Motorized Bikes

There has been a bit of talk about mechanical assistance used in road bikes in competition. Looks like a national champion from Belgium has been accused of using one. Looks like some interesting technology.




I would think the weight would not be worth the assist. The lithium batteries would not have anywhere near the energy these athletes are expending and then once it is dead you still need to haul it.

In cyclocross, where the person was caught, they sometimes change bikes every lap, it would be possible to drop the dead battery bike when it isn’t needed any more. Whether or not it would help or not, well, at least one person thought it was worth the weight penalty.

Where can I get one to haul my aging carcass to the top of the hills… :grin:

Hmmm… telescoping seatpost first or a motor assist?? lol

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Unless there is regenerative braking! :stuck_out_tongue:

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There has definitely been an interest from the older cyclists coming into the shop for an electric or mechanical assist bike. There is definitely a market for them for the recreational cyclist.

In Europe I was getting passed by grannies on E-bikes. Definitely a useful way to get around urban / suburban areas for shopping, visiting friends, etc. so they have a utility as well as recreational use. But as we all know our infrastructure doesn’t do much to support this, yet.

The weight penalty is minimal in competition compared to the “benefits” of cheating with a motor (assuming one doesn’t get caught). Road competition is straightforward to analyze because it relies on very few factors (it is the 2nd ‘easiest’ sport after running). One well known way to get a win is to make a break and make it stick. Essentially this boils down to power to weight ratio for climbing and power to drag for flat.

As for drag: clearly a motor and batteries hidden inside a frame has essentially zero effect on aerodynamic drag. So there is no aero penalty to using a motor and batteries.
As for weight: the UCI weight minimum of 6.8kg means many bikes need extra weight placed on them (ballast) just so they can weigh 6.8kg. So the motor/batteries simply replace that ballast.

In order to drop a single (equally fit) rival, the cheater has to turn on the motor just long enough to drop the chaser. This can be a very short time, probably a minute would do it in most cases. Obviously he would have to repeat this process (give himself a boost) if he is racing a pack as a pack can ride faster than a single cyclist. He would have to soft-pedal or do it on a hill so it isn’t immediately obvious he is cheating. If you work less hard on a hill you save your energy for later, it has a big effect as anyone who has climbed a hill hard will attest it can really take a lot out of you.

To further demonstrate that the weight penalty is minimal, assume a pro bike has 1kg of ballast to make it 6.8kg. I think that is a fair assumption of the weight of a motor. That means you just need to add batteries. Consider a SAFT C cell – usefully a 25.6mm diameter which fits neatly in a seat tube – it weighs 40g and can produce pulses of 14W and has a life of 450W-minutes (i.e. about 30 minutes at full pulse power). I would think than an extra 100W for 5 minutes could well win you a race (example: long finishing climb). So if the motor efficiency is 80%, that means you need only 100/0.8/14 = 9 cells, for a total weight of 360g, or roughly half a water bottle. So even if my calculations are optimistic it’s clear the weight penalty of the motor plus batteries is essentially meaningless.

Note that biometric efficiency is only 25% so humans pay a big penalty there, too, in terms of how much fat we have to carry to produce a certain amount of aerobic power.


Wow. Best answer ever.

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and in that lemond demo video, he said it was capable of 250w for 30mins. that, plus an elite level of fitness = armstrong levels of domination.

LeMond has a full bidon, mine’s only half full. That’s why he can do twice as much power for a half hour :slight_smile:

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