle to the pedal spindle using a straight line that intersected the bottom bracket (Figure 1). In each position, handlebars were moved to maintain the same position relative to the saddle. Random selection of factors, randomizing the order of positions, and blocking was done using a custom Python program.