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essaitchthrowaway3 t1_jcc3ppx wrote

What does that gear do? It is too small to be transmitting a ton of torque, so I am assuming it is to transmit the speed or distance that has been traveled.

I would probably replace that gear with a 3D printed one because I think you will have a hard time finding a replacement.

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jeffersonairmattress t1_jccbtr2 wrote

It drives the speedo cable. It would be cheaper to grab a display and proximity sensor to count revolutions of the wheel than to build this gear. It has to be ridiculously tall-toothed to register in the perforated disc- looks like a 14.5 degree pressure angle and no longer a standard gear profile. Pretty easy to just bore a flat disc of delrin to the same OD and bandsaw&file the teeth- it doesn't need to be perfect.

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jeffersonairmattress t1_jccazts wrote

I just made a similar gear out of brass, using a milling machine and a dividing head.

The problem with this gear is that you are unlikely to find a replacement; it looks like a 14.5 degree pressure angle and most gear shops are set up for 20 degrees or higher. Ther's nothing available off the shelf. I could make this gear, but it would be a $450 gear.

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VintageAda OP t1_jcf2pz7 wrote

Oof, that’s probably 10 times what the bike cost brand new. I’m currently carving out a replacement gear with my dremel. Fingers crossed.

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jeffersonairmattress t1_jccdbfj wrote

Drill a 1/8" hole down the riveted end. Squish the peened-out wings of the rivet together with vise grips. Punch it out. Take the gear to a small machine shop and ask for a flat disc of delrin bored and machined to the same OD. Trace the existing gear onto a piece of maskiing tape, slap that on your disc and bandsaw and file the profile.

It's a 9 tooth gear with what looks like a 14.5 degree pressure angle. A dividing head (and I'd guess module 3 cutter) will get you very close if you have a milling machine. You don't even need to have dividing plates because with 9 teeth your divisions are bang on 40 degrees apart- you could just paste on a printed sticker of a protarctor and work to its lines. http://www.banggood.com/8pcs-Module-3-PA14_5-Bore22mm-1-8-HSS-Involute-Gear-Milling-Cutter-p-1012467.html

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VintageAda OP t1_jcf1n8m wrote

Looks like someone purchased it, but I get the idea. This was vey helpful, thank you.

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IvanIsOnReddit t1_jccac4m wrote

Is that nylon? You could have a replacement 3D printed.

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VintageAda OP t1_jcf2sy6 wrote

Thanks, I don’t have a printer, but I’ll keep this open as an option.

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LittleJohnStone t1_jcbyn3s wrote

It looks like it's held in place with an e-clip. Use a small flathead screwdriver between the shaft and the clip to jimmy it off, then the gear should slide off.

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VintageAda OP t1_jcbzwh9 wrote

Yes, I’ve already removed that one, I mean the smaller broken gear.

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LittleJohnStone t1_jcc69xh wrote

Ah, okay. I will agree with the person who said it looks like a peened part - pin and hammer, or still it out

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DIYuntilDawn t1_jcbzekz wrote

Can't tell for sure with all the dirt on it, but it could be a snap ring. It doesn't look like it uses the same e-clip as the other gear to the left is using.

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VintageAda OP t1_jcc0ks1 wrote

Not a snap ring, unfortunately. That’s just the top of the brass fastener, it has a tubular body that passes through the gear. The second picture shows how the other side of the fastener.

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DIYuntilDawn t1_jcc2u7r wrote

I didn't see the second pic. That looks like it was peened on so the gear is probably on a flanged axle that would not come off unless you removed the axle from the bracket.

You might be able to get it off by using a hammer and a punch to try and narrow the side in the second pic so it will fit through the hole. Then have to peen it back on later. Or you could grind/file off the end sticking out in the second picture, but would likely have to replace that axle pin afterwards.

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VintageAda OP t1_jcc3qa5 wrote

Excellent, thank you. I will try the hammer and punch.

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ballpointpin t1_jccc1f3 wrote

Are you trying to restore the bike with all-original parts, or do you just want a functional speedometer/tach? If you're just looking for a speedometer/tach, then get a cheap bicycle tach with a magnet you stick on a spoke.

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VintageAda OP t1_jcf2eyx wrote

I’d prefer all original, but alternatives won’t kill me. Thank you, this is a nice workable option.

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BootyFewbacca t1_jcf5mvu wrote

Ooo get the gear off, 3D scan it, and print replacements!

Edit: if it's just speed, might make more sense to not bother and just grab some Bluetooth speed/cadence sensors instead they're cheap.

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