Wheel weights add stress to axles or bearing?

[MikePA]

Did you mean to say that extra weight on the back adds stress to the REAR axle? I suspect so...

No, that's what I meant to say, but maybe I am wrong.

If there isn't enough rear weight, the back end rises up and the pivot point is the front axle. In a perfectly balanced tractor (tractor ballet? ), as you raised a filled FEL, there'd be a corresponding and equal rise at the backend. With both the FEL and the rear end off the ground, the front axle is supporting the entire tractor plus the contents of the FEL. This weight transfer to the front axle still happens as you add rear weight to keep it on the ground, the tractor attempts to pivot around the front axle.

To use a playground example...What would happen if you kept adding equal weight to both ends of a see-saw. Eventually, if the board were strong enough, the support in the middle would break.

 

[Superduper]

No, that's what I meant to say, but maybe I am wrong.

If there isn't enough rear weight, the back end rises up and the pivot point is the front axle. In a perfectly balanced tractor (tractor ballet? ), as you raised a filled FEL, there'd be a corresponding and equal rise at the backend. With both the FEL and the rear end off the ground, the front axle is supporting the entire tractor plus the contents of the FEL. This weight transfer to the front axle still happens as you add rear weight to keep it on the ground, the tractor attempts to pivot around the front axle.

To use a playground example...What would happen if you kept adding equal weight to both ends of a see-saw. Eventually, if the board were strong enough, the support in the middle would break.

I hear what you're saying. However, in practice, it probably isn't quite as simple as a playground see-saw with a single fulcrum point. There are multiple fulcrums in the front and rear axles. If the rear ballast was not enough to offset the front weight, then yes, it is possible, even likely that the front axle could be the pivot/fulcrum point. But bear with me for a second here.... with sufficient rear ballast, wouldn't weight transfer occur with the result of transferring weight distribution to the rear. A rear biased weight distribution would thereby result in the pivot/fulcrum point to occur at the rear axle instead, which is where we want it to be? In other words, with sufficient rear ballast, wouldn't the rear axle become the pivot that would lighten the load on the front tires/axles? The key here is where is the weight distribution. In a typical tractor, the weight is distributed more towards the rear hence the need for large beefy rear tires, and small front tires. By installing and operating a loader, we cause the weight distribution to become forward biased and in the process, cause the pivot/fulcrum to move towards the front axle. By restoring the original weight distribution back to normal 30/70 or 40/60, or whatever the case may be, then the tractor rear axle would take the brunt of the weight, as it was designed to do. Try picturing what I'm saying.... I may be wrong, but if you think about it, I might be right!

Therefore, I believe that adding ballast at the rear will have the effect of taking weight OFF the front axle, rather than putting weight ON the front axle. The exception, however, is if the loader is overloaded beyond it's intended capacity (and ballasting recommendations/requirements) or gets caught on immovable object on the upstroke, then sufficient weight will transfer to the front again at which point the front axle becomes the pivot point! Darn!, did I just confuse the issue again?

 

[whodat90]

I belive you're right, but! With a notional 800lb load placed that far in front of the rear tires, how much weight would you have to hang off the back to counterbalance it? Something like a bushhog that hangs way out the back will make up for it's lack of weight with additional leverage, but a weight box or box grader that doesn't hang very far out from the 3pt has to weigh an awful lot to make up for it's lack of leverage. At some point you'd have to reach the point of diminishing returns where the tractor starts to be stressed (like that see saw) just from the sheer amount of weight you have hanging on it. Personally, I'd feel better if you figured out the max weight the front axle can carry and counterweighted the rear to give you about 80% of that load on the front when you have a max load bucket. Just seems like a nice round number.

Another thought that just occurred to me: If you have the rear ballasted enough that the rear axle becomes the fulcrum point, as soon as you dump the bucket you'll be steering with the cutting brakes.

