Tractor Rollover Myths and Facts

[Defective]

skiding a huge 990# 10' long oak tree log with his 8n that has the chain attached to the 3pt rocker
and is moving it thru soft rocky soil

Hey!

That was ME!

except the log was hooked to the drawbar & the tractor had a full cage.

Still managed to flip her over, but crawled out & went for the other tractor to flip her back...

Ended up taking 3 days to drag that log out...

 

[TMcD_in_MI]

Larry - I am with you on this, because it makes no sense to me either. The dashed line doesn't represent any real force that I can imagine. I wonder what the author was thinking?

Later Edit: I just emailed the author. I'll let you know if I hear from him.

I got a reply this morning and here it is:

The simple answer is that the line represents the rearward and downward force created when one force (the tractor) is restrained by an immovable object that rests on the ground (tree stump). I am leaving town shortly for the rest of the week so I don’t have time to cite/find the original sources where this explanation first originated. But I can tell you it comes from early tractor engineers whose work was published in the agricultural engineering research journal (now named Transactions of Agricultural Engineering) I think as far back as the late 1920s. I hope this helps.

I think this is clearly mistaken and he is just repeating what he saw somewhere else. I looked up his degrees and they are in Agriculture, Occupational Safety and Health, and Agricultural Education. It would be interesting to have a discussion with him over a cup of coffee about this, but I think I will just send a short reply trying to point out the mistake and then let it go.

Tom

 

[Tom_Veatch]

...I think this is clearly mistaken and he is just repeating what he saw somewhere else.
...

Agree! There is no possible way a flexible tension member ("unbreakable" chain according to the paper's assumptions) can transmit force other than axially along the member. That dashed line in the diagram can only be interpreted as a generic line to define how the angle is measured. Actual line of action and angle would be the centerline of the chain, cable, rope, etc.

 

[Youare]

I will only speak from personal experience on rear roll over when pulling from the drawbar and pulling with a 3PH immpleament.

While driving an older Massey Harris tricycle style tractor with a trailer full of fire wood, about 1/2 a cord, connected to the draw bar when going through a gully the front of the tractor would come off the ground. You had to have the right amount of throttle and be quick on the clutch once the weight of the trailer load pushed down on the draw bar as it entered the gully as the front of the tractor exited the gully. One level ground every thing was fine. Some times we drive on uneven ground.

The other incident happen just today. I have a Farmi winch on a Kubota L3000DT. I was pulling two maple trees one 8" in dia and the other 6" dia. from the chain hook bar on the winch which is below the axle. One of the tree butts caught on the frame of the winch as I was making a corner. The tractor tried to pick up the hole tree at this point making the front wheels come off the ground.

I have done this many times and never experienced this before. I don't know if the tractor would have rolled over backwards or not I did not have the courage to see how far it would go. I do know that given the right conditions things can happen that you are not expecting.

There are some things that are known hazzards and should be avoided, and there are other things that are safe 99% of the time. Always be aware for the unexpected.

Randy

 

[SPYDERLK]

Re "Angle of Pull"-- Quote from recent author: The simple answer is that the line represents the rearward and downward force created when one force (the tractor) is restrained by an immovable object that rests on the ground (tree stump). I am leaving town shortly for the rest of the week so I don’t have time to cite/find the original sources where this explanation first originated. But I can tell you it comes from early tractor engineers whose work was published in the agricultural engineering research journal (now named Transactions of Agricultural Engineering) I think as far back as the late 1920s. I hope this helps.

No, it doesnt help to cite something that you dont understand in order to answer a question. His ref may either be wrong or else misquoted. Certainly not explained. I can think of some ways in which this flawed pull analogy may be used to illustrate how things might appear to act in a specific pull situation, but it would require real explanation and conditional statements not apparent to his treatment of the issue. Who wants to go into a lengthy explanation of something you guess someone means. Frustrating.
larry

ps - the "properly ballasted" condition that comes up later may refer to side to side equality so that the drives would have close to equal traction. To give the benefit of a doubt ........?

 

[slowzuki]

Re the figure 5, the first figure is wrong too. A wide front end has a triangular stability shape too but it is inclined rather than flat and changes shape once a rear tire leaves the ground and the axle pivot stop is hit.

Figure 5 is interesting, the point of rotation isn't actually the contact patch if the tire is turning, we end up with a moving centre of rotation that is at the contact patch at front end lift off but moves upwards and can get as high as the centre of the rear axle theoretically.

As for the line of pull, not sure what they are smoking.

 

[SPYDERLK]

Quote: the first figure is wrong too. A wide front end has a triangular stability shape too but it is inclined rather than flat and changes shape once a rear tire leaves the ground and the axle pivot stop is hit.

Agreed. Saw that. At least ithe 4 wheeler gives you that second chance at the front axle stop. Too late if it happens on a sidecline I would guess, but good for a loader in the flat with tip due to light rear.
larry

 

[slowzuki]

Raising the roll centre going to the wide front end does help a lot with tip over, loader or not.

Agreed. Saw that. At least ithe 4 wheeler gives you that second chance at the front axle stop. Too late if it happens on a sidecline I would guess, but good for a loader in the flat with tip due to light rear.
larry