Quantification of brake data acquired with a brake power meter during simulated cross-country mountain bike racing

There is currently a dearth of information describing cycling performance outside of propulsive and physiological variables. The aim of the present study was to utilise a brake power meter to quantify braking during a multi-lap cross-country mountain bike time trial and to determine how braking affects performance. A significant negative association was determined between lap time and brake power (800.8 ± 216.4 W, mean ± SD; r = ?0.446; p < 0.05), while the time spent braking (28.0 ± 6.4 s) was positively associated with lap time (314.3 ± 37.9 s; r = 0.477; p < 0.05). Despite propulsive power decreasing after the first lap (p < 0.05), lap time remained unchanged (p > 0.05) which was attributed to decreased brake work (p < 0.05) and brake time (p < 0.05) in both the front and rear brakes by the final lap. A multiple regression model incorporating braking and propulsion was able to explain more of the variance in lap time (r² = 0.935) than propulsion alone (r² = 0.826). The present study highlights that riders’ braking contributes to mountain bike performance. As riders repeat a cross-country mountain bike track, they are able to change braking, which in turn can counterbalance a reduction in power output. Further research is required to understand braking better.     

The effects of control-display gain on performance of race car drivers in an isometric braking task

Abstract

To minimise lap times during car racing, it is important to build up brake forces rapidly and maintain precise control. We examined the effect of the amplification factor (gain) between brake pedal force and a visually represented output value on a driver's ability to track a target value. The test setup was a formula racing car cockpit fitted with an isometric brake pedal. Thirteen racing drivers performed tracking tasks with four control-display gains and two target functions: a step function (35 trials per gain) and a multisine function (15 trials per gain). The control-display gain had only minor effects on root mean-squared error between output value and target value, but it had large effects on build-up speed, overshoot, within-participants variability, and self-reported physical load. The results confirm the hypothesis that choosing an optimum gain involves balancing stability against physical effort.     

大直径无缝管弯管机驱动力矩的分析与计算

用弹塑性力学理论分析了受弯无缝管的受力特性．将管件弯曲处考虑为可承受一定力矩的铰链,由驱动转臂卡头、异轮与无缝管结合处位移、转角的约束条件与力和力矩的平衡条件求得驱动力矩值．     

高速列车刹车片检修工艺的分析

高速列车中的刹车片是制动系统的重要组成部分,对制动性能起着举足轻重的作用,刹车片是通过与车轮的摩擦实现制动,其材料应具有耐热性强、磨损量小、摩擦系数高、机械强度高等特点.在列车运行中刹车片的磨损严重,整修量及需求量很大.通过对刹车片的结构及运行情况的阐述,分析了刹车片的检修工艺,提出了完善刹车片的整修工艺、材料研制及改善的技术创新方向.     

制动器生产线精益生产的应用

简要介绍了制动器的装配工艺流程,并结合实际操作,利用精益生产的理论作为实际指导,实现以最少的人力投入,获得最大的产能。     

9.5T、13T客车前桥刮蹄机的设计

大型货车和客车一般都采用鼓式刹车,但由于零部件制造及装配误差等原因,常使车桥两端刹车鼓与刹车蹄之间受力不均,造成刹车跑偏。文章所设计的刮蹄机,较好地解决了上述刹车弊病。其刮蹄精度高,是一项实用、可靠的设计。     

湿式多盘制动器制动间隙的自诟装置的结构与原理

本文中介绍了一种湿式多盘制动器制动间隙自动调整机构的结构及工作原理,并通过计算验证由衬套、隔套的长度来确定制动间隙。     

论举重上挺动作技术中的关键动作——预蹲制动

通过对组成举重上挺动作的诸多组成部分相互关系的理论分析,和已有的科研资料及常见的实践资料分析,揭示了预蹲制动动作是对上挺发力、下蹲支撑、起立定铃等整个上挺技术起决定性、规定性影响的关键动作,强调了预蹲制动技术的教学和训练在上挺技术中的重要作用,目的是帮助广大教练员清楚认识上挺动作技术的重要环节,为改变目前我国挺举水平仍然相对落后的局面做出一些应有的贡献。     

ATV71变频器在塑料包装线升降机中的应用

包装线设备对速度和定位要求较高,大量运用减速机和变频调速。塑料包装线码垛单元的升降机就是运用无传感器恒磁通矢量的恒转矩变频调速的提升设备。为了设备运行平稳和准确定位,运用多段变频调速和电磁制动器控制,由于原设计没有考虑制动器参数对变频器的影响,使得设备运行的动态性能较差;又由于制动器动作频繁,使设备故障率较高。在充分考虑上述缺陷的基础上,设计运用了ATV71变频器,使设备运行的动态性能改善,制动频次显著降低,设备故障率明显降低。     

泰州市稻河闸基础处理的方案研究与工程实践

钢坝闸（又称底轴驱动式翻板闸门）特有的两侧重、中间轻的不利结构格局,其基础处理形式尤为重要。文章以泰州市稻河闸工程为实例,通过对水泥搅拌桩、砼预制方桩、灌注桩等三种基础处理形式对比,综合从工程造价、施工难度、现场施工质量等方面,最终确定选用施工难度适中、造价合理的灌注桩基础方案进行基础处理。