lazy susan type bearing? thrust bearing?

[sneakyimp]

This is my first post here and, based on the registration process, I’m not sure if it’s appropriate for me to post here. However, I could really use some advice from seasoned robot builders and mechanically oriented people.

I’m working on a kinetic sculpture that involves a savonius-type vertical axis wind turbine (VAWT). I’m trying to build the base which is a lazy susan type contraption. I bought a 6-inch lazy susan bearing and assembled a lazy susan but the bearing doesn’t spin freely enough and it’s really loud. I need a smoother, quieter mechanism and was hoping to get some suggestions about what I should be using.

I’ve been looking into this for quite some time and my reading has led me to conclude that I need some kind of precision thrust bearing. Not being a mechanical engineer, I don’t really understand how these thrust bearings are installed for my type of machine. They have no housing, no screw holes and no set screws and are quite narrow. I therefore don’t understand how to mount them and, although they would support axial load, I don’t imagine they would provide any lateral stability at all. Would this type of bearing need one or more radial bearings to support my disk? Would a shaft through the center keep everything aligned properly? If my shaft tolerances are off, will friction result or possibly too much travel resulting in vibration and wear?

I imagine that I would need to attach my rotating disk to a shaft by means of a flange or hub of some kind and that the hub would rest on the top of the thrust bearing (on the thrust washer) which would support its weight. I can also imagine putting a radial bearing (like a pillow block bearing) a foot or so down the shaft to provide lateral stability. I’ve attached a drawing of my thinking.

There are also tapered thrust bearings which look awesome (supports both radial and axial load!) but I fail utterly to see how I might attach these to either shaft or my turntable.

Any suggestions or help would be much appreciated.

[Al_Skierkiewicz]

Sneaky,
The bearings you linked to are very much like the lazy susan bearings. They are used in a design that has two mating faces separated by the bearing with a shaft the same diameter of the inner diameter of the bearing. Other bearings then are required to maintain side loading. Check McMaster Carr for some bearings that might be more suitable for your purpose. In many designs, the shaft is cut so that the bearing pushes against an area of larger diameter on the shaft. The inner wheel bearings in your car are an example.

[Dick_Linn]

A trailer hub and spindle could be readily adapted to this use, and are relatively inexpensive. Or get someone to cut off a front wheel & spindle assembly from a junked car.

[Tom_Ore]

Sneaky,

I have a few basic questions: like how large (and heavy) is your scuplture, how fast will it turn, how long do you want it to live, I need to know a bit more about the shape, etc. I can probably give you some assistance if you can supply a few more details.

Tom Ore (transmission design engineer in my day job…)

[MrForbes]

In addition the the questions Tom asked about the device, it would help to know what your fabricating abilities are. Having a lathe is really handy for making stuff that turns, but there are other ways to build things that allow you to use stuff commonly found at a hardware store.

One idea would be to put flanged ball bearings in each end of a tube, and put a shaft into it, and use lock collars outside each bearing to hold them in position on the shaft. The tube could be clamped to whatever holds it up, using U bolts. With periodic lubrication, even cheap hardware store ball bearings should last quite a while.

[sneakyimp]

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.

[MrForbes]

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).

We live to help others, especially if it’s a neat design challenge

I think you’ll find that a ball bearing that is not specified to be an axial bearing, can actually support a significant axial load for quite a while.

I suggest going to the hardware stores near you and see if they have any cheap flanged ball bearings, hopefully less than $10 each. Then see if you can find a steel rod or tube that will fit inside, and another that the bearing will fit into. You might need to visit a steel supplier, some welding shops sell cut lenths of various sizes of steel. Our local Ace hardware has a pretty good selection of stuff like this. It seems to be impossible to find it online (at least in a quick search), but if you find the hardware section with all the plastic hinged lid bins for bearings, and ask for the steel, you should eventually find them.

