Wow! I'm so grateful for all the attention to this matter. Thanks guys!
Al, thanks for mcmaster tip. I also like
Stock Drive Products / Sterling Instrument. I'm leaning toward a tapered roller bearing for the top bearing. The ones at mcmaster are pricey, but I've seen them for as little as $4. The problem is, I have NO IDEA how to mount my turntable atop a tapered bearing. I just don't see any housings for them and it's not clear to me where the turntable [or the hub connected to the turntable] will rest and whether the turntable needs to be rigidly coupled to the bearing or the shaft needs to be rigidly coupled to the bearing. Also, the tapered roller bearings tend to have inner diameters of 20mm and up. While this seems like a fine shaft size to support my turntable, I have not been able to find any flange mounts or hubs to couple a shaft of that size to my turntable.
My prototype I'm working on with the lazy susan bearing is a 1/4" plywood turntable that's about 24" in diameter. I cut it with a jigsaw and it needs to be lathed a bit but it's close enough for proof of concept. I expect to attach some aluminum sheet metal with L-brackets to this turntable such that the outer diameter of the VAWT blades is maybe 30" tops. The blades will probably be about 24" high (see drawing). The whole turntable and turbine will probably weigh less than 10 lbs. The majority of the force to be borne is likely from the wind blowing. It'd be nice if it could withstand 60 mph winds or something because it will be outside. For my prototype, it could be considerably less. I'm not sure how fast it will turn, but am expecting speeds topping out in the 600 to 1000 rpm range. I'll be coupling the shaft to a speed reducer...something affordable like
this I hope which will in turn connect to a rotating drum that plucks little flexible clappers which in turn hit some chimes I've cut.
Dick, I like your suggestions about the trailer hub but it sounds like a bit heavy-duty for this application. I'm imagining that the friction and inertia of those heavy parts might be a little too stiff to turn in a light wind. I don't know enough about those parts and am having a hard time picturing how it works. The hub seems obvious...the bolts would go through holes in my turntable. It's the other couplings that are not clear to me -- like you how mount it on the base platform and how you transfer the torque to a shaft.
Tom, I think I've supplied the specs here.
* About 10 lbs tops, wind is the major loading
* turbine 'blades' are about 24 inches high and about 30 inches in diameter and there will be 3 or 4
* If you look at them from the top, you'll see two sine waves crossing at right angles. Think savonius VAWT.
* How fast? I have heard 10 rotations per second is typical for home made VAWTS but don't really know.
* How long must it live? Well the short term goal is to make one that works reasonably well for proof of concept. The long-term goal is to provide the mechanical parts to my brother who is an architect so that he can make a lasting one. Let's stick to the short term for the time being. It doesn't need to last forever.
Jim, I have no access to a machine shop unless I go out and pay someone. I have basic carpentry tools no lathe. I might be able to get access to a wood shop but I can't go machining anything unless I hire someone. I like your idea of bearings and a tube, but I'm having trouble understanding how to get the bearings mounted. All the cool-looking bearings with axial load support don't seem to have a housing (or shielding or sealing).
Also, given that this is an art project, the budget's got to stay small. Anything more than about $30 for a part is pretty tough because it seems like we need a lot of parts.
Thanks so much for the help guys! Sorry for the long email.