Preventing tractor back flip

[beppington]

Maybe we should put it this way: Until there is absolute certain proof that there is some way to connect a to-be-pulled object to your tractor such that it can not flip over backwards ... everybody should assume it can happen :thumbsup:

 

[idaho2]

Does hooking up a chain short or long make a difference? Short being as close to the object as possible.

skspurling,

I'll ask again (see my original question above) since no one opined on the orignial question directly, try this: neighbors tractor stuck in mud, I come along with 20' chain, back up and run the chain thru clevis/draw bar on my tractor. Now do I back up as close as possible to the tractor in the mud and hook up "short" on the chain or do I hook up "long" as far from the stuck tractor as the chain allows? Or should I add my other 20' of chain and really extend the distance to pull out the stuck tractor?

idaho2

 

[bcp]

Long chain, so when you flip you don't land on the other tractor.

Bruce

 

[johnrex62]

skspurling,

I'll ask again (see my original question above) since no one opined on the orignial question directly, try this: neighbors tractor stuck in mud, I come along with 20' chain, back up and run the chain thru clevis/draw bar on my tractor. Now do I back up as close as possible to the tractor in the mud and hook up "short" on the chain or do I hook up "long" as far from the stuck tractor as the chain allows? Or should I add my other 20' of chain and really extend the distance to pull out the stuck tractor?

idaho2

I did not try to make my brain digest all of what I have read thus far, BUT the concept that has taken root in my mind and is germinating seems to be that the most important concept is the line of pull and it's relationship to the center of gravity of the tractor. So, without trying to let this idea sit and turn completely opaque with a firm understanding of forces and reactions, it seems that the lower the angle of pull, the less torque will be placed on the rotating axel and thereby reducing the chance of a catastrophic rotation and flipping of the tractor. My Wile E. Coyote mental image is that a large angle between the pulled object and the point of attachment will generate a downward pull at the attachment point to put it in the line of pull between the pulled object and the axel.

If I am subconciously comprehending this properly, then the longer the chain, the smaller the angle and the lower the force required to put the attachemnt point in the line of pull.


Did that make any sense to anyone else?

 

[idaho2]

Long chain, so when you flip you don't land on the other tractor.

Bruce

Hey Bruce,

Good response. :laughing:,

johnrex62,

All I'm looking for is "long or short". Simple question, don't need a politicians response. :confused2:

idaho2

 

[xtn]

No rolling action on the part of the tire is going to cause the front to lift. If your tractor rares up because the tires are frozen to the ground, you would have to be backing up. Otherwise the torque pushes the front into the ground resulting in the tractor moving forwards. The triangle illustration given earlier is backwards.

Maybe I'm misreading the above? It seems you are saying that attempting to drive forward causes your front tires to be pressed to the ground by the torque. And that that torque pressing your front tires into the ground is what results in the tractor moving forward.

I hope I'm misreading it. Otherwise your whole understanding of physics is screwed up. Explain why a drag racing car does a wheelie. A tractor driving forward has the same forces. If you tie the bumper of a drag car to a post with a chain, it's going to wheelie even worse.

xtn

 

[milkman636]

The hitch geometry provides leverage to help prevent roll over, not a guarantee.

When you are hooked to an immovable object with both of your rear drive tires firmly stuck to the gound, it is actually the engine torque that is being apllied to the now stationary ring gear in the differential that causes the front end to pitch upward.

If the torque and momentum of the rising front end is sufficient to overcome the geometry of the hitch and lever arm created by your front end, you are going to roll over. The tractor will indeed appear to move backward as it continues its pivot around the hitch point on its way to being upside down.

Of course this is all assuming you haven't installed some long wheelie bars hanging off the back of the tractor to increase the lever arm that the engine would need to overcome in order to perform this acrobatic.

 

[idaho2]

What is it, can't anyone give a simple answer During the mean time the mud is hardening around my neighbors tractor and all I want to know is hook up short on the chain or hook it up long. Oh heck, I know what's wrong, you guys and gals don't help pull tractors out of mud. That's why no one can answer my straight forward question.

 

[milkman636]

Use a long enough chain to keep your tractor from being stuck in the same mud.:thumbsup:

That's my voice of experience talking.

 

[idaho2]

Use a long enough chain to keep your tractor from being stuck in the same mud.:thumbsup:

That's my voice of experience talking.

And the answer is "Short". See, everyone, that was painless.

 

[Degolyerent]

What is it, can't anyone give a simple answer During the mean time the mud is hardening around my neighbors tractor and all I want to know is hook up short on the chain or hook it up long. Oh heck, I know what's wrong, you guys and gals don't help pull tractors out of mud. That's why no one can answer my straight forward question.

Turn the tractor around and pull it out going backwards with chain hooked to front end

 

[foreman Etexas]

What is it, can't anyone give a simple answer During the mean time the mud is hardening around my neighbors tractor and all I want to know is hook up short on the chain or hook it up long. Oh heck, I know what's wrong, you guys and gals don't help pull tractors out of mud. That's why no one can answer my straight forward question.

Get as close as u can but still leave some room so he dont bump that mahindra when u get him out:thumbsup: I would pull him using the 3 pts lift before I would the loader(puts more strain on front diffs).

 

[IronHog]

Maybe we should put it this way: Until there is absolute certain proof that there is some way to connect a to-be-pulled object to your tractor such that it can not flip over backwards ... everybody should assume it can happen :thumbsup:

I sometimes do semi professional logging with a tractor. Not what most of the people here call logging but actual harvesting of large saw timber skidded with the tractor. A drag can weigh up to two tons.

The tractor has a standard, but reinforced three point hitch using tongs to drag attached to a logging rig (metal frame that looks like one of those little fast hook up things on small CUTS). The pull is both behind and above the rear axle.

