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Bendix gear material

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Phils69

Aluminum
Joined
Nov 13, 2012
Location
Greensboro,NC
Hello all,

I need to make a replacement bendix gear on a starter for a antique fire truck. What would be a good material to use? I was thinking of the following:

8620 case hardened
4140 ph
D2
 
I have never run into this problem, but as one that earned his living for a few years when a young mechanic, I thing I would consider soft steel (mild steel). I would rather lose a tooth off the bendix than the ring gear. That is probably "un-obtainium".

JH
 
Yes ,stater gears were often quite soft ,especially Bendix types ,which can chop up a ring gear quick smart.....Whats the ring gear look like ...Bendix rings are often backed off 1/2 way across the face ,or worse ,and as mentioned ,will be hard to find .......I' d be looking at using some kind of pre engaged starter for your old truck ,even if its not correct for model........On a bit of a tangent ,the type of starter that is kindest to gear teeth is the Bosch axial type ,where the armature slides out and engages with the teeth before cranking current is applied (these had bronze pinion s and un hardened ring gears) ......Another good one is the old foot engaged pinion type ,like the WW2 GMC s had ...very easy on gears.
 
Thanks for the info guys. It's not my truck but a friend of a friends. I haven't see the truck or the flywheel. All I know is that it is a 1929 American Lefrance, not sure of the model. I haven't been able to pinpoint the engine maker either. I do know that it isn't exact but looks very similar to a Ford Model T. I am going to call a vintage parts supplier today and see if they will verify the outside diameter of the gear. The proble is after watching a video of the Model T one I believe mine is bigger being on a large truck. It may end of being I will have to try and make it. It's a 10 tooth and assuming its a standard size lol, it is 1.75" OD.View attachment 285896View attachment 285896
 

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Looks like the starter might be a North East Electric Co ,model SH or SBH...North East equiptment was used on lots of makes ,and it may be possible to get parts .....My master catalogue quotes gear sizes for some engines ,and seems they used stub tooth pitch ,possibly 7-9 pitch on larger models .
 
Don't forget the multi start thread that is in the bore - be nice if those were an industry standard (SAE)

All the '38 hand book has to say is that the pinion was:

11 teeth
8/10 pitch
20 degree pressure angle
.015 - .025" pitch line clearance

Which has nothing to do with the multi start thread in the bore
 
Hay guys think this out, there is over 150 teeth in the cast iron ring gear, 10 teeth in the pinion (15 x the wear) pinion is very thin walled with high stress,s... how would mild steel make things better? The old gear was heat treated (look at the way it failed) If the gear is machined right it will not cut up the ring gear. I would use 4140 so I would not have to heat treat ....Phil
 
A common steel for gears subject to stress and impact was the 3 1/2% nickel oil hardening gear steel....Oil hardened ,not case hardened ...recommended for first gears with sliding engagement.......Its a expensive job to fail the first tryout..........hence my suggestion of a replacement starter.....Ive mucked around with all sorts of old diesel and gas engines ,and know the pitfalls in trying to make one offs ...that fail.
 
Phils69 said:
Thanks for the info guys. It's not my truck but a friend of a friends. I haven't see the truck or the flywheel. All I know is that it is a 1929 American Lefrance, not sure of the model. I haven't been able to pinpoint the engine maker either. I do know that it isn't exact but looks very similar to a Ford Model T. I am going to call a vintage parts supplier today and see if they will verify the outside diameter of the gear. The proble is after watching a video of the Model T one I believe mine is bigger being on a large truck. It may end of being I will have to try and make it. It's a 10 tooth and assuming its a standard size lol, it is 1.75" OD.View attachment 285896View attachment 285896
Click to expand...

My 1959 Triumph TR3 came with a guide bushing through the radiator and a hand-crank clipped to the floor. For-sure a 1929-anything, 30 years older, wudda had hand-crank capability, even if it didn't have Lucas electricals and could only borrow "the dark" instead of having it built-in and optioned active.

So... given the TR3's 4-banger had begun life as a Canadian Massey-Ferguson farm tractor engine, what are the chances a 1929-whatever-the-mill-was compatible starter "complete" might yet be "out there" for old ag equipment or stationary or marine engine?

These goods didn't get design updates very often. Whatever worked just stayed in-use for ages. See Pierce-Arrow engined fire trucks, the motor production outliving its parent by a helluva long time.

Another example the keyed ignition switch of a '79 Dodge pickup. Dunno when they QUIT using that switch, back of the key, but the parts-book indicated it had been adopted by MOPAR around 1949, if not earlier, yet -surviving the 6V to 12V transition, '56-'57 for MOPAR, IIRC, as we briefly had one of each, those two years.
 
per thermite-look for autolite starters-that might be what they used on that-looks like it anyway--autolite was used on both ford and chrysler at diff times many yrs ago....
 
Not sure if you have any rebuilders local, but over the years we have relied on our local starter-generator, alternator rebuilder for many odd applications, more then once we have hauled the ruminates of a odd component to match. never failed us yet
Some time it took a little looking/research.
One time there was a very large Russian diesel engine that had all Romanian electrical and our guy came up with starter and alternator that would be a direct install.
 
Good friend of mine inherited an auto electric shop from his FIL. Anytime I need an oddball starter I go digging through his attic. From model T through gray market tractors he has had anything I have needed.

I would make from 4140 and harden it. 8620 would work great too, but carburizing is a lot more complicated than hardening 4140 for that one gear.
 
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