Tracks

[backcountry]

My Imp while driving down a straight road would always pull to the left (drivers side). A friend of mine recommended swapping the tracks. Last night I finally got the time to take the tracks off. I pulled the tracks straight on the shop floor and the one set that was on the drivers side has a very noticable curve to them. Below are some pictures. Is this a problem? Can this be corrected, and will this cause problems for my Imp? I'm guessing this maybe the cause to why the Imp was pulling to the left.

 

[schmidt]

We had the same problem on our 1200. I was told to rotate them from left to right and put them on backwards. Being on backwards was no problem and this did reduce the pulling. Make sure that the brake bands are not too tight and the machine will freely roll. Hope this helps.

 

[backcountry]

Thanks for the reply schmidt. I pushed the tracks together and the one with the slight bend is actually almost 3" shorter than the other. I also found the front tire right behind the small wheel on the drivers side rubs real bad against the leaf spring. So I think with that tire rubbing, shorter track on that same side and possibly the slight bend in the track has caused the machine to pull to the left side more.

Now I'm taking all the tires off and cleaning everything up. I will fix the tire rubbing and swap the tracks. Will update in a few weeks once all this is completed.

 

[dep6113]

so if we did a little math and said your tracks are 25 feet long they would rotate around 211 times per mile---a three inch difference would be about 52 feet difference traveled between the two tracks if your differential is pulling evenly every mile you travel---that would be quite a bit of pull to the left

if you were on a straight road the short version would be every 100 feet your snow cat travels one track is going 1 foot less. i would double check the layout either one is stretched or somebody laid out the holes wrong

 

[garygaboury]

The more I think about it the more I think one short track shouldn't affect things at all... I can understand with a different size tire on a car but I'm not sure the same applies with a track. In order for the cat to pull to the left wouldn't the left side tires have to be spinning slightly slower than the right side tires? I can't see this happening just because the track is shorter..

Any thoughts?

Gary

 

[Snowtrac Nome]

the differential is a open type differential if both side were locked together like a cat with steering clutches and brakes track length would be a factor the thing causing you to wander is going to be more resistance in one side than the other and this problem plauges bombie diffs and oc diff's some worse than others balance out your brakes and and adjust tracks properly and that will help balange your dragand extent your brake life also check all road wheels for alignment and bad bearings

 

[dpaulson]

I can't see this happening just because the track is shorter..

Any thoughts?

Gary

Here's my thought. Assuming that there are equal amount of cleats on each track, one track revolution involves the same sprocket tooth / rev as the other side. Assuming no slippage from the track to the ground, you will travel 3" shorter / revolution of track because that track length is shorter.

 

[garygaboury]

Here's my thought. Assuming that there are equal amount of cleats on each track, one track revolution involves the same sprocket tooth / rev as the other side. Assuming no slippage from the track to the ground, you will travel 3" shorter / revolution of track because that track length is shorter.

I like problems that make me think. If we are assuming that both tracks have the same number of grousers but are different lengths I still think it would track straight. In order for the tracks to have the same number of grousers the spacing would have to be slightly off but still close enough to engage the sproket correctly on both sides. If that is true then both sprockets are still spinning at the same speed...

For conversation sake I think adding another wheel to one side and adding enough track to cover it wouldn't make any real speed difference in one side verses the other.

Who knows,, I'm going to think some more...

To eliminate the tracks as the problem you could always mark the sprockets, get two helpers to watch and count rotations while you "drive". See how far out it is after 10, 20, 50? That would be my next step..

Anyone Else?
Gary

(I feel like this is a bit like the airplane on a treadmill....)

 

[dpaulson]

Lets say the right track has cleats spaced 6.0 " apart. The left track has cleats spaced 5.9" apart. This would be close enough not to cause any tooth engagement problems for the sprocket. For each engagement of the sprocket , the right side will propel the machine 6", while the left will propel the machine 5.9". This would steer the machine to te left. Your analogy of adding another wheel and enough belting would not make any difference if both (left and right) tracks have the cleats spaced equally thereby propelling each side of the vehicle the same distance.

 

[garygaboury]

Thanks dpaulson, Thats the explanation I needed to understand... Although,, based on fuzzy pictures there might be one extra grouser on the right track, I think you are on to something with the grouser spacing..

Gary

 

[backcountry]

I squeezed the tracks as close together as possible tonight. The straight track is actually 2 1/4" longer than the bent track. However, the slightly bent track when pushed up against the straight track is wrinkled due to the bend in the track. I think if the track was straight like the other they would be the same length. I have counted all the grousers and both tracks have the same amount.

I took all the wheels off and found the wheels on the left side (drivers side) where the cat was always pulling toward had one wheel badly rubbing the leaf spring and bolt. This is the wheel right behind the tiny adjustment wheel.

On the right side of the cat all 5 wheels spun very freely. I'm going to replace some tires, re-pack the bearings, then re-install the tracks on opposite sides. The front adjustment wheels are both in the same adjustment locations. Should I move the one wheel further ahead, tightening the slightly longer track, or leave them both alone?

 

[Snowtrac Nome]

I like problems that make me think. If we are assuming that both tracks have the same number of grousers but are different lengths I still think it would track straight. In order for the tracks to have the same number of grousers the spacing would have to be slightly off but still close enough to engage the sproket correctly on both sides. If that is true then both sprockets are still spinning at the same speed...

For conversation sake I think adding another wheel to one side and adding enough track to cover it wouldn't make any real speed difference in one side verses the other.

Who knows,, I'm going to think some more...

To eliminate the tracks as the problem you could always mark the sprockets, get two helpers to watch and count rotations while you "drive". See how far out it is after 10, 20, 50? That would be my next step..

Anyone Else?
Gary

(I feel like this is a bit like the airplane on a treadmill....)

no you cannot count the revs of the sprokets its still a open differential just like your car it just uses planitary gears in stead of spider gears that way you don't speed up the outside track while braking the inside one

 

[garygaboury]

Sorry for de-railing (de-tracking?) this thread.

Backcounty, good luck..

Gary

 

[mtncrawler]

no you cannot count the revs of the sprokets its still a open differential just like your car it just uses planitary gears in stead of spider gears that way you don't speed up the outside track while braking the inside one

I think you have a misunderstanding of how these steering differentials work. They absolutely do transfer power from the side being braked to speed up the opposite side. That is the core concept of how they work.

 

[Snowtrac Nome]

I think you have a misunderstanding of how these steering differentials work. They absolutely do transfer power from the side being braked to speed up the opposite side. That is the core concept of how they work.

the 3 and 4 pinion systems do chane speeds but not as dramiticaly as a spider system in a car differential

 

[Mainer]

I think there's a need to look at conservation of energy... if the engine is running at constant rotational speed then power output is constant which makes the energy input to the differential a constant. When moving forward power output to either side should be equal and energy should be output - friction...usual basic 101 engineering thing for then the differential output... so if properly applied, the steering is done in bursts rather than long drug-out braking activity...to keep friction loss to a minimum and heat down. So, if heat/friction are minimized then the power to one track should increase while the other track decreases.
So, if this is NOT the case... then either friction/heat go way up to disipate energy or engine speed must go down to compensate. Yea, realize people have differential heat issues but certainly it should be due to inapproprpiate operation (like riding the break) vs. a design whereby excess energy from braking one side is disipated through heat/friction...that would be insanely wasteful....and the means of increasing the other side improves steer so only logical.
So, obviously not being a differential guru... I'm curious about what would result in a design that is 'more' in one type and 'less' in another type...

 

[jo5]

I,d probably really check your track tension they usually will pull or drift toward the the most tension ( tighter track)