<font color="blue"> Of course, as stated, this is not possible as the load would HAVE to move or the tractor would have to slide backwards to allow the the drawbar to rotate underneath the tractor. The force from the load is pulling the front end DOWN. This is the simple physics of it </font>
I have come to the conclusion after reading different posts here at TBN that if the right conditions occur, it is indeed possible to have a tractor lift its front wheels off the ground when pulling something attached to the draw bar.
We all know that if the tires are locked to the ground, like if frozen in, or tied to something like a fence post at the rear of the tire, and the tractor is put into a forward gear, the tractor may rotate around the rear axle in a back flip.
But let's say chain is connected between the draw bar and a VERY large tree that is not going to move. Would a back flip be possible? Maybe. IF like Cliff said, the tractor could slide backwards a bit.
With great traction, two forces would come into play. One would be the tractor trying to pull forward, but since it can't move, and since it has great traction, it seems like it would want to rotate around the rear axle, lifting the front wheels.
But the draw bar being below the rear axle, would be offering a counter force to hold the front wheels down.
UNLESS the tractor could slide backwards. If the tractor can slide backwards, due to the mechanics of the system and the torque being applied to the rear axle, then the chain tied to the tree has a limited amount of holdback ability, so the draw bar has a limited amount of "counter torque" capability, and the tractor could/might/maybe tend to lift the front wheels and flip over backwards.
Some posts I have read here in the past made a believer out of me. I can see the possiblity, but don't know if I can prove it. Maybe someone else can.
One post that I remember described how when pulling a properly attached plow, the tractor being operated ran with the front tires up in the air. The farmer who owned the tractor came over to the guy operating it and asked him what he was doing. (sorry, can't remember the post, but it is here at TBN somewhere) He told the farmer it was the only way the tractor would pull the plow. Farmer tried to show him otherwise, but apparently the conditions were such that it worked the same way for the farmer...
Unlikely...perhaps so. Doesn't hurt to keep the possibility in the back of one's mind though... /forums/images/graemlins/smile.gif