IMP 1404 Track Tension

[IMP]

Is there a general rule about how much tension, or the correct amount of sag for determining proper track tension?
These are new home built tracks with a new drive sprocket and the front idler wheel is bolted all the back to allow the most slack possible. I have 55 grousers on each track on 4" centers.
With the tracks off the ground, the center two boggies have about 1 inch of space between the bottom of the tire and tire guide(I would call this the sag in the track).
I can only pick the top of the track up off the center boggies about 3 inches with arm strength. And I can only slowly roll the track by hand using all my strength (its about 10 deg in my shop and the belting is pretty stiff).
I can see about 1/4" gap between the new plastic drive sprocket and the grouser tire guide that will soon wear in allowing the grouser tire guide to fit snug to the sprocket so that should give me a 1/4" less tension when I get more miles on them (about 5 miles total so far). I think the stretch is already out of this belting because it was used on a conveyor for 7 years.

 

[Snowcat Pat]

Nice work on you new tracks! I have built tracks from the ground up and I do appreciate how much work it is.

-I think you have more than enough track tension there.-

Even though they are used, your belts will stretch during the wet months and shrink up again (somewhat) during the dry months.

Some of the resistance to rolling the track is caused by the rear end internals dragging in the oil. When you try to rotate one track the brake drums are turning in opposite directions...lots of drag.

By the way , who recovered your sprockets?

-Pat

 

[IMP]

I first sent them to Okners. Then after a week or so he realized his mold was cracked so he mailed them to FallLine and they finished the job.
On this track tension question I guess I was not clear. I am a little concerned about having too much tension on the track. If I had a way to adjust, I would slacken it in my judgment. The Imp has a pretty crude, coarse track adjustment and its already adjusted all the way slack. I dont fully understand what happened but my old track had 54 grousers on 4" centers, my new track was too short so I added one more to make it 55(used up my two spares). I think 56 grousers would have been to much slop. Besides I almost puked at the thought of having to build 2 more grousers. There has to be tremendous stress exerted on the transaxle housing when going over bumps with the track pulling on each sprocket from both side( plus, I already welded a crack in my C4 housing that is at this time is still holding). I only have 5 miles of experience with this machine so I really dont know if the track is ok or too tight it just seems to me to tight. But I know this for sure I would not want that track falling off on some snowy hill side or mud hole!!!!!!!!!

 

[NorthernRedneck]

I wouldn't worry too mush about the track tension. From what you said you've got for slack from the center boggies, I'm sure theyll be fine. Our machine recomends that new track tension be right around where you have them. Even though they are old belts, they will still stretch. So I would tend to think that you would want them a bit tighter at first to allow for some stretching. That way, you've still got adjustment options and they won't be maxed right out.

 

[GSSD06]

My Imp has 56 grousers with 4" spacing.

It may be different with my rubber covered sprockets, but I found that if I do not have the track tight enough, when I am going down hill on compression and make a turn, the track jumps a tooth on the sprocket.

I noticed some cracks in the rubber on my sprockets which I think is from grousers jumping the sprocket, but I am not positive that is the cause.

I also now try not to turn much when decelerating, especially down a steep hill.

 

[IMP]

GSSD06, your tracks sound somewhat loose. Do they have much sag in the middle with the track off the ground? Or flop around easy when you pick up the top side track?
I bet it was my new sprocket that changed my track size because I had an older rubber one now its a hard polyurethane plastic.

 

[GSSD06]

I have not had the Imp off the ground with the tracks on to look at how far they sag below the bogies. Your pictures look like your track is tighter than mine was. When I got the Super Imp, I started playing with the track tightners to see if I could find the right tension that did not skip a tooth on a down hill turn. The tension on the Super Imp seems more critical, maybe partially because of the smaller sprockets. When I found what I thought was the best tension on the Super Imp, they were tighter than the tracks on my Imp, so I moved the front idler of the Imp forward one bolt hole and I think it was a great improvement. I did not measure how far I could move the top of the tracks on the Imp, but I remember I could only get the tire guides above the center bogies by hand. My best guess from memory is that my tracks were not as tight as yours. I think my belts were probably a lot more flexible than yours, in much worse condition. I had the Imp in several hard turns with our Cascade Concrete and never any indications of the track being loose enough to walk out of a tire guide.

On a side note, I go out with another snow cat, an older Spryte that has a C-4 but with gear reduction "drop boxes". Their tracks had been rebuilt with grousers made from square steel tubing and when they put the lace on to join the belts they did not put it under one grouser, but between grousers, which made the space there wider than all the rest. Every time that space comes to the sprocket, you can see it turn the machine slightly. You can also see where it is wearing the rubber on the sprocket.

The Imp tracks and suspension are apart now and I am gathering all the pieces to put it back together. Thanks for posting your track rebuild, it is great information. I think I might make my grouser spacing on new belts a little narrower than 4".

