Recumbent Bikes Are Not Faster 8/24/07 - Warren Beauchamp Recumbent bikes are not faster than upright bikes. There, I said it. Now before you get all uppity and start writing the nasty-grams, let me explain. Most recumbent bikes are built to be comfortable rather than fast. Those comfort recumbents generally have more upright seat angles, wider tires and lower bottom brackets. That combination makes a recumbent about the same speed-wise as your average upright road bike, not faster. There are over 260 models of recumbent bikes currently manufactured, and only about 50 of them are constructed in a way that would make them faster than a road bike. 躺车不比传统自行车更快 在你想写点儿什么来反驳我这个不知天高地厚的讨厌鬼之前， 请先听我解释一下。大多数躺车是为舒适而非速度而建造的。这些的舒适躺车一般有更直立的座椅角度，更宽的轮胎和较低的离地间隙。这种组合使得躺车同直立公路自行车具有一样的速度条件，而不是更快。目前有超过260款在产的躺车，其中只有约50款的结构是使他们比公路自行车更快。 What makes those fast recumbent bikes fast? 那是什么原因使得这些躺车更快呢？ Frontal area 迎风面积 The less wind that you block with your body, the faster the bike will be. In terms of bottom bracket height, your knees should come up to just below the height of your shoulders while pedaling for best aerodynamic efficiency. The further you lean the seat back, the less air you will block. There is of course a practical limit to how far you can lean the seat back, and extremely laid-back bikes require headrests. Usually 20 degrees is the practical lower limit. At angles lower than that, you cannot see over your knees, and handling is compromised. Extremely laid-back bikes are more difficult to control than their upright seat brethren, but some people feel it is worthwhile to go faster. Reducing the seat angle from 30 to 20 degrees will result in a .5 MPH speed gain at 20MPH, or a full MPH speed gain at 25MPH. Lowracers and Highracers generally have the smallest frontal area of all recumbent bikes. 被你的身体挡住的风越少，自行车的速度就越快。基于车架高度，你踩踏时的膝盖高度应略微低于你的肩膀的高度，此时空气动力学效率最高。身体（靠背）越倾斜，你的风阻越小。当然还有一个限度，你就能往后靠多斜，特别斜的躺车车必需要头枕。通常20度是斜躺的极限。低于这个角度，你的视线就被你的膝盖挡住了， 同时操控性也会变差。 特别斜的躺车比普通自行车难以控制，但有些人觉得为了速度这样做是值得的。把座位从30度调到20度，将导致在20英里/小时的速度下平均速度会增加0。5英里/小时，或在25英里/小时的速度下增加1英里的时速。 竞速低躺和竞速高躺一般有所有躺车中迎风面积最小的。 Weight Light is good. Because the speeds going up a hill are much slower than those going back down, on any ride with a moderate amount of hills you will be spending most of your time going uphill. Anything that can be done to help the uphill speeds will greatly increase your average speed. The average recumbent bike weighs about 33lbs. Just reducing that weight to 25 lbs results in a .5 MPH speed gain on a 5% grade. Generally a recumbent bike under 25 lbs is very well optimized for weight. Under 20 lbs is very difficult to accomplish and is usually ridiculously expensive. Highracers and upright bikes can generally be built lighter than lowracers or other recumbent types due to frame simplicity. 重 轻是优点。上山速度明显小于下山速度。 在多山路上骑行， 你的时间大多花在爬山阶段。 如果可以做点儿什么，帮助你提高上坡的速度，则会大大增加你的平均速度。躺车平均重量约33磅（约15公斤）。只要减少到25磅，时速就会增加0.5英里每小时。一般25磅以下的躺车是非常轻的躺车了。20磅是很难做到的，通常价格贵得离谱。 竞速高躺和直立自行车由于车架结构的原因一般都可以建造的比竞速低躺或其他型制的躺车要轻。 Drivetrain Drivetrain efficiency is most important for high power riding such as sprinting or cranking up hills, but not as important when just cruising. To build an efficient drivetrain, reduce the number of idlers and remove the chain tubes. The drive side idler should be a hard plastic or a chain cog, and should be have as large a diameter as possible. The chain line should be kept as straight as possible, but not at the expense of frontal area or weight. Internally geared hubs are less efficient than derailleur systems. Some long wheelbase bikes such as Tour Easy can be built without any power side idlers at all, and as such can be quite efficient up hills. 传动系 传动效率在短距离竞速或是冲坡这种需要狠命猛蹬的骑行时特别重要，但在悠闲巡航时却不是很重要。一个高效的传动系统，应尽量减少导轮和链管的数量。传动侧导链轮应是一个硬质塑料轮或链齿轮，应尽可能用大直径导轮。链条应尽可能保持直线，但不能以增大迎风面积或重量为代价。轮毂内变速效率小于外变速器的效率。一些长轴距躺车可以设计为无导链轮，这样可以提高爬山的效率。 Vehicle height Most recumbent bikes are lower than upright bikes. A lowracer is faster than a higher bike for many reasons. The most obvious is that the rider, wheels and frame are all at the same height, so it will have a smaller frontal area and poke a smaller hole in the wind. Less obvious is that because the wind speed is lower close to the ground, on windy days lowracers will be less affected by the wind. 车高 很多躺车比立车矮。低竞速躺车比很多高的车更快是有原因的。 显而易见的是骑手， 轮子， 车架等高。 所以迎风阻力很小， 就如同在风中钻了个小洞。 其次的原因是风速越接近地面越小， 在大风天， 低躺受风的影响最小。 Wheels While much debate has occurred over whether small or large wheels are faster, the truth is “it depends”. Small wheels have less rotational mass so they will accelerate faster. Also small wheels have less frontal area, so are more aerodynamically efficient. Large wheels are more efficient on rough roads, and offer better cushion to the rider. Actual difference in smooth surface rolling resistance so small it is not noticeable. 轮子 虽然许多争论围绕着大小轮哪个更快展开，但这里要谈到“基于”这个词。小轮子重量小， 因而具有更快地加速度。小轮子迎风面积也小，因而空气动力学效率更高。大车轮在崎岖的道路上更有效率，能提供更好的缓冲。在光滑路面，大轮和小轮滚动阻力的实际差异并不明显。 Coda Most recumbent bikes make many compromises for price, comfort, rideability, and perceived safety. Fast recumbent bikes are still comfortable, but they take more practice to master, and are generally more expensive to obtain. Actual difference in speeds between “slow” and “fast” recumbent bikes can be amazing. The difference in cruising speeds between my “practical” commuter bike and my lowracer are about 5 MPH. That’s a huge speed difference when you are talking about human power. 结尾 很多躺车事实上是---价格，安全舒适性，行驶性能，等多种因素妥协的产物。高速躺车也很舒适，但它们需要更多的练习才能掌握驾驶技巧，同时价格明显比一般躺车贵。在速度的实际差别上，“慢的”和“快的”躺车这种差别往往是惊人的。在我的“实用”的通勤自行车和我的竞速低躺之间的巡航速度的差异是大约5英里。在人力驱动的比较上， 这个差异已经是一个巨大的速度差异了。 |
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