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Noticed this today...hairline crack in sprocket

utahwilson

utahwilson

New member
Seems the more I look at my snocat the more I find to fix. I would imagine this is consistent with everyone else. Looks like an old weld on the sprocket has a hariline crack in it. This is a project I do not want to tackle and would prefer a professional reweld. My question is ... When I call a welding shop is there a type of welding I need to reference to fix this crack? Also, can it just be welded from this side? or do I have to take the drum brack assembly off to get to the other side as well? Just put some JB Weld on it and call it good? :w00t2:

thanks

-Kevin
 

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JB weld won't fix it. Its just glorified epoxy.

Probably going to have to grind down the old weld a bit then reweld it. I'm only a 'casual' welder but I don't think there would be any reason why you'd need an expert to weld that. Grind down the excess a bit, then weld it. It may crack again at some point in the future but if you get the weld deep enough it should hold for a long time.
 
Not so fast...

That spocket is a casting. It is most likely cast iron. It was welded by brazing it with bronze it looks like to me in the picture. I don't think that it can be ground out and re welded with a TIG and iron rod as it will be contaminated by the bronze. That would be the prefered way, but wasn't common till the last 20 years. Take it to a pro, and see what he says. Not an easy part to come by, and not cheap if you do. Find the best most knowlegable welder you can find.
He will know how to weld it without warping it out of shape as well...

Regards, Kirk
 
Wilson the sprocket is indeed cast if you don't have inboard brakes it is simple to remove. loosen the chain pop the retaining nut off than slide it off the splines. take it to a welder with cast experience it will have to be ground out pre heated than welded with a high nickel rod it is repairable if you can give me a tooth count I may have access to another one .
 
When I was young, I got the privilege of working in an OLD blacksmith shop. I welded lots of cast things like that. First, you must grind ALL that brass away. All of it. Then, grind enough away to be able to weld 3/4's of the whole way through. That means some from both sides. Then get about eight "C" clamps and clamp flat pieces of steel to it so it looks like you are working on a tennis racquet. (mental image). We would then put it in the forge and heat it slowly until it is just about to show some red color. I would then weld while the blacksmith watched the forge and kept the heat just so. (sorta) Not glowing red but just before the glow starts. Weld both sides with nickel rod. Keep the heat to it for about ten minutes after you are done welding then let it cool SLOWLY. Leave plenty of extra weld on the surface and no dips in the edges of the weld. That is where cracks would start. you can clean up the areas that need it when it is almost cool enough to hold in your hands. (Keep the clamps on till the very last) The longer you can take to cool it the better. All the heating can be done with a rosebud but it will take a lot of gas. The critical parts are getting rid of all the brass, heating the whole thing up evenly. Keeping it hot while welding and cooling VERY slowly.
Paul
 
Dr. Zaugg is exactly right about how to do this. To cool it slowly so it isn't a bit brittle, I have used a bucket of ground lime stone some times refered to as slake lime. bury it in that and it will be the next day before you can handle it.

Regards, Kirk
 
utahwilson said:
this is out of my league. Looking like it is a no go for the cat this year. Thanks everyone for the advice.
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Sorry to hear that. I was hoping you had a welding shop you could take this to, and in a day or so be putting it back on. Hang in there, when you get it right, those variators are pretty trouble free. Just keep them lubed and dry is the main thing.

Wish I was close enough to loan you my ST4. I got a soft spot for kids, and snow..:flowers:

Best regards, Kirk
 
300 H and H said:
Sorry to hear that. I was hoping you had a welding shop you could take this to, and in a day or so be putting it back on. Hang in there, when you get it right, those variators are pretty trouble free. Just keep them lubed and dry is the main thing.

Wish I was close enough to loan you my ST4. I got a soft spot for kids, and snow..:flowers:

Best regards, Kirk
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Thanks, I preplanned that I would not have it running and have 5 snowmobiles lined up to haul the kids around.
 
Kevin get me a tooth count, and give me a call. I might be able to get you a sprocket. my snow tracs don't go any faster than your snowmaster ,we may have the same sprockets.
 
Kevin,

Run it.

The snow master has a cool factor of X10.

Run it. just don't drive it like you stole it. If I remember right that machine has a little snot behind it.

those little people won't know the difference.

