Tires A physics question of leverage

[AxleHub]

Given all of that, when you run over a rock with one rear wheel the tractor lifts only one side and the whole ASSEMBLY acts like a single beam.

That statement is not in disagreement with my post. But it does not prove your concept of the axle is a single beam or piece..

 

[Egon]

The total load stays the same. The internal bearing forces will change.

Egon, after reading other post's, you may be right on the total load but the internal forces comment may indicate your physic's acumen is challenged! As such I'd disregard most of your comment! You may have had an impulse response that preceded rational thought?

 

[SPYDERLK]

The total load stays the same. The internal bearing forces will change.

,,,,:thumbsup:,,,,leverage.

Egon, after reading other post's, you may be right on the total load but the internal forces comment may indicate your physic's acumen is challenged! As such I'd disregard most of your comment! You may have had an impulse response that preceded rational thought?

,,,,,,,,,,,When talking to yourself, try not to contradict.

 

[orezok]

Think about it. If the weight of the tractor remains the same, it takes the same amount of upward force on the outer bearing and downward force on the inner bearing to raise the tractor NO MATTER HOW LONG THE AXLE IS.

The point being that it takes less force on the tire on a longer axle to create the minimum force to raise the tractor than on a shorter axle. If that's what you are calling leverage - OK, but the bearing doesn't know about that.

 

[SPYDERLK]

Think about it. If the weight of the tractor remains the same, it takes the same amount of upward force on the outer bearing and downward force on the inner bearing to raise the tractor NO MATTER HOW LONG THE AXLE IS.

The point being that it takes less force on the tire on a longer axle to create the minimum force to raise the tractor than on a shorter axle. If that's what you are calling leverage - OK, but the bearing doesn't know about that.

Wrong. ... It would be true if only one wheel were extended. - - That would place the suspended weight [tractor] off center tho. This would result in a higher proportion of load borne by the wheel nearer that off center concentrated mass. ... The extended wheel would bear a lighter load, but due its increased lever on its bearing pair the bearing loads would be equal to that on the short side.

 

[dmac128]

My Kubota with AG tires had adjustable rims.
There is about 3-4" of adjustment in the rims.
I just bought wheel spacers that are 3".

Just on the science theory, which way would make the tractor more stable on a side hill?
Say the outer part of the tires touching the ground is 65" as a baseline with both settings.
With the "rim" sticking out past the end of axle or the end of the axle/spacer sticking out past the "centerline" of the tire vertically,
Causing a bit of cantilever. Which would be more stable in respect to the center of gravity overturning the tractor on a side slope.

Yes I know. Both is better.
Inquiring minds want to know. I know some of you will ponder this. **** OCD![/QUOTE]


Let's apply some actual numbers to this thread...

Here's my read on this. I made some very basic geometry assumptions for only one condition - 1000 lb. vertical load at the tire centerline. Generally, everything will be linear for any given load, i.e. if you double the load to 2000 lbs, the bearing loads will also double.

I looked at 3 geometry conditions; baseline, 4" adjustment, and 4" adjustment + 3" spacer. Each condition will give greater side slope stability, and will increase bearing, axle, diff. housing, etc. stresses as shown. I've treated the axle as a free body, meaning the forces and moments (bending) acting on it must balance so it remains static. This is why the bearing loads are not equal to the 1000 lb. applied load.

Bottom line; assuming the 4" adjustment is OEM approved, adding the 3" spacer will increase local stresses by about 9% FOR MY ASSUMED GEOMETRY. Your results may vary.

I'm guessing most of us guys on here do the occasional overload. Note however that this will be all the time and for all load conditions.View attachment IMG_1718.JPG

 

[SPYDERLK]

My Kubota with AG tires had adjustable rims.
There is about 3-4" of adjustment in the rims.
I just bought wheel spacers that are 3".

