fill ag tires @ 50% or 75% for lowest Vertical Center of Gravity (VCG)?

[ovrszd]

Well, gravity only ever points straight down, so weight will point that way no matter where you put it. That will never change.

In terms of front loader counterweights and ballast, there are several factors at play, and two pivot points to be aware of.

Putting liquid in the rear tires (or using wheel weights) is a very easy way to stabilize a tractor when any implement/weight is installed forward of the front axle. Doesn't matter if it's a front loader or a snowplow or something else, when it's in the air it has leverage about the front axle and will reduce the downforce and traction of the rear wheels. If you want to counter that effect, then liquid in the rear tires is a very simple and easy solution to fix those problems. It doesn't have to be a lot of liquid, because the liquid's lever arm to the front axle is long, generally a lot longer than the lever arm of the front implement to the front axle.

The problem with the above approach is that it doesn't take weight/load off the front axle. But we're just talking about empty implements and doing it with the goal of restoring downforce and traction to the rear wheels to what they were prior to installing the front implement. And we can make a fair assumption that the tractor manufacturer has sized the front axle and wheels to carry the load of those front implements.

Counterweight *behind* the rear axle becomes important when you carry additional load in the front implement, say a load of dirt in the front bucket. It's that scenario where we now need to offset the weight and leverage of the load, and we also want to reduce load on the front axle and tires. The only way to do that is to make the rear axle become the pivot point for the levers. That is why we go with rear ballast boxes or counterweights. Their position behind the rear axle creates a moment (force x distance) that will offset the moment created by the load in the bucket.

All weights on the tractor will always act straight down, and all weights on the tractor can have leverage relative to the pivot points of the front and rear axles. This is important to visualize. Weights over axles will improve downforce and traction of the wheels on that axle but they won't generate moments about that axle. But they will generate moments about the other axle.

Very well written!!!!

If we remember nothing else out of this, be it this, the fulcrum when using a loader is NOT the rear axle. It's the front axle.

Any weight added rearward of the front axle becomes counter balance. Even the operator.

Any weight added rearward of the rear axle adds counter weight to the rear axle.

Back to the original intent and question of this thread. Rear wheel weight adds stability to the tractor. Effective stability. The weight added to the rear wheel above the axle only becomes a negative when the side slope is very severe. By that time you won't care whether the tire is 75% full or 50% full.

 

[ovrszd]

If you add 650 lbs of fluid in a tire, you make that tire weigh 650 lbs more than it did before. That weight, when used as ballast, is hanging off the axle as the rear of the tractor is being lifted. There is no front/behind, it hangs off the axle.

Yep. Somehow that is being misunderstood by BrokenTrack.

 

[ruffdog]

Yep. Somehow that is being misunderstood by BrokenTrack.

I think brokentrack wants to change the fulcrum by moving the location of the weight. Weight on the rear axle helps if only the front axle is the fulcrum. Hanging weight to the rear of the rear axle moves the fulcrum to the rear axle...sort of.

 

[ovrszd]

I think brokentrack wants to change the fulcrum by moving the location of the weight. Weight on the rear axle helps if only the front axle is the fulcrum. Hanging weight to the rear of the rear axle moves the fulcrum to the rear axle...sort of.

Yep. The "subject" got changed in the midst of defending a position.

 

[mtsman2]

I had to get out of this thread. It went waaaay off track. Some posters (BT) actually did not read or understand the original question, then ridiculed me, then contradicted themselves from one post to the next, then posted irrelevant information, then posted incorrect information. How could anyone have thousands of posts and still not have correct information?? Can you imagine a new person reading this information? I am not an expert but I just want be safer and I paid attention in math class.

I am sorry for the confusion. I just wanted to know if 50 or 75% fill was preferred for better VCG, while static on a slope, no load in the bucket. i went back a year or two and did not find any info with this specific topic. yes, tractor moving on a slope adds many additional factors and I did not wish to get that complicated. Fortunately, posters such as OVRSZD, ACZLAN, S219, RD & HP were able to keep it on track and give me good information about my question. OVRSZD understands what I am asking and I am going to read his posts multiple times. Basically if I get into a sketchy slope situation by the time the effect of a lower VCG by using 50% fill (vs 75% fill of which 25% may be above the VCG) comes into play its going to be too late anyway. TY all.

