Broken Bobcat, Variable Drive Snap Ring Groove Worn

thynes · Feb 2, 2015

Hi, my "tool", a Melore Bobcat M600 is currently broken in my driveway. This old bobcat, has a goofy variable sheave drive system. It is similar to a snowmobile, but is hydraulically actuated to squeeze the sheave together to get variable speeds.

So there is a groove that a snap ring fits in that is worn, so that now instead of a "square" bore it now has a ramp on the thrust face. This lets the snap ring pop out when under load. See the pics for more detail.

I am not sure what is the best way to fix this. I have considered brazing up the groove and having it re-machined, but that is a lot of work and money, to be sure. I have also considered assembling the pulley and putting maybe 3 braze spots, sort of a tack weld to hold the whole mess together. This is less desirable, as it makes future repairs VERY difficult...

I also considered using JB Weld, or some sort of epoxy, to fill in the gap after assembly. This would only require heat to take apart in the future...

Anyone have any thoughts?

Regards,
Tim in Mass

merlynr · Feb 2, 2015

(quoted from post at 07:15:59 02/02/15) Hi, my "tool", a Melore Bobcat M600 is currently broken in my driveway. This old bobcat, has a goofy variable sheave drive system. It is similar to a snowmobile, but is hydraulically actuated to squeeze the sheave together to get variable speeds.

So there is a groove that a snap ring fits in that is worn, so that now instead of a "square" bore it now has a ramp on the thrust face. This lets the snap ring pop out when under load. See the pics for more detail.

I am not sure what is the best way to fix this. I have considered brazing up the groove and having it re-machined, but that is a lot of work and money, to be sure. I have also considered assembling the pulley and putting maybe 3 braze spots, sort of a tack weld to hold the whole mess together. This is less desirable, as it makes future repairs VERY difficult...

I also considered using JB Weld, or some sort of epoxy, to fill in the gap after assembly. This would only require heat to take apart in the future...

Anyone have any thoughts?

Regards,
Tim in Mass

Try www.skidsteerforum.com Couple of good Bobcat mechanics there.

thynes · Feb 2, 2015

merlynr,

Yea, skidsteerforum is a good one. I have also posted it there, but have no responses yet. I figured I would ask here also, as there are a lot of clever people who post here too.

Regards,
Tim in Mass

Steve@Advance · Feb 2, 2015

Not knowing what goes up in there... Would you be able to sacrifice a little length and cut a new groove further down, beside the old one?

Or like you said, assemble it and weld the ring in, get one last use out of it.

Bob · Feb 2, 2015

There appears to be plenty of "meat" there to check it in the lathe and square up/deepen the groove a bit.

You can probably use a bit thicker snap ring with a wider cross section, as well.

circus · Feb 2, 2015

In the standard trany of my truck a external circlip came out of its worn grove. Didn't want to tear it all apart so I brazed a bridge joining the ends together. That was 10 years ago and it's still working. I don't see why it wouldn't work on a internal circlip.

NCWayne · Feb 2, 2015

If the piece can be taken off easily, then the best route would be to add some weld to the end, and have it re-machined. I doubt very seriously JB weld would work in a situation like that due to the forces involved holding everything together.

Now if getting the piece off is going to require a lot of major disassembly, then my suggestion is to use a MIG welder, with .035 wire, and carefully weld around the outside edge of the groove to build it back up. If you were to cut yourself a small disc of copper the right thickness to fill the groove, but small enough to move around and it not be stuck when you got done, it would aid greatly in getting the weld laid in without messing up what groove is still there. From there, using a die grinder and a small cutoff wheel you can recut the groove, and then switch to a grinding wheel to resize the ID so the parts can slip back inside.

Basically as long as you don't damage the bore on the backside of the groove your OK. Since nothing rides to the outside, getting the meat back in the shaft to hold the snap ring isn't exactly rocket science, so using the tools mentioned, -vs- having it actually machined will work just fine.

jimg.allentown · Feb 2, 2015

It might help to know what the assembly looks like when it is together.
Some ideas....
If the actual location of the snap ring is not critical, how about having a new groove cut a bit farther in?
How about "squaring up" the groove and using a thicker snap ring?

As to brazing, I have found over the years that brass (even full hard) does not stand up well to stressed parts. Also tends to be brittle when full hard. Soft when annealed. Silver solder is a better brazing material, but still softer than desired to hold a snap ring in place.

Roger in Iowa · Feb 2, 2015

IN addition to below.

The snap rings have one "sharp" side and one "rounder" side. Put the load to the sharp side.

Den N Ms · Feb 2, 2015

thynes,Maybe use a dremel to square up the grove and find a wider/thicker snap ring also it would also have more spring tension to hold in place.

87nassaublue · Feb 2, 2015

How much trouble is it to get that shaft out? Perhaps, the solution is simple. I'm wondering if you can take it to a machine shop, and have them cut a new snap ring groove just behind the worn out one. Perhaps they could help you out with a minor modification.

Years ago, I had a jaguar that had problems with the wheel studs pulling out of the hubs. I finally got frustrated with it, got some ford studs and took them to a red-neck machine shop, had them drill out the holes and press in ford studs. That was an amazing permanent fix that was also cheap.

thynes · Feb 2, 2015

Guys, some good stuff here. I need to figure out of this is cast iron or maybe cast steel.

