Electric assist pedals
As per title, an electric assist system for your bike, but it's all in the pedals which can just be swapped with your normal ones. Can't quite see how this is supposed to work- could it?
And according to the article he's a finalist in a Barclays business competition.Posted 7 years agoLabWormyMember
So, ignoring what the twisty turny torquy stuff works against, have a look at the energy involved…
Li-poly batteries have an energy denisity of around 350Wh/L (from PowerStream)
This is 1260000 joules/litre
Looking at two typical pedals with a length of 10 cm, a depth of 2cm, and the battery width of 1cm, then the volume will be 4 x 10 x 2 x 1 = 80cm, this 80/1000 = 0.08l.
This gives us 1260000 x 0.08 = 100800 joules.
Given E = mgh, this re-arranges to h = E/mg (sorry, edit).
g ~ 10 (ie that rounded up 9.81 from school) and mass of bike & rider = 100kg.
So the batteries (100% efficiency all round), would lift you up 100 metres.
So in the real world you would be paying £200 to lift you through ~50m (50% efficiency) around 300 times (recharge cycles of Lithium batteries).
Bargain …..Posted 7 years agobristolbikerMember
have to oppose the rotation of the pedals and so do more work?
Precisely, the pedal effictively becomes a motor where the shaft is fixed to the crank. If it's got sufficient power to make a difference, it could feel quite funny to use, balancing the normal pedalling forces and reacting the 'motor' forces….Posted 7 years agomountaincarrotMember
Hi MrSalmon,Posted 7 years ago
You don't do work without movement. Power = force x velocity. The rotational velocity of your feet is effectively zero, so you don't do any "work". The pedal does the work by rotatig the crank. All your foot does is act as a fixed torque arm – which must indeed feel strange.
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