I use my post hole digger to plant my chestnuts on rocky, gravely slopes. most times I drill with the tractor perpendicular but sometimes I have go semi parallel to a slope to drill. The tractor is NOT moving, STATIC! And I still had other posters who chose not to listen and tell me 'all theoretical discussions are moot without the tractor moving', lol.

yes, the PH digger can place unusual moment arms of torque on the 3ph at any given time and these are all unknowns. So I have done as much as I can to attempt to prevent an unknown from potentially causing a rollover. I have spacers, wheel weights + filled rears and I drill slow. Be safe out there.

 

[ovrszd]

I had to get out of this thread. It went waaaay off track. Some posters (BT) actually did not read or understand the original question, then ridiculed me, then contradicted themselves from one post to the next, then posted irrelevant information, then posted incorrect information. How could anyone have thousands of posts and still not have correct information?? Can you imagine a new person reading this information? I am not an expert but I just want be safer and I paid attention in math class.

I am sorry for the confusion. I just wanted to know if 50 or 75% fill was preferred for better VCG, while static on a slope, no load in the bucket. i went back a year or two and did not find any info with this specific topic. yes, tractor moving on a slope adds many additional factors and I did not wish to get that complicated. Fortunately, posters such as OVRSZD, ACZLAN, S219, RD & HP were able to keep it on track and give me good information about my question. OVRSZD understands what I am asking and I am going to read his posts multiple times. Basically if I get into a sketchy slope situation by the time the effect of a lower VCG by using 50% fill (vs 75% fill of which 25% may be above the VCG) comes into play its going to be too late anyway. TY all.

I use my post hole digger to plant my chestnuts on rocky, gravely slopes. most times I drill with the tractor perpendicular but sometimes I have go semi parallel to a slope to drill. The tractor is NOT moving, STATIC! And I still had other posters who chose not to listen and tell me 'all theoretical discussions are moot without the tractor moving', lol.

yes, the PH digger can place unusual moment arms of torque on the 3ph at any given time and these are all unknowns. So I have done as much as I can to attempt to prevent an unknown from potentially causing a rollover. I have spacers, wheel weights + filled rears and I drill slow. Be safe out there.

Thank you for the update. Hopefully you will benefit from information given here.

Threads often "drift". Just have to wade thru it to find information that helps you.

Sorry for any confusion in this one.

 

[zzvyb6]

I only fill to 50%.

1) IThe ride is so much better with some air to compress inside the tire. This also reduces the chance of a blowout and the fluid from being compressed into the carcass.

2) The tractor cg is usually pretty close to the crankshaft centerline. That's pretty much the same as the rear axle centerline. So Any fluid above the axle shaft hurst ; any below helps.

3) It's easier on the clutch, transmission and rear gears because it doesn't contribute as much to the rotational inertia.

4) Its easier to dismount or change the track width with a lighter tire than a heavier one. And if its too heavy, it can be drained out and refilled. With iron weights, it takes another tractor with a loader of a heavy jib crane to mount them on the axle.

 

[California]

A perspective that I visualize, that I haven't seen mentioned. This would be one element of a theoretical analysis:

A loaded tire is exerting (some) anti-rollover force until you are tipped sideways so steep that the weight of the tire is now downhill of the tractor's CG.


(After thinking about this a lot I bought a $700 ROPS for the Yanmar as soon as they became available).

 

[Hay Dude]

I only fill to 50%.

1) IThe ride is so much better with some air to compress inside the tire. This also reduces the chance of a blowout and the fluid from being compressed into the carcass.

2) The tractor cg is usually pretty close to the crankshaft centerline. That's pretty much the same as the rear axle centerline. So Any fluid above the axle shaft hurst ; any below helps.

3) It's easier on the clutch, transmission and rear gears because it doesn't contribute as much to the rotational inertia.

4) Its easier to dismount or change the track width with a lighter tire than a heavier one. And if its too heavy, it can be drained out and refilled. With iron weights, it takes another tractor with a loader of a heavy jib crane to mount them on the axle.

Agree with everything but #4.
I can put 100lb wheel weights on without a crane. If they’re over 100, 2 guys can do it in a few minutes with an impact wench. Also, it’s not necessary to remove cast weights if the tires need to be replaced. If fluid filled, the fluid needs to be removed & replaced. More time consuming.

 

[LouNY]

Agree with everything but #4.
I can put 100lb wheel weights on without a crane. If they豎*e over 100, 2 guys can do it in a few minutes with an impact wench. Also, it逞ｴ not necessary to remove cast weights if the tires need to be replaced. If fluid filled, the fluid needs to be removed & replaced. More time consuming.

My weights are 300# each, a bit much to manhandle;


That said, yes non liquid filled tires are much easier to dismount and repair.

Also I am fairly certain that Titan Tire in their tire book recommends only a 40% fill when tires are liquid filled.