Source for sprockets?

Hi all,
I've searched around the net for sprockets for a project and am
suffering a case of sticker shock for what seems to me should be a
common product.
We're making a home-brew 'tower clock' with one hand on a 0.750" OD
shaft and the other hand on a 2.250 inch shaft, and planning on driving
the two shafts separately, each with its own servo/stepper motor.
I'll put a small sprocket on the servo motor and a larger one on the
'hand shaft' - and for simplicity in the servo driving software I'm
planning on both hand shafts using the same number of teeth.
What I can't find is cheap sprockets (either chain or cog belt) about 3"
in diameter that I can bore out the center to 2.250" to allow the larger
hand shaft to fit through.
As a side question, if I find steel sprockets are they hardened or
easily machinable?
Anyone got a favorite sprocket source they'd like to share?
Thanks in advance
Carla
"Dear God: please grant me a fat bank account and a slender body - I
hope you don't get it backwards like last year..."
Reply to
Carla Fong
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I used both bicycle and motorcycle sprockets and chain on my home-made sawmill. Since both had to transmit substantial power I left the sprockets hard and splined the shafts slightly oversized so the sprockets broached a tight-fitting seat when pressed onto the softer shaft.
I used a 52-tooth lathe change gear to index the transmission shaft to machine it for the 13-spline motorcycle sprocket.
Annealing isn't difficult because you have the visual indication of color change to dark blue, or the red glow, and can check for machineability with a file.
-jsw
Reply to
Jim Wilkins
I haven't used them because every time I weld together parts machined to final size I have to correct for some heat distortion, for example a built-up fork joint that closed tighter. Do they generally run true after welding? -jsw
Reply to
Jim Wilkins
My favorite source is the local scrap yard. I have not picked up any sprockets, but there is always a bike or two there. A bike shop might be worth checking.
Dan
Reply to
dcaster
This is too easy.
Old bicycle freewheels/casettes. 99% are are steel, and hard. Older ones would be better for you as newer ones are thinner and have specialised tooth forms that vary and are intended to make it easier for the chain to derail, which you would not want. Look for five-speed or six-speed; they came in common combinations of teeth, won't be too hard to get matching teeth.
They get tossed as junk when the teeth are a bit worn but you don't care, you want registration and a few percent power-loss or remaining wear (decades, likely) is no matter.
A 30-tooth rear has a diameter of just under 5 inches. The central bore is usually around 1.5 inches, and frequently they have cutouts; so you can hit them on the "spider" with a blowlamp and soften them there for cutting/drilling.
Any good bike shop will have loads, and chain. Tell them what you're doing & smile and they could be free.
Reply to
xpzzzz
Hmm, good question. It probably depends on the intended use. I don't know.
SPACELY, of course. Ask George Jetson. (Sorry, had to do it.)
There's a guy in Canuckistan (Canada, for those of you in Rio Linda) who does wooden sprockets/gears, if you want a DIY project. He has tons of vids on YouTube. Matthias Wandel is a wonder.
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I'm kinda partial to his square and oval gears, but I'm odd.
Otherwise, see these:
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Love it.
Reply to
Larry Jaques
Interesting request. Go by a vitamins or health food store. And if you can find the time, gradually start taking 20 grams and then more of dietary supplements twice a day. But don't miss a day !!
Reply to
mogulah
Only if you clamp the piss out of them first, then weld a bit on one side, then a bit on the other. SOP for not warping when welding.
Reply to
Karl Townsend
MyMaster-Carr has sintered toothed-belt sprockets (I'm guessing that is what you are looking for, not metal chain sprockets). They are VERY machineable. Not REAL cheap, but a lot cheaper than Stock Drive Products or W. M. Berg.
Jon
Reply to
Jon Elson
Hey Carla,
Buy up a couple of old bicycles at garage sales. The sprockets they use are "good stuff".
Take care. Good luck with the project.
Brian Lawson XXXXXXXXXXXXXXXX
Reply to
Brian Lawson
I needed two identical sprockets to drive the two lift screws at the same rate so I went to a bicycle shop. Two new-old-stock 3-speed rear hub sprockets plus a short chain remnant cost me $13, IIRC.
I do a lot of engineering design while poking through piles of used stuff. The necessary preparation is knowing the minimum size that's strong enough and the maximum that will fit, plus the limits of my machining ability to make adapters for other than standard-sized keyed shaft hubs. -jsw
Reply to
Jim Wilkins
Thanks George, that was the winning solution!
From your links I got the tradename of what we needed and then found 'Weldasprockets' at my local farm / implement store for about $13 each (40 chain, 26 teeth) and was easily able to bore out the center to my spec... Threading the material for setscrews near the perimeter was a bit dicey as that area seems to be hardened... but everything worked out fine.
Thanks again!
Carla
Reply to
Carla Fong

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