Keep oil in the bearings, they should be fine

[Tom_Ore]

Your device is fairly small and the loads are low. A flanged ball bearing would handle the loads just fine. The challenge may be getting a solid attachement between the turntable and the shaft. I checked McMasterCarr and it looks like even a very small bearing (say 3/8" shaft) will handle the loads. The problem is that this may be too small of a shaft to attach to your turntable. I’m wondering if you can get by with plastic bushings rather than a rolling element bearing.

[MrForbes]

Or bronze bushings. They are commonly available with a flange. Check the bins at the local hardware store.

Also think about redesigning the bearing configuration…how about putting the bushings or bearings in the rotating part, and have the shaft supporting it. Or use a long bolt, as long as it’s large enough in diameter.

The attached photo shows one of those cheap flanged ball bearings, 1/2" bore, 1-1/8" OD, pressed into a piece of red oak. The hole in the oak was made with a Forstner bit. This is something we were playing with as an idea for mounting wheels to a wood chassis robot. Good quality plywood would probably be better than hardwood.

[Dick_Linn]

You could bolt the hub (or weld, if it is steel) onto a base. Use one tapered roller bearing in the top. Drop your turntable shaft through it and down through a pillow block bearing.

Here’s a steel hub with bearings for less than $20.

https://www.surpluscenter.com/item.asp?item=1-3093&catname=wheels

EDIT: Didn’t notice how small it (the turbine) is. A flanged bearing in a piece of wood should do fine. I used to get 5/8" ID sealed flanged bearings from Northern Tool, in the go-kart section. If you don’t need precision, hand truck wheel bearings might work - you can get a whole wheel for about $4. on sale at Harbor Freight. Magliner sells their “precision” red bearings for about $2. each.

http://www.magliner.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=273&category_id=41&manufacturer_id=0&option=com_virtuemart&Itemid=30

If you are a decent woodworker and have some hard maple, make some wooden bearings.

[sneakyimp]

So grateful for the input. Really sorry for this long message, but I’m still confused about a couple of things – mostly the details of how these bearings and bushings couple together and how to make sure torque is transferred from the turntable to the shaft and finally to a speed reducer.

Jim, I’ve attached a drawing of your suggestion as I understand it. The idea is that, using u-clamps or flange mounts, I mount a pipe or tube to the chassis of my contraption and fit in its end a flanged bronze bushing, flanged plastic sleeve bearing, or flanged ball bearing in the top end of the tube. It’s obvious that the shaft goes through the middle of the bushing/bearing and that the bushing/bearing goes inside the pipe/tube and that the flange needs to be large enough to it doesn’t fall down the tube, but I don’t really understand:

1. How does the bushing/bearing support the weight of my turntable? In my attached drawing I have the hub resting directly on top of the bushing/bearing but this doesn’t look like it would work unless the inner race of the bearing sticks up higher than the other parts of the bearing. Might I need a washer? Shaft collar? Gastket? Some kind of spacer sleeve? Also

2. Should the shaft by tightly coupled to the inner part of a ball/roller bearing or is it OK if the shaft just goes through?

3. My experience with the lazy susan suggests that scavenging a hardware store will hardly result in tight tolerances. Rather than driving all over town, I’d be happy to buy precise parts from sdp-si.com or mcmaster.com if I can be sure I’m getting what I need.

I really like the image you sent with the bearing. I can see that the inner bearing race is slightly taller than the surrounding bearing parts which would permit it to directly support a turntable, perhaps with a washer or hub as or sleeve as the actual point of contact. The Forstner bit also seems really useful. Am I right in thinking I could sink a flanged bearing into a hole drilled in plywood by a Forstner bit? Perhaps shimmed with a little tape?

Tom, I really like your idea of using a flanged ball bearing, perhaps just dropped into a piece of plywood drilled with a Forstner bit. Any thoughts on using a tapered roller bearing for this? At $10 delivered with a 3/4" shaft, these seem like the ideal top bearing to me but I don’t really know how to mount it to my chassis (Forstner hole?) or how to rest the turntable/hub on it. Suggestions welcome. I’ve done a drawing for this too. Also, what about flange mounted bearings? Might any of these mounted bearings work? I’m thinking these options would help me skip the whole pipe/tube finding step.

