In all seriousness, please do take the suggestions of the helpful and knowledgeable posters above who are correctly encouraging everyone to
use appropriate counter balance when doing loader, fork, or grapple work. It absolutely
WILL remove stress from your front axle and make the operation much safer. The only way to be able to utilize your loader's full lift capacities safely and with minimal undue mechanical stress is to have good counter balance/weight, especially if you have a lighter tractor with less built in weight. I love the diagrams and models too!
Also - please note that
1) ballast, and 2) counter weight/balance, are not one in the same. Loaded tires or axle weights provide
ballast which is additional weight on axles or ground, and this aids in stability, traction, etc... In order to properly use a loader, or a rear mower in a machine without a loader, one should apply weight either
rearward of the rear axle to counter balance the loader stress on your front axle, or perhaps
put suitcase weights on your front end to counter balance the tendency of the front end to lift off the ground when mowing or pulling a 10 ton trailer like the guy in the picture above.
It's not a simple concept and building a quick model might be helpful, and fun if you have kids! For those who are interested but are not physicists or engineers that understand this due to education and everyday application of force, vectors and moments, try this one on for fun.
Take two thread spools and tape Popsicle sticks across the top of each. You now have two teeter-totters. Next, overlap the Popsicle sticks a bit and tape them solidly together. You now have a representative model of your tractor. The spools represent the front and rear axles which are the
fulcrums, or pivot points. You can use your fingers to test loading scenarios and and use small weight scales to show how the moments and application of force at differing distances from the front or rear axles cause changes in the relative loading of the front and rear axles as you shift the center of gravity back and forth. Every time you lift either the front or rear spool you will have found the scenario that moves the center of gravity just past the opposite axle and then places all of the weight on that other axle/spool. You could put a ton of weight over and beyond the front spool, but as long as you apply a sufficiently heavy counter weight
past the rear spool, you will have
NO additional force imparted to the front axle. As others have correctly stated there are nuances when motion is introduced, but if properly counter balanced they will never cause problems. Only if there is a catastrophic shifting of CG (center of gravity) due to load shift, or perhaps your rear counter weight getting hung up on a hill or ditch would you see any risks. Operate safely and it should not be a major concern.
Proper counter weighting will allow you to break your loader frame before your front axle ever gives up, and that probably only happens if "bulldozing" where you can apply more force to the loader than it was designed for. Finally, to tie this together from a semantics standpoint, one can use "ballast" in a "counter weight" application. It's just that the ballast must be placed behind the rear axle, or perhaps in front of the front axle to be able to properly counterweight the forces affecting the opposite end when pulling a heavy trailer or rear implement.
Below is a good diagram that will demonstrate how your spool model will work. In Australia they recommend against filling radial tires for ballast... They also spell "tyre" wrong.
I still think liquid tire ballast is best for basic stability and traction, but I have not used a tractor with radials tires, so maybe there is a point there.
Stay safe all!
https://www.worksafe.vic.gov.au/__data/assets/pdf_file/0009/12240/140861_Chorus_WS_Tractor.pdf
