More is better...Less is better...

[herbenus]

This is an interesting thread. I'm tempted to let the fluid out of my tires and build a ballast box. I did a crude force model and it showed I'd need 6000 pounds, 3 feet from rear tires, to lift front axle. It's only at this that front axle load goes to zero. Now you guys can get out your tape measures and if you know where your CG is, you can get a better number. But this tells me I'll need a lot of ballast to really have much affect. And of course, we don't want front axle forces to go to zero...

Having said all this, I still believe there is a benefit in using ballast box, or implement, as opposed to fluid in tires.

Since I'm rambling anyway, imagine you load up loader with enough rocks, or hydraulic force, to lift rear. Then yes, all weight is on front. Now add enough ballast in box to just bring rear back down. At that point, all load is still on front. You then have to add a bunch more to decrease front axle significantly, by pivoting on rear. I know this was all already stated earlier. Just a different visual.

I think I will get out my tape measure and plug some real numbers into model. I think the CG is given in my manual. If not maybe someone can tell me where to find this.

Of course as someone stated, just make more trips instead of maxing out load and beyond.

 

[JATO_RaT]

Randall, great points and thoughts especially with regards to moment and the shock loads which as you mention do in fact exceed any load you could place on the tractor. The axles are being beefed up on Kubotas newest models but then, the loaders are increasing in load capabilities as well. Good comments... Rat...

 

[rdbrumfield]

Thanks Rat.

 

[Rick Jay]

<font color=blue>Say your tractor is stitting there and you put 1,000 lbs in the loader. How much does this increase the downward pressure on the front wheels? Looks like the front axle would feel more than 1,000 lbs.</font color=blue>

Bill, and others...

Even though the loader is in front of the front axle, the connection to the tractor is between the front and rear axles, so wouldn't the rear axle carry some of the weight. Obviously, if the rear axle is up in the air, the front gets it all.

Just asking, these types of problems in Mechanics class used to drive me nuts. One of the reasons I went into Electrical Engineering instead.

~Rick

 

[rdbrumfield]

Rick; think of it a a teeter toter with the front axle as the pivot. the more weight on the bucket the less on the back, and the added weight of both transferring to the front axle.

 

[frank_f15]

i guess this is a question that could go on for ever. i don't know the corredt ans. but my feelings are the loader will only lift so much weight, and the rear should stay on the ground, the only time my back end(tractors back end that is/w3tcompact/icons/smile.gif) is if i hook a root or go into a dirt pile off center or on a grade. now transporting a load in the fel , then a heavier rear end would help. hope i got across what i am thinking?

 

[Hoeman00]

I've carried HEAVY loads on my Deere 710 loader
(close to 10k), when doing this I extend the hoe
back and drop the boom.
My 710 has a wt. balance of 90% rear 10% front
w/o load.
On a CUT w/ hoe extend the dipper stick and
most will lift front wheels off ground w/o load in bucket.
So w/ no weight on front wheels when u load bucket
u are carrying just that weight.
I go for rear ballast.
This is web site to Nebraska tractor tests, I don't see
CUT tests, they give the CG and many other specs
for ag tractors.
http://tractortestlab.unl.edu/index.htm
Does anyone else test CUT ?

 

[WVBill]

<font color=blue>"Having said all this, I still believe there is a benefit in using ballast box, or implement, as opposed to fluid in tires.
</font color=blue>

Except that as pointed out, balast in the rear tires does not increase the weight carried by the rear axle. Nor, for that matter does it have any effect on the weight carried by the front axle - UNTIL weight in the FEL tries to lift the rear off the ground. THEN the weight of the tire ballast begins to be felt by the rest of the tractor (what proportion is felt by the front v.s. the rear I'll leave to the physicists).
The point is that ballast in the tires v.s. hanging on the 3 pt is:
1) there always in terms of increased rear wheel traction
2) not there until needed in terms of additional weight on the tractor axles.

... I think...

 

[hazmat]

Bill,

Nice to hear from a fellow Mech E. While you're crunching the numbers sketch up a Free Body Diagram, A picture is worth a 1,000 words. Also run some calcs on a 10, 20 & 30 degree slope. I'd help you out, but I'm a bit busy right now.

 

[Anonymous Poster]

Looks to me now that the center of gravity of the tractor+attachments tells the story.

The center of gravity is usually somewhere between the two axles. IF it get in front of the front axle, due to a heavy loader load, then the tractor tips forward and lifts the rear wheels off the ground.

If the CG gets behind the rear wheels, the point of no return in a back flip situation, the tractors tips backwards on its own.

One can picture the effect of adding weight to the tractor. It will cause a change in the position of the center of gravity. Add weight to the front, and the CG will shift to the front. Add weight to the rear and the CG will shift to the rear.

The amount of weight being supported [percentage wise] by the axles will be relative to where the CG is. If we add weight to one end or the other, this will cause the center of gravity to move towards the added weight. And a greater percentage of the total weight will be supported by the axle at the end where the weight is added.

Without doing some calculations I don't know for sure if adding weight to one end actually decreases the weight being supported by the axle at the other end...my guess is that it does...anyone know for sure?

Now...what about the angle of the slope the tractor is sitting on? /w3tcompact/icons/laugh.gif/w3tcompact/icons/laugh.gif/w3tcompact/icons/laugh.gif Just joking...

Bill in Pgh, PA