Rear wheel width setting vs. Bucket Width

[cartod]

I agree with you on most of this, but wonder about this last point. When you are on a significant side hill I'd think that once the uphill rear comes off the ground enough for the front axle to hit the stop you have likely already lost it. Does anyone know of any actual facts on this?

Terry

Hey, that's my point!:laughing: Isnt this why they took 3 wheeled ATV's off the market. If you are traversing a down hill slope, the wider your rear tires are set the easier it is for the tractor to tip forward on the down hill side. Not trying to start a fight just trying to figure it out..

 

[CobyRupert]

I agree with you on most of this, but wonder about this last point. When you are on a significant side hill I'd think that once the uphill rear comes off the ground enough for the front axle to hit the stop you have likely already lost it. Does anyone know of any actual facts on this?

Terry

I think the actual facts are: "It depends."
"The point of no return comes when the center of gravity of the tractor and load in the bucket goes over the line of rotation which is the line from the outside edge of the rear tire and the outside edge of the front tire on the low side. " is true.
I think there could be situations when the c.o.g. is forward (because of a FEL load) where the front axle 'stops" stop it from going over.
Imagine a situation where the the uphill rear tire (only) drives over a rock or stump at the same time the downhill rear (only) falls into a woodchuck hole on a side hill with a very full FEL load.

 

[CobyRupert]

...of course this is when you've gone way beyond the pucker zone, and are into change your pants territory.

 

[vtsnowedin]

I think the actual facts are: "It depends."
....
...Imagine a situation where the the uphill rear tire (only) drives over a rock or stump at the same time the downhill rear (only) falls into a woodchuck hole on a side hill with a very full FEL load.

What your scenario does is increase the angle of the slope the tractor is resting on. If the difference is enough to put the COG past the line of rotation a roll over will occur. If your full load in the loader is held high this point will be reached sooner then if the load was held close to the ground.
Three wheelers got banned because they tip over easily when turned sharp at speed. The same physics apply to tractors and quite a few rollovers happen when turning fast from a road into a drive. Another reason they don't make many tricycle front ends anymore.

 

[CobyRupert]

I was trying to imagine a scenario where cog is "outside" the vertical line of the downhill rear tire, but not front tire, and the "stops" save you.

 

[ovrszd]

Sure it counts but when you get too wide in the rear you start to create a tricycle. Your front axle is free floating as im sure you are aware. There is a false sense of security by going to far, or so says my simple math book.

Missouri Department of Transportation sometimes contracts mowing along the Interstate Hiway that I travel frequently. The contractors normally have their tractors set as wide as possible.

The only reason I don't have my tractor set wider is because I was taught to keep the inside track of front/back equal for AG use.

As for the tricycle theory. A wide front tractor, mechanically, is a tricycle until the front axle oscillates to the stopper either direction. Then and only then does the wide front increase stability.

A minimal amount of stability can be gained by widening the front tire track width. But mostly what's gained is it minimizes the effect of either front tire falling into a hole because the triangle created between the oscillation point and the contact patch of each tire flattens out.

But again, once the axle oscillates to the stopper, then all equations change and the width of the front track is effecting the stability of the tractor.

This leverage can work against you too. If on a sidehill and the upper front tire rides up on an obstacle far enough to cause the axle to oscillate to the stopper it will have increased leverage to try to tip the tractor over.

 

[cartod]

Thanks, Lots of very smart people hang out here. I aint one of them.

 

[ovrszd]

Thanks, Lots of very smart people hang out here. I aint one of them.

Ain't no stupid people here. Everyone contributes.

I have learned a LOT about rollover conditions from 4wheeling with Jeeps/Buggies. I've been in a dozen or more side flops where I ended up on my side. I've been in three rollovers where I ended up on my top and once back on my wheels. I've been in one tip over backwards falling off an 80' high bluff. I've gained a pretty good feel for looming danger.

I've also honed those skills on my tractor. I started with a B2910 Kubota. I thought it was relatively stable but was affected a lot by uneven terrain.

I then got an L4400 Kubota. I thought it was a lot more stable and less affected by changing conditions. I felt pretty comfortable on it and used it frequently in steep timber terrain.

Then I got my M9540. It is many times more stable than the other two tractors were. I think that's mostly because of it's bigger footprint. It is less affected by changing terrain. The front axle oscillates a long ways. Rarely do I have one tire off the ground because of uneven terrain.

I believe the most important thing to remember is when you have a load on the FEL, all balance of the tractor changes. That's when decisions made concerning slope enters the danger zone!!!! I use a Grapple a lot. It's very common for me to have one rear off the ground. I've grown accustomed to that and am vividly aware of what all four tires are doing.

 

[vtsnowedin]

I was trying to imagine a scenario where cog is "outside" the vertical line of the downhill rear tire, but not front tire, and the "stops" save you.

No that's impossible. The line of rotation is from outside edge of rear tire to outside edge of front tire. If the COG is outside that line, stops or not ,she’s going over. If the COG is still inside the line your not going to go over again on the stops or not. What dropping a front tire into a hole on the low side all the way to the stops does is move the COG forward and to the low side by changing the plane the tractor is resting on.
It's the plane the tractor is resting on that matters not the shape of the ground between the wheels. Of course all the ground gets its turn as you drive over it with first the front axel then the rear so stay out of the chuck holes.

 

[vtsnowedin]

This is worth a read for those who haven't seen it.
NIOSH FACE Program: West Virginia Case Report 02WV003 | CDC/NIOSH