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Old Today, 07:52 PM
USA, ME, Ellsworth
Joined May 2008
16,690 Posts
Originally Posted by sr175 View Post
Your comment on the flat on the shaft reminded me of something. I have tried making a flat or a groove in a motor shaft before and the metal was so hard that nothing worked. What kind of dremel attachment do you use to do that? I think i have the wrong attachment to work this hard of metal.
What KC Flyer said!

Has to be an abrasive process for shafts in the typical motor. You can see the process in these threads:

Making and Replacing a Brushless Motor Shaft - http://www.rcgroups.com/forums/showthread.php?t=1240725

HexTronik DAT-750/DT750 Replacing a Shaft - http://www.rcgroups.com/forums/showp...postcount=1080

Prop Savers - Fitting, Using, Testing, & Making Thera-Band Bands - http://www.rcgroups.com/forums/showthread.php?t=1419378

I could not live without my Dremel tool. The abrasive cutting discs come in a variety of types and thicknesses. The one I use for adding flats, cutting shafts, and cutting snap ring grooves is the Dremel #409 abrasive disc and it is held in a #102 arbor. That will cut a groove that is about 0.025" wide and, of course, with continued cutting will cut all the way through a shaft.

Use them with light pressure and wear eye protection. They can and will shatter in use occasionally. The fragments are not heavy or particularly dangerous but you definitely do not want to get them in your eyes. A light caress with the disc at full RPM and at a right angle to the shaft will produce a stream of sparks and a nice little flat. And that stream of sparks is the perfect load on them for cutting.

I recently got some diamond coated rotary cutting discs at Harbor Freight and they are simply wonderful:


There are five discs in the set and I am still on the first one of them after a number of cuts.

As you use the Dremel and abrasive cutters, keep in mind that the stream of abrasive debris coming off of the cut is not without health dangers (eyes, lungs, etc.) and can be damaging it if gets into the wrong place. Direct it away from yourself and put delicate things like motors in a plastic bag if you cut a shaft with a running motor (the perfect way to do it for the perfect cut).

I have a tuna fish can with about 1/4" of water in it on the bench. I most often hold the item (shaft, screw, whatever) over the can and let the water catch the spark stream.

I think I have worn out two Dremel tools so far but it has taken over 50 years to do it...

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Old Today, 10:17 PM
Planes in flames,,,
jetpackninja's Avatar
Gravity Sucks
Joined Aug 2010
3,394 Posts
I appreciate what you guys see and your comments are definitely appreciated.
In fact, on of the winds was taking a shortcut over the top of the tooth.
Fortunately I could feel it when I assembled the motor and packed it back down over the tooth with a credit card (number one motor winding tool!)
Thanks for your eyes!

Originally Posted by KC Flyer View Post
It's hard to tell from the pic, but your last winds look to be pretty close to the magnets.

I had a rewind where a wire was a bit loose, crept up between the teeth and got buggered up by the spinning magnets. Now I try to thread the last turn(s) of each tooth through the middle or bottom of the bundle to lock it in so that everything is tight. I've also used a drop of CA to secure loose wires as well.

Your winds look very neat otherwise - just don't want you to lose a motor/ESC to something easy to prevent.

Where did you get the upgraded bearings? Are they sealed?

FWIW, I recently rewound one of these motors for a CTH Widowmaker where both bearings were the big size (8mm OD x 3mm ID x 4mm thick). It is now 8T/23g with a 7x6 APC clone prop cut down to 6".
Yes, the bearings are sealed. I got them from this place.

I popped for the sealed ceramic for a couple of my favorite planes.
The rest will get the sealed 99 cent bearings.

Great. This is one of the gotchas with this little motor.
I have seen three different combinations of bearing sizes.
And now four different combos with the big bearing in the front and in the back

I'm running the Assassin on an 8 turn with the regular 7x6 prop... I may need to prop down and see if I get better flight times. 32 apms and 412 watts!
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