Author Topic: Force multiplier  (Read 33958 times)

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Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #250 on: February 12, 2023, 12:01:56 am »
Yes, I am saying we can construct a mechanism so that when the human pulls on the rope, the gearbox mechanism moves towards the wall.


You are the smart one here, you figure it out.

I am pretty sure everyone else reading this thread can make a post that says, "I can see how to construct such a mechanism."

Let's see how many do.


I think I know what you have in mind so keep in mind that the input and output string can not be offset. It should be as in the diagram.
Offset equal and opposite forces will create a torque (rotational force) and that is not what we are discussing here as the is no offset in diagram (a)

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #251 on: February 12, 2023, 12:02:37 am »
I can easily see how to construct such a mechanism.

See replay I made to IanB.  Offset is not allowed.

Online IanB

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Re: Force multiplier
« Reply #252 on: February 12, 2023, 12:08:02 am »
I think I know what you have in mind so keep in mind that the input and output string can not be offset. It should be as in the diagram.
Offset equal and opposite forces will create a torque (rotational force) and that is not what we are discussing here as the is no offset in diagram (a)

If there is any offset between the two strings then the rotational torque created will cause them to line up in a straight line. If the two strings are normal flexible cords, there is no way for them not to be in a straight line when pulled taut as shown.
 

Offline PlainName

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Re: Force multiplier
« Reply #253 on: February 12, 2023, 12:10:21 am »
I can easily see how to construct such a mechanism.

See replay I made to IanB.  Offset is not allowed.

Who needs offset? Just you, I think.

I get the impression that you'll start disallowing this and that until we're eventually left with a single piece of string and no mechanism. Whether it is offset or not is irrelevant - as you note, that would cause some torque until it naturally aligned anyway.
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #254 on: February 12, 2023, 12:20:43 am »
If there is any offset between the two strings then the rotational torque created will cause them to line up in a straight line. If the two strings are normal flexible cords, there is no way for them not to be in a straight line when pulled taut as shown.

Not quite sure you understand what I mean by offset.
I'm referring to a spool with two diameters with the string connected to wall on one diameter spool and the one connected to human on the other diameter.
In that case there will always be a an offset and they will not be on the same line as the spool is constantly falling over.
As soon as the two equal and opposite forces are offset you get a rotational force. It is like in case (a) I will apply the force F1 to other part of the wheel other than the bottom directly in line with the F2.
So the two separate strings should look as in the diagram as if it was a single string.
So say you have a cube box and two holes in the middle of opposite faces just as large to have the string pass trough. Then inside you can have whatever you want (of course not a battery and motor :)).
 

And why not have the exact mechanism in case (a) ?
« Last Edit: February 12, 2023, 12:27:29 am by electrodacus »
 

Offline cbutlera

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Re: Force multiplier
« Reply #255 on: February 12, 2023, 12:22:14 am »
I am pretty sure everyone else reading this thread can make a post that says, "I can see how to construct such a mechanism."

Let's see how many do.

As a child back in the 1960s, I had toy astronaut called "Major Matt Mason".  One of his accessories was a jet pack with two strings emerging.  You could attach the upper string to the back of a chair, or some other suitable object.  Then when you pulled the lower string downwards out of the bottom of the jet pack, the pack would reel in the upper string and rise to the top of that string.  Sadly I could find no on-line videos that showed it working as it was intended.
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #256 on: February 12, 2023, 12:48:59 am »
As a child back in the 1960s, I had toy astronaut called "Major Matt Mason".  One of his accessories was a jet pack with two strings emerging.  You could attach the upper string to the back of a chair, or some other suitable object.  Then when you pulled the lower string downwards out of the bottom of the jet pack, the pack would reel in the upper string and rise to the top of that string.  Sadly I could find no on-line videos that showed it working as it was intended.

I was only able to find some photos.
What about the mechanism in case (a) witch is the one of interest. If I roll some string on input wheel and another string on output wheel. and tie one of them to a wall and pull on the other.

What is your prediction ?
Will anything move except for stretching the belt a little bit ?

My prediction is that it will not move as the ability to slip is eliminated.

