Preventing tractor back flip

[xtn]

If the pinion can climb a stationary ring, what prevents it from climbing a slowly rotating ring? You can climb a stationary ladder. Can you not also climb a telescoping ladder at the same time it is extending? Does your climbing action necessarily and absolutely prevent the thing from extending?

Ooooo I just thought of an elaboration to the above ladder analogy that really brings it into alignment with the tractor scenario.

Suppose you are on the upper segment of an extension ladder. Suppose there is a rope attached to your belt buckle that goes down, through some tackle (let's suppose at a 4:1 ratio), and is configured to raise the upper section as you climb.

Now it's going to take you extra leg power, because for each 12" rung that you climb up, you're actually moving your whole body up 15". The twelve inches from one rung to the next, as well as the 3" (remember the 4:1 ratio tackle...) that you have pulled the rung up as you took the step. That's not to mention the fact that you're lifting the weight of the ladder segment as well. So it will take plenty of extra leg muscle. But it is doable.

So you're the pinion gear. You're exerting power against the ring gear and climbing. As you do so, the torque is exerted through the ring gear, through the tires to the ground, raising the nose of the tractor, lowering the drawbar, and rolling the tires and ring gear back by way of wrapping the whole assembly up and over the chain. That whole path of the torque is your "tackle."

That all makes sense in my head. Please tell me somebody else is able to read my inadequate description and get the concept!?!?!?

xtn

 

[Reg]

Yet AGAIN.
The point where the chain attaches to the draw bar does NOT move forwards, it MIGHT move slightly backwards, according to the height of the attachment point of the other end of the chain to the load.
The contact patch of the tires does NOT move backwards.
(BOTH regardless of the amount of traction, i.e. even it were on a cogged rail)

BTW, I can dead lift almost 350 lbs - "almost" because I used to be able to - a couple of years since I did though (-:
I could lift a 200 lb man standing in a bucket if the bucket and handle were strong enough.
I can not lift my own 190 lbs by the handle of the bucket if I am standing in that bucket.

Extend the above example - it doesn't flip with a normal length draw bar properly used.

 

[xtn]

... This fact is developed in previous threads and was linked earlier. Starting over at 0, xtn is doing a good job, but probably dont know nuttin about whats really going on cuz he doesnt design tractors.

May I humbly suggest the possibility that those threads may have arrived at different conclusions had I been a part of them?

 

[Egon]

May I humbly suggest the possibility that those threads may have arrived at different conclusions had I been a part of them?/QUOTE]

Don't think so!:thumbsup:

 

[xtn]

Yet AGAIN.
The point where the chain attaches to the draw bar does NOT move forwards, it MIGHT move slightly backwards, according to the height of the attachment point of the other end of the chain to the load.
The contact patch of the tires does NOT move backwards.
(BOTH regardless of the amount of traction, i.e. even it were on a cogged rail)

BTW, I can dead lift almost 350 lbs - "almost" because I used to be able to - a couple of years since I did though (-:
I could lift a 200 lb man standing in a bucket if the bucket and handle were strong enough.
I can not lift my own 190 lbs by the handle of the bucket if I am standing in that bucket.

Extend the above example - it doesn't flip with a normal length draw bar properly used.

Please review my drawings. Do you think they are in error? They clearly demonstrate that with a fixed length chain, as the nose of the tractor rises the rear tires' contact patch does move backwards. They also demonstrate that the connection point on the drawbar can move forward, depending ONLY on the arc the chain allows. The geometry requires these things as absolutes.

You can lift yourself in a bucket if you're pulling on a rope over a pulley or other tackle that is connected to the bucket. This is the analogous to the tractor situation. If the engine has enough power to lift the nose at all, then the paths I've illustrated may be reached. I say may because the further up the nose goes and the closer the drawbar gets to the ground, the more effort (power) is required because the mechanical advantage declines. But the advantage does not decline to zero unless the drawbar extends beyond the radius of the tires, so with enough power the flip can happen.

So I stand by my original statement: The tractor could flip UNLESS:

1. There is not enough power, or
2. There is not enough traction, or
3. The vector created by the resisting load reaches an angle that points it under the tires' contact patch.

Please note that the drawbar reaching the ground OR a sufficiently high connection to the immovable load such that the chain points down at a high enough angle to point at or below the contact patch of the tires... will satisfy #3.

 

[xtn]

May I humbly suggest the possibility that those threads may have arrived at different conclusions had I been a part of them?

Don't think so!:thumbsup:

Then we are equally arrogant.

xtn

 

[SPYDERLK]

May I humbly suggest the possibility that those threads may have arrived at different conclusions had I been a part of them?

It would have been a help, yes, but the threads I linked ultimately reached congruence with this one in the basics. You never know about conclusions - they differ among participants regardless of actual fact.
larry

 

[xtn]

Additional point for LD1 to consider:

Although relative to a fixed coordinate system in space the tires are rolling backwards and therefor so is the ring gear...,

...RELATIVE TO THE AXLE HOUSING, REAR END CASE, PINION GEAR AND INDEED THE WHOLE TRACTOR, which are all rotating rearward at a higher rate, the ring gear is rotating forward as it should.

 

[Baby Grand]

Considering an immovable load, an unbendable draw bar, and an unbreakable chain, combined with unlimited torque, horsepower, and perfect traction, I believe what would happen would spin us up a freaking singularity and the birth of a new universe. Maybe we're messing with things that should be sorted out by the various deities.

I can hear George Carlin now ... Father, father, can God make a tractor so stable he himself cannot back flip it?

 

[xtn]

Let's forget all the details we've been discussing and ask ourselves two questions:

1. Is it possible for the nose to rise up when pulling at all? At least to some equilibrium point? ANY equilibrium point?

2. Is it possible for the nose to rise up with momentum?

If your answer to both of those is yes, then you must believe it is possible to backflip a tractor by pulling a load. Sure, there are other conditions and factors that may prevent it happening, but it's POSSIBLE.

xtn