Track Maintenance for Old Men

[cloudcap]

As we loaded the Imp after our last outing my wife noticed that one of the backing plates was torn loose (a couple of the bolts had broken). She's not a particularly mechanical person, so I was pleased that she noticed something amiss and mentioned it. I guess she's learned a trick or two after being married to an engineer for 30 years.

I ordered a bunch of new Grade 8 bolts and nylock washers from McMaster-Carr and today I pulled the cat into the garage and threw it up on jackstands. I replaced the broken bolts and then noticed that a *lot* of the bolts on the tracks were loose. They had nylock nuts so the nuts were tight to the bolt, but you could rattle 30% of the bolt/nuts with your fingers and another 30% spun easily in the hole with a wrench.

I started tightening up the loose bolts while working from the side of the tracks, but it was difficult and uncomfortable reaching the inner half of the grousers -- you had to kneel and reach in through the wheels and across the top of the tracks. It stopped being fun in a hurry.

After a bit I had the bright idea of working from the back of the tracks instead of the side. I was able to set up shop with a bucket to sit on, plenty of light, and all my tools within easy reach. I used a section of pipe as a pry-bar to advance the tracks so that I was able to work on each grouser while it was right in front of me. Still a lot of work, but *way* easier.


So here's the $10 question -- just how tight are the nuts and bolts on a track supposed to be? "Rattle loose" just seems too loose to me -- the bolts spin and eventually wear through the aluminum backing plates. I'm tightening them till they're moderately hard to twist with a wrench, but maybe that's too tight. So what's your advice?

Thanks

Ron

 

[Sylvia Tunaskas]

Not sure if this applies to your Imp. I was told by the mechanic that works on my LMC 1200 that the proper torque for my unit was 30 foot pounds "rolling" torque. I have no idea what rolling torque is, but in your 30 years of engineering experience you may understand this concept. In tightening the bolts on my grousers I found it much easier to con a buddy into helping. (one on the top nuts and another on the underside bolts) Hope it helps.

 

[Snowtrac Nome]

your imp looks like it has the tube grousers i would caution you against too much torque as you may colaps the grouser i wouldn't use nylock i use boma lock nuts they are stamped and good for a second use in a pinch

 

[BigAl]

your imp looks like it has the tube grousers i would caution you against too much torque as you may colaps the grouser i wouldn't use nylock i use boma lock nuts they are stamped and good for a second use in a pinch

I agree .......for once !

 

[cloudcap]

your imp looks like it has the tube grousers i would caution you against too much torque as you may colaps the grouser i wouldn't use nylock i use boma lock nuts they are stamped and good for a second use in a pinch

So what's a "boma lock nut"? I didn't turn up anything by that name with a Google search (in fact, the only usage on the Internet seems to be in this tread). McMaster-Carr has "Flex Top Expanding Hex Nuts"

and "Distorted-Thread Hex Nuts".


Since you mention boma lock nuts being "punched" I'm assuming that they're the Distorted-Thread nuts. Would you agree?

Also, what's the drawback with nylock? Most of the existing nuts on the tracks are nylock along with a few Flex Top. I haven't come across any nuts that are punched.

Thanks

Ron

 

[Cletis]

Agree with DDS.

Would it make sense to torque the tube grousers to the same torque as the track splice torque recommendation, what ever that might be?????

 

[Mtn-Track]

Hi Ron,

On my Tucker with the 1500-series tracks, Tucker says to torgue the bolts to 20 foot-pounds using ny-lock nuts. They recognize that this may seem "loose", but they say it's enough to hold the backing plates but not too much as to damage the belts. They also enforce the rule of not using ny-locks twice. Once you take a ny-lock nut off, replace it with a new one.

Hope this helps.

 

[Snowtrac Nome]

boamalock nutts are simalar to your deformed thread lokg=k nuts except the stamps are it the top where your nylock part is at on your conventional nyloc nuts are and yes Al just come out of the closet and admit snow tracs rule and krustys drool

 

[cloudcap]

Thanks for everyone's suggestions -- this has been very helpful.

When I started this job I knew I'd need two nuts/bolts to replace the broken ones, so I ordered 50 each thinking it couldn't hurt to have one or two extra. And of course, when I got into the project and started tightening loose nuts I used my 48 "extra" nuts/bolts to replace ones that broke. That got me 3/4 of the way through one track. Clearly I need to expand my concept of "a few extra".

