Pull from the front or the rear?

[bcp]

If you want to feel a little safer, pull from the fixed drawbar, with the chain running under a raised implement, like a box blade.

Bruce

 

[WranglerX]

What people have to differentiate here is there is two examples (definition) of "drawbar".... One is a horizontal bar with holes in it mounted in 3PH hitch and able to raise up and lower down.... Other example is a bar (or plate) extended out from under chassis at a fixed height (usually below differential/axle height) with a single hole in it.....

Think people need to be more specific in defining "drawbar" in these sort of discussions...

Dale

 

[strantor]

The forces would be extreme. But you don't need vector analysis to imagine the scenario where the rear axle can't move forward (due to the drawbar chained to an immovable object) and a mechanical driveline continues to send torque to the rear axle that has perfect traction. If nothing breaks then rotating the tractor up and over backward is inevitable. I suppose if the drawbar extended out beyond the tires and didn't bend then the rotation would end when the weight of the tractor rested on the tip of the drawbar so the tires lost traction.

Here's a thought experiment...
1. Imagine pulling an immovable object from the top of the ROPS. That's not an abstract concept and I think we can all agree the tractor would flip. The forward force would create a downward force on the rear wheels (more traction, "digging in") and an upward force on the front wheels. And then the she flips.
2. Imagine a 12" drop trailer hitch installed in place of a draw bar, so that the ball is maybe 1" off the ground, pulling against an immovable object from the ball (as close as we can get to the exact opposite of scenario #1). The opposite forces would be at play. Downward force on the front wheels and upward force on the rear wheels until they spin (opposite if "digging in," traction decreased below that of not pulling anything). This is a little bit more abstract than scenario #1 but I think most of us could still agree: the tractor won't flip over backward.
3. Replace the 12" drop hitch for a 6" drop hitch. All the same forces from scenario #2 are at play, but to a lesser degree.
4. Pulling directly from the axle pumpkin. The are no forces induced by the pull on the immovable object. The only forces at work are those inherent in the tractor itself. The torque of the engine on the rear wheels, trying to turn, lifting the engine up. Kinda abstract but not really. Drag cars do it all the time. No forces induced by a pull on an immovable object, yet they still lift in the front.
5. Pulling from the draw bar. This is going to be somewhere between scenario 3 and 4. There will be forces induced by the pull, but they will be in opposition to the tractor's inherent proclivity to flip itself over backward.

So I conclude that pulling from the draw bar is, at a minimum, safer than drag racing.

 

[strantor]

What people have to differentiate here is there is two examples (definition) of "drawbar".... One is a horizontal bar with holes in it mounted in 3PH hitch and able to raise up and down.... Other example is a bar (or plate) extended out from under chassis at a fixed height (usually below differential/axle height) with a single hole in it.....

Think people need to be more specific in defining "drawbar" in these sort of discussions...

Dale

Point taken. I'm talking about the one under the rear axle that points fwd/aft.

Sorry until now I hadn't considered there was more than one type of draw bar. Probably why some of these posts didn't make sense to me.

 

[CalG]

Pull from the draw bar (not the three point spreader!)

Fit a draw bar as long as you can get, and make sure the bar is below axle level.

With that combination , the tractor can't flip unless you are pulling well casing!

 

[strantor]

I just wrapped a two-hour-long session of watching competitive tractor pull "fail" videos on YouTube. It was a sport I had no real interest in until now. I think I need to print a retraction:

So I conclude that pulling from the draw bar is, at a minimum, safer than drag racing.

Yeah, not so much. I think people just watch this stuff for the inevitable carnage. I saw all kinds of explosions, rollovers, fire, departures of heavy iron into crowds of people, wheels flying off, tractors broke in half... it was like watching an episode of "1,000 Ways to Die" with a particular focus on tractors pulling from a point below the rear axle. What I did not happen to see in two hours of looking specifically for it, was a clean backwards flip as a result of pulling from below the axle. I saw front tires get off the ground, but they never get higher than a certain point and then they come back down. Maybe it's the operator letting off the throttle before it rolls over backwards, but statistically speaking, surely in two whole hours of watching hundreds of bad judgement calls made in a very specific situation, I would have seen at least one guy screw that up. I didn't. I think it's physics keeping them from flipping over. I think that as long as you keep the pulling point below the axle, the tractor's torque forces can only raise the front end up so high before the load's countering forces make it lose traction and come back down.

That being said, I realize that those are highly modified tractors built for a singular purpose and probably more closely related to a helicopter than they are to my CUT. I don't plan to go out and try to pull mountains over with my drawbar. It's just a curiosity for me, and if anybody has evidence to the contrary I'd be glad to see it.

 

[CalG]

I just wrapped a two-hour-long session of watching competitive tractor pull "fail" videos on YouTube. It was a sport I had no real interest in until now. I think I need to print a retraction:

Yeah, not so much. I think people just watch this stuff for the inevitable carnage. I saw all kinds of explosions, rollovers, fire, departures of heavy iron into crowds of people, wheels flying off, tractors broke in half... it was like watching an episode of "1,000 Ways to Die" with a particular focus on tractors pulling from a point below the rear axle. What I did not happen to see in two hours of looking specifically for it, was a clean backwards flip as a result of pulling from below the axle. I saw front tires get off the ground, but they never get higher than a certain point and then they come back down. Maybe it's the operator letting off the throttle before it rolls over backwards, but statistically speaking, surely in two whole hours of watching hundreds of bad judgement calls made in a very specific situation, I would have seen at least one guy screw that up. I didn't. I think it's physics keeping them from flipping over. I think that as long as you keep the pulling point below the axle, the tractor's torque forces can only raise the front end up so high before the load's countering forces make it lose traction and come back down.

That being said, I realize that those are highly modified tractors built for a singular purpose and probably more closely related to a helicopter than they are to my CUT. I don't plan to go out and try to pull mountains over with my drawbar. It's just a curiosity for me, and if anybody has evidence to the contrary I'd be glad to see it.

There is a reason those events made video.

You can't fix stupid!

 

[RickB]

What people have to differentiate here is there is two examples (definition) of "drawbar".... One is a horizontal bar with holes in it mounted in 3PH hitch and able to raise up and down.... Other example is a bar (or plate) extended out from under chassis at a fixed height (usually below differential/axle height) with a single hole in it.....

Think people need to be more specific in defining "drawbar" in these sort of discussions...

Dale

As if the distinction hasn’t been made several times here already.

 

[MossRoad]

Well, here's a horror story.... pretty much encompasses all things discussed that last few days...

Pulling from drawbar.
Pulling from front.
Pulling with a loader.
Pulling with a truck.
Narrow front end tractor.

Yikes! It has it all.

Tragic ending.

Tractor Operator Killed While Moving A Trailer.

 

[widefat]

Well, here's a horror story.... pretty much encompasses all things discussed that last few days...

Pulling from drawbar.
Pulling from front.
Pulling with a loader.
Pulling with a truck.
Narrow front end tractor.

Yikes! It has it all.

Tragic ending.

Tractor Operator Killed While Moving A Trailer.

A few weeks ago I was clearing a fallen tree. I cut the tree into tractor manageable sections, used a choke chain on the log, and attached the chains to the integral draw bar. HST, Low range, slow and easy. I had already done this to several logs with no issues.
What I did not take into account was the bowling pin shape of this particular log, and I hooked it up with the heavy end the farthest away, ie, I choked the smaller end. As I came around a wide corner with a very gentle slope, the log started to roll. It jerked the tractor sideways enough to wake me up. Has I been going faster, or if the slope had been greater, I very well may have flipped the tractor. I tractor moving sideways is never a good thing.