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hitch angle July 06, 2017 01:59PM
Does the hitch angle make a difference

Re: hitch angle July 06, 2017 03:58PM
Nope

Re: hitch angle July 06, 2017 04:57PM
Yes, it actually does because the hooking point will be closer towards the front or rear of the tractor depending on the angle. It doesn't change it much but it does change some.

Re: hitch angle July 06, 2017 11:52PM
Nope, as long as your hitch and the supporting members are rigid.

Re: hitch angle July 06, 2017 11:56PM
Makes no difference what so ever.

Re: hitch angle July 11, 2017 01:11PM
IF its closer to the rear end yes but it could now be illegal if you have your drawbar on bothe 18 inches from the center of the axel and 20 inches high no difference But if you built your hitch 18 inches from the center with the drawbar horizontal at 16 inches then raise it up to 20 without moving the front pivot point your now at 16 and cheating in that case yes it will help

Re: hitch angle July 07, 2017 12:57AM
If it makes no difference at all why is there a hitch angle rule?

Re: hitch angle July 07, 2017 01:17AM
There must be some sort of advantage, otherwise, why would all of these aftermarket hitches hook at an angle, I've seen some people have them adjusted as much as sitting at close to a 45 degree angle. Maybe it has something to do with pulling on a 90 degree angle from the hook point of the hitch.

Re: hitch angle July 07, 2017 04:20AM
Go to your local playground, find the teeter totter, bring 2 tractor weights, a folding chair, a 10' piece of rope, a couple pairs of C-clamp vice grips, a piece of flat iron and another piece bent at a 45 degree angle (both same length). Put folding chair under one end of teeter totter, set a tractor weight on that end and let chair support it, go to other end, tie the rope to it, lay weight on ground about 3' back, thread rope through tractor weight handle, now pull on rope. Take mental note of how hard it pulls to lift the other end and how high you can lift it (may have to move the weight on the teeter totter closer to the axis so it doesn't lift the other weight off the ground). Now clamp that 45 degree piece of iron on and tie rope to it and pull, results??? Bet it's a lot harder to pull on that angle to lift the other end of the teeter totter and you won't be able to lift it as high. To give this experiment a fair shake to you should have a 4"x4" piece of wood or something to put under the 45 degree angle so your hook point stays the same.

Re: hitch angle July 07, 2017 01:55PM
Your experiment if seriously flawed for a number of reasons.

You need someone to draw you a free body diagram to explain why it makes no difference on hitch angle as long as it's rigid.

Hitch length and height matter.

Hitch angle is as important as hitch color!

Re: hitch angle July 10, 2017 09:44AM
Assuming the angled hitch is constructed right, I would be on the side of hitch angle makes a difference in one force of pulling which would be the chain and sled with tractor "at rest". So lets say you have a plain straight hitch, put brakes on-on the tractor with sled hooked up, now sled backs up (lets just assume it has the power to do this and leave that out of this), As it pulls back it will want to straighten/make the chain parallel to hitch/hitch parallel to chain, so it pulls the front end of tractor off the ground say 2', chain is now straight with hitch, now it will just want to drag the whole tractor backwards, rear wheels sliding.

If one were to construct an angled hitch as such, lets say Point A is 1' in front of axle and 1' above, Point B is axle/axis and Point C is hook point (Point C hook point is same length distance from tractor and ground as flat hitch, but now ending at a 45 degree angle). So the beginning of hitch is Point A and it's pivot point is Point B, Point C remains the same (other then the angle its coming in at). Now at rest lets just say the chain ends up being 30 degrees pulling on a 45 degree hitch angle, when sled backs up with tractor brakes on, Point C will actually fight to push Point A down to straighten the chain will it not? Thus not allowing the front end of the tractor to lift. The key to this is the hook point has to be at/end at 45 degrees, if you did all this and on the last 6" of the hook point, made it parallel to the ground, everything angled goes out the window, if you were to brace Point C by running a bar to say 1' under Point B, it also throws everything out the window.

As for the other force at hand, that would be the engine power applied to the ring and pinion trying to turn the wheels, if it can't turn the wheels, the pinion climbs the ring lifting the front of the tractor and it doesn't give a crap how it's hooked, it just wants to go round and round that ring if allowed to do so.

