J_J said:
As everyone should know, if you are picking up a load at or near the maximum, you may be able to lift and carry that load in a straight line. But as soon as you make a turn, the PT pucker comes into play. Why? You have changed the equalization for your machine and load. When you straighten out the PT, the pucker will go away. Essentially, when you turn, you are shifting the balance in favor of the load. Sad but true.
Exactly. There are two factors involved, and two ways to tip your tractor.
You can think of your PT as three point forces, with the front wheels as a pivot point. One point load is the bucket and its cargo. This includes some weight from the arms. There is a second point load at the rear of the tractor, aggregated from the engine, wheels, frame, wheel motors, wheel weights, gas tank, your butt, etc. The third load does not really do anything here, as we can view it as acting on the front axle - the pivot point.
When you move in a straight line with a load up front, you can think of your tractor as a see-saw. Its a simple lever. As long as the weight in back is sufficient to counterbalance the lever arm at the bucket, no problem.
What happens when you turn? You do two things. First, you shorten the effective wheelbase of your tractor. That lever arm to the rear of the tractor is now shorter than it was before. This may cause you to tip forwards. As you tip forwards, if the bucket is lifted high in the air, it gets worse yet, since the bucket load is now farther out in front of you. This makes for an effectively LONGER lever arm in front, making you tip even more.
When you turn, the rear load is no longer centered on the axis of the tractor. So now that big load out back is hanging off to one side or another, but also, the bucket acts as an uncentered load too. Once the center of mass of the tractor moves far enough to one side or the other (outside the wheelbase of your tractor) then you tip to that side.
John