Knowing that Tucker recommends torquing nylocks to 20 foot-pounds is useful. There's no way I'm going to use a torque wrench on each and every nut (I just don't love my snowcat that much...), but I'll do a few to get a feel for what a properly tightened nut/bolt feels like. From there I'll free-hand it using an impact gun on the front and a hand-wrench on the back (you can turn the bolt w/ the hand wrench and feel it tightening up).

I'm on the fence re nylocks vs. distorted-thread nuts. Reusable is nice, but I'm also OK with disposable. Minimally I'll need to use nylocks to get a feel for how tight to get the nuts since I suspect that distorted-thread nuts have more resistance and would throw the torque wrench off. Maybe I'll do some of each just to get a feel for how they work over time.

I suspect that I'll be rebuilding tracks in three or four more years (the belting is showing signs of age), so I can use the next few years to see what fasteners work best for me.

Regards

Ron

 

[weatherby]

What I did when rebuilding my tracks on a Thiokol 601, is I tightened the nuts as tight as I could before anything started to distort, such as the grouser, backing plate, or the rubber belting bulging on the edge. I never checked the lbs per sq. inch but because I had 2560 bolts to tighten, I set my air impact wrench to match my hand tightening then used the impact wrench to do all the rest of them.

I also used nyloc nuts just to stay with the originality of the factory, however, I feel the other lock nuts listed above are much better.

I hope my experience helps.

 

[dpaulson]

Stover nut

 

[Blackfoot Tucker]

What I did when rebuilding my tracks on a Thiokol 601, is I tightened the nuts as tight as I could before anything started to distort, such as the grouser, backing plate, or the rubber belting bulging on the edge. I never checked the lbs per sq. inch but because I had 2560 bolts to tighten, I set my air impact wrench to match my hand tightening then used the impact wrench to do all the rest of them.

I also used nyloc nuts just to stay with the originality of the factory, however, I feel the other lock nuts listed above are much better.

I hope my experience helps.

Weatherby,

I'm curious where you got your grouser backing plates. They look like they are an aluminum stamping.

All three Tuckers I've owned used different style backing plates. The current ones are 1/4" thick by 1" wide and have straight edges which IMHO cause excessive stress on the rubber belts as they run around the idler wheels on the carrier ends. I would think a backing plate with radiused edges would be easier on the belting.

Suggestions, comments?

P.S. Glad to see you back on the forum...

 

[weatherby]

I agree with you on the raised edges of backing plates, and I assumed most if not all cat manufacturers did that to there backing plates for the reason you stated, and also to make them more rigid against bending

Having seen Cloudcaps backing plates, I just assumed those were changed from the factory plates sometime in the past, because they look nothing more than maybe 1/8"x1" 6061 aluminum flat stock, but maybe it is 7075 aluminum which would be a much better choice in this situation because it will be hard to get a decent torque on the bolts with out distorting those backing plates with the softer 6061 aluminum.

Those are the Thiokol factory spec. backing plates on my tracks, however, because most of my backing plates were damaged beyond repair and missing, myself and a friend of mine (a tool maker by trade) made a die to re-manufacture the Thiokol 6 series backing plates, so all the backing plates you see on my tracks were stamped out by me on a hydraulic press in my shop.

In the pic, the backing plate on the left is the one I make, the middle one is the same but has been bead blasted, the one on the right is a factory original after it was bead blasted.

The second pic shows the jig we made to bore the holes exactly the same every time.

 

[Borvig]

Would you be kind enough to post pictures of the die you made to form your backing plates? The results look very good. What type of stock did you use? I need to replace the flat backers on two sets of tracks for Tuckers. Something in the neighborhood of 830 pieces.

 

[weatherby]

Would you be kind enough to post pictures of the die you made to form your backing plates? The results look very good. What type of stock did you use? I need to replace the flat backers on two sets of tracks for Tuckers. Something in the neighborhood of 830 pieces.

Thanks Borvig, I used 5052 sheet aluminum for my backers. For a flat backer 6061 would probably be a better choice. 7075 is even stronger but much more expensive. Keep in mind, the higher the Brinell hardness the more likely it is to crack when it is bent.