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

[Rick Jay]

Yeah, I can picture that easy enough IF only the front axle were there. And I realize that the force of gravity from the bucket and contents is straight down towards the center of the earth.

Where I get a bit fuzzy in the whole analogy is that the bucket is connected to the loader frame which connects to a point mid-way between the front and rear axles.

The tractor will pivot around the front axle, but isn't atleast part of the applied force on the rear axle side of the pivot point, where the loader frame connects to the tractor?

I understand the force of the loader bucket pivoting the tractor around the front axle. What I'm not clear on is how much, if any, of that force is distributed through the tractor frame toward the rear axle.

Now you guys know why I went E.E. /w3tcompact/icons/smile.gif.

What I would love to see is a tractor with a scale under each wheel with an empty bucket and then again with a known load in the bucket. That should tell how the weight is distributed when the bucket is in the carry position.

I'm sure all the force must get transferred to the tractor frame, or else they wouldn't have to reinforce all that metal in the loader supports.

I should go dust off my old Statics/Dynamics book, but just the thought of that is bringing back some pretty horrid memories. Yuck.

Can we talk about tractor electrical systems instead? /w3tcompact/icons/laugh.gif

~Rick

 

[rdbrumfield]

the only down force on the rear tires from the loader is from carrying it. As soon as you start to apply weight to the bucket it start to lift the weight off the back tires. basically you are lifting the back of the tractor with the rear mounting points of the loader and shoving down with the front mounts.

 

[Maurice]

I finally saved enough to have 2 cents to add.

The way I can visualize it is laying a 2X4 over 2 blocks with the ends hanging over a foot or two. At this point both blocks are supporting equal amounts of weight. Add weight to one end, maybe the front, the front support will now have a higher percent of the over all weight on it. However if you add weight(balast) to the back end the percentage decreases even though the over weight being supported has increased.

Might be kinda simplistic, but does it sound right?

 

[Rick Jay]

O.K., I think I'm shaving some of the fuzz off my thinkin'.

The force due to the weight and any load in the bucket is downward at the bucket. Since this is on the opposite side of the pivot point (front axle) from where it's attached, the loader support brackets are actually exerting an upward force on the tractor frame. Thus it's trying to pivot the tractor about the front axle by lifting it from where the loader attaches to the frame of the tractor.

This lifting force is always there (unless the bucket is resting on the ground) whether the bucket is filled or empty. Obviously, more weight in the bucket increases this lifting force behind the front axle, thus "encouraging" the tractor to tip forward about the front axle.

I'm glad I went E.E.

~Rick

 

[MDNick]

Rick,

I can see your confusion, but it doesn't matter a darn where the weight connects to the tractor. What matters is where the weight is and how far from the pivot points (both axles). You could have 2,000 lbs 20' behind the rear axle bolted on a chunk of angle iron that runs all the way to the grill, and it's still the 20' behind the axle that matters. It's all a system of weights and balances, with the weight pointing mostly straight down (neglecting the negligble fact that the earth is a sphere and gravity points to the center, most CUTS aren't long enough for that to matter)/w3tcompact/icons/grin.gif.

My take on all this (yes, I have a phsyics degree) is fairly simple. As much weight on the rear end as possible. The more the merrier. Pile it on. Wheel weights and loaded tires are the best. If you are lifting the rear end off the ground, you don't have enough weight. Period. Even connected to an immovable object, you should run out of hydraulics before a loss in gravity. Yes, all weight picked up by the FEL is on the front axle, and lightens the rear end (which puts that rear weight onto the front axle). Conversely, all weight behing the rear axle is on the rear axle and lightens the front end. As stated previously, the rear is much beefier, so rear weight is good. Anything you can pick up with the FEL should not hurt or endanger the tractor. And with enough weight on the rear end, any weight in the FEL won't matter on any slope you would take the tractor on empty, within reason. At some point common sense has got to take over. If I have 1,000 lbs of ballast on the 3pt, and pile in (note that you must put it in by hand, my FEL couldn't pick this up) 2,000 lbs of lead in the FEL and take it over a 30 deg slope, I am going to have a problem. Well, I wasn't real bright and was asking to die. I had it coming. Most likely the world would be a better place without me.

Weight is good.
More weight is better.
As much as you can pile on (within intelligent reason) is best.

 

[Rick Jay]

MDNick,

Thanks, I've been mulling it around in my noggin' and it all makes sense now. I was just getting a bit caught up on the loader attachment. I knew it didn't seem right, but just took me awhile to reason it all out.

Actually, that's better than when I was in college. Back then I used to figure it out about 2 weeks after the test. /w3tcompact/icons/laugh.gif If I was this quick in college, maybe I would've gone M.E. Naaaaahhhhhh...... /w3tcompact/icons/smile.gif

~Rick

 

[rdbrumfield]

Just keep in mind that those little bolts-nuts between you legs that hold the front part of the tranny to the back part, actually only the top few are what is keeping the rig in one piece when you pile on all that weight. I have seen how ugly it can be.

 

[OkieG]

I am among those of you who would like to think that if the loader can pick it up, the rest of the tractor should be able to move it w/o undue wear and tear.

If I understand MDNick, I think he has it right. Any weight behind the front axle will help keep the back tires on the ground (using the front axle as the pivot point). The farther behind the front axle the weight is, the better able it is to keep the back tires planted (longer moment arm). As weight is added behind the rears on the 3pt, the rear axle becomes a pivot point, too.

If the rear tires are on the ground in the first place (even if they're light), 3pt ballast will actually lighten the weight load on the front axle, because the 3pt weight will use the rear axle as a pivot to lighten the front.

