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.

 

[Egon]

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

Trying to confuse us uneducated boys with verbage? :thumbsup:

Just come up with a force diagram with all the forces to prove your point. Verbage in quantity doesn't.

 

[SPYDERLK]

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.

Yes, thats what I said:

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.

Interesting that it is done. I thot it might be used to downsize the differential by introducing a further gear reduction afterward in the L/R axles.

 

[ovrszd]

Yes, thats what I said:
Interesting that it is done. I thot it might be used to downsize the differential by introducing a further gear reduction afterward in the L/R axles.

Sorry, I thought you implied that the reverse rotation setups did NOT have a lifting affect.

I think those setups were used for two reasons.

First being as you offered, didn't have to use as big of gear ratio change in the third member.

Second, they gained main chassis height, or what is commonly known as "row crop" design. Early Fords advertised that gain. Brands that did not use that design set their tractors on much taller tires to try to achieve that height. Was very much needed when "laying by" corn, or what is commonly known as cultivating. Could do it when the crop was much taller.

 

[SPYDERLK]

Trying to confuse us uneducated boys with verbage? :thumbsup:

Just come up with a force diagram with all the forces to prove your point. Verbage in quantity doesn't.

I explained it in previous posts. msmith1wa understood and described an example :

I am going to propose something that is not practical but takes what SPYDERLK is saying a little further.

Lets say there is an object that is to heavy or is theoretically immovable. Now lets dig a trench out from this object. Now fabricate a hitch that has the pull point below ground level. Now back the tractor up to the immovable object so that the trench is between the tires so that the hitch can be installed without dragging. Now pull on the immovable object with the tractor.

Will the tractor lift the front tires and tip over backwards? No it will not, in fact it will do just the opposite and actually force the front tires into the ground.

>>> Then you reiterated the impossible <<<...

>>>As soon as the tire's stop moving the front of the tractor goes up. It requires sufficient torque and the rear must have enough traction so they rotate more slowly than normal for the gearing being used.<<< :thumbsup:

The force contributed by the drive shaft must be included in the sum of forces and acts at the point the pinion contacts the ring gear.p:thumbsup:

Why do some four wheel drive tractors have weights on the front when just the fact the tractor is hitched low and pulling would do the same thing?

Do yourselves a favour and look at a picture of a ring gear and pinion. What happens when the ring gear is locked in position as would be the case with sufficient traction!

View attachment 371314

[Were seeing the reason the gear climb description is a problem.]

... I dont think youre going to be able to break free of it.

 

[CalG]

What I don't get is why the tractor doesn't tip over sideways as the transmission input shaft tries to "walk around" the first gear on the lay shaft.

It seems that that is where the engine power is the most direct!

;_)

Really, I do get why,..

but pulling trees up hill is a task worth considering carefully. The OP has more information than one can shake a stick at. Hopefully a prudent operator would hitch low, carry low and go slow. that and stay off the side slopes! For ALL the reasons discussed

 

[ovrszd]

What I don't get is why the tractor doesn't tip over sideways as the transmission input shaft tries to "walk around" the first gear on the lay shaft.

It seems that that is where the engine power is the most direct!

;_)

Really, I do get why,..

but pulling trees up hill is a task worth considering carefully. The OP has more information than one can shake a stick at. Hopefully a prudent operator would hitch low, carry low and go slow. that and stay off the side slopes! For ALL the reasons discussed

I assume you are just trying to be funny.


But then,,,, if you don't know why the front tries to lift under power, you probably also do not know why the machine in fact does try to tip over sideways. This action is not visible on a vehicle without suspension but it is very noticeable in all others. Especially those with high torque engines such as big bore gassers or diesels. Go sit in a truckstop for 5 minutes watching the Semis come and go. You'll see both actions live and in person.


In an attempt to use examples that you might be familiar with, I also reference Super Stock cars at the drapstrip. Explain to me why they lift the left front tire first, then lighten the entire frontend and shift all that weight into traction to the rear tires???

 

[CalG]

I assume you are just trying to be funny.


But then,,,, if you don't know why the front tries to lift under power, you probably also do not know why the machine in fact does try to tip over sideways. This action is not visible on a vehicle without suspension but it is very noticeable in all others. Especially those with high torque engines such as big bore gassers or diesels. Go sit in a truckstop for 5 minutes watching the Semis come and go. You'll see both actions live and in person.


In an attempt to use examples that you might be familiar with, I also reference Super Stock cars at the drapstrip. Explain to me why they lift the left front tire first, then lighten the entire frontend and shift all that weight into traction to the rear tires???

Why those are examples of INERTIA at work.

If those durn drag cars weren't in such a big hurry, why I bet a fellow would never know they had such big engines in them.

Exactly the same reason why the cars at the drags "lift their front ends. The contact patch is below the center of mass, and that contact patch is trying to be in a place up ahead that the center of mass is not quite prepared to go at the same time.

Perhaps confusion over dynamics and statics is the root of all these comments.
One takes calculus, the other just needs to solve triangles ( force vectors) .

It's easy enough for me to simplify a slow moving tractor to the condition where statics describes everything.

Now that speeding drag car or the rocking big rig. I would need to call on "the calculus". to describe the results.
Lets not get all "wound up" in hotchkiss drives and the need for ladder bars or I'll just be beside myself.....;-)

 

[ovrszd]

Egon and my points are simply that there is no need for calculus or dynamics or statics or vectors or triangles or any other such methods of description. It's very simple. I was just curious if you could explain it. But now I'm not sure.

I scrounged thru my boneyard but couldn't find an intact third member. I'll check at my Son's shops and if I find one I can explain it all with 30 seconds of video, no charts, graphs, vectors or formulas. Just simple logic.

 

[Egon]

Egon and my points are simply that there is no need for calculus or dynamics or statics or vectors or triangles or any other such methods of description. It's very simple. I was just curious if you could explain it. But now I'm not sure.

I scrounged thru my boneyard but couldn't find an intact third member. I'll check at my Son's shops and if I find one I can explain it all with 30 seconds of video, no charts, graphs, vectors or formulas. Just simple logic.

I've explained it more than once. I've also sat on tractors hitched low with the front wheels off the ground.

 

[Egon]

I assume you are just trying to be funny.


But then,,,, if you don't know why the front tries to lift under power, you probably also do not know why the machine in fact does try to tip over sideways. This action is not visible on a vehicle without suspension but it is very noticeable in all others. Especially those with high torque engines such as big bore gassers or diesels. Go sit in a truckstop for 5 minutes watching the Semis come and go. You'll see both actions live and in person.


In an attempt to use examples that you might be familiar with, I also reference Super Stock cars at the drapstrip. Explain to me why they lift the left front tire first, then lighten the entire frontend and shift all that weight into traction to the rear tires???

Engine rotation forces transferred to the frame.