You need balast or you will trash your front axle!!!! really?

[murphy1244]

A safe bet Murph

I ain't ended up in Oz yet but you never know. My manual states to have 1045 lbs on the back. How about yours? Well I think we use the same book?

 

[gladehound]

I'm not an engineer but I did take several years of physics in high school and college. Maybe the laws of gravity and deflection have changed since then.

Perhaps I've said it wrong.

The lift cylinder anchor point to the tractor is where the weight is actually lifted. The further back that lift point, the further back the weight is applied to the tractor. I incorrectly stated the pivot point of the loader.

With the skid steer, the pivot point is over the rear axle so the lift point of the cylinder can be further back so more weight can be supported by the rear axle (actually spread the weight more evenly over both axles by moving the weight to the rear).

If people say that is wrong, then it's a matter of semantics or you guys are all nuts!

After 150 round robbin posts, I have no doubt! We're ALL nuts! :laughing:

Some of us are right and nuts. Some are wrong and nuts! :laughing:

You are right that the lift cylinder pushes on the tractor. At the same time the lift arm pulls on the tractor. This creates a torque on the loader frame and tractor frame. This torque pushes the front axle into the ground and removes weight from the rear axle.

If you move the loader arms back, the same amount of torque would remove less weight from the rear and add less weight to the front compared to the loader arms being more forward, because the torque has to act on a longer lever arm to the front axle (pivot point).

However, if the load in the bucket is kept a constant distance in front of the front axle, it will affect unweighting of the rear axle and weighting of the front axle the same way regardless where the loader attaches to the machine. This is because moving the loader attachment back, adds and equal amount of length to the loader arms as it does to the distance from the loader mount to the front axle. The longer loader arms increase torque on the loader frame / machine frame given the same weight on the end of the loader. And these two factors (increased loader arm length and increase distance from lift point to front axle) cancel each other out. The weight change on the front axle is the same. Note: this example assume the loader itself has no weight. obviously it does, and for this reason having more of the loader closer to the rear axle will in and of itself change the weight distribution. But it will not change the effect that any weight added to the bucket has on weight transferred to the front axle (except that you will now be able to transfer more before you tip)

 

[4570Man]

I'm not an engineer but I did take several years of physics in high school and college. Maybe the laws of gravity and deflection have changed since then. Perhaps I've said it wrong. The lift cylinder anchor point to the tractor is where the weight is actually lifted. The further back that lift point, the further back the weight is applied to the tractor. I incorrectly stated the pivot point of the loader. With the skid steer, the pivot point is over the rear axle so the lift point of the cylinder can be further back so more weight can be supported by the rear axle (actually spread the weight more evenly over both axles by moving the weight to the rear). If people say that is wrong, then it's a matter of semantics or you guys are all nuts!

Why can you still tip a skid steer? The distance between the load and the front axle is the only thing that matters. My tractor loader mounts behind the front axel, but still lifts the rear axle when I put a load on the loader. I have a subframe mounted backhoe, but can still lift the front axle off the ground.

 

[ovrszd]

Okay, I can't stand it any longer. I'll take a stand on the skid steer example.

The loader arms on the skid steer must mount at the rear of such a compact machine to get arms long enough that it can raise the bucket to an acceptable height. If the length of the arms is mandatory and you hinged them at the front of the machine the bucket would be 5 feet farther forward from the machine. All practical design features would be lost.

With the SS bucket as close to the front tires as possible, and the hinge point as far rearward as possible, it can still stand on it's nose if the bucket is overloaded. Been there, done that many times.

I might as well dive in with both feet. There is a situation where adding rear ballast adds weight to the front tires rather than removing it........

 

[CalG]

oldpilgrim

Think about what you are saying objectively.

The typical tractor has two axles . ALL LOADS CARRIED BY THE TRACTOR ARE CARRIED ON THOSE TWO AXLES. regardless of where the lift points. pivot points, etc of the load supporting mechanism (FEL) are located. The tractor may as well be a solid beam with a single sliding weight on it. Move the weight anywhere on the beam and measure the weight on both axles.


Try to look at the example the same way that centers of gravity (CoG) are described. A LOCATION that is equal to ALL THE MASS were located (concentrated) in a single point.

Forces such as weight work the same way.

 

[gladehound]

I ain't ended up in Oz yet but you never know. My manual states to have 1045 lbs on the back. How about yours? Well I think we use the same book?

Mine says 1047 (because 1046 is too little and 1048 I too much) :laughing:

Despite the precision of listing the weight to the pound, they fail to give any recommendation on how far back the weigh is! And that makes me chuckle!

 

[jenkinsph]

4) The 'Math' behind all of this jaw boning would be taking Moments (force times distance) from any convenient single point in the side view and summing them up. Same analysis used to figure out where a previous threadster's trailer axle needed to be in order to reduce his tongue load. Yes, you need to include the tractor's wheel weights, center of gravity and total weight, loader content weight, ballast box weight and the distances from each point mass to the chosen central moment point. Then its just sophmore High School algebra.

I agree with this^^^^^^
While I have found this thread to be entertaining to read the above paragraph is the correct way to solve the problem. At least that was the way I was taught in structures class in school.

 

[ovrszd]

Mine says 1047 (because 1046 is too little and 1048 I too much) :laughing:

Despite the precision of listing the weight to the pound, they fail to give any recommendation on how far back the weigh is! And that makes me chuckle!

I can usually tell in the tractor seat when I've reached the magic number.

 

[CalG]

Okay, I can't stand it any longer. I'll take a stand on the skid steer example.


I might as well dive in with both feet. There is a situation where adding rear ballast adds weight to the front tires rather than removing it........

As covered in several previous posts, the rear counter weight can not add weight to the front axle, but it can add to the forces experienced by the front axle when a heavy weight is carried forward of the front axle. The example would be "lifting" a heavy object with the FEL while rear counter weights are in place. Ballisted tires or add on wheel weights will do the same. It's all been covered over and over. Weight behind the axle is just another case of the same thing.

There is really no front or back in these considerations. If the tractor were completely symmetrical with a CoG located at the midpoint between the two axles, loads at one end would be reacted at the other in exactly the same way. Vis a Vis ;-)


Might be a handi piece of equipment ;-)

 

[4570Man]

Mine says 1047 (because 1046 is too little and 1048 I too much) :laughing: Despite the precision of listing the weight to the pound, they fail to give any recommendation on how far back the weigh is! And that makes me chuckle!

Yeah. 1047 on the 3 point hitch won't provide nearly as much ballast at the end of a 8' boom pole.