• flanged-mounted nylon bearing
• pivot-type pillow block bearing
• stamped steel mounted ball bearings - these are $12-14, but look pretty good with inner bore ranging from 1/2" to 1" and the description says “ideal for moderate capacity radial or thrust combined loads”. I could just screw them on and go it also looks like they have set screws so it’s pretty obvious how they couple to the shaft and the chassis.

Dick, if I could get the tapered roller bearing AND the hub for $20 that would be a dream come true. I’m wondering, however, if the hub can apply torque to a shaft using those parts? If I’m not mistaken, that hub assembly looks like the hub spins freely on the shaft (or spindle?). I need my turntable to forcibly rotate my shaft, transferring torque to the speed reducer. Please let me know if I’m misunderstanding something here.

Those magliner bearings look really good (and cheap). The fact that they are sealed is GREAT. It was way too easy to get sawdust in that lazy susan bearing and this thing is likely to live outside in Los Angeles which is extremely dusty. Unfortunately, the page doesn’t specify the bore diameter. Also, still wondering about how to get the turntable/hub to rest on the inner bearing race without rubbing up against the outer collar or bearings. Washers? gasket? shaft collar? The second attached drawing could be easily (and affordably) modified to use those bearings instead.

I think we’ll have this bearing thing affordably sorted momentarily here if you guys can help me understand the mounting and coupling of these bearings. The Forstner bit hole looks pretty promising for some of the more affordable bearings and the flange-mounted and pillow block bearings are a more expensive but elegant-looking solution.

Again, sorry for the length but here are a couple of final things I’d like to ask.
COUPLING THE SHAFT TO MY TURNTABLE TO TRANSFER WIND POWER TO SHAFT
Aside from the question of how to rest my turntable on a bearing’s race, I’m wondering where the heck I can find a suitable hub/flange mount to couple my turntable to the shaft. I found these universal aluminum hubs which are perfect except they only fit smaller shafts. Except for this one (which doesn’t look particularly stable against lateral forces), I haven’t had much luck finding hubs for shafting over 3/8" – which is a problem if I use the tapered roller bearing because those are all for 3/4" and higher shafts. Threaded hubs, splines, and keyed shafting are probably not an option because of my inability to machine the shaft or the bearings. Ideally this would use a set screw or clamping mechanism and would have all the holes already drilled in it.

COUPLING SHAFT TO SPEED REDUCER
I’ve seen shaft couplings and I’m guessing this is what will be needed to couple my shaft to the speed reducer, but they seem so pricey – $10 at least for such a simple thing. If anyone knows of some alternative, I’d love to hear it.

[sneakyimp]

Not sure what happened with my other post, but it’s apparently awaiting moderator approval. Here’s the second drawing - I wasn’t allowed to attach two images to the prior post.

[sneakyimp]

I’m going to try this again. Hopefully it won’t need moderator approval?

So grateful for the input. Really sorry for this long message, but I’m still confused about a couple of things – mostly the details of how these bearings and bushings couple together and how to make sure torque is transferred from the turntable to the shaft and finally to a speed reducer.

Jim, I’ve attached a drawing of your suggestion as I understand it. I mount a pipe or tube to the my chassis and fit in its end a flanged bronze bushing, flanged plastic sleeve bearing, or flanged ball bearing in the top end of the tube. It’s obvious that the shaft goes through the middle of the bushing/bearing and that the bushing/bearing goes inside the pipe/tube and that the flange needs to be large enough to it doesn’t fall down the tube, but I don’t really understand:

1. How does the bushing/bearing support the weight of my turntable? In my attached drawing I have the hub resting directly on top of the bushing/bearing but this might not work unless the bearing has an extended inner race that’s higher than the rest of the bearing. Might I need a washer or shaft collar? Some kind of sleeve?

