fill tires or not?

[xtn]

I don't think it moves it very much though. It's equivalent to "unsprung weight" on cars, which has minimal effect.

That post is wrong on a couple of levels.

Since a tractor typically has no suspension in the rear at all, any weight added into the tire - or with wheel weights for that matter - is effectively fixed in location relative to the rest of the tractor just as suitcase weights would be. In other words, the entire tractor is "unsprung weight," and acts like a rigid instrument regardless of where you add weight. The only exception is the front axle which pivots.

Even if the rear axle was "sprung," the weight would still have the same effect. It just wouldn't take effect until after the suspension bump travel was reached, that's the only difference.

xtn

 

[meburdick]

I realize that there is no suspension. That's why I quoted the phrase.

On cars, unsprung weight is anything added to the wheels, axles, or other points that do not float on the suspension. This is added in the same area, but can't be considered unsprung for the exact reasons you cited. Again, the reason for the quotes.

I wasn't stating that this is the term to use. I was using a phrase that many people know that would help them gain a better understanding of what I was trying to describe.

 

[xtn]

I realize that there is no suspension. That's why I quoted the phrase.

On cars, unsprung weight is anything added to the wheels, axles, or other points that do not float on the suspension. This is added in the same area, but can't be considered unsprung for the exact reasons you cited. Again, the reason for the quotes.

I wasn't stating that this is the term to use. I was using a phrase that many people know that would help them gain a better understanding of what I was trying to describe.

Gotcha. But then why state that adding such weight will have minimal effect? If you add weight to any rigid structure, it will change the CG directly and exactly in proportion to its distance from the previous CG and its weight relationship with the existing total weight. It's simple math and it's true for any added weight, be it suitcase weights, liquid tire ballast, an implement, or a few hundred pounds of used chewing gum stuck on the underside.

Moving the CG rearwards helps counterbalance a loader. Moving it downwards - the most effective method of which would be loading the bottoms of the tires - helps reduce the tipping angle of the machine.

 

[MossflowerWoods]

I jumped to the end...

FILL THEM!

My dealer uses "RV Anti-Freeze" it is potable and completely non-toxic in the event of a leak.

FILL THE REAR TIRES!

Enjoy the new tractor!

Be well,

David

 

[meburdick]

Gotcha. But then why state that adding such weight will have minimal effect? If you add weight to any rigid structure, it will change the CG directly and exactly in proportion to its distance from the previous CG and its weight relationship with the existing total weight. It's simple math and it's true for any added weight, be it suitcase weights, liquid tire ballast, an implement, or a few hundred pounds of used chewing gum stuck on the underside.

Moving the CG rearwards helps counterbalance a loader. Moving it downwards - the most effective method of which would be loading the bottoms of the tires - helps reduce the tipping angle of the machine.

I was thinking that you're adding weight both above AND below the center of the axle, so the effect on moving the center of gravity is not "profound". At the same time, by adding the raw weight to the outboard portion of the axle, you are increasing the moment arm on the outer edges and requiring more counterforce to tip the machine. If you were to hang an equal amount of weight directly under the machine's current COG, so that it almost touched the ground, it would have more impact on moving the COG but much LESS impact on reducing tip.

 

[vtsnowedin]

This is a interesting statics problem but it has been thirty five years sense I sat in a classroom so I'm a bit rusty. If you look at the point where the axle enters the rim of the tire and resolve the forces there. You have the weight of the machine ,cab and operator as a force down and an equal reaction force coming up from the ground through the tire sidewalls and the rim. Add liquid ballast in the tire and it is a force down that reacts through the tire sidewalls and tread contact patch. The only extra load to the axle is the few square inches that are directly over the axle so perhaps 95 % directly down not felt in any way by the axle. Try to tip the tractor over and the whole weight of the tire ,rim and ballast becomes a weight hung on the end of the axle that has a lever arm equal to the distance to the point the tractor is rotating around. That would be the tire that fell into a hole. So you have weight that doesn't load the tractors axles in normal operation that comes into play automatically anytime a tire tries to lift.
Then consider a ballast box on the 3PH. That weight hangs off the draft links and levers against the rear end trying to raise the front end. The load resolves as a force down at the end of the axles that the bearings and rim has to resist. Going over rough ground it will magnify the impact of every bounce. So from the point of view of you rear end and axle bearings I'd say that fluid filled tires are less stressful then a ballast box or bolt on wheel weights for that matter.

 

[xtn]

I was thinking that you're adding weight both above AND below the center of the axle, so the effect on moving the center of gravity is not "profound". At the same time, by adding the raw weight to the outboard portion of the axle, you are increasing the moment arm on the outer edges and requiring more counterforce to tip the machine. If you were to hang an equal amount of weight directly under the machine's current COG, so that it almost touched the ground, it would have more impact on moving the COG but much LESS impact on reducing tip.

True.

 

[SPYDERLK]

Water is the way to go for the southern states. Do it at home ... convenient as air. Here in Virginia I use it in my 7520 -- a ton of weight for about 25 cents. Long about Christmas I start parking it in the manure pile, but this year wasnt cold enuf to require that even.
larry

 

[MossflowerWoods]

Water is the way to go for the southern states. Do it at home ... convenient as air. Here in Virginia I use it in my 7520 -- a ton of weight for about 25 cents. Long about Christmas I start parking it in the manure pile, but this year wasnt cold enuf to require that even.
larry

Larry,

REALLY!?!?!?!

My place just south of Fredericksburg gets down into the TEENS for most of the day, more than few days each winter.

I know it takes longer for a large volume of water to freeze than a small volume, but I'm amazed you don't have issues...

My tires are full of RV Antifreeze...

David

 

[meburdick]

It all comes down to what the temp of the *water* is. Even though the air drops to well below freezing, the water temp could remain at 35 or so as a result of heat entering the water from the tire, which came from the ground (which possibly isn't frozen).

I believe he also said he parks it in the manure piles when it's that cold, and that's likely how that extra tiny little bit of warmth is keeping the water from freezing.