Offline cbutlera

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Re: Force multiplier
« Reply #257 on: February 12, 2023, 01:08:21 am »
Quote
In any case you isolate the subject and look forces acting on each of them.

No, no, no!  You are confusing it with Newton's first and second laws of motion.  Newton's third law of motion applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body.  Do you understand the difference between one and two?

You misunderstood what I wanted to say (it is my fault as it was not clear).

When I say isolated I mean you look at groups for two objects (there are a total of 3)
So a pair is book and table and then the other pair is table and ground.

Well you have just demonstrated why the book at rest on a table is a good example with which to illustrate Newton’s third law.  There are more significant force-pairs acting in this example than the two that you have identified.  Can you identify the other Newton's third law force-pairs?

Quote

How would the answers of either yes or no to this question have any relevance to Newton’s third law?  Either way, the force exerted by the right hand end of the rope on the hook/elephant, would be equal and opposite to the force exerted by the hook/elephant on the right hand end of the rope. And similarly for the pair of forces between the left hand end of the rope and the man’s hands, and the pair of forces between the man’s feet and the ground, etc.

Correct so that also means the that you have the same force on each side of the Newton meter and if you replace that with whatever else you want like a gearbox with input connected towards the human (left) and output towards the wall (right) the forces will remain equal on both sides of the gearbox as the gearbox with a floating body can not do any force multiplication.

That may or may not be true, depending on the circumstances.  The tension meter is one body with several forces acting upon it.  Newton’s third law applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body.  You cannot use Newton’s third law to conclude that the forces applied by the rope on either side of the tension meter are the same. 

Remember, the tension meter has a mass, and the rope has a mass per unit length.  The rope and tension meter may or may not be accelerating.  You cannot assume that they are not accelerating.

Quote
But IanB apparently think that is possible based on his answer.
Looking forward to your answer.

Well I know that it is possible, because mechanical analysis shows that it is possible, and as I mentioned in another message, as a child I once had a toy that worked exactly that way.  So I have seen experimental evidence too.
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #258 on: February 12, 2023, 01:11:16 am »
So if I spool some string on anticlockwise on input wheel and clockwise on the output wheel with output on the bottom then pull them apart nothing will move and the string will remain spooled on both sides.

It is like what happens in this video is just that I also eliminate the slip on the output wheel https://odysee.com/@dacustemp:8/stick-slip-removed-from-front-wheels:0


If any of you thinks the wire will unspool I can find the model and do a short video.

Offline jonovid

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Re: Force multiplier
« Reply #259 on: February 12, 2023, 01:11:56 am »
my father had one for lifting engines out of cars.
endless chain block
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Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #260 on: February 12, 2023, 01:21:02 am »

That may or may not be true, depending on the circumstances.  The tension meter is one body with several forces acting upon it.  Newton’s third law applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body.  You cannot use Newton’s third law to conclude that the forces applied by the rope on either side of the tension meter are the same. 

Remember, the tension meter has a mass, and the rope has a mass per unit length.  The rope and tension meter may or may not be accelerating.  You cannot assume that they are not accelerating.


Well I know that it is possible, because mechanical analysis shows that it is possible, and as I mentioned in another message, as a child I once had a toy that worked exactly that way.  So I have seen experimental evidence too.

That drawing is a bit bad as the string is not perfectly horizontal so yes the gravity will play a role in case you consider string has mass since the the connection at the wall that is higher will see a larger force due to gravity acting on the string.

If you replace the newton meter with mechanism in case (a) so spool the string on the wheels and also keep the string perfectly horizontal so there is no gravity involvement then nothing will move.
The reason nothing move is because you eliminate the ability to slip at both wheels.

If you disagree I'm ready to spend some time finding the toy vehicle and do a short video demonstrating that.
Of course I can make changes to case (a) and allow motion but the particular case (a) is discussed. How it works is relevant else you may not be able to do a correct prediction.

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #261 on: February 12, 2023, 01:23:12 am »
my father had one for lifting engines out of cars.
endless chain block

Yes it has 3 points not just 2 so of course it can do force multiplication.

