Broken gear - Calling all machinists/ welders

[CT_Tree_Guy]

*** This post reflects a vast departure from my prior frolics on Gilligan's Island, brought about by the great advice I've received here. I apologize to poor Phil for the "blind-siding" I inadvertantly gave him in this post. *** (Edited after reading his next post).

Phil -

Thanks for the thoughts, excellent stuff as usual. This crane is crucial to my tree business (although less crucial now that the "tree-bota" does most of the loading of the crane truck) so I [now - ed.] want the new gear to be as strong as the original gear, if not stronger, given that it failed. While I am not a prime beneficiary of the Bush tax cuts, I don't want to [am no longer tempted to, thanks to all of you - ed.] cut any corners on this part. I like to do things once, and do them right. [Finally came to my senses - ed.]

Among my Dad's various assignments in his 23-year Naval career was a tour of duty on the "Board of Inspection and Survey", whose task it was to oversee the construction and overhaul of naval vessels. He also served for 4 years as liaison between the Navy and various pacific northwest shipbuilders and outfitters. Those experiences and others led him to make the following observation: "It seems that there's never enough money available to do things right the first time, but always enough money to fix the screwups that result from failing to do so". He's no longer with us, but his wise words remain. We'd all be honoring him by putting them into practice.

Thanks again all for all the help. Feel free to keep it coming, and I'll do my best to ensure that your efforts result in an outcome that my Dad would be proud of.

Best regards, John D.

 

[philshel]

John,

I must apologize than as I misread your original post. Under the conditions and attitudes you have expressed, I would find an OEM replacement or have your part replicated to specs. By that, I mean have the surface and cross section Rc’ed and recreate the hardness profile in a 43 series steel or possibly one of the alloys such as Incoloy, which were designed for load strength and wear/tearing resistance. In my opinion, priority is still with reproducing similar surface hardness as the original and its mate. Otherwise, what you will end up doing is basically knurling the softer of the two gears until you get a tooth misalignment, and back where you started.

Phil

 

[CT_Tree_Guy]

Please Phil, I feel bad enough already to have unthinkingly put you into the middle of my remembrances of my wonderful father. It is I who owe YOU a sincere apology for doing so. Once I started thinking about him, it just poured out of me, and I lost sight of the ramifications of my words.

Thanks for yet MORE great advice on the subject. This thread has been amazing - now all I'll have to do is print it out, bring it to my machinist, and say "here - what they said". /forums/images/graemlins/smile.gif

I do love this place, thank you all very much for the help - please feel free to keep it coming - and for putting up with all my many moods and modes.

John D.

 

[philshel]

John,
There is absolutely no reason for you to apologize. I do not feel like you put me in the middle of anything, I scanned your original post and jumped to an incorrect conclusion. No harm done. Good luck with the rebuild, let us know how it goes, and if you don’t take pictures along the way, many members will be sorely disappointed/forums/images/graemlins/grin.gif. Lastly, please don’t hesitate a sec to ask more questions, someone here will know the answer.

Phil

 

[3RRL]

Hope you don't mind my late input here...
I've had experience with gears and would recommend you have that gear made new. I've repaired broken teeth on gears but it ends up being expensive anyway, because you have:
-Welding cost
-Re- machining both ends of gear where weld goes over and grinding the Major Dia. or OD
-Matching the involute arc of existing gear shape
-Probably making a carbide endmill with that arc on it or grinding it
-Then you end up with a harder or softer tooth ...
-you'll probably have a couple of hundred bucks it by then?

My suggestion is to find a machine shop to turn the major diameters of the cluster gear and have him send it to a gear maker near you like the one I use "Gear Technologies" in CA. You'll be surprised how inexpensive it ends up for a brand new one. You can look for a gear guy on the web or ask you machine shop guy to do it, if he doesn't already use a regular guy.

I can't tell exactly by your drawing, but you, or someone mentioned it is around Ø2" or Ø3" so it's what...6" long or so? Probably costs around $100 for the machine shop and $100 for the gear guy to do it. $50 for heat treat.

