How much side slope can my tractor handle?

[plowhog]

I was gathering up cut rounds yesterday. I was driving the big tractor with a trailer behind it; my friend the smaller SCUT. He has a little tractor time, and I told him to keep the bucket low, advised of tipping issues, etc.

Things mostly went well. Except he needed to take a bucket full of rounds to the trailer, and raised the bucket to maximum height and held it there traversing over the forest floor. Yikes. After he got it dumped I pointed out that if either front wheel found a hole, the tractor would be on its side (and him) faster than he could recover. So we dodged one yesterday.

 

[2manytoys]

I've read this thread with interest. One thing to remember is that on SCUTs and small tractors the seats are often above the rear wheels. The operators weight has a greater affect on these as for center of gravity and the more you weigh the higher the COG.

 

[ovrszd]

Very true.

I started to welcome you to TBN based on your post count. Then noticed by your join date that you've been here 8 years. Silent type huh?

 

[RayIN]

IMO the biggest issue with newer small tractors is the factory rims that cannot be reversed to widen rear wheels stance.

 

[SmallChange]

I think this is an important question and it's a shame there isn't more information available. For example, it would be very helpful if specs for a tractor could include the slope that would cause tipping in, say, a dozen configurations (R4 vs R1 in filled and unfilled states, FEL+bucket vs FEL only vs no FEL). It makes me want to find the right shape piece of ground with a tree above it, and tie a rope from the top of the ROPS to the tree, and search for the tipping point.

Modern 3D design software would make it pretty easy for the manufacturer to run through dozens of scenarios. In fact, I suspect they already do this to help themselves design a safer product, and just don't share the results. Sadly, I can see a big legal downside for them sharing the results, even though that would make the overall situation safer!

 

[ning]

Ancient thread but worth a re-read.

I recall watching a video where a fellow used a come-along to find the tipping point of his tractor (not traction limited - this was on concrete). It was a lot larger of an angle (like tilted more) than you'd've expected.

The problem is that knowing at what point it would tip is an academic question because the moment any slip occurs... and then the slip stops... the side forces induce a rotation as if the tractor was tilted more.

And, of course, the fact that nobody's got perfectly smooth ground.

Nonetheless I see some value in knowing that a, the engine has a maximum operating angle in whichever direction (for proper oiling) and b, in a perfect static situation the tractor will roll at this other angle, so don't get anywhere near it.

My sense is that you can estimate the angle by measuring weight blocks of the tractor - rear tires (filled or not), rear axle unit, engine, frame, cab, loader - draw then as boxes viewed from the back with an estimated weight; and estimate the center of mass from that. Once you have that, you can draw an angle from the center of mass to the center of the tires, and assume that's somewhere near the rollover angle.

On my tractor, my seat is definitely above the CoM - almost everything is below it (other than the hood of the tractor, a bit of the loader, and the ROPS, and the tops of the tires - everything below my butt is way bigger), so a safe guess is that if my butt isn't vertically over the middle of the tire, there won't be a rollover - if I'm not moving.

My butt puckers way before that, anyways.

 

[RaydaKub]

I think this is an important question and it's a shame there isn't more information available. For example, it would be very helpful if specs for a tractor could include the slope that would cause tipping in, say, a dozen configurations (R4 vs R1 in filled and unfilled states, FEL+bucket vs FEL only vs no FEL). It makes me want to find the right shape piece of ground with a tree above it, and tie a rope from the top of the ROPS to the tree, and search for the tipping point.

Modern 3D design software would make it pretty easy for the manufacturer to run through dozens of scenarios. In fact, I suspect they already do this to help themselves design a safer product, and just don't share the results. Sadly, I can see a big legal downside for them sharing the results, even though that would make the overall situation safer!

Even that would be inadequate however. It's much more relevant for a SCUT than a Quad-trak, but how much does the operator weigh? Is there a toolbox mounted on the side? How big is the hole you are going to hit (gopher, woodchuck, fox, badger)? The tires are filled, but to what % and what liquid? And maybe the most important question, how fast are you driving?

There simply isn't a definitive answer for any given tractor, muchless all of them.

 

[IndyIan]

On really steep stuff, I've kept my loader on, and just kept the back end pointing down the hill, keeping the fat end of the stability triangle where I need it. With a HST you can crabwalk across the hill at the top and back down the next row. With the loader low and a light duty ~500lb 5' mower on the back, I was more worried about watching the oil pressure light and covering the brake pedal in case the hst started sucking air and sending me rolling backwards.
The slope map says some of this is up to 25 deg, far to steep to go across safely in my tractor, as there's rocks and ground hog holes. I did this for tree planting prep, and now its all trees.