Offline jonovid

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Re: Force multiplier
« Reply #262 on: February 12, 2023, 01:35:19 am »
my father had one for lifting engines out of cars.
endless chain block

Yes it has 3 points not just 2 so of course it can do force multiplication.
life your self in a cage  = 2 points
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Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #263 on: February 12, 2023, 01:42:55 am »
life your self in a cage  = 2 points

Points of contact on which forces can be applied.
You can not do force multiplication with only two points as in that case the forces can only be equal ignoring any acceleration force.
If you have 3 points then you can use the 3'rd point as a leverage in order to be able to do force multiplication.

Online Nominal Animal

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Re: Force multiplier
« Reply #264 on: February 12, 2023, 01:48:07 am »
I will not say that 2:1 is anywhere close to 1:1. I will understand if it was 1.1:1 but not 2:1
That is because you do not understand the kinematics here.  Review the math in my reply #92.  In your vehicle, the wheels are the same size, \$r = R\$.  Per your definition, gear ratio \$G = 1/\lambda\$.  Using \$x\$ for the vehicle speed right, and \$y\$ for the treadmill surface speed left, kinematics analysis shows that
$$x = y \frac{\lambda R}{r - \lambda R} = \frac{y}{G - 1} \quad \iff \quad \frac{x}{y} = \frac{1}{G - 1}$$

Instead of testing these, you rely on your hand-eye coordination and a single video clip as "proof".  That is not science, it is religion.

Before I look at your math please specify how are the two wheels connected in your setup ?
Before I look at your question, please specify what your astrological sign is?

It does not matter, because it applies to your setup.  \$G\$ is the gear ratio.  \$G \gt 0\$ for a direct belt, \$G \lt 0\$ for a twisted belt.
For belt pulleys, \$G = d_\text{driven} / d_\text{driver} = N_\text{driver} / N_\text{driven}\$, i.e. the ratio of the diameter of the driven wheel to the diameter of the driver wheel, or equivalently the number of rotations of the driver wheel per driven wheel rotation.

It even applies to chain and gear gearboxes, with \$G\$ being the input:output turn ratio.

I must say, electrodacus gives a completely new meaning to the term dodgy.
I bet if they were to spout their theories outside in the rain, they'd manage to not get wet; they dodge so much.
« Last Edit: February 12, 2023, 02:04:51 am by Nominal Animal »
 

Offline cbutlera

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Re: Force multiplier
« Reply #265 on: February 12, 2023, 01:51:24 am »

That may or may not be true, depending on the circumstances.  The tension meter is one body with several forces acting upon it.  Newton’s third law applies to "the mutual actions of two bodies upon each other". It has no relevance to the forces acting on any one body.  You cannot use Newton’s third law to conclude that the forces applied by the rope on either side of the tension meter are the same. 

Remember, the tension meter has a mass, and the rope has a mass per unit length.  The rope and tension meter may or may not be accelerating.  You cannot assume that they are not accelerating.


Well I know that it is possible, because mechanical analysis shows that it is possible, and as I mentioned in another message, as a child I once had a toy that worked exactly that way.  So I have seen experimental evidence too.

That drawing is a bit bad as the string is not perfectly horizontal so yes the gravity will play a role in case you consider string has mass since the the connection at the wall that is higher will see a larger force due to gravity acting on the string.

If you replace the newton meter with mechanism in case (a) so spool the string on the wheels and also keep the string perfectly horizontal so there is no gravity involvement then nothing will move.
The reason nothing move is because you eliminate the ability to slip at both wheels.
...

That has nothing to do with it.  Please read what I wrote above again.

You are trying to answer the question, will the tension meter (or some gearbox in its place) move?  If it is starting from rest, and if it is going to move, it will have to accelerate.  So the question becomes will it accelerate?  If it does accelerate, the net force acting upon it will not be zero.  So you cannot assume that the net force acting on it is zero, and then conclude from that that it cannot accelerate.  That is circular reasoning.

