Spare part wanted

Hello all. Can anyone help . one of the brush holders on my Warco WM16 mill has over heated and melted the plastic resulting in the brush not running true. I have approached Warco for a replacement but they can only offer me a new motor. Does anybody know where I might find a holder or maybe I could make one . Regards Farmer Dave

Edited By Farmer Dave on 10/02/2016 20:26:43

The brush holders in older motors and dynamos were often made of folded thin brass, clipped onto a flat board of Tufnol. It may be that if you need to make new parts this would be easier to make up than copying the original exactly. I would try with the thickest brass shim stock, perhaps.

Or you might try the other retailers of similar mills (ie the same but a different colour, etc) as they may have a more helpful parts stock. You can be fairly sure that the motor is an off-the-shelf part in the country of origin, and not a special for Warco or even mills.

Hope this helps

Tim

And if you do make your own, it may help to make both holders rather than just one. The critical thing is to keep the positions of the brushes around the commutator correct - ie on the same radius as the originals, in relation to the case of the machine. A motor will run with brushes advanced or retarded from the proper position but will produce less power and tend to overheat.

Cheers, Tim

I would be inclined to pop into your local motor rebuild place and see if they can help. Worth a try!

You may find a plastic brush box from an old washing machine motor will fit the bill when modified. You maybe lucky from some one else who has replaced his motor for the same reason as you and now has a spare brush box. For some reason or other these motors seem to fail all to often. John

You might be able to 'mould' a replacement using soimething like JB Weld or another epoxy putty.

Neil

thank you all for your suggestions, I wondered about JB weld ,might try that option 1st. Dave

Hi Dave,

Brush failure due to overheating seems to be common on these motors. Usually because the copper pigtail joint in the carbon of the brush fails causing a bad joint which then becomes open circuit, forcing the current through the spring that is applying pressure to the brush. The spring which is not designed to carry the amount of current that it is now being forced to carry, starts to heat up and looses its tension. This allows the brush to bounce around on the commutator causing more sparking and subsequent heating leading to failure.

One fix is to turn a PTFE plug to be a tight press fit into the top casting, then drill and broach a rectangular hole to suit the carbon brush. A new heavier gauge spring to push on the carbon brush and a cross drilled hole at the back end for an insulated crimp blade, the type that you can crimp a wire in at one end and place into a terminal block at the other, used to hold the brush and spring in place whilst providing an electrical connection.

HTH.

As John says the copper to carbon joint is often poor. I picked up one of a new set, for a repair job on another type of machine but clearly low end import source, by the wire and the brush fell off under its own weight. I recall finding an effective way to fix it but darned if I can remember what I did!

Getting back to the OP's query imagine that sort of plastic unobtanium thingy would be a good candidate for 3 D printing given a half decent machine. Might need to smooth out the inner bore to get a really free moving brush if using a hobby machine. Might be worth asking around to se if someone local has one and is willing to do the job for a suitably modest quantity of drinking vouchers. Modelling might be more effort then its worth unless something close can be found which can simply be tweaked dimensionally.

Clive

Hi Clive,

3D printing would be a good candidate for these brush holders if a suitable high temperature melting point plastic can be used.

One of the reasons that I used PTFE is that it can withstand 200 degrees and I happened to have some used seals from acid control valves that I cut down. The center hole was drilled out and then a silver steel broach made to cut the rectangular profile. At a pinch the original brass guide could be pressed into a suitable size hole in the PTFE.

Forgot to add, PTFE is very slippery as is the carbon brush, it also needs very sharp tools when cutting it.

Edited By John Baron on 11/02/2016 22:04:40