Initially I assumed it was cast iron, hence my thoughts on brazing, but if it is cast steel, it might be easier to MIG weld it... I will need to spark test it. I am a little worried that welding it might shrink the bore a bit, as there is a piston that needs to fit inside. It is not a super close fit, but it may close up enough that it binds. I will have to think about that some more.

I also like the idea of copper backing to simulate the snap ring, then weld to fill the gap, and file as necessary. This would be time consuming, but I think it would be a solid repair that would be able to be disassembled for future service.

I may not get to this for a week or so. I really don't have spare time at the moment.

Keep the ideas coming, I really appreciate it.

Regards,
Tim in Mass

JMS/.MN · Feb 2, 2015

If it"s similar to the drive that was on my 1530 Case (which was then current technology before hydrostatic) I"d opt first to disassemble, take to machine shop to rebuild.

The other fix? find a washer about the thickness of your snap ring, with an OD equal to the non-splined portion, drill some small holes in it, and spot weld it to the main assembly with the snap ring in place. (if it doesn"t interfere with the next component) Then the weld could be ground off when you fix it next time. But really, I"d prefer to take it to a machine shop! It lasted how many years as an original? Good repair should as well.

thynes · Feb 2, 2015

Guys, some good stuff here. I need to figure out of this is cast iron or maybe cast steel.

Initially I assumed it was cast iron, hence my thoughts on brazing, but if it is cast steel, it might be easier to MIG weld it... I will need to spark test it. I am a little worried that welding it might shrink the bore a bit, as there is a piston that needs to fit inside. It is not a super close fit, but it may close up enough that it binds. I will have to think about that some more.

I also like the idea of copper backing to simulate the snap ring, then weld to fill the gap, and file as necessary. This would be time consuming, but I think it would be a solid repair that would be able to be disassembled for future service.

I may not get to this for a week or so. I really don't have spare time at the moment.

Keep the ideas coming, I really appreciate it.

Regards,
Tim in Mass

Chris(WA) · Feb 2, 2015

That splined shaft is NOT cast IRON!

Jim in MN · Feb 2, 2015

One thing I haven't seen mentioned is a call to a salvage yard. Never know, might be able to buy a used one cheaper than you think.

JD Seller · Feb 2, 2015

Take a small cut off wheel on a die grinder. Grind the outer edge back square. The just find a wider snap ring or even double one like you have. Like someone else posted make sure your putting the square side of the snap ring out. They are stamped out of sheet steel before they are hardened. So one side is more square than the other.

I would not braze anything like that. It will soften the housing and the snap ring. That housing IS steel not cast iron. So it your going to weld/repair it then use a MIG wire welder.

ss55 · Feb 3, 2015

Dumb question: Have you tried using a new snap ring?

Bret4207 · Feb 4, 2015

It's not cast iron, 100% surety of that. It's a machinable steel casting. Have the same thing on my 444 Bobcat. Nice, soft steel. I'd either take it and get the groove cut deeper or do the Dremel job the same way.

thynes · Feb 4, 2015

To answer the question, did I install the snap ring correctly, yes I did. The flat side was to the worn thrust face. Just for the heck of it, I put the snap ring on backwards, and it promptly came apart in a matter of seconds, not the 10 minutes it took the last time I put it together.

I also have a question for the guys that are sure this is steel. I went and look at the part tonight and I can see where it is a cast part. For example it has the outline of of a part number data plate that was screwed into the casting blank. The screw heads are plainly visible.

So this is cast steel?

I have never welded cast steel before, as least that I know of. What special precautions, if any are there?

Maybe I will get some time this weekend to give this some more attention. I keep getting home too late, and it is already dark out, not to mention how cold it is...

Regards,
Tim in Mass

Bret4207 · Feb 5, 2015

There's not very much real cast iron out there. Steel castings have been around for a long, long time. You've probably welded on steel castings before without realizing it. There are any number of examples of machinable cast steel out there. Look up the differences between iron and steel, it's a few percent of this and a little of that. Rifle bolts, hydrualic pumps, engine blocks, bolsters, tractor front axles, there's all sorts of steel castings that get welded on.

Dusty MI · Feb 5, 2015

Take a slug or a washer or split washer, they are available, and grind it to fit inside the snap ring so it can't collapse.
I did that once on a M. M. Unti-Harvester's power steering.

thynes · Feb 22, 2015

Update:

So since today was the first day, in a zillion days, that it wasn't colder than a witch's teat, I did some work on the Bobcat.

There is an endcap that holds the whole mess together. This cap has a "register" relief cut on the backside. This relief was a little wallered out allowing the outer sheave to wiggle and in turn work the snapring groove. I mig welded up the worn area on the endcap and turned it back to size on the lathe. Now end cap is a nice tight slip-fit with no wiggle.

I did a quick and dirty dremel grind on the snap ring groove with a thin grinding wheel. I have a flex shaft on this dremel. It works VERY nicely. How did we survive before dremels?

The snap ring did not pop out after I re-squared the groove. I was able to move the Bobcat out of the middle of the driveway, and off to the side, near my welder. I think I may try to double up two snap rings and see how it looks. The doubling of the rings will bring the piston to it's correct position to compensate for the wear, and my dremel work.

If I don't like how it finally looks, I may end up welding it in place. For now I will sit on it, as it is dark and I am done working for the day.

-Tim in Mass

Charles in Aus. · Feb 22, 2015

Nice to know how it turned out .

Broken Bobcat, Variable Drive Snap Ring Groove Worn

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