It is a solid shank cluster gear so it can't be wire EDM'd...only the larger gear shape, but not the smaller diameter gear. Plus wire EDM is very slow and expensive. Looks like a standard 14-1/2° pressure angle. The gear guy will probably broach it out of .20 carbon steel and then you can case harden/carburize it for wear a resistant, durable surface and higher strength core. Just bring the old gear and he will measure it over pins to determine the pitch diameter. He'll probably have the correct broach to do it and it will fit.

 

[CT_Tree_Guy]

Rob -

Thanks so much for the great post. I'm increasingly amazed at the incredible information I'm getting from you all. I learn more and more with each post. Great tip about the gear shop in CA, I'll probably contact them and send them some pics and measurements. As I said, it's sounding more and more as if all I have to do is hand the gear and this thread to a good machinist and my troubles will be over. Nice to hear that you think it might not be too many $$$$.

I hear you about the EDM. Amazing technology, but yes,slow and expensive. I have a friend who does it, different outfit from the father and son machine shop I mentioned. And I see what you mean about it not being able to cut the smaller section of the gear with wire EDM (Electrical Discharge Machining?). Cost aside, is this the type of thing that an EDM "drill", vs wire-type, could do?

Again, thanks for the info, I'm very glad to shared it - don't sweat being "late" - that was very timely. /forums/images/graemlins/smile.gif

Best regards, John D.

PS to Phil - After all this help, I will HAVE to supply pics /forums/images/graemlins/smile.gif

 

[3RRL]

</font><font color="blue" class="small">( Great tip about the gear shop in CA, I'll probably contact them and send them some pics and measurements.)</font>

Sorry, wrong guy I mentioned earlier. Here is the correct name:
Gear Design and Machining
9375 Archibald Unit 603
Rancho Cucamonga, CA 91730
Greg Duggar PH & fax: (909) 948-0204


</font><font color="blue" class="small">( IAnd I see what you mean about it not being able to cut the smaller section of the gear with wire EDM (Electrical Discharge Machining?). Cost aside, is this the type of thing that an EDM "drill", vs wire-type, could do?)</font>

Not an EDM drill but you could use an EDM sinker machine and make electrodes to burn the arc shapes...still way too slow and expensive. Have to grind several electrodes out of graphite first, then EDM. Graphite for electrodes is very expensive and you'd have to form grind the tooth shape. An EDM drill is primaliy used to burn starter holes for wire EDM in hardened materials. You would then take the hardened piece to the wire EDM and "through cut" whatever shape you need. The EDM drill is also used to make holes in hardened steel for other applications. Many moldmakers are now wiring their ejector pin holes after heat treat instead of drilling and reaming before heat treat like I did in the old days.

</font><font color="blue" class="small">( Again, thanks for the info, I'm very glad to shared it - don't sweat being "late" - that was very timely.)</font>

Better late than never, I guess...
Thanks,

 

[KubotainNH]

Tree guy, what was the outcome on this? Just curious /forums/images/graemlins/smile.gif

 

[CT_Tree_Guy]

Kubotain -

God, I'm so embarrassed. /forums/images/graemlins/blush.gif

After all the great advice, and all the concern you all have demonstrated for my little problem, I still haven't taken the gear out yet! I've had an unusual amount of distractions lately - family "problems", big projects in the shop and at home, labor problems, and of course, those pesky customers who want their trees taken down. /forums/images/graemlins/smile.gif

My back is up against the wall now though, as I have two non-tree jobs that call for the crane. I can't let myself down, much less all of you who were so kind to help, so I'd honestly say that within one week from today I'll have that little bugger pulled out and on its way to recovery.

Rob/3RRL has incredibly generously offered to machine a blank from the appropriate material, and then send it to his other machinist friend in California that he mentioned in one of his posts. What a guy, huh? Thanks Rob, you're the best! And thanks again to all of you who so generously offered your help and great advice. It's about to be put to good use, and I promise details and pictures as the repair process FINALLY gets underway.

Take care, John

*****

Hey, this just inspired me to made up a joke -

"I was going to become a procrastinator, but I think I'll put it off for a while". /forums/images/graemlins/laugh.gif

 

[3RRL]

Hey John (CT Tree Guy)
</font><font color="blue" class="small">( God, I'm so embarrassed.)</font>

Not you...I don't think so! /forums/images/graemlins/grin.gif
I'll send you a PM.