Common knowlegde has it that you can deliver little power at the dead
spot, i.e. when the cranks are about vertical. However, I have found a
way to get hill (rolling up) climbing power from the dead spot if you
have a wide and ‘springy’ tyre. Here’s how I think it works:
I stand up on the pedals. When the front pedal goes down, virtually
all my weight is on that pedal. If required, I add some ‘weight’ by
pulling on the handle. So almost all of my body weight is moving down.
Now when the pedal approaches the bottom position, my body’s inertia
wants to keep it moving down. This causes the tyre to compress and
store energy. Since my leg is stretched at this point in time this
causes essentially no muscle power. While the bottom pedal rounds the
bottom part of its circle the tyre decompresses again and launches me
a little up into the air; this is also ‘for free’, muscle-energy-wise.
I use this lift to get to standing on the other pedal. That of course
requires a lifting of the body, but I get a part of it ‘for free’.
Also, the tyre is momentarily almost fully decompressed, thereafter it
starts to compress again which means that the axle goes less steep up
than the road/trail surface. So it is as if the unicycle effectively
rides a less steep incline.
So the tyre goes through two compression/decompression cycles per one
full revolution of the wheel. All of the above only works if the wheel
rotation, and hence the load change from leg to leg, works in
resonance with the tyre bouncing. If I do it right, I can almost
dance up a hill. If the hill gets too steep to keep the resonance
pace, the scheme breaks down and I’m back on my own.
I note that at the end of the day, you have delivered all the energy
yourself. Overall, there is no free energy (TANSTAAFL). But the energy
delivery is spread over more of the wheel rotation, and that feels
like a good thing.
Probably people have done this for ages (though it’s NEW for me), but
then maybe they didn’t think of this explanation. I’ve never seen it
described like this.
Klaas Bil - Newsgroup Addict
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