Broke one of the most preached rules

[Reg]

The height of the draw bar only affects the initial tendency to rotate backwards.
At least in theory you could mount a draw bar to the top of your ROPs and if you could build it rigid enough and LONG enough it would also reach the wheelie limit when the tractor rotated backwards enough for the shackle to get down to ground level.
In PRACTICE it would have to be very long indeed to self limit at a reasonable wheelie angle and building it rigid enough and still light enough to be practical would be a challenge.
Obviously the C of G has to stay ahead of the rear axle's center line or it would in fact flip over backwards.

Draw bars below the axle just help us reach the point of self limit with very short draw bars.

BTW, I saw a few interesting wheelie skid shoes on some old pulling tractors at a tractor meet today.
Anyone else go to Rehoboth Mass ?
Today the garden tractors were pulling, but some of the big ones were already there for their pulls tomorrow.

 

[DWCox]

Wow, you guys are more daring than I am. Whenever I pull anything requiring a chain, I always make sure I have my large box-blade attached. It adds weight, stability, a place on top to hook the chain, and is one huge wheelie bar even in its highest 3-point setting (on my tractor, that is).

 

[tallyho8]

But what if it's on a conveyor belt?

Providing that the conveyor belt is going clockwise and the speed makes the wind velocity exceed the requirement for maximum lift, IT WILL TAKE OFF

 

[horse7]

Refer to the 2 images attached:
In image A the tractor is trying to go forward with the wheels spinning forward and is 6 feet from the immovable object.
In image B the tractors wheels are still spinning forward but the tractor is now only 5 feet from the immovable object where it would have to be if the chain were a consistent length and the front end was now lifted.

So your theory is that if the tractor produced enough torque going forward, the wheels would slip and go backward as the front end lifts?

When the tires slip, there is still a torque on the tractor around the rear axle. If the torque is sufficient to lift the front end even with the tires slipping, you have one of the preconditions for lifting the front end. Another pre-condition is that either the load can move [but would still have a sufficient force due to dragging] or the tractor can move.

What happens is that (ignoring smaller effects such inhomogeneous surfaces, elastic links, load movement, etc.). the tractor actually moves backwards with the tires slipping trying to pull the tractor forward, and the front end can lift off the ground.

Note that this can happen with MFWD and chains attached under the belly to the front of the tractor (one of the old styles I've heard of that some people swear by), it is just harder to do. Also harder with R4s with the lesser traction vs. R1 for a given surface...

It is possible to completely prevent the possibility of the tractor flipping backwards, by the simple expedient of never using it!

 

[Reg]

Refer to the 2 images attached:
In image A the tractor is trying to go forward with the wheels spinning forward and is 6 feet from the immovable object.
In image B the tractors wheels are still spinning forward but the tractor is now only 5 feet from the immovable object where it would have to be if the chain were a consistent length and the front end was now lifted.

So your theory is that if the tractor produced enough torque going forward, the wheels would slip and go backward as the front end lifts?

It does go backwards, but by such a small amount as to be unnoticed as the front end rises.
NOT a time to be sight lining up the barn and telephone poles to detect backward movement.
IS a time to throw the clutch, or get off the forward hydro pedal if so equipped.