Preventing tractor back flip

[xtn]

I believe you'll find most experts will disagree with your statement and thought processes on this subject.

So, your blanket statement "Wrong" is in error...as is your math.

It wasn't a blanket statement. It was conditional based on typical drawbar configurations, and even allowed for an alternative condition when I said, "OR."

The fact is we have a tractive force at the contact patch trying to move the whole assembly forward. Any resistive force in the other direction that has a vector passing above that tractive force point will tend to tilt the whole assembly back towards the resistive load as the the tires try to move themselves forward.

If the contact patch moves forward, and any fixed point above that contact patch doesn't move forward, then the assembly must tilt up and back. Pretty simple no matter what anybody else says. The tires are trying to claw themselves out from under everything else that is restrained. (The above includes only typical drawbar configurations and relatively straightforward chain angles. As detailed in my prior post there are possible setups that would actually lock the front end of the tractor down.)

 

[Short Game]

We need to build on previous effort rather than repeat from 0 every time it comes up.

Well, I'm not going to search it all out and read it. It's good that I get it in nearly real time here. I want to get it, and figure it out, and correct my wrong guesses. I know it's good for me.

With all the smoke that has come out of my ears, I'm glad I have a winch to pull with. I've uprooted some pretty sizable trees by hanging a block 12 feet up. With the front of the tractor tied to another tree at near ground level, the only thing I've worried about is snapping a cable. The only work the tractor did was charge the winch battery. That strikes me as funny.

 

[JoeL4330]

sorry to repeat; check out 50 seconds into Backflip With Tractor - YouTube

 

[xtn]

RoyJackson...

Your second link explains it pretty well in the section titled Drawbar Leverage. And it fits perfectly with what I've said.

Typical geometries tend to raise the front of the tractor... until the drawbar reaches a low enough point that the vector of the restraining force points below the contact patch of the tires.

Nowhere does either of you links say that as long as the drawbar is below the axle the front of the tractor will stay down, as you have claimed. You are the one that is wrong.

 

[SPYDERLK]

This was well hashed over on TBN in the thread linked in my previous post and in links on that thread. We need to build on previous effort rather than repeat from 0 every time it comes up.
larry

Well, I'm not going to search it all out and read it. It's good that I get it in nearly real time here. I want to get it, and figure it out, and correct my wrong guesses. I know it's good for me.

With all the smoke that has come out of my ears, I'm glad I have a winch to pull with. I've uprooted some pretty sizable trees by hanging a block 12 feet up. With the front of the tractor tied to another tree at near ground level, the only thing I've worried about is snapping a cable. The only work the tractor did was charge the winch battery. That strikes me as funny.

I see that you have posted several times on this thread. Yet the time it takes to follow a pertinent and resolved link, given to you, is too much.
http://www.tractorbynet.com/forums/buying-pricing-comparisons/146173-why-4-wheel-drive-2.html#post1691951
larry

 

[Short Game]

I see that you have posted several times on this thread. Yet the time it takes to follow a pertinent and resolved link, given to you, is too much.

Well, Larry, the time I'm goofing off here right now is probably too much. I should be in the seat finishing my mow, as there is possible rain tonight. I'm not dissing your effort. It sounded like volumes had come before and I'm lysdexic and a slow reader, That idea scared me off. This thread has kept my interest and made me think. That's why I'm here and enjoying it. But now, I must get to work in meat-space.

 

[RoyJackson]

RoyJackson...

Your second link explains it pretty well in the section titled Drawbar Leverage. And it fits perfectly with what I've said.

Typical geometries tend to raise the front of the tractor... until the drawbar reaches a low enough point that the vector of the restraining force points below the contact patch of the tires.

Nowhere does either of you links say that as long as the drawbar is below the axle the front of the tractor will stay down, as you have claimed. You are the one that is wrong.

No such thing as 100% safety. Too many variables (such as topography).

Anyway, the drawbar, as designed below the rear differential, is the lowest part of the tractor....and the safest place to hitch for pulling.
There is no way for the restraining force can be below the contact patch of the tires. Physically impossible...we're discussing real life considerations, not theory, correct?

 

[JoeL4330]

Note, in the video Backflip With Tractor - YouTube that the tractor that flips has a drawbar ...and, given the momentum generated, it simply digs in lifts the rear wheels a little but doesn't stop the flip.

 

[RoyJackson]

... But they themselves would be wrong. This was well hashed over on TBN in the thread linked in my previous post and in links on that thread. We need to build on previous effort rather than repeat from 0 every time it comes up.
larry

Larry...do you design tractors? Do you...other then theory, know anything about tractor design and the dynamics involved?
Although I'm in Quality Assurance (not design...automotive and (currently) aerospace, but not tractor specifically), I did a fair amount of study on safe usage of a tractor as I didn't want to become an unfortunate statistic. Does that make me an expert on tractor design...nope...but it does make me a very knowledgeable owner of tractors.

As far as your previous threads...once they're off the first page of a forum...I doubt anyone reads or has knowledge of them (BTW, that applies to all posters, not just you). This topic has gone on (now and then) for at least 10 years...sort of like the "HST vs. Gear" debates.

 

[RoyJackson]

Note, in the video Backflip With Tractor - YouTube that the tractor that flips has a drawbar ...and, given the momentum generated, it simply digs in lifts the rear wheels a little but doesn't stop the flip.

I think you're missing something here, Bro...the discussion is concerning pulling with a drawbar to reduce the possibility of a back flip. The video doesn't really have much to do with that.
First rear rollover I ever heard of (on TBN, IIRC) was a Nebraska farmer who had left his tractor out in a field overnight. Next morning he started his tractor, put it in gear and the machine rear rolled on him. Tires were frozen to the ground. Drawbar wasn't part of the incident.
In that video, how the draw bar is used (isn't used, actually) has no effect on that roll over...stupidity (along with some liquor, I'd wager) does.