2. My experience with the lazy susan suggests that scavenging a hardware store will hardly result in tight tolerances. It’s probably easier to pay a little more from sdp-si.com or mcmaster.com if I can be sure I’m getting what I need.

I really like the image you sent with the bearing. I can see that the inner bearing race is slightly taller than the surrounding bearing parts which might permit it to directly support a turntable, perhaps with a washer or hub as the actual point of contact. The Forstner bit tip also seems really helpful. Am I right in thinking I could sink a flanged bearing directly into a hole drilled in plywood by a Forstner bit? Perhaps shimmed with a little tape?

Tom, I really like your idea of using a flanged ball bearing, perhaps just dropped into a piece of plywood drilled with a Forstner bit. Any thoughts on using a tapered roller bearing for this? At $10 delivered with a 3/4" shaft, these seem like the ideal top bearing to me but I don’t really know how to mount it to my chassis (Forstner hole?) or how to rest the turntable/hub on it. Suggestions welcome. I’ve done a drawing for this too. Also, what about flange mounted bearings? Might any of these mounted bearings work? I’m thinking these options would help me skip the whole pipe/tube finding step.

• flanged-mounted nylon bearing
• pivot-type pillow block bearing
• stamped steel mounted ball bearings - these are $12-14, but look pretty good with inner bore ranging from 1/2" to 1" and the description says “ideal for moderate capacity radial or thrust combined loads”. I could just screw them on and go it also looks like they have set screws so it’s pretty obvious how they couple to the shaft and the chassis.

Dick, if I could get the tapered roller bearing AND the hub for $20 that would be a dream come true. I’m wondering, however, if the hub can apply torque to a shaft using those parts? If I’m not mistaken, it looks like that hub spins freely on the shaft. I need my turntable to forcibly rotate my shaft, transferring torque to the speed reducer. Please let me know if I’m misunderstanding something here.

Those Magliner bearings look really good (and cheap). The fact that they are sealed is GREAT. It was way too easy to get sawdust in that lazy susan bearing and this thing is likely to live outside in Los Angeles which is extremely dusty. Unfortunately, the page doesn’t specify the bore diameter. Also, still wondering about how to get the turntable/hub to rest on the inner bearing race without rubbing up against the outer collar or bearings. Washers? gasket? shaft collar?

I think we’ll have this bearing thing affordably sorted momentarily here if you guys can help me understand the mounting and coupling of these bearings. The Forstner bit hole looks pretty promising for some of the more affordable bearings and the flange-mounted and pillow block bearings are a more expensive but elegant-looking solution.

Again, sorry for the length but here are a couple of final things I’d like to ask.
COUPLING THE SHAFT TO MY TURNTABLE TO TRANSFER WIND POWER TO SHAFT
Aside from the question of how to rest my turntable on a bearing’s race, I’m wondering where the heck I can find a suitable hub/flange mount to couple my turntable to the shaft. I found these universal aluminum hubs which are perfect except they only fit smaller shafts. Except for this one (which doesn’t look particularly stable against lateral forces), I haven’t had much luck finding hubs for shafting over 3/8" – which is a problem if I use the tapered roller bearing because those are all for 3/4" and higher shafts. Threaded hubs, splines, and keyed shafting are probably not an option because of my inability to machine the shaft or the bearings. Ideally this would use a set screw or clamping mechanism and would have all the holes already drilled in it.

COUPLING SHAFT TO SPEED REDUCER
I’ve seen shaft couplings and I’m guessing this is what will be needed to couple my shaft to the speed reducer, but they seem so pricey – $10 at least for such a simple thing. If anyone knows of some alternative, I’d love to hear it. Also, the speed reducer looks to have a shaft diameter of 6mm so we need to couple some larger shaft (10mm? 3/8 inch?) to it.