Also be aware that the open front diff with no brakes on the front wheels, this allows one tire to spin backwards as the other goes forwards, and you can have no effective front braking at all, even with ags, they can pack up a tire with mud very fast if spinning backwards. This is also true with the back axle and the HST, if you don't actually apply the brakes, one rear tire can plug up and spin backwards while the other rolls forwards, even if the drive to the rear diff is stopped. I learned this going forwards a steep but short slope out of our muddy barnyard with a good bucket of manure on the front. I was backing off the speed with the HST and then got off the forward pedal totally, and I just kept moving forwards and watching one side tires spinning backwards as I kept going! Then I hit the brakes, and the rear tires locked, but the fronts kept going... I only went 20' at like 3 mph and I remembered to drop the loader eventually, but it was very exciting, and I backed down that hill after that with no problems.

 

[SmallChange]

There simply isn't a definitive answer for any given tractor, muchless all of them.

I'm not saying it would be definitive. But you have to compare this approach with the alternative, which is eyeballing the slope and guessing.

It occurs to me there is a mechanism for determining when the tractor is almost ready to trip. Uncouple the left and right brake pedals if they're coupled together. Then, lightly brake on the uphill side. If the rear slips very easily, it is carrying very little weight.

 

[RayIN]

It's not only depressions that can cause a roll-over. I remember one time I was brush-hogging a neighbors field (@ $30/hr) and the upper rear wheel ran over an old tree stump about 6" high with the outer edge of the uphill drive wheel.
The slope was gradual and not steep but the effect of running over that stump had me ready to abandon ship.
Come to think of it, that was the last time I cut anyone else's property.

 

[scootr]

We got gophers and ground squirrels, both are ferocious diggers. On a slope if the hole don't get you the mound will. That's why I always maintain a margin of error and I put spacers on all corners. I know I know, Some are rolling their eyes about front spacers but I still feel it takes more to lift a tire off the ground if it is further out and it just looks and feels better that way.

 

[SmallChange]

Seems like it wouldn't be that hard to build a lock into the pivot for the front axle. Then the balance would be determined by the two tires on the downhill side, rather than the downhill rear plus the center of the front.

Are there any tractors that let you lock out the pivoting action on the front axle?

Come to think, some telehandlers do something like this, don't they?

 

[CalG]

Reality?

The CoG of most tractors is a point about where a shifter base would be on a "traditional" tractor so configured. (Not the stalk by the steering wheel!" ;-)

Draw a line between that point and the contact patch of the rear wheel and you will have a good feel for the tip over angle for a tractor at rest.

Change the CoG with a bucket full , at undetermined height, rear weight of implement and the line shifts.

Add the Dynamic element of inertia and there is really no telling!

Flying by the seat of one's pants is a worthless metric.

In all cases, SLOW the F Down!

Take the dynamic uncertainty out of the consideration, an one is left with feeling YOU will fall out of the tractor before the tractor it's self will tip over.

Seat belts and ROPS!

 

[SmallChange]

In all cases, SLOW the F Down!

Yeah, this! I think it's worth figuring out more accurately and objectively where tipping starts in a nearly static situation, but if we're going too fast that all goes out the window. I don't think high speed tipping dynamics could be figured out much without computer simulations.

If you want to go fast, use a car. That's why they're designed the way they are, to handle it.

 

[RayIN]

I think I found the ideal slope tractor, but it's out of production and only available in Europe.
Massey Ferguson 3435 has a very low center of mass for an 80 HP tractor.

 

[ning]

I think I found the ideal slope tractor, but it's out of production and only available in Europe.
Massey Ferguson 3435 has a very low center of mass for an 80 HP tractor.
View attachment 1861480

@ericm979 bought his tractor with smaller wheels specifically for this reason

 

[CalG]

My Hurlimann Prince 435 is in some circles referred to as an orchard tractor.

It does carry it's weight lower than many similar HP Ag tractors.
It sure does well on my steep and terraced property.

 

[SmallChange]

My Hurlimann Prince 435 is in some circles referred to as an orchard tractor.

Orchard tractors are cool. I need one. Haven't come up with a plausible reason why yet, though.