Moving cut tree branches & logs

JWR · Sep 28, 2025

Mostly wrong. Way away from the valid context of the discussion (e.g. farm tractor trying to pull a log.) I will use the TBN messaging to reply to you.

SPYDERLK · Sep 28, 2025

CalG said:
We have run into an impass of understanding.

What does the term "MOMENT" mean to you?

If I may elaborate....

I like to consider thought problems of mechanics in the most extreme conditions and then walk back to real world possibles.

What if the conditions were:
Infinite engine power to turn the wheels.
A perfectly non- slipping clutch between engine and rear tractor axle.
Unlimited grip of the tires at the ground engagement point.
All members are unbreakable. and pivot or slide without friction.
The load object is UNMOVABLE.

What happens when the clutch is let out and the load is secured by way of "the properly located and installed standard drawbar below the level of the rear axle center." ?

Interesting mind game there. Lets posit a large CUT with rears about 5' dia and drawbar at about 19" height that will touch ground with a backtip of ~45 degrees. Very heavy duty HST that works perfect at any angle.

Very little motion is possible so even slo mo will be quick.

Tractor will move about 1" to account for elasticity, then stop as the front rises while the rears continue ahead.
The drawbar is being rotating under and must pull the tractor backward as it does. The only way this can happen on steady forward turning drive wheels is for the tractor to tip back so quick that the wheels roll relatively backward as it happens.
As the tractor goes higher the drawbar will pull it backward faster until ~90degrees, then that effect will slow. But we now have an an extremely small backtipping lever (drawbar at ground) still being acted on irresistably by the forward wheel force on an upended "balanced" tractor. Forcing the small lever favors a geometric increase in tip rate to keep the net wheel motion backward.
Itll probably hit the ROPS so fast at around 100degrees the wheels will come up, and then fall over on its side.

JWR · Sep 28, 2025

SPYDERLK said:
Interesting mind game there. Lets posit a large CUT with rears about 5' dia and drawbar at about 19" height that will touch ground with a backtip of ~45 degrees. Very heavy duty HST that works perfect at any angle.

Very little motion is possible so even slo mo will be quick.

Tractor will move about 1" to account for elasticity, then stop as the front rises while the rears continue ahead.

The drawbar is being rotating under and must pull the tractor backward as it does. The only way this can happen on steady forward turning drive wheels is for the tractor to tip back so quick that the wheels roll relatively backward as it happens.

As the tractor goes higher the drawbar will pull it backward faster until ~90degrees, then that effect will slow. But we now have an an extremely small backtipping lever (drawbar at ground) still being acted on irresistably by the forward wheel force on an upended "balanced" tractor. Forcing the small lever favors a geometric increase in tip rate to keep the net wheel motion backward.

Itll probably hit the ROPS so fast at around 100degrees the wheels will come up, and then fall over on its side.

Cannot happen in the context of pulling a log with a farm tractor whose drawbar is below the center of the rear axle. Quite strange that with millions of tractors designed this way people are not aware of the reality. It cannot happen as described.

JWR · Sep 28, 2025

These comments are missing currently in this thread but show up in Spyder's post #42.

Originally CalG had asked what happens in these conditions:

Infinite engine power to turn the wheels.
A perfectly non- slipping clutch between engine and rear tractor axle.
Unlimited grip of the tires at the ground engagement point.
All members are unbreakable. and pivot or slide without friction.
The load object is UNMOVABLE.

What happens when the clutch is let out and the load is secured by way of "the properly located and installed standard drawbar below the level of the rear axle center." ?

Answer: the engine stalls. There is obviously no such thing as infinite engine power.

Aggie66 · Oct 1, 2025

All information is appreciated. I’ve been exposed to many different concepts and educated thanks to all. In the end I’ve decided to have a dozer move it.