[sneakyimp]

Upon further reflection, those tiny universal aluminum hubs look way too small (only about .8 inch outer diameter and max 6mm shaft). I’ve been looking for hubs all afternoon and can’t seem to find much at all. So far I’ve found these:
Packard Fan Hub - 1/2" bore, 2 set screws, 3 mounting holes. other specs unavail. $3.96
Chicago Die Casting 2122 1/2 Die Cast Hub - 1/2" bore, 1 set screw, 4 mounting holes, outer diameter 2.75 inches, $4.99.

I was rather hoping for a considerably larger hub – maybe 6" outer diameter. I can’t believe hubs are so hard to find.

[J11]

Hi Sneaky,

I recently built a turntable that sounds like it is probably similar to what you are looking at making using a large diamter ring style turntable found here.

McMaster-Carr

If you’d like more info. let me know and I will try to get you some pics. etc.

Good Luck! BTW- You came to the right place for help!

[Dick_Linn]

In your case, the trailer hub would have to be stationary, just like the upper bearing in your picture. It’s probably overkill anyway.

The Magliner hand truck bearings should be 5/8" inside diameter, like most hand truck axles.

In your illustration with the tube, you could use two oil impregnated bronze bearings if you can get a good fit. They are cheap and a flanged type will support the end load. You can get them at McMaster-Carr or MSC.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3742

[jspatz1]

The reason the 3-piece thrust bearing in your original post does not have mounting features is that they do not really require mounting. Get one that fits your shaft closely, and it is simply guided by the shaft itself, doesn’t need mounting. There is nothing wrong with your original sketch, just need a thrust bearing that fits your shaft. Move the pillowblock bearing up to a high position just under the thrust bearing, as that is where all the side loads will be, and just guide the lower end of the shaft with a loose-fitting bushing.

If you really want a low-profile, lazy-susan type bearing without having a verticle shaft, these ring bearings from McMaster are pretty nice (http://www.mcmaster.com/#catalog/116/1110/=94ojgg), but may be more than you are wanting to spend

[jspatz1]

I haven’t had much luck finding hubs for shafting over 3/8" – which is a problem if I use the tapered roller bearing because those are all for 3/4" and higher shafts. Threaded hubs, splines, and keyed shafting are probably not an option because of my inability to machine the shaft or the bearings. Ideally this would use a set screw or clamping mechanism and would have all the holes already drilled in it.

COUPLING SHAFT TO SPEED REDUCER
I’ve seen shaft couplings and I’m guessing this is what will be needed to couple my shaft to the speed reducer, but they seem so pricey – $10 at least for such a simple thing. If anyone knows of some alternative, I’d love to hear it. Also, the speed reducer looks to have a shaft diameter of 6mm so we need to couple some larger shaft (10mm? 3/8 inch?) to it.

Here are some aluminum hubs that might be suitable http://www.andymark.biz/hubs.html AndyMark has many hubs, bearings, shafts, collars, and bearing holders that might suit your needs. FRC robot builders rely heavily on AndyMark for parts.

For a cheap shaft coupling, with the low torque you are dealing with, a short piece of stiff rubber tubing and hose clamps might be suitable. The flexibility will allow for a some misalignment in your assembly.

Be careful of “sealed” vs. “shielded” ball bearings. “Sealed” bearings have some friction from the seal and are not free-wheeling. “Shielded” will keep out most dirt and debris, but are low friction. I assume with a wind application you are looking for as low friction as possible.

[Tom_Line]

@jspatz1

Here are some aluminum hubs that might be suitable http://www.andymark.biz/hubs.html AndyMark has many hubs, bearings, shafts, collars, and bearing holders that might suit your needs. FRC robot builders rely heavily on AndyMark for parts.

For a cheap shaft coupling, with the low torque you are dealing with, a short piece of stiff rubber tubing and hose clamps might be suitable. The flexibility will allow for a some misalignment in your assembly.

Be careful of “sealed” vs. “shielded” ball bearings. “Sealed” bearings have some friction from the seal and are not free-wheeling. “Shielded” will keep out most dirt and debris, but are low friction. I assume with a wind application you are looking for as low friction as possible.

I was going to point him at the andymark hubs as well.

