Broken gear - Calling all machinists/ welders

[CT_Tree_Guy]

Well, I've gone and done it. I broke a large tooth off a large gear, the "pinion rotator drive" gear that rotates the turret on the Powers PM-300 6-ton crane on one of my International Loadstars.

It's made of pure Unobtainium, so it HAS to be repaired, or duplicated. Does anyone have any experience with repairing a broken tooth on a gear? It's a straight-cut gear vs. helical, so that might simplify things somewhat.

I don't know the exact composition of the gear, but it's a steel alloy of some sort, hardened. Can the missing tooth be built up with MIG or TIG, then machined, then hardened? Should the gear be softened prior to welding and machining, then the entire gear rehardened? Or do I have to bite the bullet and have the entire gear duplicated from scratch?

Any help would be greatly appreciated, including any contact information anyone might have for any machine shops that might specialize in this type of repair.

Thanks, John

 

[BigAl]

We had a old guy here in town that could weld anything made . I never saw anyone who could do the work this guy could . He fixed many graders with broken teeth on the main gear circle . You need a machine shop not a welding shop . I would call around to some of the different shops in your area and see who they reconnmend . Most shops do not want to reconnmend their competition so also call some heavy equipment repair shops to see who does their work . Worst case is to have a new part cast . We have done this before with good results .
Allen

 

[CT_Tree_Guy]

Big Al - Thanks, I'm starting to feel a little better. I know lots of local guys who are into the big machinery so I'll start picking their brains, just thought I'd start right here at good ol' TBN.

I'm pretty sure the gear is machined vs. cast, which is probably a good thing. I bet it would be a lot more difficult ($$$$) to cast a new gear than to machine it, which would only be $$$, not $$$$. /forums/images/graemlins/tongue.gif

Anyone else have any words of encouragement for me? /forums/images/graemlins/smile.gif

 

[RoyJackson]

"Anyone else have any words of encouragement for me?"

If the gear hasn't been completely destroyed, have the machine shop check the hardness, or check it on the mating gear(s). That way, you won't have one of the gearset harder or softer then the others.

If the old gear isn't completely destroyed, a machine shop can use it as a pattern to duplicate it.

 

[JustGary]

I would seriously consider having a machine shop dovetail a new tooth into the gear. If they need to weld it they can just tack it in place at the ends. That way you don't have to worry about retempering or anything. They should be able to test the hardness of the existing teeth and use a suitable piece of bar stock for the replacement tooth.

By the way, where's the photo?

Good luck with it, I'm sure you'll have it going again in no time.

- Just Gary

 

[CT_Tree_Guy]

Thanks for the reply Roy. No, the gear isn't completely destroyed, just one tooth out of maybe 6 is broken off. I'm still wondering if I can get away with having this gear repaired or if I'm going to have to have a new one machined.

Here's a scan from my manual showing the gear in question; there's a blown-up picture 2 posts down.

 

[CT_Tree_Guy]

Thanks Gary, I never knew about the dovetailing approach, sounds like a likely winner. So building up with welding and then machining isn't really one of the approved approaches?

 

[CT_Tree_Guy]

Here's a blowup of the gear.

 

[Kyle_in_Tex]

Have you got a price on a new one?

Just guessing that it looks like its made on maybe a 2-3" piece of round bar stock. Welding or dovetailing could work, but I'd sure check what a new one goes for prior to patching it. Gear teeth are usually "hobbed" by a special cutter. A simpler endmill could be ground to match the teeth and recut one at a time. This is what a local shop will probably do.

 

[CT_Tree_Guy]

</font><font color="blue" class="small">( It's made of pure Unobtainium, so it HAS to be repaired, or duplicated )</font>

Kyle, I wish I could just order a new one (Or maybe I don't - $$$$$?) The company that was the last vestige of McCabe-Powers, the manufacturer of the crane, finally pulled the plug on operations about 6 months ago. I tracked down an old contact from that company, American Fleet Services, Houston TX, and he told me that there are still a bunch of parts sitting in a warehouse, but no one manning the store. He said that the whole shootin' match including inventory, blueprints and manufacturing rights could be had for about $120K. Anybody wanna buy a crane? /forums/images/graemlins/smile.gif

Ah, the joys of owning old iron. It is one heck of a crane though, legendary in the utility industry. A lot of them also had augers and pole-grabbers - I have another Loadstar like that. It'll dig some dandy 24" holes for pole barns. Part of their problem was that they built them too well - they lost market share to cheaper competitors. Kinda surprised I was able to break the gear with the hydraulics though - I'll have to check my relief settings/valves. Or maybe it was just the gear's time to go - it is 33 years old after all.

The '72 International Loadstar 1700 it's mounted on is an all-wheel drive that was originally owned by Long Island Lighting. I feel very fortunate to have acquired it. I have it outfitted with a log bunk, and that crane will pick up any log that grows in the northeast.

Here's a picture of the old girl, getting loaded up by the Kubota 5030 "tree-bota". She ain't pretty but she's paid for, and she's a BEAST. She'll carry 16,000 lbs. of logs without complaining. And I went through her from stem to stern when I got her, replaced everything, so she's safe. I just never had a chance to put any lipstick on her. /forums/images/graemlins/smile.gif

GVW 26,000 lbs., which is nice, just under CDL.