You didn't reply with any further Newton's third law force-pairs in the book resting on a table example, beyond the two that you mentioned previously.  I can tell you if you really can't do it, but it would be much better if you could identify them for yourself.
« Last Edit: February 12, 2023, 01:54:54 am by cbutlera »
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #266 on: February 12, 2023, 02:23:33 am »
Before I look at your question, please specify what your astrological sign is?
:)

It does not matter, because it applies to your setup.  \$G \gt 0\$ for a direct belt, \$G \lt 0\$ for a twisted belt.

It even applies to chain and gear gearboxes, with \$G\$ being the input:output turn ratio.

I must say, electrodacus gives a completely new meaning to the term dodgy.
I bet if they were to spout their theories outside in the rain, they'd manage to not get wet; they dodge so much.

In my setup a 2:1 gear ratio means for each full rotation of the input wheel (right) output wheel will make half of a rotation.
Both wheels in my setup have the same diameter the sprockets have different diameters.

A direct or twisted belt will make no difference in the gear ratio only the direction the wheel rotate.
All gear ratios and belt configurations result in a locked gear except for the 1:1 gear ratio with and twisted belt.

So no matter the gear ratio with direct belt the vehicle can not move without wheel slip.
The gear ratio is relevant when input wheel slips as at that point the energy stored in the belt powers the vehicle F3 = F4 but offset due to gear ratio thus it can move the vehicle oposited to F1 direction.


So ignoring forces in case (a) and looking just a kinematics (so like pushing the vehicle body relative to ground and having a freewheeling treadmill )
For a 2:1 gear ratio you have

X = 1m relative to ground
Y = 2m distance the input treadmill surface moved relative to ground.

In your example it seems you considered the input wheel diameter half of the output wheel diameter and that is not what it happens in case (a) with both wheels having the same diameter so input wheel needs to make 2 full rotations while the output wheel just makes one.
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #267 on: February 12, 2023, 02:33:24 am »
That has nothing to do with it.  Please read what I wrote above again.

You are trying to answer the question, will the tension meter (or some gearbox in its place) move?  If it is starting from rest, and if it is going to move, it will have to accelerate.  So the question becomes will it accelerate?  If it does accelerate, the net force acting upon it will not be zero.  So you cannot assume that the net force acting on it is zero, and then conclude from that that it cannot accelerate.  That is circular reasoning.

You didn't reply with any further Newton's third law force-pairs in the book resting on a table example, beyond the two that you mentioned previously.  I can tell you if you really can't do it, but it would be much better if you could identify them for yourself.

case (a) is nothing more than a gearbox with floating body.
Due to the way the belt is connected in case (a) and the place the forces act on it, it is a locked gearbox thus there will be no acceleration if wheels are not allowed to slip and if you use a string then they can not slip thus it will not move.
The net force will be zero and there will be no acceleration.
If we use a twisted belt instead then there will be acceleration so during acceleration period F1 = F2 + m*a so both Newton's 3'rd law and 2'nd law are involved.

I'm not really interested in the twisted belt or variant just the the direct belt connection of case (a).
That mechanism can not accelerate unless slip is allowed and the use of strings will eliminate any slip thus nothing will accelerate unless you consider the small rotation of the wheel while the belt is stretched but that will be all.
Only when that case (a) is on a surface and it can slip it will be able to move.

As mentioned if you disagree I can do a video as I still have that toy car somewhere.

Offline cbutlera

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Re: Force multiplier
« Reply #268 on: February 12, 2023, 02:53:30 am »
That has nothing to do with it.  Please read what I wrote above again.

You are trying to answer the question, will the tension meter (or some gearbox in its place) move?  If it is starting from rest, and if it is going to move, it will have to accelerate.  So the question becomes will it accelerate?  If it does accelerate, the net force acting upon it will not be zero.  So you cannot assume that the net force acting on it is zero, and then conclude from that that it cannot accelerate.  That is circular reasoning.

