I've only heard it mentioned once in an article.
It's ring shaped and has a hole in the middle which is useful when something has to go or pass through its middle.
I need it, exactly for that reason:
I always thought it just meant a motor in which you can see the armature as compared to a "can" motor which is fully enclosed.
See the pics here - (found at random)
...R
Google "ring motor". How big of one do you need. Some are available to turn wind mill power generators when there is no wind.
Paul
Thanks. This is weird, in google I can see some good image results, but websites results aren't good.
I think one with no more than 5 cm hole would work, the RPM needs to be adjustable to 720 or 900 rpm. Not sure about the torque.
Its a motor with an open frame - no technical jargon is implied. This usually means its
intended only to go inside a machine where the case protects it from water and dirt ingress.
You could also google hollow shaft motor.
As you have found they are largely industrial and big.
Have a look at a supermarket 3 axis barcode scanner
you may get an alternative idea from that.
Edit
From your picture they look like thin section ring bearings
Ring bearings and large thin section bearingssometimes called slewing bearings are normally only rated up to less than 100 rpm.
I know little about ring motors though i suspect they are something special
Edit , i have just discovered that ring motors are desinged to fit on a central shaft which fills in the hole.
...but where can I get them?
I get some image results when searching "hollow shaft motor" or "ring motor" but not much info.
Here's the eBay search results: hollow shaft motor for sale | eBay
All are for some kind of gimball. Could work if the shaft hole was not so tiny.
jantran:
...but where can I get them?I get some image results when searching "hollow shaft motor" or "ring motor" but not much info.
Here's the eBay search results: hollow shaft motor for sale | eBay
All are for some kind of gimball. Could work if the shaft hole was not so tiny.
When I looked at your Ebay link, Ebay showed me several other motors people were looking at. Seems they are all for mounting digital cameras. I think the Gimbal mounting relates to using two motors for movement in two dimensions.
You may need to search for similar camera mounts until you find one that fits your project.
Paul
What motors did you see? Were they all "gimball motors"?
I've only found ones with only 1 cm hole. That won't do. At least 3 cm hole (aperture) will be needed. And I can't find any info on the RPM (I need around 700-900) and torque for these.
Scroll down on that Ebay screen and see the 25mm opening motor.
Paul
You can post links too. I checked every motor in the link I posted. Most of them don't even mention the shaft diameter. Don't see one with 25mm shaft diameter. maybe search results are different between users or user locations, I don't know.
And again, I don't see the RPM mentioned anywhere.
Can you post link please.
That sounds like an apeture motor to me and they are far too slow for th op
here you go
looking at others they appear to run about 800 rpm.
the kv rating , on a model motor which is 4 poles 50 KV would mean 50,000 rpm per volt.
that is very high so maybe you have to divide the no of poles .
not sure how you drive these motors either
Looking at your origional picture im thinking that it may be an outrunner.
Which bit rotates ? Inner or outer ring.
Edit.
Does the whole globe rotate, just the mirrors and screen ?
Its difficult to envisige what is going on.
Hard question to answer as that is just an illustration and for the original display I'll need to disassemble good portion of the device to know.
All I can say is the hole is about 5 cm wide.
Why do you ask though? I'm assuming youre asking whether the whole globe rotates to have an idea on how much torque is needed? The whole globe rotates. The motor is attached to the globe with screws.
If the whole globe rotates I would think that apart from starting torque there is very little air resistance and running torque requirements will be fairly low.
Had it been the innards , air resistance would have required evacuation which has heat implications for the motor which would probably needed water cooling.
I did not realise this was an existing unit and thought it was something you were trying to fabricate.
That being the case is there no makers name you can find for spare parts ?
If you do disassemble can you post pix please, that's a rather curious motor.
Standard out-runner configuration, the side the wires go in is the stator, the outer case and
other side is all rotor. Bear in mind this is a sensorless BLDC, you'll need a feedback loop of some
sort to tame it.
I searched for "outrunner motor" but all I found were small toy airplane motors with very thin shafts...
Thats because there are a lot of them.
Basically the stator is the inside shaft or ring with the rotor oustide , gives better torque.
Not toys btw.
I have one about the size of 1/2 smartie tube.
Puts out over 1 hp , can be pretty dangerous.
Edit
Despite the terminoligy , i think thats pretty much what you have, just the inner and outrunners are flat rather than concentric.
Similar to a pcb or high speed scanner motor with a hole in it.
I have actually been looking for something similar for a couple of years which is why your post caught my interest.
I meant toy as in not a "real" airplane.
But anyway, all I'm saying is by searching "outrunner motor" I see only motors for toy planes. If you're having better luck than me, please post what you found.