He can get ground aluminum bar that will fit in them from mcmaster. I would used flanged roller bearings to support the longitudinal loads, with a single thrust bearing at the top to ride on. Picture included.

For the speed reducer I would consider gates belting and pulleys, or 25 chain and andymark sprockets.

In addition, don’t we get some dandy pillow-block jounted bearings that are self-aligning from igus that would work perfectly for this that he could bolt to a 2x4? I believe we used ours this year in a prototype shooter design, but if someone has them laying around that might be an easy way to do this too.

Thrust bearing: McMaster-Carr
Flanged Bearing: McMaster-Carr
1/2" aluminum precision ground shaft: McMaster-Carr

Use andymark hubs. Attach by drilling a hole through the hub and the shaft and pinning (can be done with a drill press so you dont’ have to do any broaching for hex shaft or milling for keyways). Andymark has 25 chain sprockets that will bolt up to the hub directly for power transfer.

Use a hole saw to drill holes for the linear bearings then press them in. Put everything on the shaft before screwing in the short 2x4 portions to make sure it’s lined up and freely rotating.

[sneakyimp]

J@GMFlint, I tried one of those 6" square lazy susan bearings that I bought at True Value hardware and i really liked the lateral stability and simplicity of it, but It doesn’t spin as easily as I’d like and it’s far too noisy. Those large-diamter ring-style turntables look pretty interesting.

Dick, I tried finding the sleeve bearings / bushings at my local hardware store and they didn’t have any. Home Depot didn’t have any bearings at all as far as I could tell so I went to Grainger Industrial supply. Thanks for the link on those bushings/bronze bearings. Those prices look good and I’ll probably be buying some here shortly.

I broke down and bought two 2-bolt flange mount ball bearings and a 5" aluminum pulley with 1/2" bore.

jspatz1, thanks so much for the advice about the thrust bearings. I kind of thought they might work that way. The problem I’m having is that only a few of the flange bearings and pillow-block bearings I’ve seen have an extended inner race – I worry about the lower thrust washer rubbing on the outer race of my flange/pillow block bearing and causing friction. Of course, it is a thrust bearing? Not really sure how it works. I suppose I’ll have to just watch the dimensions carefully.

Thanks for the tip about the andymark hubs. I had seen some on a couple of the robotics sites I stumbled across but the lack of a set screw looks like trouble. I’m not really sure how I would couple these to the shaft. I’m not using keyed shafting or hex shafting.

Thanks for the tip about shielded/sealed bearings and yes I’m looking for very low friction. The bearings I bought at Grainger (which appear to be sealed) seem pretty stiff and the inner diameter is too small to fit the 1/2" steel tube I bought. They were also fairly pricey (@$16) so I think I might take them back and get some flanged bearings (and a thrust bearing!) instead.

The 5" pulley I bought looks like it’ll make a nice hub. It’s nice and wide and I’ve drilled 4 holes in it. I’m a bit concerned about the shape of it though as the part containing the set screw is precisely the shape that would scrap against the outer race of a bearing [see attached image].

Truly excellent suggestion about coupling to the speed reducer. I was considering trying to have the shaft machined to 6mm at the end. I’ll figure that out once I’ve costed out the options. Thanks also for bushing suggestion, I’ll probably get one of those recommended by Dick.

Tom, thanks for the drawing! And thanks for the suggestions about pulleys and belts. I had originally looked into that and decided that it was going to be difficult to get spin ratios high enough. I probably need 20 or 50 to 1 unless I want my entire song playing several times per second. That’s pretty tough with pulleys.

Thanks for being sensitive to my inability to key the hubs and bearings. I’m going to look for some flanged bearings tonite and see what I can find.

I’ll also be looking for shafting that will actually fit into the tolerances I get from grainger. Is it safe to assume their 1/2" shafts will fit into their 1/2" bearings or do manufacturers expect customers to machine these parts after purchase?

EDIT: Forgot to attach picture of my hub. Note the set screw bulge and the holes I drilled.