Totally of topic motor question

[klmjr]

Hi,
I dont fly airplanes but I am very interest in making a motor that can spin at 50000 rpm to use in a pcb drilling machine I made. This is using bvery small 1/8" shank bits. They have to turn very fast for best results. I was thinking a single stack would probably be enough power but what kind of stator count? The smaller the better? (ie 6 instead of 12) and a delta winding?
I can put a fan on it if necessary and would run the esc from a 12v power supply. Was thinking might have the shaft flush with the endbell with a longer shaft out the back and a 3mm to 1/8 adapter. I can do the machine work but not sure about the motor specs I would need. Read about 1000 messages so far and am still pretty confused as to rpms that can be developed without a prop on the end.
Thanks
Keith

[Q]

50.000 rpm is extremely fast.
One 22.7mm stator can deliver about 40W. Use the thickest wire you can find/handle or, better yet, use as many multiple strands as you can get in the stator. I'd go for an 10 turn motor in delta to start with.

You can use a 12 arm stator and only wind 6 arms. Just skip one arm after each wind. With 6 arms wound, you can use 4 magnet poles. Just glue magnets with the same poles next to each other in the bell to get a curved one.
If you want to go all the way in speed, go for a 3 arm stator with only 2 magnets. That way you have the maximum speed possible.

[ScubaSteve]

If you want to go all the way in speed, go for a 3 arm stator with only 2 magnets. That way you have the maximum speed possible.

Jeez that would definitely be a fast one... :shock:

[Q]

Steve, have you never considered the fact that many inrunners are a three coil, 2 pole motors? With many inrunners the maximum rotational speed is set by the structural strength of the rotor and the maximum switching speed of the ESC.

[klmjr]

I found this in a old seagate 80 MEG scsi drive (ST-296) to be exact. It has 12 poles but six are large and 6 very small in between.

The next picture is the other parts I already have.The bearing is a special 80000 rpm rated unit. The black tube is a DA300 collet extension 1/2" diameter and will be used as the support for the can I will make out of mild steel. A aluminum bearing support tube will carry the collet extension with the drill extending down. the extension will only extend up to the top of the can. The little drill in the collet on the left is a very common size for pcb work it is .028 inches. Now question is since i only want 6 poles anyway would it be a good idea to grind out the small poles so I can fit bigger wire? or just leave well enough alone? The little baseplate it came on is very nice, 3 little screws hold the stator in place making it easy to remove and try different windings.
Would 15 by 4 by 2 n45s be good enough for this? Or should i look for 12mm as that is the rotor height? I can make the can opening any size I want as it is being made from a 1 1/2" steel bar I just happen to have sitting around. Oops pics are backwards. Oh well

[swatson144]

You would want the magnets to be as long as the stator. Since this is stationary and weight don't matter a little longer won't hurt. 12x5x2mm N50 happen to be a realative bargain at www.engconcepts.net as the qty break happens at 25 pc.

So we avoid confusion the poles are the magnets, the teeth or arms are the protrusions from the stator.

these things need an even number of poles. You are looking at 3-6 teeth and likly 2-4 poles for your speed. The can can be fairly heavy to be a fly wheel.

Let's take a look at JC's gbl_00001 motor, which is a 22.7 x 5mm 9teeth 12 pole which has a reduction of 6 and a kv of 1969 rpm/v;

GBL_00001 14T 24AWG Wye (1) 22.71mm (12) 5x5x2mm N45 4.5 4 3.97 9 36 14964

let's say you run from a 12v (13.2 v) PB source as you'll need no servos/BEC

01 motor you'd get 26,000 rpm no load.

same motor as a 1 reduction (2 pole) would get you about 160,000 no load

same motor in 2 reduction (4pole) would get you your 52,000 rpm.


Soo If I had to take a guess at what I'd do with your stator...6 Teeth ABCabc 4 pole 14t.

If you just want to check it out as a proto 3 teeth ABC with 4 poles, then if it was too slow just pop 2 of the mags out and run it as a 2 pole.

If I'm not mistaken the 6 Teeth ABCabc 4 pole 14t. should actually make about 75,000 no load. I don't know if a controller would keep up though.

Dealing with these low pole motors you'll want to soft start them and may even require flicking to start.

I imagine this as a drill press type setup and can't imagine wanting a 3 oz rotor/flywheel in front of my face turning 75k. I can sorta imagine the way that dude would get around if loosed though!

[klmjr]

The idea of standing in front of thar sucker spinning that fast would give me the willies to. I plan on a 2 inch id steel tube fitting over the rotating hub with a small fan blowing down the tube for cooling. That way the easy way out is straight up thru the fan if it ever lets loose. the can will be machined out of a steel bar and planning on 1/4" walls for strength. I will post pictures when I get it done. Have to build a esc also. Dont need real light weight or size so I will just breadboard one up.

[swatson144]

Forget the fan . Just scorp some tube over the 2 air holes. IE cut the tube at an angle and solder braize etc to make scoops. I'd think a fan at that speed would be stupid loud and nasty drag. Though you probably meant an accessory fan seperatly powered.