General > General Technical Chat
Mess with your minds: A wind powered craft going faster than a tail wind speed.
IanB:
--- Quote from: electrodacus on August 29, 2021, 11:48:58 pm ---With 1:1 gear ratio and no slip is allowed the treadmill will be locked so there will be no movement.
--- End quote ---
Indeed. But if there is a generator to motor connection instead of a 1:1 belt, then there can be torque conversion and differential wheel speeds. In this case the system will not be locked.
--- Quote ---The treadmill will try to push the vehicle back while the back wheel will try to move the vehicle forward so there will be equal but opposite power acting on the belt. In real world the M wheel will slip unless friction between wheel and red box is higher than treadmill power so assuming treadmill is not overpowered the vehicle will move backwards (right to left).
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Which wheel slips depends on the coefficient of friction and the weight above the wheel. If there is a heavier weight on M wheel, then maybe the G wheel will slip and the M wheel will grip. Or maybe both wheels will slip a bit. In any given case, you cannot state what will happen without defining further details.
bdunham7:
--- Quote from: electrodacus on August 29, 2021, 10:09:13 pm ---Now if you connect the wheel G and M with an ideal belt and gear ratio is 1:1
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1:1 doesn't work as I wrote previously (correcting my own error) because those equations of motion that you didn't solve would result in a divide-by-zero error, infinite speed to the right and infinite force.
PlainName:
--- Quote --- the treadmill will be locked
--- End quote ---
What is locking it? It would only be locked if the vehicle is prevented from moving.
We've agreed that without the belt the G wheel is free to rotate and hence doesn't move the vehicle, so with the belt, the only thing working against the G wheel is the M wheel.
The only thing preventing the M wheel from turning is the vehicle, and since the vehicle is free to move the M wheel will move the vehicle.
electrodacus:
--- Quote from: dunkemhigh on August 30, 2021, 12:32:24 am ---
--- Quote --- the treadmill will be locked
--- End quote ---
What is locking it? It would only be locked if the vehicle is prevented from moving.
We've agreed that without the belt the G wheel is free to rotate and hence doesn't move the vehicle, so with the belt, the only thing working against the G wheel is the M wheel.
The only thing preventing the M wheel from turning is the vehicle, and since the vehicle is free to move the M wheel will move the vehicle.
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Yes the vehicle will prevent from moving. Think about this way the G wheel is breaking so treadmill pushes the vehicle from right to left and then the M wheel if it can have enough traction and ideal vehicle will push with equal force in the opposite direction so it is like a wedge.
What prevents the M wheel for turning the the G wheel not the vehicle as M wheel is connected to G wheel.
So in summary
a) unconnected wheels ideal vehicle as you mentioned will just free spin and vehicle will stay in place.
b) connected wheels with 1:1 gear ratio will still have the vehicle stand still but this time the treadmill will also stop if slip on wheels is not allowed
In real life there will be losses so power on G will be higher than power at M and so vehicle will move backwards.
c) any gear ratio and real vehicle will result in vehicle moving from right to left.
PlainName:
--- Quote ---the G wheel is breaking
--- End quote ---
OK, to be explicit the G wheel is being braked by the mass of the vehicle acting through the M wheel, yes? In other words, if the M wheel had no grip then the G wheel would again be free to rotate and the vehicle wouldn't move either way?
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