Can all tractors flip over easy?

[jigs_n_fixtures]

There's nothing special about pulling a load from below the rear axle to prevent it flipping backwards, and this does not make the load push the front down harder.

The lower the load is pulled from, the better. If the load is pulled from exactly ground level it does not provide up ward or downward force on the front. Pulling from anywhere above ground level tends to lift the front, in proportion to the height of the pull. Pulling from below ground (such as with a ripper or subsoiler encountering an obstacle at its bottom) pushes the front down. Front downward force changes from positive to negative as you move the load downward through ground level.

Nothing changes particularly at axle height, there's only the general trend that lower is always better.

Learn to draw a free body diagram and your opinion will change.

If the tension on the pulled load is below the center of the axle that moment is trying to pull the nose down. If pull from the load is above the center of the axle, it adds to the tendency to bring the nose up.

 

[npalen]

There's nothing special about pulling a load from below the rear axle to prevent it flipping backwards, and this does not make the load push the front down harder.

The lower the load is pulled from, the better. If the load is pulled from exactly ground level it does not provide up ward or downward force on the front. Pulling from anywhere above ground level tends to lift the front, in proportion to the height of the pull. Pulling from below ground (such as with a ripper or subsoiler encountering an obstacle at its bottom) pushes the front down. Front downward force changes from positive to negative as you move the load downward through ground level.

Nothing changes particularly at axle height, there's only the general trend that lower is always better.

I'm sorry, but this is bad information.

 

[SmallChange]

Learn to draw a free body diagram and your opinion will change.

I'm a degreed professional physicist with 41 years experience, and used to tutor physics students in free body diagrams among other things. I think your free body diagram is drawn wrong.

I think you're imagining the wheels blocked in place somehow and the tractor free to pivot at the axle, in which case pulling below the axle but above the ground will lower the front. However, this isn't what is happening if the tractor is holding its position by driving (or braking) its own wheels.

A flipping tractor is pivoting relative to the ground at the point it contacts the ground. If you imagine a tractor with gigantic wheels, this becomes more clear. When a tractor flips backwards, the axle travels rearward, it's not stationary. Points on the tractor and wheel below the axle also travel rearward, just not as far.

All of this is related to geometric points in the tractor system such as the axle and, more importantly, the contact point with the ground. The center of gravity isn't especially important here, at least not until we start asking exactly how hard we're pulling, what the tractor weighs, et cetera.

 

[LouNY]

This thread is almost getting hilarious. There are so many variables involved in any tractor roll over, lay over or rear roll over.
I've lived and operated tractors much of my life on steep hills with fully mounted, semi mounted and towed (trailered) equipment.
I have pulled from fixed drawbars, lift arm drawbars, and 3 point hitch drawbars.
I've had an unknown number of tractors spin out from insufficient traction for the load, I've had tractors rear up from trailed loads and mounted loads,
including 3 point hitch mounted loads when the implement met an unmovable object and the tractor had the traction to keep moving or more traction on the ground then the force needed to lift the front end from the rotational force of the tires and the pulling force of the load.
Talk about getting the adrenaline flowing have those front tires start heading for the sky and then sitting there with the front tires several feet in the air with the clutch in and the brakes on trying to ease the front end back down so as not to break things when the tires touch down.
Now this talk of free body diagrams, oh boy. Drawings for dynamic events.
"A flipping tractor is pivoting relative to the ground at the point it contacts the ground" NO.
It is pivoting around the axle centerline if flipping from the applied load. If flipping only from a lifting load with the tires not rolling possibly.
If flipping from spinning out while pulling a load up a grade, then being pulled back down the grade by the load and suddenly regaining traction it is again rotating around the axle centerline.

You all have fun beating this to death.

 

[SmallChange]

Perhaps the most helpful thing would be to always pull difficult loads with the drawbar. Meaning, the official fixed drawbar, that sticks out of a receiver and has holes for various hitches. Not a "cross drawbar" on the arms.

Drawbars are designed to make flipping backwards practically impossible. Not only are they down low, they are also further back than the ground contact point (and axle). And, they are rigid to the frame, unlike "cross drawbars" where the arms can swing up (most of them can anyway).

By design, because they're behind the contact point and axle, as the tractor starts to rear up, the drawbar goes down, which decreases the leverage trying to flip backwards. This is by design, to prevent flipping backwards caused just by pulling too difficult a load.

Of course you can flip backwards pointed up a steep slope, or adding weight behind the wheels, or for other reasons. But by design you can't do it simply by pulling too hard at this drawbar.

 

[LouNY]

ever been to a tractor pull??????

 

[MossRoad]

ever been to a tractor pull??????

They’re required to have wheelie bars.

 

[LouNY]

They’re required to have wheelie bars.

Otherwise they have the capability of flipping completely over with a drawbar hooked pulling load.
Exactly my point....

 

[ptsg]

Don't they raise the drawbar on those pull tractors to increase the traction on the rear axle? Which is completely the opposite on a tractor, as it pulls under the axle and not above or inline.

 

[CobyRupert]

Otherwise they have the capability of flipping completely over with a drawbar hooked pulling load.
Exactly my point....

Been going to those tractor pulls up the road from you since I was about 4 years old in the 1970’s, back when there was a picket snow fence to separate the fans from the edge of the track, 20’ of bleacher seats and the rest of the fans where on top of pickups and cattle trucks backed up to the track. Plenty of beer and cops to break up the fights...but back to the subject.

…I think they can flip backward because it’s a dynamic load..rotational momentum is required as well as a change (lessening) to the pulling action/traction of the tires, happening at the exact right moment.

In a more “steady state” pull, you will often see the front end rise to an “equilibrium” height and stay there, defined by the geometry of drawbar, and axle heights (and front end weight and pulling force, etc..)

2cents