What causes flip overs?

[HiTechTed]

I have read (and learned a lot) on this forum, about safety as well as quite a few other things. I tend to be overly-cautious and I go out of my way to be as safe as possible. I love my tractor but not enough to die operating it, if you catch what I'm saying.

Anyway, I have read some of the horror stories about pulling stumps out with your CUT. I am going to ask the dumb question of the day: what causes the tractor to actually flip over backwards? Bear with me, but in my mind I'm thinking that since the rear wheels aren't moving but you are giving it the gas, is the tractor actually "riding around it's own axle," so to speak? Is that why it happens so fast?

I can see the advantage of using the drawbar for pulling, since it's lower to the ground. If a tractor is starting to flip, does using the drawbar help in any way to stop the flip, or at least slow it down, somehow?

 

[SPYDERLK]

I have read (and learned a lot) on this forum, about safety as well as quite a few other things. I tend to be overly-cautious and I go out of my way to be as safe as possible. I love my tractor but not enough to die operating it, if you catch what I'm saying.

Anyway, I have read some of the horror stories about pulling stumps out with your CUT. I am going to ask the dumb question of the day: what causes the tractor to actually flip over backwards? Bear with me, but in my mind I'm thinking that since the rear wheels aren't moving but you are giving it the gas, is the tractor actually "riding around it's own axle," so to speak? Is that why it happens so fast? YES.

I can see the advantage of using the drawbar for pulling, since it's lower to the ground. If a tractor is starting to flip, does using the drawbar help in any way to stop the flip, or at least slow it down, somehow?

The frame mounted drawbar is almost completely safe if its end extends outside the circle made by the rear tires. As the tractor rears up the end of the drawbar will come down to the ground reducing tip leverage to zero.
larry

 

[kebo]

You pretty much answered your own question but I will expand.... When one pulls from the rear of the tractor with the attachment point above the rear axle, that gives the load (being pulled) a tremendous leverage advantage to help pick up the front end of the tractor. To compound that, at the same time the rear wheels are trying to drive the tractor forward, if the load is not moving and the rear wheels don't spin out, something has to give. With enough torque applied, these two factors can cause the front of a tractor to rotate around the rear axle and flip over, very quickly!!

This is why the preferred attachment point is the drawbar, which is below the rear axle. When you pull from the drawbar, as the load and tractor move forward, the load actually is helping to pull the front end down, helping to prevent flip overs.

However, don't be lulled into a false sense of security that it can't flip over even when pulling from the drawbar because it can! With enough torque applied from the engine, and with the wheels finding enough traction (not spinning) that torque has to accomplish some sort of work.... which is to overcome the weight of the front half of the tractor and flip it over.

One option is to pull from the front. This is not the most efficient way to do it, but for a two wheel drive tractor it will greatly reduce the chances of the front end raising up and flipping over. If you have a 4x4 tractor, the driven front tires can still cause the rear of the tractor to raise up with enough torque applied, but not many tractors are capable of doing that because the rear half of the tractor is usually heavier than the front half. Especially if it has loaded tires and wheel weights. The teeth in the ring & pinion gears aren't really designed to bear the greatest stress that way, so just be careful not to over do it from the front.

 

[Gary Fowler]

I dont belive that any tractor can pull a wheelie if you are pulling from the belly attached drawbar whether it sticks out past the wheels or not. Reference any tractor pull where they hook to the drawbar and pull the sleds with engines producing thousand HP or more. As the front in come up, the pull angle starts to lift the rear tires. The the tractor cant exceed 45 degree lift with the front end prior to the load lifting the rear tires and the front end falling back. You will get the continuous lift and fall action till you stop the torque to the tires. The exception to this might be if you used a drawbar in the lift arms and put it on float. You would then not be raising the rear end and if you had enough traction and power, it could flip.
I have seen where folks run a cable or chain that is attached to the drawbar and then ran under the tractor and attached to a stump or whatever. I suppose this would be the safest method and assured that the tractor wont flip by doing this. DONT attach to the FEL on 4 WD tractors if you have one with lift hooks welded on. You will do a nose stand very quickly as the more you pull the more weight you put to the front drive and if will stand you on end. IF you dont have the FEL lifted too high, you will only go till the bucket hits the ground. Even with the bucket low on the ground, this is not a good thing to do. If you want to pull stumps there is a good thread here on how to build a lever so you can hook to the stump, run your chain over a vertical pipe or other strong object then hook to the tractor. Chain must be sufficient length that your tractor cant be hit by the vertical pipe. This give you vertical lift to pull the stump.

 

[HiTechTed]

Thanks for the replies. I'm not wanting to pull stumps, I was just using that as an example. I kind of had an idea of how it happened but when you think about it, it's hard to believe a machine like that can flip over so quickly.

 

[Travelover]

Thanks for the replies. I'm not wanting to pull stumps, I was just using that as an example. I kind of had an idea of how it happened but when you think about it, it's hard to believe a machine like that can flip over so quickly.

Yes, as has been stated, the tractor is really rotating about its rear axle. If you think about it, the rear axle only has to rotate one revolution to put the tractor on its back, if the tires don't slip.

 

[Argosy]

Yes, as has been stated, the tractor is really rotating about its rear axle. If you think about it, the rear axle only has to rotate one revolution to put the tractor on its back, if the tires don't slip.

If the tires were locked to the ground (nearly impossible) it only has to rotate a little over a quarter revolution to flip. From horizontal to vertical is 90 degrees, anything past that gravity will put it on top of you.

 

[rd_macgregor]

This sounds like another good argument for R4 tires vs. R1's.

BOB

 

[rjkobbeman]

Remember the higher you hook up, not only are you increasing the mechanical advantage to cause a flip, you are also increasing down pressure on the tires... which increases traction.

 

[teg]

This sounds like another good argument for R4 tires vs. R1's.

BOB

Would be good to know if ANY flips pulling stumps are ever with R4's??? My guess... from my experience, would be NO. They slip way too easy, and I'm fine with that.