I found an old (early 70s) puzzle book that contained the following problem:
"A bicycle is supported on level ground such that it can't fall over sideways. The pedal cranks are orientated vertically. A string is tied to the bottom crank and pulled gently backwards. Does the bike move backwards or forwards?"
The answer, as given, was "backwards", with some brief cod-science about the string "unable to overcome the force of the gears", but it got me thinking. With today's modern low gearings for those dark side machines and some mountain bikes, is it possible to have a similar situation whereby a constant rearward pull on the string caused the bike to the bike moves forwards?
With today's modern low gearings for those dark side machines and some mountain bikes, is it possible to have a similar situation whereby a constant rearward pull on the string caused the bike to the bike moves forwards?
At first thought, you'd need a *really* low gear. Intuitively, it would seem that it's distance rather than ratio that counts - so you'd need a gear that causes more linear movement in the pedal than in the bike.
So a sub 1:1 rotation ratio won't necessarily cut it: you'd need an additional scaling related to your pedal circle diameter and wheel size.
I found an old (early 70s) puzzle book that contained the following problem:
Quoted message said:
"A bicycle is supported on level ground such that it can't fall over sideways. The pedal cranks are orientated vertically. A string is tied to the bottom crank and pulled gently backwards. Does the bike move backwards or forwards?"
Quoted message said:
The answer, as given, was "backwards", with some brief cod-science about the string "unable to overcome the force of the gears", but it got me thinking. With today's modern low gearings for those dark side machines and some mountain bikes, is it possible to have a similar situation whereby a constant rearward pull on the string caused the bike to the bike moves forwards?
Only to the point of the pedal being horizontal. I have just tried in on the trike, and it moved forward.
The answer, as given, was "backwards", with some brief cod-science about the string "unable to overcome the force of the gears", but it got me thinking. With today's modern low gearings for those dark side machines and some mountain bikes, is it possible to have a similar situation whereby a constant rearward pull on the string caused the bike to the bike moves forwards?
Only to the point of the pedal being horizontal. I have just tried in on the trike, and it moved forward.
Well, yes, I figured only to the point of horizontality.
Thanks for the evidence at first hand, not having a ludicrously low-geared machine myself. But, what's this? ...empirical evidence? It'll never do, not in this newsgroup ;-)
The answer, as given, was "backwards", with some brief cod-science about the string "unable to overcome the force of the gears", but it got me thinking. With today's modern low gearings for those dark side machines and some mountain bikes, is it possible to have a similar situation whereby a constant rearward pull on the string caused the bike to the bike moves forwards?
Quoted message said:
Quoted message said:
Only to the point of the pedal being horizontal. I have just tried in on the trike, and it moved forward.
Quoted message said:
Well, yes, I figured only to the point of horizontality.
Quoted message said:
Thanks for the evidence at first hand, not having a ludicrously low-geared machine myself. But, what's this? ...empirical evidence? It'll never do, not in this newsgroup ;-)
I'm sure someone will argue against me, don't worry.
The gearing on the trike by the way, front chainring, 27 tooth, rear sprocket 34 tooth, wheel size 406, I think that is about 15" per revolution.
Well, yes, I figured only to the point of horizontality.
Not even to the point of horizontality. Only while the backward movement of the pedal (where the string is attached) relative to the bike is greater than the consequent movement forward of the bike relative to the ground. That is, it moves forward only while the point where the string is attached is moving towards you. While you *might* be able to stand on a spoke, you can't push with this taut string.
Brendan -- Brendan Halpin, Department of Sociology, University of Limerick, Ireland Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F2-025 x 3147 [email hidden] http://www.ul.ie/sociology/brendan.halpin.html
> The answer, as given, was "backwards", with some brief cod-science about > the string "unable to overcome the force of the gears", but it got me > thinking. With today's modern low gearings for those dark side machines > and some mountain bikes, is it possible to have a similar situation > whereby a constant rearward pull on the string caused the bike to the > bike moves forwards?
Quoted message said:
Quoted message said:
Only to the point of the pedal being horizontal. I have just tried in on the trike, and it moved forward.
Quoted message said:
Well, yes, I figured only to the point of horizontality.
Quoted message said:
Thanks for the evidence at first hand, not having a ludicrously low-geared machine myself. But, what's this? ...empirical evidence? It'll never do, not in this newsgroup ;-)
I'm sure someone will argue against me, don't worry.
