Pneumatic Motors?

shardbearer · Thu Sep 13, 2012 9:18 pm

Does anyone have information on pneumatic motors? You know, put air in, shaft spins, like is used in dentist drills and pneumatic wrenches? Where can I buy them, and if I can't, how can I build one? Ebay has a few beat up ones covered in grease and rust from the 1800s, Mcmaster has a few giant ones, overpowered for what I need and a minimum of $150, over 1000 for the decent ones. Anyone have an idea? I need it to be under about 4 inches to a side, and as light as possible, it's for an engineering competition.

I wonder if I can make one out of PVC? Maybe take a 2" threaded Plug and Cap, drill holes in the middle of each, glue in ball bearings. Make a rotor with 6 or 8 blades on a shaft, glue shaft onto bearings. Drill holes in sides of cap, attach input. How would I get ball bearings airtight?

jackssmirkingrevenge · Thu Sep 13, 2012 10:34 pm

On a very simple level, make a turbine.

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Just a stream of compressed air from a thin nozzle directed into turbine blades, generating high rpm which you would have to gear down for most applications, and a funky whine

PVC Arsenal 17 · Thu Sep 13, 2012 11:20 pm

You can get a dentist's drill for pretty cheap on ebay

inonickname · Thu Sep 13, 2012 11:26 pm

shardbearer wrote:Does anyone have information on pneumatic motors? You know, put air in, shaft spins, like is used in dentist drills and pneumatic wrenches? Where can I buy them, and if I can't, how can I build one? Ebay has a few beat up ones covered in grease and rust from the 1800s, Mcmaster has a few giant ones, overpowered for what I need and a minimum of $150, over 1000 for the decent ones. Anyone have an idea? I need it to be under about 4 inches to a side, and as light as possible, it's for an engineering competition.

I wonder if I can make one out of PVC? Maybe take a 2" threaded Plug and Cap, drill holes in the middle of each, glue in ball bearings. Make a rotor with 6 or 8 blades on a shaft, glue shaft onto bearings. Drill holes in sides of cap, attach input. How would I get ball bearings airtight?

Dentist drills are small impulse turbines. I wouldn't recommend replicating one as they need very high speed bearings and are tricky to build accurately and balanced without machine tools (which I'm guessing you don't have).

Die grinders are usually run on vane motors which would be completely impractical to machine in your circumstance.

I'd recommend trying a tesla turbine. As they are bladeless (only use round disks) they can be made without a lathe and mill if you're the slightest bit creative. It's easy to get a solid 20k rpm and reasonable efficiency from a homebuilt one.

If you're up for a challenge a wobbler engine can be built on a drill press, though it would be a tricky process (very easy on a lathe and mill though).

There are sites on the web that offer steam and pneumatic engines, either assembled, as a kit, or a casting kit. Beware that some engines will only work with a flame or heat source (stirling cycle) and not with pressurised air or steam.

D_Hall · Thu Sep 13, 2012 11:37 pm

You're not very clear on your application, but I've had good luck using an air ratchet for certain applications. Reasonable torque. Built in speed reduction. Dirt cheap.

inonickname · Fri Sep 14, 2012 12:22 am

D_Hall wrote:You're not very clear on your application, but I've had good luck using an air ratchet for certain applications. Reasonable torque. Built in speed reduction. Dirt cheap.

Sounds like he just wants to make it for enjoyment.

Technician1002 · Fri Sep 14, 2012 12:51 am

An air drill or die grinder is a good source of air turbine motors of a larger size. A die grinder is an air powered oversize Dremel tool. Look for used air tools for sale.

inonickname · Fri Sep 14, 2012 1:05 am

Oh, didn't notice the "it's for an engineering competition". Derp.

You're going to have to tell us some parameters...

Do you want lots of power? High RPM? Efficiency? Linear power delivery? Something suitable for integrating into a car or boat? A demonstration piece?

sagthegreat · Fri Sep 14, 2012 5:24 pm

Google: Tesla turbine, u can get 20,000 rpm from 70 psi of air. and u can make one from a old harddrive

inonickname · Fri Sep 14, 2012 8:49 pm

sagthegreat wrote:Google: Tesla turbine, u can get 20,000 rpm from 70 psi of air. and u can make one from a old harddrive

It must have alloy discs though, not ceramic ones.

I don't see why people limit themselves to harddrives or cd's, you could cut your own aluminium disks from sheets using a holesaw.

sagthegreat · Sat Sep 15, 2012 11:51 am

for people like me, that are 15, is way easier to use a harddrive

Zeus · Sat Sep 15, 2012 7:06 pm

Holesaw, $15. Power drill, $20

I was using holesaws at 7, and I started using the big drills at 8. And Tesla turbines have no torque.

inonickname · Sat Sep 15, 2012 7:24 pm

Zeus wrote:Holesaw, $15. Power drill, $20

I was using holesaws at 7, and I started using the big drills at 8. And Tesla turbines have no torque.

Well they do, you just have to know their application. Though taking an excessive torque load from a tesla turbine will make it terribly inefficient.

Edit: And I'm 18, and I've been using plenty of tools since before I was 15. I had my own lathe at 14/15

sagthegreat · Sat Sep 15, 2012 7:33 pm

the problem is getting my parents to buy proper tools. I build all my stuff with 1 drill and a file as a saw.... -.-

inonickname · Sun Sep 16, 2012 1:58 am

sagthegreat wrote:the problem is getting my parents to buy proper tools. I build all my stuff with 1 drill and a file as a saw.... -.-

A drill is fine... Like said, holesaw, The drill can be improvised as a lathe with emery cloth to true all the disks to each other.

Pneumatic Motors?

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