Run it. You are getting the sprocket welded either way.
Something about regreting the things I did.... or regretting the things I didn't do.

$.02 please.
 
I agree with RED! Take those kids on a ride. You do not have to break the sound barrier.
Them Kids first!! Says me.
I will pay your .02 to whatshisname!!!!!!!!!!!!!!!!!!
 
x3
you may not have a good shop for cast welding nearby but damn near anyone can redo that brazing and keep you rolling until the snow is gone.... pull it after the kids go to bed and drop it at a shop in the morning... back on that night.. and good for the weekend. :)
 
Knowing nothing about snowcats but having welded for 40 years (with a father who has been a master welder and instructor for over 50 years), I would first suggest taking a grinder to it briefly to find out if it is cast iron or cast steel. It does make a difference in how to repair. With cast iron, you will only get sparks to fly off of it for a couple of inches. With cast steel, you will see sparks fly like you are used to seeing. If it is cast steel, which I suspect but have no certainty since I've never even seen a snow cat in person, I can tell you how to fix it reasonably easy and fix it right. The reason I suspect it is cast steel instead of cast iron is because cast iron is generally used where something is going to take high heat and a lot of heating and cooling cycles (like an engine block). However, cast iron isn't really that strong; all things considered. The teeth on the sprocket definitely are steel and not cast iron. Therefore, that is why I suspect the sprocket is made of cast steel, teeth and all. The simple grinder test will either confirm or reject my suspicion.
 
Here's my $.02 on welding cast, start a little pile of BBQ charcoal get all your grinding done then put the piece to be welded in the charcaol and let it pre-heat there until just showing red take it out and weld it with nickel rod then [ut the piece back into a pile of charcoal under and on top of the piece and leave it there until the charcoal burns out and the piece it cool. The charcoal will keep the piece hot and go out slowly which will let the piece cool slowly which will keep the cast from having heat stresses in it. Has worked for me many many time just takes time.
 
Blackfoot Tucker said:
UtahWilson,

There's a company in SLC called Precision Casting Repair.

I have used them twice and been more than happy with the quality of workmanship and the prices have been reasonable as well. I recommend them highly.

Here's a link: http://www.precisioncastingrepair.com/
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Just talked to Steve at precisioncasting. I sent him some pictures and he will reply with an estimate. My eye's still hurt from looking at their webpage though. :glare:
Thanks for all the great advice.

I was up late last night thinking over my options. I have put about 9k into fixing this snowcat already and the thought of having it stranded out there with a broken sprocket is not worth the risk. Whole reason for a snowcat is to safely transport family and friends to the cabin. That and the X10 cool factor. :clap:

Don...looks like 44 Teeth. Thanks for the phone call and advice.
 
I got two estimates back $1600 and $800. $800 consists of molding and then epoxying a plate to both sides and also bolting the plates together.

Noticed the below stamped on the varrator housing the other day. However, I have counted 3 times and I come up with 43 teeth on the sprocket.
 

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utahwilson said:
I got two estimates back $1600 and $800. $800 consists of molding and then epoxying a plate to both sides and also bolting the plates together.

Noticed the below stamped on the varrator housing the other day. However, I have counted 3 times and I come up with 43 teeth on the sprocket.
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If it is cast steel, and not cast iron, they are only about $1200 over what we could do it for. But, hey, it's only money. :wink:

My dad just repaired the block on a supercharged Shelby Cobra Mustang. He saved them just over $8500 and they've already had it on a dyno twice since (basically running the heck out of it - which I would do myself instead of finding out if the weld is good when you're on the track)
 
utahwilson said:
I got two estimates back $1600 and $800. $800 consists of molding and then epoxying a plate to both sides and also bolting the plates together.

Noticed the below stamped on the varrator housing the other day. However, I have counted 3 times and I come up with 43 teeth on the sprocket.
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Holy CR*P... I'm stunned! That's way, way more than I would have thought.
I'm sorry for the recommendation.
 
I have used a welding shop in Murray for welding many metal articles. He is very reasonable. His shop is about 4850 south just behind the stores on state street on the east side of the street. He is a good welder. If I can help further call me. Wade 801-450-8143
 
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