How did this Tractor Flip?

[RoyJackson]

Since we're all guessing...
IF the trailer hitch was on the draw bar and IF the hitch was a standard ball and IF the rear tires did not break traction, it's possible the trailer's tongue weight in conjunction with the slope stopped forward movement. The rear tires had enough traction to rotate the tractor around it's rear axle...during the rotation, the hitch ball disconnected from the trailer's hitch receptacle.
All speculation, of course...but that's my guess.

 

[JoeL4330]

My two cents: no draw bar and pulling from the 3ph, which floats up as the tractor does its "wheelie" ...a stout, fixed drawbar would have acted a little like a wheelie-bar

 

[buickanddeere]

Ford N series widow maker. Owner/operator could not find the bucks for a real drawbar. So they used the three point hitch. Small tractor with too much load on too much hill began to spin. Operator jerked the three point hitch up for traction. Up and over she went.

 

[vtsnowedin]

My WAG :3ph too high and when he came to that grade with way too much load on behind he ran out of power and lugged down. He stopped and shifted gears, perhaps down two instead of one then popped the clutch!!

 

[CurlyDave]

I agree: no drawbar, 3 pt hitch too high, no rops.

The first two things caused the tip over, the last exacerbated the injuries to the operator.

One thing that absolutely did not happen is that the tractor rotated about the rear axle. If you watch video of this kind of turnover it looks like this happens, but only because this is what you eyes and brain expect to happen. I have watched many videos of this type of turnover. If you slow them down enough and really pay attention, the the pivot point is the place where the rear wheels contact the ground.

 

[TomSeller]

I agree 3 pt hitch too high and above center. Recipe for death. I am glad the guy was only injured. Lesson: USE A FRAME MOUNT DRAWBAR, NOT 3 PT DRAWBAR

 

[Arc weld]

Probably didn't have stay bars on the 3 point to keep it below axle level. A 3pt floats so you wouldn't have to lift on it

"the pivot point is the place where the rear wheels contact the ground." The rear wheels can't move so they stay put and the tractor rotates on the axle the wheels are attached to. It's less force to flip the tractor than to pull the wagon. It does happen very fast.

 

[bcp]

Can't tell how the tractor in this first video is hitched, or if the tire is tied. But it is rotating around the axle.

From 6 to 9 seconds:
Antique John Deere Tractor - YouTube

Can't tell on this one-too fast-bad angle:
8N Ford tractor rolls over backwards - YouTube

Bruce

 

[Jim Shooz]

The load on the trailer is Kiwifruit and he was taking the bins from the pickers, to the loading point. The drivers are usually youngish (although this guy was 61) and going like.....(rather quickly). There is no ROPs as the tractors have to fit under the vine overhead. He had just come to the end of the row and was about to turn. Turning at the end of the row is usually yank the wheel over and stab the brake on the inside wheel. The gang is paid by the bin and there is a lot of pressure to finish and move on to the next orchard.

I am surrounded by Kiwifruit orchards.

 

[RoyJackson]

One thing that absolutely did not happen is that the tractor rotated about the rear axle. If you watch video of this kind of turnover it looks like this happens, but only because this is what you eyes and brain expect to happen. I have watched many videos of this type of turnover. If you slow them down enough and really pay attention, the the pivot point is the place where the rear wheels contact the ground.

That contradicts my post...and I kind of agree with you. Now, I've never watched slow motion videos of a tractor doing a back-flip...well, apparently not as close as you have. But, if the tractor's rear tires don't rotate and the mass of the tractor does have to rotate...I cannot see anyway it could not rotate about the rear axle.
As an example from many years back...there was a farmer (in Nevada, IIRC) who had left his tractor on his field one day. The next day he started his tractor, engaged a forward gear and the tractor rotated about the axle as the rear tires were frozen to the ground.
Granted...the contact point of the tires to the ground was the cause, but it seems the axle would still have to be the rotational axis...not the tires' patch
Does that make sense?

 

[SPYDERLK]

That contradicts my post...and I kind of agree with you. Now, I've never watched slow motion videos of a tractor doing a back-flip...well, apparently not as close as you have. But, if the tractor's rear tires don't rotate and the mass of the tractor does have to rotate...I cannot see anyway it could not rotate about the rear axle.
As an example from many years back...there was a farmer (in Nevada, IIRC) who had left his tractor on his field one day. The next day he started his tractor, engaged a forward gear and the tractor rotated about the axle as the rear tires were frozen to the ground.
Granted...the contact point of the tires to the ground was the cause, but it seems the axle would still have to be the rotational axis...not the tires' patch
Does that make sense?

In that special case - yes.

 

[ArtMech]

My guess is an operator is pulling incorrectly designed trailer. The trailer axle is too far behind the point calculated according to the load distribution rules. I mean the vertical load of a trailer hitch is higher than the tractor's draw bar or 3ph could be able to carry while towing this trailer safely.

 

[CurlyDave]

I think I way overstated that. The center of mass rotates about the contact point. The tractor looks like the whole thing rotates about the axle, but look very closely and the rear axle moves backward a small amount before the overturn.

If the tractor really rotated about the axle, and the axle didn't move, hooking up a chain below the axle would always be safe, and it is not. For a 2WD tractor, the forward torque is the weight of the tractor multiplied by the distance of the center of mass in front of the contact point of the rear wheels. The overturning torque is the friction force at the contact point on the ground multiplied by half the height of the chain, or hitch above the ground. Keeping the chain or hitch low is certainly helpful in keeping the overturning torque small, but if the tractor has good traction and a low gear, a hookup below the rear axle can cause an overturn.

A solid drawbar, mounted to the differential or the frame of a tractor is safe because as the tractor rises, the attachment point lowers. This reduces the overturning torque. Any old piece of steel will not always be safe as a drawbar. An engineer at the factory worked out the geometry, and the factory-supplied drawbar is going to lower the chain or hitch, reducing the overturning torque sufficiently to prevent an overturn.

* * * * *

Locking the rear tires to the ground as in the freezing example, is a different situation. There it really does rotate about the rear axle.

 

[Jim Shooz]

I think that the trailer would have been connected to the tractor by the 3ph. The base of the trailer is a series of rollers. When the trailer gets to the loading area the front of the trailer is raised, the bins roll to the back and the tractor/trailer drive out from underneath. I don't think they would have the time/take the time, to unhitch, unload, reload empty boxes, and hitch up again.