Slopes and tractor tilt

[Jaylegger]

This brings up a thought I've had about the design of Most all ROPS, I'm sure the Manufactures and Safety Inspectors have their reason for this design, although inquiring minds want to know?
Why is a ROPS design with rounded/curved corners at the top?
seems to me that with this design a tractor could continue to roll as stated if on a hillside, as appose to one that would have 90% corners, or even some I've seen have the bar extend out past and over side uprights, Looks to me a square corner ROPS would limit the roll over to a simple side roll,
anyone care to elaborate on this round corner design?

In addition to any cost savings, the curved corners are less likely to snag or hang up on brush/trees and less likely to cause damage anything you may inadvertently come into contact with. Tee type corners may also present an impalement hazard should one get thrown from the tractor during a roll-over.

 

[Reg]

Right now I think I'm at about this point in my thinking on this;
A loader and bucket raise the center of gravity of MOST tractors - although a design that lowered it might be possible and "interesting", it isn't available to most of us (now).
The attached loader therefore makes the tractor more prone to tipping.
The forward weight bias is another factor in instability.

Ahh but...
There is always a "butt".
The earlier instability on a lesser grade MIGHT be preferable to later instability on a steeper grade, i.e. one might just KEEP OFF the really dangerous side slopes.
A slight tip, the threat of a rollover at a few degrees being preferable to an actual rollover on a very steep grade - even if you DID manage to mow an extra few thousand square feet before tumbling.

Having the bucket available to drop and provide a wide support base for the front of the tractor - vs the pivoting front axle - could be a saving factor.
I don't have enough data to do all the arithmetic on this - and in any case I don't have "text book" side slopes on which to gather data.

So, I will continue to leave my bucket on, I will continue to carry it very low, I will continue to have my hand on the joystick at (almost) all times, I will continue to bear in mind that I must steer DOWN the slope if/when things feel tippey - albeit at the modest angles that I am limited to.
Oh yeah, I will continue to pick up "stuff" that I find when mowing and bring it back in the bucket.

and that thing about the seat belt... I should probably USE it when the ROPS is up, whether I am on a side slope or not (-:

 

[TripleR]

Right now I think I'm at about this point in my thinking on this;
A loader and bucket raise the center of gravity of MOST tractors - although a design that lowered it might be possible and "interesting", it isn't available to most of us (now).
The attached loader therefore makes the tractor more prone to tipping.
The forward weight bias is another factor in instability.

Ahh but...
There is always a "butt".
The earlier instability on a lesser grade MIGHT be preferable to later instability on a steeper grade, i.e. one might just KEEP OFF the really dangerous side slopes.
A slight tip, the threat of a rollover at a few degrees being preferable to an actual rollover on a very steep grade - even if you DID manage to mow an extra few thousand square feet before tumbling.

Having the bucket available to drop and provide a wide support base for the front of the tractor - vs the pivoting front axle - could be a saving factor.
I don't have enough data to do all the arithmetic on this - and in any case I don't have "text book" side slopes on which to gather data.

So, I will continue to leave my bucket on, I will continue to carry it very low, I will continue to have my hand on the joystick at (almost) all times, I will continue to bear in mind that I must steer DOWN the slope if/when things feel tippey - albeit at the modest angles that I am limited to.
Oh yeah, I will continue to pick up "stuff" that I find when mowing and bring it back in the bucket.

and that thing about the seat belt... I should probably USE it when the ROPS is up, whether I am on a side slope or not (-:

Yes, there is always a "but or exception" etc. We NEVER removed the FEL on our CX80 as it was a bear to remove/install and never had anything approaching a close call. We have replaced it with a M8540 and mowed our entire property last year with the FEL and no issues. We will probably take it off this year some as some obstacles have been removed and sans FEL the tractor rides smoother and is more maneuverable.

On our BX2660 and L5030, I routinely remove the FEL.