You didn't reply with any further Newton's third law force-pairs in the book resting on a table example, beyond the two that you mentioned previously.  I can tell you if you really can't do it, but it would be much better if you could identify them for yourself.

case (a) is nothing more than a gearbox with floating body.
Due to the way the belt is connected in case (a) and the place the forces act on it, it is a locked gearbox thus there will be no acceleration if wheels are not allowed to slip and if you use a string then they can not slip thus it will not move.
The net force will be zero and there will be no acceleration.
If we use a twisted belt instead then there will be acceleration so during acceleration period F1 = F2 + m*a so both Newton's 3'rd law and 2'nd law are involved.

I'm not really interested in the twisted belt or variant just the the direct belt connection of case (a).
That mechanism can not accelerate unless slip is allowed and the use of strings will eliminate any slip thus nothing will accelerate unless you consider the small rotation of the wheel while the belt is stretched but that will be all.
Only when that case (a) is on a surface and it can slip it will be able to move.

As mentioned if you disagree I can do a video as I still have that toy car somewhere.

There is no Newton's law of the locked gearbox. There is no Newton's law of the slipping wheels.  You just keep quoting your own made-up laws of mechanics as if they represent some kind of proof.

Again, you haven't replied with any further Newton's third law force-pairs from the book resting on a table example.  So I can only assume from that that you don't know, and yet you claim to be an expert on that subject.  I'll give you a clue, gravity is involved.  Now can you list any more of the force-pairs?
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #269 on: February 12, 2023, 03:13:44 am »

There is no Newton's law of the locked gearbox. There is no Newton's law of the slipping wheels.  You just keep quoting your own made-up laws of mechanics as if they represent some kind of proof.

Again, you haven't replied with any further Newton's third law force-pairs from the book resting on a table example.  So I can only assume from that that you don't know, and yet you claim to be an expert on that subject.  I'll give you a clue, gravity is involved.  Now can you list any more of the force-pairs?

Seems like you are changing the subject but fine.
A locked gearbox is no different from a solid object so if you apply a force at one end and the other end is constrained like say tied to a wall then net force can only be zero.

I don't even care if someone even heard of Newton as long as it can predict what happens in cases (a) to (c)

The answers I here from people that answered here is gearbox so force multiplication or just completely ignoring forces and using kinematics only.

If that was to be true a 1:1 gear ratio will still have the wheels rotate and that is just not the case. So invalidating your claims can be as simple as showing that gearbox will not move.
But a kinematics only model will predict that wheels rotate at same speed since is like applying a force to the vehicle body relative to ground with a freewheel treadmill.
So none of your theories can predict what happens when you perform the test as it needs to make correct prediction independent of gear ratio.

Offline james_s

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Re: Force multiplier
« Reply #270 on: February 12, 2023, 04:04:49 am »
 :horse:
 

Online Nominal Animal

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Re: Force multiplier
« Reply #271 on: February 12, 2023, 05:28:44 am »
For a 2:1 gear ratio you have

X = 1m relative to ground
Y = 2m distance the input treadmill surface moved relative to ground.
No, I don't.  It was a typo in the table I fixed in the last edit, 40 minutes before you posted that.

For a 2:1 gear ratio, the vehicle moves right the same distance as the surface of the treadmill moves left, both with respect to the ground.

You keep insisting the gear ratio does not matter.  Yet, a gear ratio of 4:1, as shown in my table in reply #240, would require the vehicle to move only 0.333m right when the surface of the treadmill moves 1m left, both with respect to the ground.

I don't care if you don't believe me, that's fine.  But refusing to test a larger gear ratio is utterly unscientific.

I guess you already know that if you do, it proves even to yourself that you are wrong.  But that is the nature of science: testability, not belief, is the key.
 

Online Nominal Animal

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Re: Force multiplier
« Reply #272 on: February 12, 2023, 05:54:38 am »
The answers I here from people that answered here is gearbox so force multiplication or just completely ignoring forces and using kinematics only.

If that was to be true a 1:1 gear ratio will still have the wheels rotate and that is just not the case.
How about you stop lying, please?

The kinematics analysis shows without a doubt that a gear 1:1 ratio is a singular point: if there is a driven wheel on a treadmill, connected (via e.g. a belt) to a driving wheel of the same size with a 1:1 gearing, with driven and driving wheels rotating in the same direction, the vehicle does not work: the velocity ratio is undefined (division by zero) or infinite.

