need gears for light-duty wind project

I'm not a mechanical engineer. I'm working on a kinetic sculpture
that will connect a vertical-axis wind turbine to a drum mounted on a
lazy susan type platform (a board on a thrust bearing). I need to
couple the two with some gears -- spur, bevel, helical, whatever --
and I need the wind turbine to turn about 30 times for each turn of
the rotating drum.
I've looked everywhere for gears online and have found gears that are
very expensive and industrially machined which are overkill for my
project. I've also found small assorted gear packages that seem to
light and too small to incorporate into a project built mostly from
wood, screws, and nails. These packs of assorted plastic gears also
seem to lack the proper shafting, hubs, and couplings in order to get
everything to connect.
I was hoping someone might recommend a place where I might obtain some
gears for this project. Minimally, all I need is two gears (with
100-1 tooth ratio) that I can screw directly onto the pieces of wood.
Obviously, really small gears would require extremely precise
placement of my wood components so bigger gears are desirable.
Assorted plastic gears with appropriate shafting and connector hubs
would also be acceptable. Any help would be greatly appreciated. I
could really use some standardized gears and shafting that I can
connect without the need for a machine shop. Ideally I wouldn't need
all kinds of shaft couplings and shaft collars and stuff.
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Dear sneakyimp:
That is difficult in a single gearset.
"... and I have no interest in the gearing of an old car."
Why not just use a belt and pulley system? Much more forgiving of misalignment. Can use surgical tubing as the belt. Might still need an intermediate pulley pair if you really need 100:1.
David A. Smith
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Hi David!
Thanks so much for your response.
I had considered using bike chain and old bike sprockets. The best turn ratio I could hope for in that situation is about 5 to 1 because the big chainwheels top out at about 55 teeth and the small cassette cogs have a minimum of about 12 teeth. So far that seems to be my best option. I'd be forced to drill holes in the sprockets for mounting, but that seems doable.
Your surgical tubing suggestion sounds interesting. If I can get 30:1 or even 10:1 I think I'll be pretty happy. I'd really like to keep this to just two gears/hubs if possible -- otherwise it starts to get sort of Rube Goldberg-esque and I have to put in lots of extra parts. Where might one get these pulleys/hubs? Are they standardized? I can imagine automotive fan belt hubs being quite useful. I'm also a bit worried about the surgical tubing actually bringing enough torque to the equation. What if it gets wet?
As for gears, I'd be perfectly happy with plastic toy gears if I could be sure to get all the parts. These gears looked great until I realize that the inner bore is perfectly round -- meaning they won't apply any torque to the shaft unless you notch them or alter the gears:
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There are plenty of places to buy industrial metal gears of various materials but they get quite pricey because you need keyed shafting, hubs, bearings, shaft collars, etc. This place looks amazing:
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But one gear with 200 teeth is $42:
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and I would still need to buy shafting and have the gear machined, etc.
The Plastic Timing pulleys are looking pretty promising and delightfully standardized and searchable. Still pricey though. For example this double-flanged pulley with 18 grooves (i.e., 'teeth'), set screw, 0.25 inch bore for 0.25 inch timing belt that has an outer diameter of 0.438 inches:
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Because of the pitch of .080" (MXL) It would supposedly mate with this double-flanged pulley with 130 grooves (i.e., "teeth"), set screw, 0.25 inch bore, for 0.25 inch timing belt and outer diameter of 3.29 inches:
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I would still have to buy the timing belt for about $4, shafting for $5 or $10, and I have yet to find any kind of hub part whereby I'd couple the shafting to my rotating wooden parts.
Any tips on getting cheap pulleys/hubs for the surgical tubing approach? What about surgical tubing?
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