Welding Bull Gears

I would like to hear successful ways that anyone has welded broken teeth in a traction engine bull gear? How many teeth can you weld at a time, and how long do you have to wait to weld more to prevent cracking?

Thank you,

Jeff Smith

I did something like that used to repair smaller gears. Made up a rough blank of the tooth from CI. Drilled and c'bore for largest cap screw I could fit in the blank. Milled the broken area on gear flat. Carefully positioned my blank tooth on gear and used transfer punch to mark hole position on gear. Next drilled/tapped holes in the gear. Screwed it all together with grade 8 cap screws. Then the join was carefully welded and then machined to profile. Has held up well so far but haven't done any heavy pulling with my engine.

NICK

If you are REAL lucky, depending on the vintage and make, you may actually have steel gears.

As for welding CI gears, One or two teeth might be doable, you'll have 2 choices keep it cool, or keep it hot. Finding an oven big enuff to keep a bull gear dull cherry (for days) could be... interesting.

Otherwise your only choice is to weld cold. You'll do a short bit here (about a 2-3" long single pass bead) then go away for a while, do another short bit, go away, etc, etc. Eventually you'll build it up a bit oversize and grind it back to shape. drilling and tapping the gear for a couple studs to form a core for the new tooth might not be a bad idea, especially if the tooth is completely gone.

If it needs a LOT of teeth, there are a couple companies that can/will cut you brandy new steel gears from scratch. (They'll use yours as a pattern) It isn't particularly cheap, but if you have an odd engine (or intend to pull with it), this may be the best solution.

Jeff; How many teeth will you be deaing with here? The problem with taking your gear to a proffesional is that they simply don't want to take the time to do the job right (time is money). I have had good luck with welding with nickel and peening to relieve stress, only heating enough to take the chill off. Most welding shops will want to use a high stainless content rod and it is simply too brittle. Trying to heat a complex thing like a bull gear may create more stress than welding it cold and peening. As far as welding with cast iron or brazing, this is mostly a lost art.... Just my opinion...

The amount of teeth that I would like to fix is all of them. The amount that my steam friends may talk me into would be far less. Maybe fifteen teeth give or take a few. I like everything perfect, and have been toying with the idea of having 1/4" plates laser cut at a nearby facility and laminating them together, machining off the old teeth and shrinking the new gear over the existing casting and welding it into place. But I am looking for other ideas just to think about before I do anything that drastic. I do know that Willis Abel has welded many gears over the years on engines and the craftsmanship is incredible. It was very hard to tell where gear teeth had been welded and ground back into shape. I can't recall, but I think that he said that they only weld four teeth a day, but I will try and call him to verify (will post for other's reference if I can get him).

As for brazing cast iron, my father and I have been brazing cast iron for many years with very good success. My mother and my wife do not like us using their ovens to heat engine parts in, but until I can build another building and put my own oven in, they will have to cope. I have seen dad pin and braze many gears on gas engines and other items over the years. He has also done many for other people and all are still in service today with no problems. As for the cast iron rod, I have only ONE friend that I have seen weld with that and do a good job that actually holds, but he has a welding shop and a reputation for welding cast, so he gets a lot of practice each day welding it. The down side is, I would have to ship the gear 1000 miles to where I grew up and have him weld it. The shipping is not the problem; it is being there to look at it periodically to inspect the work should he have any questions.

The engine is an 1895 Peerless Model 'R' and has wooden spoke wheels on the front and back, so I will not be pulling the engine. I am in the process of restoring the engine and I can see that it is going to be a long slow process being that I want everything to be perfect, probably nicer than it left the factory.

Thank you.


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