Slopes and tractor tilt

[JoeL4330]

No one has addressed my FRONT wheel set out question. If the REARS are spaced out shouldn't the front wheels be out too? I found a site via E-bay that is selling spacers, various distances for $280-$350 or so. Good idea? I'm sure it will add some stress to the front hubs but so would a roll over Suggestions? I'm all ears hear...here..heere.. OK, I'll stop. thanks

Widening the front wheels certainly will improve things some and, as you note, increase stress on wheel bearings, etc.

However, widening the fronts when the rears are already wide does not improve things as much as you might guess...your "base", now, is a trapezoid and you are trying to make sure that the perpendicular (to the center of the earth) stays inside that base.

Right now, your CG is (probably) in the center of that trapezoid so that widening the fronts by, say, 6" only widens the portion of usual concern (in the middle of the trapezoid) by, say, 3" ...if the CG is more to your front, you gain a little more, and if it's toward the rear, you would gain a little less [think of that old farmall that had nearly a tricycle front end ...or, your child's tricycle, for that matter]

...but, whatever you do gain may just make the critical difference. It also may give you a little more courage ...which could be good, or could be bad.

My guess is that the reason we don't see more cases of sideways rollover in normal use (and, remember, we generally practice contour plowing) is that one's seat-of-the-pants message (pucker factor) kicks in before the tractor's design limits ...and, that's as it should be. [as on the tricycle, where the child generally falls off before the tricycle rolls over]

 

[RoyJackson]

trapezoid

See what I mean, TripleR?
Now, is that a cool word or what? THREE syllables too!!

 

[TripleR]

See what I mean, TripleR?
Now, is that a cool word or what? THREE syllables too!!

I think maybe I seen one of them things in a circus act once I did, yup I sure did.:laughing::laughing:

 

[The Haymaker]

First thing I noticed on reading the original post, and maybe someone has pointed it out, is mowing near maximum sidehill, plus diagonally down hill, is BAD. If I am working close, I always try to go either straight up or angled up.

The pivoting front end significantly raises CG and decreases stability.

My apologies if someone else has pointed this out, don't care to read 7 pages of safety poliza rants.

Never tested what FEL does to CG, but I take it off because 1: it's in the way and 2: I hate having it hammering away for the four hours it takes me to mow.

 

[Mistyridgefarm]

I believe I understand what you are saying; we agree that design can (and modern design does) leave the CG unchanged (with empty standard bucket in the carry position). I'm guessing we also agree that instability/rollover occurs when a perpendicular (to the center of the earth) from the CG falls outside the base. Where I have trouble is that your model says that no matter how much I load the bucket or how high I raise it with that load, the CG remains constant and the tractor will remain upright on a given (sub-critical) slope. Do I understand that correctly?

My intuition is that if I load the bucket and keep it below the CG I am less prone to tip...sorta like the toys I referenced in a previous post...or the tightrope walker with the long balance pole, whose arms are always in the same sockets. But, I'm always happy to learn something new.

Sort of. I was merely pointing out everyone. Is talking about cog and that the fel raises it. It does if you raise the loader above the connection points. It is the lever you must consider. There is something to the point someone made about taking weight off the rear. Since the front pivots it is all about rear weight and width. You can almost mow a verticle slope with dials.

Load your tires, go slow. Most of the time, your uphill rear wheel will start to slip or your front end will want to slide downhill when you are approaching tip over.

That being said, a good 4wd tractor with proper ballast going up and down is the best way. Untill my other house sells, I'll have to be content with side hill work with the 2wd and taking it easy. I have one slope I can only do half with the big JD and mow the rest with the little one, I can hang off the uphill side and just about mow anything unless the front slides.

Btw- i never take the fel off the 5300. Just keep it lower than the mount points. My tires are loaded max. Almost forgot, there is also a difference if you use pull type or 3 pt. The pull keeps almost constant weight on rear where the 3pt takes off a lot of it when you lower to the tailwheel.

Every Tractor is different. That is why most of mfrs will not put a rollover spec. If you think it is too steep, then listen to that little voice. That us the best advice I can offer.

 

[SPYDERLK]

TK100M slope question

This formula gives the limit of stability slope angle;
limiting slope angle = arctan (1/2 the rear wheel track/vertical height of the cg).
In this case, the limiting slope angle was 36.3ｰ assuming no other loads on the vehicle. If you hit a bump and it tips the tractor slightly down slope, you could tip over at a lower slope angle.

This gives you an upper limit on stability. Given that tractors often operate on a rough ground, you really wouldn't want to operate at this limiting angle. I would limit myself to oerating at a maximum of 80% of this angle and keep my speed down to preclude big tipping from rough spots. You can also increase the track of the rear wheels and gain some stability.
Iif you know the effect of the loader installation on the verticle height of the cg, you can compute the limit for a tractor with a loader installed.

hope this sheds some light on the discussion.

