Hill Climbing Primer

[SPYDERLK]

http://youtu.be/sZBjNKhcWtY

Low hitched tractors lifting the front end. This is supposed to be impossible eh?

No. ... Great video. Those are such tractable engines. Looks like they pull good down to the last putt.

 

[ovrszd]

You gotta watch out for the Wee Folk. Afore you know it they will have you partaking of their Magic Brew and all you will see is two flat front tires from overload and your tractor sitting in a big hole it dug when turning the front end under.

And they'll convince you that the tractor your squished under is really sitting upright and all is good.

Heheheheh... No my friend, they'll never accomplish that.

I'm an optimist. I believe we all know the same thing about this, that is the fact that the front rises with power applied. I just think we differ in how we understand it and explain it.

Your attached pic of the ring gear and pinion clearly shows the effect of turning the pinion for forward motion. Also your descriptions have further explained the concept.

Again, I'm an optimist. I'll just wait for it all to become clear. No worries.

 

[ovrszd]

This has become quite silly. Any setup of driveshaft to rear axle will be set up to rotate the wheels forward when power is applied in a forward gear. Moving the pinion from the front to the back of the ring gear would only mean the drive shaft rotation direction was reversed not that the torque was now applied downward. And pinions don't climb up a ring gear as much as they walk around the circle. Stop the circle and the walk goes faster. Like walking up the down escalator and having them shut off the power. And last but not least is the weld the axle to the housing theory. That would amount to applying a very good parking brake and you would stall the engine, nothing more.

Very clearly stated. Actually got Larry to agree with part of it. Unfortunately he passed over the critical point and focused on the weld the axle part,,,, which we all know,,,, has nothing to do with the pinion versus ring gear scenario we are trying to explain.

I totally agree with your statement about the pinion not climbing the pinion, but instead walk around the circle. That is exactly what is happening. Which explains why the same forces are applied even if the pinion is moved to the rear of the ring. Well stated.

 

[ovrszd]

I'll dig around in my spare parts pile and see if I have a complete third member. If so I'll video an example of the "walking around the circle" phenomonen we are talking of.

 

[SPYDERLK]

Very clearly stated. Actually got Larry to agree with part of it. Unfortunately he passed over the critical point and focused on the weld the axle part,,,, which we all know,,,, has nothing to do with the pinion versus ring gear scenario we are trying to explain.

I totally agree with your statement about the pinion not climbing the pinion, but instead walk around the circle. That is exactly what is happening. Which explains why the same forces are applied even if the pinion is moved to the rear of the ring. Well stated.

I'll dig around in my spare parts pile and see if I have a complete third member. If so I'll video an example of the "walking around the circle" phenomonen we are talking of.

You might want to take a look at why a setup with the ring gear driven the opposite direction that the tires turn would still produce the same result.

 

[ovrszd]

You might want to take a look at why a setup with the ring gear driven the opposite direction that the tires turn would still produce the same result.

Wouldn't that action simply move from the ring gear to whatever gear setup reverses the direction??

 

[CalG]

Over backwards ...or to make an observation on the idea of draw bar location and length.

Imagine, if you will.

The tractor is hitched to a load on flat ground, There is a chain between the load and the draw bar. (no vertical constraint) In this imaginary situation there are two "special cases".

First, the tractor draw bar ridgedly extends 4 ft. past the rear wheels horizontally at "normal draw bar height. (lets say 18 inches high).

The second special case is that the tractor straddles a trench just over four feet deep The load also straddles this trench.. The idea in this visualization is that the draw bar can go below grade when and if the tractor rears it's front.

---/O---

Can the tractor go overbackwards in this example? At some point, the angle of the chain fixed to the load will apply a lifting component to the rear of the tractor, that should comense as soon as the hitch point of the tractor is lower than the hitch point of the load. The decrease in traction coupled by the self righting lever arm of the long draw bar should assure that the tractor will not go over. But, perhaps the soil is very grippy ;-)

It is begining to look like the tractor is acting as a self powered winch hooked to an immovable load. The winch line gets rolled up on the spool (the tractor tire).

Which suggests, that if one were contemplating bolting a bare wheel rim outboard of the tire to use with the wheel jacked off the ground as a winch. Be sure to set the tractor in REVERSE gear so as to preclude flopping the tractor ;-)



This all goes back to the very early post on this thread regarding draw bar design. Taken to some extream condition, design features usually make themselves obvious.

 

[SPYDERLK]

Wouldn't that action simply move from the ring gear to whatever gear setup reverses the direction??

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

 

[Egon]

You might want to take a look at why a setup with the ring gear driven the opposite direction that the tires turn would still produce the same result.

Just jack up the back end and turn a tire.

 

[ovrszd]

CalG, in your example, the front of the tractor will become lighter as soon as power is applied. Whether it lifts off the ground is determined by the amount of traction transferred to the rear tires. With your example, very little traction will be transferred due to the height of your drawbar versus height of the load. Is it possible for this tractor to tip over backwards?? No way. And it's because your hitch height will immediately begin to remove traction weight from the rear tires and the tractor will simply spin.


Larry, I thought of an example where the drive gears rotation is backwards. A WD45 Allis Chalmers tractor, or many, many other models that use an additional set of gears outboard of the main gear case. These designs create a situation where the axle shafts coming out of the third member assembly are turning backward. At the outer end of that shaft is a straight cut gear. It turns a larger straight cut gear which is fastened directly to the shaft that the rear tire is fastened to. The reverse rotation of the first shaft, thru the two gears, creates a forward turn of the shaft the tire is fastened to. These tractors display the very same "light front" affect that a standard setup creates. No change in the end result.