General > General Technical Chat
Newton's third law problem.
electrodacus:
--- Quote from: Nominal Animal on November 20, 2022, 07:00:58 pm ---A simplified example is a pair of wheels with almost as large a pulley in between, with a thread rotated on the pulley. What happens when you pull the thread?
If you start examination at the zero-movement state, you'll find that the angle at which the thread exits the spool, with respect to gravity down, largely determines whether it starts moving or not. If you pull the thread exactly level, the forces do not leverage the wheel to turn so that it would travel opposite to the direction the thread is being pulled to. If you pull the thread slightly upwards or downwards from level, the forces are no longer balanced, resulting a small torque on the wheel, so it'll start traveling opposite to the direction the thread is being pulled to. If you pull the thread nearly vertical, the torque is maximized, and it is easiest to get the wheel to travel (away from where you are pulling the thread).
(The same applies to acceleration: it will only accelerate as you pull harder, if the thread is not exactly level. The minimum angle for a constant velocity depends on the losses, and the minimum angle for acceleration depends on losses and rotational inertia.)
This is why omitting any forces, and only looking at some, will often lead to unphysical results. Would you have considered the effect of the thread angle? It is not obvious until you examine all of the forces acting here, not to me at least.
When the pulley is exactly the size of the wheel, you cannot get it to move (in the opposite direction of where you pull the thread).
When the pulley is larger than the wheel, the angle of the thread no longer matters, and it is easy to get the wheel to move (in the opposite direction of where you pull the thread).
Here, the treadmill is a continuous thread, and the pulley/wheel size ratio represents the gearing between the driven and driving wheels of the "car".
--- End quote ---
I know the tread problem is the same and same stick slip hysteresis and energy storage is involved.
But I think the belt vehicle is an easier example to understand and see the effects. Especially with a long stretchy belt and slowed down video.
The charge discharge frequency can be quite high for most mechanisms and will be impossible to see without slow motion video.
But I should make a drawing where all forces will be placed (currently the forces acting on vehicle body are not drawn) and I will make it just as a lever system to maybe be even clearer that F2 can not be different from F1 as F1 is the reason F2 exists and vice versa.
bdunham7:
--- Quote from: electrodacus on November 20, 2022, 08:27:11 pm ---Motion amplification ? What will that even mean ?
--- End quote ---
If you have a lever with a fulcrum and the ends of the lever have different distances to the fulcrum, then a small motion on the short end becomes a large motion on the long end and vice versa. Like I said, Archimedes.
--- Quote ---Are you saying power output of the back wheel can be higher than power input on the front wheel ? Since it sounds like that.
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I didn't say that. You appear to be 2000+ years short of even understanding the term 'power'.
--- Quote ---What video and please explain what you see if you do not agree with my explanation of what happens.
I clearly see a vehicle that is not moving relative to the ground and a front wheel that moves while belt is stretched so force increases and so is power that it is stored (stretched belt is stored energy).
Then when force is large enough the front wheel slips allowing the back wheel to push the vehicle using the energy stored earlier in the belt and when that belt is discharged the cycle repeats.
--- End quote ---
Your video. I don't see any wheel slippage at all. I see a bit of jerkiness and stretching of the rubber band, all accentuated by the stop-action of the slow frame rate, but none of what you describe. Even if the band were entirely inflexible or the equivalent function was implemented with gears, the result would be the same.
electrodacus:
--- Quote from: SiliconWizard on November 20, 2022, 08:31:55 pm ---Wasn't this already shown in one of the threads on people being completely wrong about electricity?
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Do not change the subject. This is a problem where everything can be seen and you are still getting things wrong.
AndyBeez:
Reciprocal: a connecting rod between a piston and a wheel is replaced with a shock absorber. Does the wheel rotate if the shock absorber is 'storing' energy?
Nominal Animal:
--- Quote from: electrodacus on November 20, 2022, 08:17:36 pm ---The claim I make and it is proved by the video's I shwed is that no vehicle including this one can move from left to right without both energy storage and stick slip systeresis.
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Sure it can. Just swap the gearing ratio, and replace the rubber band with a non-springy belt.
--- Quote from: electrodacus on November 20, 2022, 08:17:36 pm ---You need to twist the belt (infinite symbol shape) in order for this mechanism to not be locked so changing the gear ratio will not help with anything.
--- End quote ---
No, you don't. Just make the floor-wheel gear or pulley larger than the treadmill gear or pulley, and be amazed. The bigger the ratio (rear size to front size), the easier it moves.
Please, try it. I'm not tricking you. I showed you math that *proves* it works. The only reason for you to not try it, would be to avoid being proven wrong. Keep your mind open, friend, and try it.
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