General > General Technical Chat
Force multiplier
james_s:
:horse:
Nominal Animal:
--- Quote from: electrodacus on February 12, 2023, 02:23:33 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.
--- End quote ---
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.
Nominal Animal:
--- Quote from: electrodacus on February 12, 2023, 03:13:44 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.
--- End quote ---
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).
electrodacus:
--- Quote from: Nominal Animal on February 12, 2023, 05:28:44 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.
--- End quote ---
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).
IanB:
--- Quote from: electrodacus on February 12, 2023, 05:56:49 am ---I have no idea
--- End quote ---
Can we just end the thread here, please?
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version