Hill Climbing Primer

[CalG]

Those paragraphs in the NASD paper on Draw Bar Leverage explains thing right.

At least for the practical man ;-)

 

[Egon]

Those paragraphs in the NASD paper on Draw Bar Leverage explains thing right.

At least for the practical man ;-)

Did you notice " Rear axle torque" ?

 

[Egon]

No. The key point is "Dont matter how low you hitch". Falsifies Egons whole statement.

Wrong!

 

[CalG]

Did you notice " Rear axle torque" ?

Clear and concise! Not a word about "Pinions climbing ring gears".

I suppose when you get to know things, you use the simple and most correct term to describe the condition.

;-)

 

[SPYDERLK]

Awww Larry,,,, I thought we had covered this already??

If the rear tires do not lose traction and the drivetrain has the power to continue to turn the pinion and the load does not move, the tractor will do a wheelie, "dont matter how low you hitch" That is a true statement and all of the analysis given by yourself and CalG proves it.

So, as Egon, youre stuck on the issue that pullpoint cannot totally offset a backtip. My posts attempt to show the fact that it can. I include some of them for your review:

Computer graphics are too much of a PITA so that wont happen. The info is all there to experience when you use dueling levers of different length. Forget rotation around the axle. Driving force is at the ground. The tip lever is the wheel radius. The anti tip lever is the distance from the axle down to the pull point. When the anti tip lever is as long or longer than the tip lever no amt of traction will tip the tractor in a smooth pull. The tractor will stall or break with hardly a twitch.
larry

Absent acceleration the only effect to tip the tractor comes from the force it exerts rearward on the ground. This acts thru the lever equal to the tire radius -- the axle to ground distance ... the drive lever. Any resistance to tractor motion applied below the axle has a countering effect on the ability of the drive lever to tip the tractor. A tractor drawbar is not low enuf to fully counter this. -- We wouldnt like it if it did, because it would prevent weight transfer to the main drive wheels. We want to have a good bit of weight transfer to the rear for traction. ... So the drawbar is carefully placed an appropriate distance below the axle to provide this transfer. Good if its not too much for safety. ... So the thinking designer manipulates the drawbar length extending behind the axle factored against its height so that the backtip providing weight transfer is moderated due to a simultaneous progressive lowering of the pullpoint. Physics can be analogous to free money to the attentive designer. ... Still, this passive system has its limitations. >The drawbar must extend back beyond the tire circle for best effect. Some do some dont. It depends on 3pt arm length and placement. A long drawbar may interfere - or may be set short for one function and not lengthened for an aggressive pull. For an aggressive pull you want a long drawbar so that the end comes to ground early enuf in tip cancelling the drive lever soon enuf to fully protect against inadvertent very aggressive traction or changes in drive lever orientation ... [think a sudden hook up where the tractor rips itself out of the hole youve dug trying to pull. Force points are shifting and the momentum of a quick tip may not be possible to arrest.

The tires interact with the ground. The pullpiont also interacts with the ground. Its effect is governed by its position [^ v < >] wrt the axle. The gears acting and reacting thru everything in the chassis give you a torque output onto the pivot of the drive lever - axle. This yields a rearward force on the ground from the end of the lever [tire] in inverse proportion to the levers length. If theres no resistance theres ~no torque. The tractor just glides ahead. With resistance comes torque. Depending on where that resistance is applied to the chassis the tip torque on the chassis can be either proportionally increased or offset. A pullpoint between axle and ground offsets ... and at ground level fully cancels tip.

... Whats the pull point of a dragster?
larry

Yes - And still stopping short. ... If you dont move to the final effector point -- the end of the drive lever [ground], you always leave the situation with a more complex and indirect solution. The sound byte concept walking/climbing is convenient but seems to lead directly to the simple assumption that with enuf torque coupled it will always happen. Assessing at the final effector points of drive and load quickly shows the fallacy of that assumption.
larry

>>> Thats just it. It cant happen when the pullpoint is below tire contact. Both the propulsion lever and the pull [load] lever bear equal force ; one pushing forward, the other exactly offseting that push by pulling back. The pull lever is longer so the net torque is to tip the tractor forward. The ring gear is factored into the push lever. Theres no other effect in a steady state or stationary pull. Acceleration or a hill would introduce COM effects.<<<

>>All side tip forces would remain as if the tractor is off. Drive and driven torque are equal and opposite.<<

Try this:... Put a metal plate on the ground. Attach two small crescent wrenches to it a few inches apart. Attach a big crescent between them. Stand on the little ones while pulling up on the big one. ... Thats how you pull yourself up by your bootstraps.

........................larry

 

[Egon]

Clear and concise! Not a word about "Pinions climbing ring gears".

I suppose when you get to know things, you use the simple and most correct term to describe the condition.

;-)

Yup. And at the center is a ring gear and pinion which are used to make it happen.

 

[SPYDERLK]

Wrong!

Cant understand it for you. Sorry.

 

[ovrszd]

So, as Egon, youre stuck on the issue that pullpoint cannot totally offset a backtip. My posts attempt to show the fact that it can. I include some of them for your review:

larry

No Larry, I did not say that at all. I've never said that. You know I've never said that. I've always had the same position in this. My position is that when power is applied there is a lifting force on the front of the tractor. You've actually agreed to that position. You agreed to me and then you confirmed this to CalG. I can copy/paste your agreements, but I assume you know what you've said, as I know what I've said.

There's no need for you to "bold" print to me or to copy/paste several of your replies that have absolutely nothing to do with that position.

Larry, you know that what I've said all along is true and correct. And you also know that it has nothing to do with pull point. You've admitted that also.

You actually had yourself out from under this discrepancy. So are you now saying that is incorrect??

 

[Egon]

Cant understand it for you. Sorry.

I definitely would not want your understanding of it.

 

[ovrszd]

Larry, in regards to my position. Rather than copy/paste your statements that rarely have anything to do with my statements, why don't you copy/paste any of my statements and then explain to me why they might be in error??