[tatter06]

I have been testing some nsr shark 20k/21.5k motors for the Wales and West races and I have one 21.5k motor in my batch that is fairly quick but vibrates noticibly more than the other motors. Is there anything I can do to smooth it out, I don't really want to throw out a quick motor at £15 a pop but it vibrates so much I'm sure it won't be very driveable. The w&w rules mean I can't open the can.

[Nonfractal]

I'm afraid that I don't know of any way to balance an armature without opening the can.
You have got me thinking about how it might be possible though. 
Alan.

[nkarres]

Run it in for 2 hours on 6 Volts. A drop of oil (only a drop) to the front and end of the shaft and than 30 minutes on 9 Volts. That should do it!!!!!

Nico

[tatter06]

OK will give running in a bit longer a. Go, can't do any harm at this point!

[Kevan]

I'm afraid that I don't know of any way to balance an armature without opening the can.
You have got me thinking about how it might be possible though. 
Alan.

epoxy putty shoved into an armature stack gap, just like NSR do...maybe the green epoxy putty normally found has come off that motor, there may be evidence...

[Nonfractal]

I'm afraid that I don't know of any way to balance an armature without opening the can.
You have got me thinking about how it might be possible though. 
Alan.

epoxy putty shoved into an armature stack gap, just like NSR do...maybe the green epoxy putty normally found has come off that motor, there may be evidence...

True Kev,
However, the problem isn't fitting the putty , resin or other substance to the armature ,
 It's figuring out where to put that weight. 
Maybe trial and error would work but something that could be added and removed would probably get spat off during testing.
Of the 5 shark motors I have lying around in boxes, only one shows any evidence of balancing (see blue resin in the pic) 

Alan

   

[Kevan]

I have a fair few Sharks with epoxy putty in, if you can't open the can (which is a 5 second job with a Shark) then you only have 3 places to try.

[tatter06]

So I ran it in for 2 hours at 6v and 30 mins at 9v and it does seem to have made the vibrations less violent although still more than other motors. 

I didn't know the blue/red!/green gunk was for balancing, this motor doesnt have any but a few of my 20k sharks do.

Even if I did open the can, how would I know where to add any ballast?

[Nonfractal]

You'll need jig like this.
The armature will roll showing the heaviest side.
Add epoxy to the lighter side and keep testing 'till there is no longer a heaviest side. 
   

[BAracer]

So I ran it in for 2 hours at 6v and 30 mins at 9v and it does seem to have made the vibrations less violent although still more than other motors. 

There's a clue...if that technique worked, it's not out of balance.