Just on the science theory, which way would make the tractor more stable on a side hill?
Say the outer part of the tires touching the ground is 65" as a baseline with both settings.
With the "rim" sticking out past the end of axle or the end of the axle/spacer sticking out past the "centerline" of the tire vertically,
Causing a bit of cantilever. Which would be more stable in respect to the center of gravity overturning the tractor on a side slope.

Yes I know. Both is better.
Inquiring minds want to know. I know some of you will ponder this. **** OCD!


Let's apply some actual numbers to this thread...

Here's my read on this. I made some very basic geometry assumptions for only one condition - 1000 lb. vertical load at the tire centerline. Generally, everything will be linear for any given load, i.e. if you double the load to 2000 lbs, the bearing loads will also double.

I looked at 3 geometry conditions; baseline, 4" adjustment, and 4" adjustment + 3" spacer. Each condition will give greater side slope stability, and will increase bearing, axle, diff. housing, etc. stresses as shown. I've treated the axle as a free body, meaning the forces and moments (bending) acting on it must balance so it remains static. This is why the bearing loads are not equal to the 1000 lb. applied load.

Bottom line; assuming the 4" adjustment is OEM approved, adding the 3" spacer will increase local stresses by about 9% FOR MY ASSUMED GEOMETRY. Your results may vary.

I'm guessing most of us guys on here do the occasional overload. Note however that this will be all the time and for all load conditions.View attachment 473599

You really need to know the spacing between each axle bearing pair, and the placement of wheel center wrt the outer bearing to get a good handle on % load increase. ... The proportion increase in bearing load seems it would be much higher -- ~ 50%

 

[orezok]

Wrong. ... It would be true if only one wheel were extended. - - That would place the suspended weight [tractor] off center tho. This would result in a higher proportion of load borne by the wheel nearer the center. ... The extended wheel would bear a lighter load, but due its increased lever on its bearing pair the bearing loads would be equal to that on the short side.

You're grasping at straws now. NO ONE only widens one axle.

Perhaps you could show me a diagram that displays how the force on the outer bearing increased to an amount greater than the original force with the narrower axles.

SHOW ME!

 

[orezok]

You really need to know the spacing between each axle bearing pair, and the placement of wheel center wrt the outer bearing to get a good handle on % load increase. ... The proportion increase in bearing load seems it would be much higher -- ~ 50%

The load can ONLY increase if the weight of the tractor increases. No matter how long the lever, it can never exert more force to the bearing than is required to move the bearing upward. It's simple physics.

 

[SPYDERLK]

Think about it. If the weight of the tractor remains the same, it takes the same amount of upward force on the outer bearing and downward force on the inner bearing to raise the tractor NO MATTER HOW LONG THE AXLE IS.

The point being that it takes less force on the tire on a longer axle to create the minimum force to raise the tractor than on a shorter axle. If that's what you are calling leverage - OK, but the bearing doesn't know about that.

Wrong. ... It would be true if only one wheel were extended. - - That would place the suspended weight [tractor] off center tho. This would result in a higher proportion of load borne by the wheel nearer the center. ... The extended wheel would bear a lighter load, but due its increased lever on its bearing pair the bearing loads would be equal to that on the short side.

You're grasping at straws now. NO ONE only widens one axle.

Perhaps you could show me a diagram that displays how the force on the outer bearing increased to an amount greater than the original force with the narrower axles.

SHOW ME!

That was the point as to why your Hulk example was not realistic to the real situation [in which a tractor is centered between its support points - wheel/wheel.] It was not centered for Hulk. Ref 2nd quote above.

You really need to know the spacing between each axle bearing pair, and the placement of wheel center wrt the outer bearing to get a good handle on % load increase. ... The proportion increase in bearing load seems it would be much higher -- ~ 50%

The load can ONLY increase if the weight of the tractor increases. No matter how long the lever, it can never exert more force to the bearing than is required to move the bearing upward. It's simple physics.

Again : Extending support points increases bearing load because the extended support points exert more leverage on the bearing pair.