Putting these forces together, it's easier for the pinion to climb the ring when the sled/chain is helping pull down on the straight hitch/"teeter totter" (as Scott B was I believe getting at), if the hitch is angled (again... built correctly) the pinion will not get this initial help "pre-parallel chain".

Re: hitch angle July 11, 2017 10:17AM
Quote
Forces Applied
Assuming the angled hitch is constructed right, I would be on the side of hitch angle makes a difference in one force of pulling which would be the chain and sled with tractor "at rest". So lets say you have a plain straight hitch, put brakes on-on the tractor with sled hooked up, now sled backs up (lets just assume it has the power to do this and leave that out of this), As it pulls back it will want to straighten/make the chain parallel to hitch/hitch parallel to chain, so it pulls the front end of tractor off the ground say 2', chain is now straight with hitch, now it will just want to drag the whole tractor backwards, rear wheels sliding.

This is incorrect. The pivot of the "teeter totter" is the rear axle. You have to extend the force vector of the chain up, if it passes below the axle the chain will attempt to pull the front end down. If it passes above the axle it will cause the tractor to rotate about the rear axle until the force is directed at the rear axle. It then will want to drag the whole tractor backwards with the rear wheels sliding.

No matter how or where the drawbar is attached to the rigid frame, as long as it's rigid the forces and torques on it have to balance and all rotation has to happen around the rear axle.

You are absolutely correct about the pinion climbing the ring gear & in fact the standard chain length causes it to point under the axle with any tire over 60" tall. BTW the angle of the standard chain is much less than 45°, it's closer to 25°.

Edited 1 time(s). Last edit at 07/11/2017 03:33PM by Jake Morgan.

Re: hitch angle July 11, 2017 01:52PM
Actually, on big sleds the chain length, per NTPA and NAOSOI is 46", plus or minus 1/2".
Mini sled chains are to be 36", plus or minus 1/2"

Re: hitch angle July 11, 2017 02:34PM
Not claiming to be a physics expert but I do know that my hot farm tractor had a relatively short wheelbase and it was always a bear to drive straight no matter where we put our moveable weight (typically had 1000 lbs to play with) We changed the angle of our hitch one day just to try something new and it has never run straighter. Literally a night and day difference. We raised the "front" of the hitch to be closer to the rear end, only moved it about 3 inches but it made all the difference. To anyone saying hitch angle doesn't matter, I strongly disagree because I've experienced it.

Re: hitch angle July 12, 2017 07:35AM
The hook self centers better. It has to climb uphill if it get off center. The hook might also hook slightly higher depending on how the inside of the hook fits the opening in the hitch. If the hook has a larger radius than the hitch opening, it will not sit all the way down.

Re: hitch angle July 12, 2017 05:25AM
Yes, 46" is what I used. A 46" chain hooked 20" above the ground make the angle of the chain to the ground 25.8°.

Re: hitch angle July 12, 2017 09:51AM
Deere Puller, you are correct with the pivot point being above hook point and pulling back and down, it will not raise front. I was staring at a truck when typing that out and the axle location completely escaped me. However (work with me one this), lets say tractor tires are chained to ground, now back sled up, pan will lift off ground and chain then becomes so tight, almost like a bar, so then it will apply the down force of the weight of the front of the sled to the drawbar, therefore bringing the front of the tractor up, (similar to take off when the pan of the sled gets picked up sometimes). That being said, I would retract hitch angle making a difference as far as that force is applied (picking up sled pan as stated in scenario). I am still thinking the angled hitch is relevant as far as applied to the ring and pinion climb assistance factor, with a straight hitch that pinion climb is gonna get assistance until it pulls the hitch/tractor to "25.8 degrees", after that it has to work harder to pull that hitch under the tractor/pivot point. With a hitch at a 25.8 degree angle to begin with, the "pinion climb" should loose that assistance it would have gotten otherwise, correct???

As for the angles, I was referring to the hitch as 45 degrees, I approximated the chain at 30 degrees. I didn't intend those angles mentioned to be taken literally, just throwing them out there for a baseline for trying to picture what I was describing.