 

[IMP]

I would be very interested what your track sag is when you get things together. I know My belting is way heavier than what they recommend so Im sure that has something to do with the track stiffness. And maybe it just needs to be run more(Ill work on that this weekend). I did the three grouser overlap to splice my belts (no lacing) and so far it seems to work good. If you want some ideas to get your holes drilled perfect I have an easy system. Just let me know.

 

[GSSD06]

I would appreciate any input you have on hole locations. I purchased a hand punch used with a hammer which works great on the few holes I have punched. I had thought about making a jig for three or four rows of holes, but was leaning towards measuring from one end of the belt to the other with a tape measure to avoid accumulating error every time I moved the jig. I read a post where an overhead crane was used to stretch the belt and get the desired hole spacing under tension. I was planning to buy two ply conveyor belting with the thicker top and not worry about getting the snow cat version with the same thickness top and bottom.

 

[IMP]

I will get some photos of my method and jig to better explain everything within the next few days. But the way I did it there is no compounding errors, no measuring, and brainless so you cant screw it up. I drilled rather than punched my holes, It was fast and easy. I will take a photo of the drill also.

 

[IMP]

GSSDO6, Photo # 1. Here is the jig I made to drill all the holes in the conveyor belting. The only thing I did that made everything simple and mistake free is this. See the three rows of six holes, After I drilled all nine holes in the belt I would only advance the jig two rows, I would overlap the third row with the previously drilled holes and pin the jig to the belting by tapping two bolts through the jig into the belting. That way you always reference the jig two your prior drilled holes and then all errors are eliminated from then on as long as your jig is right.
Photo # 2. I made several attempts before I got the holes for the jig centered and spaced right. The method that helped me drill dead center to build my jig was tac welding the correct size washer in exactly the right place onto my jig steel. The washers acted as a guide to keep my bit from wandering as I drilled into the jig steel.
Photo # 3. The rubber bit I bought at home depot, I think it was called a centering bit. But it worked great at cutting the belting through the jig. All the holes in everything were drilled 5/16, No oversized holes. Hardware was all 5/16 grade 8. Everything fit snug. Hope this helps.
Im surprised not many people responded to my track tension question. Everyone with one of these rigs must have some kind of opinion on the subject

 

[GSSD06]

Thank you IMP, the pictures and descriptions are very helpful.

I would guess this is a busy time for a lot of snow cat owners, otherwise you might be getting more responses.

I was out twice last week and will be out again twice next week. There is more snow this year here in the Seattle area mountains than for many years.

I am planning to buy new two-ply belting similar to the Goodyear Plylon B used on the snowcats originally but standard conveyor belting with the thicker top cover for conveying dirt, etc. This will probably stretch more than what you are using and so I will spend some time looking at older posts and measuring my Super Imp with different track tensions to get an idea how much stretch there is and what spacing to use. I have been planning to put the holes into a relaxed belt with slightly closer spacing.

 

[mtntopper]

Im surprised not many people responded to my track tension question. Everyone with one of these rigs must have some kind of opinion on the subject

Great job and info on your track setup. As to responses on the track tension, it is often set to personal preferences as to how you want it. I run mine a little tight but the best explanation I have ever heard is run it just tight enough it does not slip for longer life and it requires less hp to turn the tracks that way. I error on being tighter than that as I do not want to untrack my snow cat in a snow bank in the middle of nowhere.

 

[dubie]

i am new at this an have one track tight an one is lose, what is the best way to tighten them
thanks dubie

 

[GSSD06]

My Imp 1404 has a front idler that can be bolted in different places to change tension.

If you measure the "sag" in the tracks, how much difference is there between the two tracks?

You probably should look closely for weak springs or any other issue that might make the one track loose.

Do you have any pictures?

 

[dubie]

hi i will check out the springs. but how do you tighten the tracks do you use a jack or? to tighten the tracks
thanks

 

[IMP]

hi i will check out the springs. but how do you tighten the tracks do you use a jack or? to tighten the tracks
thanks

This is where you adjust the small front wheel forward one bolt hole to tighten the track. But check for other problems if one track is tight and the other loose. Pictures??? we can help!

 

[GSSD06]

Great pictures Imp.
Sorry it took so long for me to get back on.
Here also is a picture of the lace that holds my track belts together, yours might look similar.
Typically you pull the belts together with something, remove the long bolt in the lace and then release the belts.
Once the tracks are off or very loose you can move the ider to adjust.
Some people just overlap the track belts and bolt both ends to a couple of grousers.
You really want to find out why one track is loose and one is tight.
Where are you located?

 

[dubie]

HI SO YOU REMOVE THE TRACK, MOVE ONE BOLT HOLE TO TIGHTEN THEN PUT TRACK BACK ON? JUST AS SOON AS I BUY A NEW CAMERA I WILL SEND SOME PICTURES, BECAUSE I NEED THE HELP

THANKS

 

[dubie]

OH BY THE WAY I,AM WASILLA ALASKA

 

[GSSD06]

Yes, that is how you adjust the track.

Renton, Washington is a bit too far away to stop by.