So, filled tires and rear tire weights will help keep the rears on the ground, but will not lighten the load on the front axle like weight on the 3pt will.

OkieG

 

[Rick Jay]

Yup...I think that's the way I understand it. But what do I know? /w3tcompact/icons/laugh.gif

~Rick

 

[OkieG]

<font color=blue>Wheel weights and loaded tires are the best.</font color=blue>

Actually, in the context of a full loader bucket and concern about "overloading" the front axle, I may disagree with Nick on this one point.

Wheel weights and loaded tires are good, but 3pt weight might be better. /w3tcompact/icons/smile.gif Not only keeps the rears on the ground, but may ease the load on the front axle.

OkieG

 

[JohnMiller3]

<font color=blue>…Wheel weights and loaded tires are good, but 3pt weight might be better…</font color=blue>

Need both for optimum results… /w3tcompact/icons/smile.gif

The smaller the tractor (lesser mass) with a loader… proper ballast becomes an even more important issue…

Two things should be done…

1) by loading the rear tires either with liquid fill or use wheel weights or combination of both… this will make the tractor much more stable… (imagine tying a moveable anchor of say an additional 1500 lbs. to your COG)

2) use a 3-pt ballast weighted accordingly to take the stress and strain off the front tires and front axle (not uncommon to have 2000 lbs. hanging off the back)

With the right combinations of ballast, and while still maintaining control of your steering and keeping the front end on the ground… you will actually lift up and move a greater capacity of weight in your bucket than the mfr. spec’s indicate… /w3tcompact/icons/smile.gif

 

[OkieG]

Here is an interesting tidbid from another thread:
<font color=blue>we have had Deere start to balk on paying warrantys on frontend failures when no ballast is used on the tractor

IMPORTANT: Total ballast requirements consist of:
An optional choice for wheel weighting, plus
Mandatory 3-point hitch weight</font color=blue>

You can click here</font color=green> to read the whole post.

1/29/03 11:21 PM Addendum

Sorry to all who have tried the "link" in this post. It worked earlier this evening when this post was originally made (09:06 PM). The blue text is a direct copy/paste from the "link". The "link" post seems to have been deleted.

 

[OkieG]

John,

You beat me to it.

<font color=blue>Wheel weights and loaded tires are good, but 3pt weight might be better.</font color=blue>

And both are probably best. /w3tcompact/icons/smile.gif

OkieG

 

[herbenus]

Agreed. 3pt weight results in rear tires acting as pivot point, reducing force on front axle. Wheel weights or fluid ballast do not, although they do help to stabilize and keep rear down.

 

[cpicton1]

John,

I use wheel weights on my BX2200 Kubota. I also use rear ballast on the 3PH when using the FEL. I had been thinking of adding liquid ballast to the rear tires for extra weight and traction. I then discovered that the Operator's Manual warns against using wheel weights and liquid ballast at the same time. It says it could cause transmission damage. I imagine that the larger tractors can use both at the same time without worrying about that kind of damage but owners of the Kubota BX models should beware of doing so.

 

[19th_VA]

Just out of curiousity, what would be the upper limit of weight added to the rear tires? Both from the standpoint of the tires themselves and the tractor axle (though I guess there's not much wear on the axle since the weight is directed down?-I'm not a physics major!). I'm considering superflex, which adds 412 pounds to each tire. The tractor weighs about 3800 without the extra weight and is 35 hp.

 

[hazmat]

<font color=blue>Need both for optimum results…</font color=blue>

Well said John.

My manual states that the tires should be filled and or weighted and to add ballast to the three point hitch as well. It even goes on to state what the acceptable front / rear weight distribution is. I don't have it in front of me to quote exactly.

If I get a chance I'll sketch up a Fee Body Diagram showing what MDnick described.

Randall,
You are absolutely right, the front axle will last longer if you only lift what you can w/o using ballast. Problem is on the small tractors, they can't lift a usefull amount w/o the ballast. If my manual states to add weight, then I assume that they've designed the front axle to handle it for the servicable lifetime. Trouble is, how long is the service life?

Regarding the little screws that hold the tranny together. They are loaded in tension which is what screws do best. A grade 8 1/4" bolt will fail at around 4,000 pounds, a 3/8 will fail arounf 9,000# (per bolt). Yes tractors do split, but they are either grossly under-engineered or grossly abused.

 

[OkieG]

<font color=blue>Problem is on the small tractors, they can't lift a usefull amount w/o the ballast.</font color=blue>

Where ballast is real helpful is when lifting even a moderate load with bucket forks. The moment arm really magnifies the impact (leverage) of the item being lifted. It can make the rearend real light. I think that is a good demonstration (in reverse) of how effective 3pt counterweight can be at easing the force on the front axle.

A couple years ago our SAMs Club had broken up a section of parking lot concrete in preparation for installing gas pumps. A Deere TLB (probably a 310) was clearing the broken pieces from the parking lot to a dump truck. You know how little the front tires are on those commercial TLBs. The TLB operator dug his bucket deep into the concrete pile and began to lift. The concrete didn't budge, but his rear tires, including backhoe raised right up off the ground with no hesitation. Tires were a couple feet in the air before he eased them back down. Amazing power!...and amazing force applied to the front axle. I wonder if those commercial units have front axle trouble?

 

[rdbrumfield]

Yes, they do, I have seen the front spindles of a couple that had parted company of the axle.
Construction equipment takes a pounding that most homewoner folks would never put their cut through.
As an equipment operator, I do work my personal rig on the high end of it's capacity, that is why I don't fill the tires, just have the mower or tiller back there. I do make more trips, but haven't had any problems with the axle or noticed any oil seepage from the trans housings either. Like one fellow said."that's my story and I'm sticking to it."