 

[firemanpat2910]

sounds to me like we need to build a container under the tractor with seperate compartments,high speed pumps and weight sensors on all wheels, that would automatically change the ballance point. That is until the sensors mess up and we do handstands/wheelies and flips

 

[Superduper]

When all else fails, I'm thinking follow manufacturers recommendations. Surely some amount of research and testing went into the design and published recommendations. In this case, to counter balance the loaders weight and 1650 lb capacity for the 300cx loader, the manufacturer recommends:

A: Filled rear tires with CaCl solution to 75%. Estimated weight 600lbs.
B: 3 Wheel weights per rear wheel, at a weight of 52lbs a peice, or 312 lbs total
C: 1100 lbs at the hitch.
D: Mount front and rear wheels at the wide position.
E: Additional weight may be required under certain conditions.

All of the weight (2000 lbs. +/-) is at the rear tire or behind.

I don't believe you need to place all the weight behind the rear tires or else, as others have observed, the front tires will become quite skittish. The key is to maintain enough rearward weight bias to keep front weight within specifications and maintain safe operation. As you can see, the manufacturer specifications are quite specific. BTW, the published specification is for 3x20 tractors. Since this loader can be used on several other models, their respective numbers are slightly different.

 

[MikePA]

Darn!, did I just confuse the issue again?

Nope, at least I don't think so.

 

[Iowachild]

Man, there sure are a lot of folks into physics here., and this discussion has been entertaining to read, but I think Superduper said it best: "When all else fails, I'm thinking follow manufacturers recommendations." Well at least until the warranty expires.

 

[ovrszd]

When all else fails, I'm thinking follow manufacturers recommendations. Surely some amount of research and testing went into the design and published recommendations. In this case, to counter balance the loaders weight and 1650 lb capacity for the 300cx loader, the manufacturer recommends:

A: Filled rear tires with CaCl solution to 75%. Estimated weight 600lbs.
B: 3 Wheel weights per rear wheel, at a weight of 52lbs a peice, or 312 lbs total
C: 1100 lbs at the hitch.
D: Mount front and rear wheels at the wide position.
E: Additional weight may be required under certain conditions.

All of the weight (2000 lbs. +/-) is at the rear tire or behind.

I don't believe you need to place all the weight behind the rear tires or else, as others have observed, the front tires will become quite skittish. The key is to maintain enough rearward weight bias to keep front weight within specifications and maintain safe operation. As you can see, the manufacturer specifications are quite specific. BTW, the published specification is for 3x20 tractors. Since this loader can be used on several other models, their respective numbers are slightly different.

Very well stated. Another difference I think we get confused about is effect of adding weight to the tire/wheel versus adding weight to the 3pt.

Tire/wheel weight is the most effective because it puts the weight where it's needed, at the tire, without adding stress weight to tractor.

When we add 3pt weight to gain traction while operating a loader we add stress weight to the axles/bearings. It is also only useful when we have weight on the loader. Otherwise it becomes a detriment because of causing the front end to be light.

Knowing the difference is how guys with 2wd tractors such as Soundguy can effectively operate a loader. They fully understand how to add ballast weight to gain the maximum effectiveness. Everything they do is to effectively add traction to the rear 2 wheels.

Us 4wd guys just tend to grab any old attachment we can find to accomplish the task. "Neccessity breeds innovation."

 

[N80]

Man, there sure are a lot of folks into physics here., and this discussion has been entertaining to read, but I think Superduper said it best: "When all else fails, I'm thinking follow manufacturers recommendations." Well at least until the warranty expires.

I agree, and it kind of follows the old saying "when all else fails, read the manual."

The physics are very complicated and are beyond me, but I have noticed that the more time you spend with a tractor, the better idea you get of where the weight needs to be. You can tell when the tractor is balanced for any given task if you just pay attention. When I first got the tractor I was pretty oblivious to this sort of thing, but it didn't take long to be able to tell when it was to light in the back or the front. A little experience, a little common sense and a good understanding of the manual goes a long way.

 

[scott_vt]

If a tractor is worth its bacon, it will have enough built-in integrety to handle weighting.

I'd say not having enough weight to perform their intended duties would be a MUCH greater "ill effect".

Mornin Farm,
I think that statement pretty well sums it up IMHO !