This has been told you time and time again, yet you somehow keep claiming that we claim that even in that case the vehicle would work.  That is a dirty rotten lie, and you should be ashamed.

The singular point at 1:1 gear ratio is also at the core of the explanation of exactly why the gear ratio matters, and how gear ratios like 4:1 and higher work much better for such a demonstration vehicle, as lower gear ratios involve high relative speeds, and for acceleration from standstill, require such forces that tend to twist and bend the vehicle instead of behaving as a rigid structure.  To repeat once again, here is a graph of how the ratio of the velocities with respect to ground, treadmill surface speed (leftwards) to vehicle speed (rightwards), as a function of the gear ratio \$G\$ behaves:


At 1:1, the vehicle would need to move at plus or minus infinite speed, which is obviously unphysical and describes a nonfunctioning vehicle.
The graph describes the same information as the table in reply #240.

The fact that at gear ratio \$G = 0\$ the velocity ratio is \$1\$ means that if the driven wheel is locked (will not rotate), the vehicle will move in the same direction and at the same speed as the surface of the treadmill.  Similarly, at \$G = \pm \infty\$ the velocity ratio is zero, meaning that if the driven wheel rotates freely but the driving wheel is locked, the vehicle will not move at all.

All this, just from the kinematics analysis, which you refuse to review (and much less understand, even though it is the simplest level at which one can examine mechanisms).
« Last Edit: February 12, 2023, 06:04:29 am by Nominal Animal »
 

Offline electrodacusTopic starter

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Re: Force multiplier
« Reply #273 on: February 12, 2023, 05:56:49 am »
No, I don't.  It was a typo in the table I fixed in the last edit, 40 minutes before you posted that.

For a 2:1 gear ratio, the vehicle moves right the same distance as the surface of the treadmill moves left, both with respect to the ground.

You keep insisting the gear ratio does not matter.  Yet, a gear ratio of 4:1, as shown in my table in reply #240, would require the vehicle to move only 0.333m right when the surface of the treadmill moves 1m left, both with respect to the ground.

I don't care if you don't believe me, that's fine.  But refusing to test a larger gear ratio is utterly unscientific.

I guess you already know that if you do, it proves even to yourself that you are wrong.  But that is the nature of science: testability, not belief, is the key.

Maybe the confusion comes from the fact that you are using something other than what I show in case (a). Your example vehicle there is very strange and drawing at least for me does not show what the relation between the two wheels of different size is.

For that vehicle 2:1 gear ratio will be exactly the same as a 1:2 gear ratio. In fact there is no 1:2 gear ratio is the same 2:1 gear ratio just turned 180 degree as input wheel is always the one with the smaller pulley.
While in your table not only there is a 1:2 gear ratio but it looks like it will behave completely different.

There is always and input and output wheel and since the input wheel is always the one with the smaller pulley you can not have a gear below 1:1 so no such thing as 1:2 possible as it will actually be a 2:1 and you will just confuse the input with output and of course all sort of wrong conclusions can be had if input and output are defined wrong.

I will love to have this clarified and I have no idea what is your magic vehicle doing as you sure not use the vehicle I describe in case (a) witch has wheels of exactly the same size and there is no vertical offset between the wheel on treadmill and the one on the ground/redbox

The purely kinematic motion of that vehicle (a) same as if vehicle was pushed by applying a force between ground and body with a freewheel treadmill will be

For 2:1
X = 1m (distance the vehicle body moved relative to ground).
Y = 2m (distance the treadmill surface moved relative to ground).
if you want to look at speed instead of displacement then for 1m/s vehicle speed relative to ground the freewheel treadmill will move at 2m/s

For a 4:1
X=1m
Y=4m

Nothing complicated or strange as in your table (likely do to some strange vehicle you are using with different wheel sizes and no clear description of the relation / connection between those two wheels).

Online IanB

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Re: Force multiplier
« Reply #274 on: February 12, 2023, 06:04:53 am »
I have no idea

Can we just end the thread here, please?
 


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