 

[JoeL4330]

Interesting debates but I think several points are amiss. First, today's loaders are attached at only one place on the tractor, coincidentally just about perfectly in the cog of the maichine. That isn't a mistake. It distributes the weight perfectly. There is no change to the cog since all the weight is always loaded to the same points on the frame. What is changing is the torque arm of the loader weight. On a side hill, the height of the arms above or below the attachment points act as a lever. Same weight, same cog, just a longer lever. No different than swinging a backhoe up the hill. The weight is the same but th lever is moved longer and opposite the down hill side. The same but smaller thing occurs with the loader.

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.

 

[TripleR]

You guys are way smarter on this stuff than I, so I won't address that, my concern in adding weight on a FEL increases the likelihood of rolling a tire off and also takes weight off the much more stable rear axle. Added weight also increases the possibility of slip or crabbing creating ruts and adding a later hazard. I am sure I am missing something, but very interesting thread.

Oh, I am repairing flood damaged levees and am crossing slopes with a full bucket and it is scaring the heck out of me.

 

[RoyJackson]

You guys are way smarter on this stuff than I

Nah...we just think we're smart...toss in a few multi-syllable words (like mul-ti-syl-la-ble) to impress people

Oh, I am repairing flood damaged levees and am crossing slopes with a full bucket and it is scaring the heck out of me.

Be safe...I'd wager those levees are shifting around some...

 

[Boeing]

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

 

[RoyJackson]

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

There have been several threads on this subject...one within the last week or so. The SEARCH function is your friend, so give it a try.

This is one of those controversial issues. Some folks say "yes, widen the front end" and others don't think it's any help and will accelerate wheel bearing wear.
The front axle on a 4WD tractor pivots so widening the track would be a limited aid to stability. However, it can pivot only so far and that will happen as the tractor begins to cross a slope (rather then a sudden lurch to the side)...then it will hit it's stops and will not pivot further. So, you might see a degree of increased stability by widening the front track. But it won't help as much as widening the rear.

I did swap the front tires on my previous tractor and it did feel better...but that might have been more psychological then anything else. I haven't swapped the fronts (or spaced them out) on my current tractor as I don't think there would be any advantage to it.

So, you can try swapping your front wheels (check the rim to hub offset first to ensure you will end up with a wider track) and see what you think. The disadvantage is you may have to replace those wheel bearings sooner then expected.

 

[flusher]

They are filled, thank goodness. I have a lot of hilly terrain and old logging roads throughout the property. I know one of the best teachers is seat time and I plan on getting as much as possible.

My 10 acres is flat hayfield with ditches on two sides. However, I were in your hilly situation, I'd mow those hills using something like my 1964 MF135 diesel--a field tractor modified (i.e. lowered) for mowing orchards. The 28" dia rear rims were replaced with 16" dia rims that accommodate wider tires (BF Goodrich 18.4 - 16A 6 ply) and the front axle spindles were replaced with shorter ones to keep the tractor level.

The squat ratio of the 135 (track of the rear wheel to outside of the tire divided by the height of the axle mid-line) is 4.15. My 2008 Mahindra 5525 has 28" dia rear rims and the squat ratio is 2.84-- quite a bit more tippy than the 135. Larger squat ratio= lower CG = improved stability on slopes.



Rollovers are no fun and relying on the ROPS/seatbelt or the no seatbelt/baleout on the up-slope side method is asking for trouble IMHO.

 

[TripleR]

Nah...we just think we're smart...toss in a few multi-syllable words (like mul-ti-syl-la-ble) to impress people


Be safe...I'd wager those levees are shifting around some...

That sure is the truth, my pucker factor was pegged out. I just parked the tractor after hauling fill for two days to try to stabilize as best as I can in preparation for a full on assault as soon as it dries up and stops raining.

I may wind up renting something before it is all over or I may just have someone do the more difficult ones and concentrate on the others myself.

This is just one of them and it was taken before the last couple of rains and the hole is big enough to hold a compact car now. It also washed away a couple of truck loads of rock I had hauled in to use on my roads.

 

[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