Baby Grand hit it on the nail talking about CG. FarmWithJunk hit it also, but used another term besides CG.
You add ballast to change your Center of Gravity (CG). An example is extending a backhoe bucket straight out to move your CG aft on the tractor.
The photo below shows me moving a complete pine tree to the burn pile. I had to raise the loader up high to get the tree moving. The tree is way over the weight of my loader lifting the whole tree, so I drug it. With the loader this high, the rear tires starting lifting when I put it low range reverse.
I extended the backhoe and slowly drug it to the burn pile with no rear tire lifting. The CG moved aft to favor more weight on the rear axle.
My 7 foot loader bucket can handle 3900 pounds. The backhoe weighs 1600 pounds. However, numerous times I have had to extend the backhoe to raise a stump out of a hole.
Someone here mentioned the triangle of the CG or something like that on a slope. When you fill the rear tires and on a slope, the CG tends to stay within your "safe" center of gravity envelope. When you add ballast to the 3PH, you may have the ballast too high and it will move the tractor's center of gravity way to the downhill side and past the tires of the tractor. I am thinking of a weight box on the 3PH lifted here. Depending on the slope angle, this will cause the CG to help tip the tractor over.
Think of a pendulum hanging from the centerline of your tractor. As you go sideways up a slope that gets steeper, the pendulum will swing from directly under your tractor towards the downhill tire. The pendulum illustrates how your CG can move on a slope and cause a tip over.
You can read up on the center of gravity by researching weight and balance in aircraft.
hugs, Brandi