Re: hitch angle July 12, 2017 11:57AM
One problem - your assumption that the pivot point is the axle. It is not. The pulling vehicle makes contact with the track at the bottom edge of the tire, not the center of the axle. This is confusing and counter-intuitive, but true.

One way to make sense of this is to pretend the tire has gear teeth around it, and the track has mating gear teeth so there will be no slippage. Now, lock the brakes, and pull on the hitch of your choosing (height, length, etc). What happens? The front will come up. The pulling point is above the pivot point (intersection of the tire and the ground). The brakes holding the axle have a similar effect on the system that the axle applying torque to the wheel does - the difference is only a matter of values, but the concept is the same.

For more information, Google "free body diagrams". They are used in engineering analysis to simplify complex force problems into just solving the boundary conditions.

Re: hitch angle July 13, 2017 05:12AM
details matter, shoot.... that is true. If the brakes are locked on the tractor, the axle has no way to pivot, so essentially the tractor would become a big sideways L shaped piece of iron, short side of "L" bolted to ground on a pivot and long side would be frame rails. Say the short side of the L is 40" high, so hook a chain at 20" (half that) and pull, it will raise the front end (long side of L).

That being said if we can all agree that to be true, apply the angled hitch theory again, both straight and angled of course must end at same hook point so far back from short side of L, as you pull the chain with a straight drawbar until 26 degrees is obtained on the drawbar you are actually gaining some leverage per down force, after that it begins to become counter productive. Pull on the angled drawbar (lets just say it is 26 degrees) it should be counter productive the whole time pulling on the chain, right?

Re: hitch angle July 13, 2017 05:21AM
I have honestly lost brain cells by reading this thread. Before anybody should talk about simple physics, they should first understand them. Spend more time reading than drinking and you might understand the mechanics better.

Re: hitch angle July 13, 2017 10:21PM
The brakes are not locked, the tractor frame rotates around the rear axle. Take a scale model tractor and notice that the axle is directly above the point where the tire contacts the table. Now lift the front end 45 or even 90 degrees and note that the axle is still directly above the tire contact point because it is the center of rotation. There is a torque at the axle where it is rotating the tire and you need to include that in your free body diagram.

I don't have time right now to draw up the free body diagrams, but you need to do that for the drawbar, showing the chain load and the loads at the pivot pin and support bolts (presuming an Engler style drawbar). Then apply those loads to the tractor frame along with it's center of gravity, the torque on the rear axle, and vertical support at the axle(s).

Re: hitch angle July 13, 2017 06:02AM
Great thread folks. Enjoy the nuts, bolts, forces, and angles in pulling.



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Re: hitch angle July 07, 2017 07:17AM
They call that the Roberts rule from when he ran 20 years ago. Doug got on here an explained it a while back

Re: hitch angle July 07, 2017 08:46AM
any bar that we choose to use to "PRY" something needs to be at an extreme angle to lift or move anything, any thing

Re: hitch angle July 07, 2017 05:14PM
If you could take the time to search the forums that Doug Roberts has commented on, you would find the discussion where Doug explained why he ran an extreme angle on his hitch back in 1996 and why the governing people decided to enforce a rule that regulates the degree of slope on your FLAT IRON hitch point. If that doesn't make sense, search the forum for the discussion so you may be humbled the same way I was after saying "it's physics, if it's all rigid it won't make a difference". I was wrong, if you don't understand Doug's hitch, you are too. To all of those people up there saying it doesn't matter, if they are not thinking of it the way Doug did, and the way I did until he explained his reasoning and why he had to weld the upper edge back up on the drawbar ever couple pulls it wouldn't make sense I guess. It wasn't a theory. It was simple genius physics and for him, it was a temporary solution to fix the lack of front end weight he needed. On a perfectly weighted tractor, the drawbar angle would not be any advantage, but, if you can't put as much weight on the front as you need, or you are unsure how to balance your tractor correctly, it will certainly make your hook to the sled more forgiving.

Re: hitch angle July 07, 2017 10:53PM
An angled hitch has the effect of making the hitch itself into "another link in the chain" and the force point is now higher and closer to the rearend.

My non-scientific way to look at it.

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