Only if the CG is directly over the rear wheels on a tractor. -- An impossible situation since it would back flip. You have to allow for the longitudinal position of the CG as well, and since its well forward of the rear axle its going to reduce resistance to sidetip. A tractor always simulates a tricycle. No stability contribution from the front.
larry

 

[Jeffnew]

So this all seemed like a nice theoretical discussion until it happened to me. I was moving some smallish boulders (200-300 pounds) across a shallow slope that I've navigated several times in my BX2660 while mowing. It's maybe a 5% grade left to right.

Except I've never done it with a boulder. I was keeping the bucket close to the ground, and still felt the rear uphill wheel lift off. I was able to bang the bucket down onto the ground and get everything stabilized... and then I just sort of pushed the boulder the last 50 feet. And no, I didn't have a ballast box attached -- that was to be my next purchase. My daughter told me the uphill wheel was almost a foot off the ground by the time I noticed and pushed the FEL down.

This brought the whole front/rear distribution debate into very sharp focus. This had nothing to do with the vertical CoG (the bucket was maybe 6" off the ground) and everything to do with how unloaded the rear wheels were.

Fortunately no injuries and no damage and I'm thankful that I learned this lesson the easy way.

 

[k0ua]

So this all seemed like a nice theoretical discussion until it happened to me. I was moving some smallish boulders (200-300 pounds) across a shallow slope that I've navigated several times in my BX2660 while mowing. It's maybe a 5% grade left to right.

Except I've never done it with a boulder. I was keeping the bucket close to the ground, and still felt the rear uphill wheel lift off. I was able to bang the bucket down onto the ground and get everything stabilized... and then I just sort of pushed the boulder the last 50 feet. And no, I didn't have a ballast box attached -- that was to be my next purchase. My daughter told me the uphill wheel was almost a foot off the ground by the time I noticed and pushed the FEL down.

This brought the whole front/rear distribution debate into very sharp focus. This had nothing to do with the vertical CoG (the bucket was maybe 6" off the ground) and everything to do with how unloaded the rear wheels were.

Fortunately no injuries and no damage and I'm thankful that I learned this lesson the easy way.

I am glad nothing bad happened, and you were fast enough to get that bucket down, More people need to read your post, so many do not understand the danger in not having proper ballast. Not only is it dangerous, but without proper ballast, you are missing out on the full capabilitys of your tractor. You tractor will pull/push/lift more with proper ballast. Thanks for posting this.

James K0UA

 

[Jerry/MT]

Only if the CG is directly over the rear wheels on a tractor. -- An impossible situation since it would back flip. You have to allow for the longitudinal position of the CG as well, and since its well forward of the rear axle its going to reduce resistance to sidetip. A tractor always simulates a tricycle. No stability contribution from the front.
larry

The cg does not have to be over the rear wheels for this relationship to hold. It's just a simple static stability relationship. The assumption is that the rear track is the widest(and is rigid) and will react out tipping loads untill the line of action of the CG falls outside the rear track.(Front tractor axles usually pivot so they can't support a moment about the longitudinal axis.)
It 's not a complete dynamic analysis by any stretch of the imagination. I doubt anybody here has all the data to conduct one of those anyway. I merely offered it as a way to get an idea of the stability limit and no more. Moving across a rough slope introduces additional destabilizing loads that are not accounted for in this relationship.

 

[SPYDERLK]

I was talking lateral stability ... but coincidently, when the rear is unloaded you have no lat stability and longitudinal only against back tip. You can neither decelerate or negotiate a sideslope without setting the overhung front weight down.
larry

So this all seemed like a nice theoretical discussion until it happened to me. I was moving some smallish boulders (200-300 pounds) across a shallow slope that I've navigated several times in my BX2660 while mowing. It's maybe a 5% grade left to right.

Except I've never done it with a boulder. I was keeping the bucket close to the ground, and still felt the rear uphill wheel lift off. I was able to bang the bucket down onto the ground and get everything stabilized... and then I just sort of pushed the boulder the last 50 feet. And no, I didn't have a ballast box attached -- that was to be my next purchase. My daughter told me the uphill wheel was almost a foot off the ground by the time I noticed and pushed the FEL down.

This brought the whole front/rear distribution debate into very sharp focus. This had nothing to do with the vertical CoG (the bucket was maybe 6" off the ground) and everything to do with how unloaded the rear wheels were.

Fortunately no injuries and no damage and I'm thankful that I learned this lesson the easy way.

I am glad nothing bad happened, and you were fast enough to get that bucket down, More people need to read your post, so many do not understand the danger in not having proper ballast. Not only is it dangerous, but without proper ballast, you are missing out on the full capabilitys of your tractor. You tractor will pull/push/lift more with proper ballast. Thanks for posting this.

James K0UA

So that they can vicariously experience the realization that real life simulates theory?
larry