Flex-shaft motor malfunction

Can any orchidian masters of electronics theory tell me why a
flex-shaft motor will occasionally stop after it runs fine for awhile.
Seems that after the moror gets warmed up from use it starts a
whinning noise and the shaft stops turning. During one episode when
it malfunctioned I took the cable off and could hold the shaft of the
motor at full rheostat power. The two contacts that can be removed
from the side of the casing are lengthly and seem to be
fine…Robert R. Wooding…

   why a flex-shaft motor will occasionally stop after it runs fine
for awhile.

Sender: owner-orchid@ganoksin.com
Precedence: bulk

Robert, it sounds as if the motor bearings are going out on the motor
in your flex-shaft. I’m not familiar with the type of bearings in
them, whether they’re the sleeve or ball bearing type. If they are
the sleeve type, heat is being produced by the bearings rubbing
against the motor shaft. This will cause them to close on the shaft
like a pair of pliers and eventually lockup the motor. Ball bearings
can run dry and cause lock-up also. In either case, professional
service is required.

Keep in mind Robert that this is just a possible cause based upon
what you wrote.

Charles Heick

Dear Mr. Roert: All flexshaft otors eventually wear out. However,
depending` on the medium you are cuttng, grinding etc. you will
probably colect dust particles in and around the bearings. This tends
to over heat and wear them out. I might suggest checking both front
and rear bearings for xcesive gnk build up. You mght also check the
rushes for wear. They may e worrn down to their casing, at which
point they need replacing. If this sems like alot of work----IT IS.
Dust WILL get into even the smallest of places turning lubricant into
agritty glue causig excesive early wear.

Rick Blahnik

    tell me why a flex-shaft motor will occasionally stop after it
runs fine for awhile. Seems that after the moror gets warmed up from
use it starts a whinning noise and the shaft stops turning. 

There may be several reasons. 1) the speed control isn’t making
proper contact and has become intermittent. 2) the motor bearings
are gummed up and/or ‘stuffed’! 3) the commutator is dirty or the
brushes are getting stuck 4) the shaft of the flexible drive has
become gummed up with old oxidized grease 5) the handpiece bearings
are gummed up and/or stuffed! 6) the motor winding is unhealthy. So:-

  1. remove the plug from the power supply and remove the case of the
    controller to check. If it is an electronic control, you’ll have to
    get professional help; otherwise wipe it thoroughly with a kero rag.
  2. Squirt kerosene or CRC556 or WD40 through the bearings to wash out
    gunk. Drain well, and relubricate with a fine oil (3-in-1?) Clean the
    commutator with a kero rag. DON’T use an abrasive. 4) wash out the
    flexi drive with kero, drain and relubricate. 5) ditto. 6) if the
    above remedies don’t improve the situation, you have a real problem:
    you’ll find it cheaper to get a new motor. Let us know how you get
    on. Cheers, – John Burgess; @John_Burgess2 of Mapua
    Nelson NZ

Hello Robert,

If you have confirmed that the problem is in the motor and not the
(foot) speed control (which it seems you have indeed done) it sounds
like a poor electrical connection in your motor that opens up when
the motor gets warm.

The opening of the electrical connection can be small enough that you
might not be able to see it and allowing electrical arcing across the
gap causing poor and erratic motor operation. The symptoms you
describe also can be related to “motor brushes to commutator”
problems. The motor commutator is the motor armature part that the
brushes make contact with. This commutator has copper segments that
could be badly worn, dirty or otherwise deteriorated–causing the
problems you have described. If at full power of the speed control
rotating the motor shaft by hand makes it spin up again then the
brush and commutator contact is suspect. If rotating the motor shaft
by hand does not make the motor speed up then an intermittent open
circuit is most likely the culprit. Since this type of motor is a
universal AC/DC series wound type of motor, this intermittent open
circuit can be in the field coils or the armature windings. Usually
where this problem occurs–arcing will leave black marks to help
visually identify it.

I hope this helps. I repair these motors often and if you have any
other questions please feel free to contact me further or you may
send me the motor and I will provide a free estimate on the cost to
repair it for you. Regards,

John Cranor, The Jewelry Equipment Dr www.equipmentdr.com

Check the carbon pile in the foot reostat. If it looks worn or has
broken pieces replace them from another footpedal. I never throw them
away I use the old ones to scavenge pieces to repair others. If it is
an electronic foot pedal check all the slide connections to make sure
they are working proper to control the reostat. First place I would look. Frank Goss

It could be that the copper contacts the brushes touch are worn or
totally burned up. Inspect them if the copper ring that the brushes
touch have a 2 to 3 mm deep groove in it then it is time to replace
the armature. It can be ordered directly from most tool companies
though they will not list the part in their catalogs. You will have
to ask specifically for the one you want. Have the make and model
Number handy. Also know if it is an older “bushing” or newer
"bearing" model. These parts could be binding as well and may need
replacing. The bushings are no longer available but the bearings are
easily obtained from whoever your favorite tool supplier is. Ptock2