And after riding hundreds of wheelies on a tractor I can tell you it would take a complete fool on an operator to flip one (with any weight forward) backwards.

If you are running right once the front end gets so high you start to lose traction or the tractor starts to stall (giving you time to back off or hit the clutch).......to flip one over you'd need to get in a rather low gear, have plenty of traction (might even need a diff lock), be hooked to a static object, and throttle that thing over in a violent fashion........

 

[idaho2]

Now we're getting the answers that alot of viewers and some posters have been waiting for.
I've pulled out alot of different types of machinery, vehicles and tractors over the years from mud to snow banks. Everything at the moment is dependent upon the siuation at the time. Saw how this thread was going nowhere with the "logic, etc" so I posted the question and we finally have some common sense answers.

Thanks, IronHog, foreman Etexas and Degolyerent.

 

[Egon]

If confused draw a force vector diagram around the centre of the rear axle.

If that doesn't work block the rear wheels so they can't move and apply the power. Don't even need a load on the back end.:thumbsup:

 

[JoeL4330]

I never had any classes in this stuff, but I am confused by the statement:

"If your tractor rares up because the tires are frozen to the ground, you would have to be backing up"​

Look at the tractor from, say, the "driver's" side: for the tractor to move forward, the wheels would turn counter-clockwise (rotor) relative to the axle housing (and the rest of the tractor, stator). If sufficient torque were applied to the wheels but they were immovable, then the tractor (now the rotor) would rotate clockwise (raise up) with respect to the wheel (now the stator). [of course, viewed from the passenger side, trying to go forward, the wheel wants to turn clockwise and/or the tractor wants to turn counter-clockwise]

So, it seems to me, that trying to go forward in the wheels-frozen situation is what would raise up the front of the tractor ...no? not "backing up"

 

[k0ua]

I never had any classes in this stuff, but I am confused by the statement:

"If your tractor rares up because the tires are frozen to the ground, you would have to be backing up"​

Look at the tractor from, say, the "driver's" side: for the tractor to move forward, the wheels would turn counter-clockwise (rotor) relative to the axle housing (and the rest of the tractor, stator). If sufficient torque were applied to the wheels but they were immovable, then the tractor (now the rotor) would rotate clockwise (raise up) with respect to the wheel (now the stator). [of course, viewed from the passenger side, trying to go forward, the wheel wants to turn clockwise and/or the tractor wants to turn counter-clockwise]

So, it seems to me, that trying to go forward in the wheels-frozen situation is what would raise up the front of the tractor ...no? not "backing up"

I agree with you, I posted the original post about the tires frozen to the ground, again I have no first hand experience, having never done it or seen it, but I have read about it and it seems plausible to me. The ring gear would be immovable, and the pinion would climb it. Just like a "funny car" with soft slicks with a good hookup to the asphalt, for some milliseconds the tire does not want to spin and a lot of torque is applied to the pinion/ring gear and the pinion climbs the relatively immobile ring gear and brings the front end of the car up off of the ground. Of course the tires eventually slip and spin and the front comes down, usually, of course the whellie bars on the back prevent it from going all the way over. That is my story and I am "sticking":laughing: to it.

James K0UA

 

[Short Game]

Back in the day, I wonder how many trying-to-be bikers rode those insane Kawasaki three cylinder 2-strokes right out from under their butts? You could do it in about any gear if you shifted at the top of the power band.

Well, if I really want to pull something tough, I put on my box blade with the 12,000 pound Warn winch on it. I chain my front end to something solid and pull with the winch. All four wheels tend to stay on the ground. Doing my part to prevent a back flip.

 

[orezok]

Back in the day, I wonder how many trying-to-be bikers rode those insane Kawasaki three cylinder 2-strokes right out from under their butts? You could do it in about any gear if you shifted at the top of the power band.

Well, if I really want to pull something tough, I put on my box blade with the 12,000 pound Warn winch on it. I chain my front end to something solid and pull with the winch. All four wheels tend to stay on the ground. Doing my part to prevent a back flip.

I still have a 75 Kawasaki H2 triple. I still remember it as being one of the nastiest handling bikes ever made. Yes you could carry the front wheel in any gear just from the torque.

It's on my list of things to restore when I retire. It's a 100% complete bike and I bought many NOS parts for it years ago.

 

[Reg]

Yes of course you're right. Depending upon the height of the draw bar, how far back it is from the rear wheel center line, and the angle the chain is at when pulled tight, there is some point at which an equilibrium must be reached. So technically the tractor won't flip over on it's back completely.

That is... unless you start figuring in momentum and materials elasticity. I mean what happens if the equilibrium point is reached while 2000 lbs of tractor front end is rotating up with some speed?

xtn

How far back it is doesn't matter, how long it is and the arc its end describes as the front of the tractor rises DOES matter.
I may have made the "mistake" of assuming that the O/P would use an appropriate draw bar for the tractor in question, i.e. one that would get down to ground level WAY before the tractor gets the front wheels too far off the ground.

Sure, I can pretend that the draw bar is about as stiff as a loaf of bread and that the chain is in fact a bungie cord.

With a jerk ... ? maybe you can get the answer you WANT, but I think it depends where you run out of slack.
For as long as you have slack the chain is essentially NOT THERE, i.e. that is a different experiment, One might as well ask "can tractors wheelie ?" the answer to which is "YES".

As posed by the O/P the draw bar can be assumed to have unlimited bend resistance and the chain just doesn't "give".
This is close to reality, draw bars can be bent, but not from straight pulling - at least I've never seen it happen from JUST pulling.

Though I have to admit that some folk use stretchy nylon rope where they SHOULD be using chain (-: