Rebuild Break In

[Martyn]

Monty, I've read the five pages of motor break-in sticky notes and still have some questions as it pertains to rebuilds. As you noted in a recent post if one is quite careful as little a .0005 can be removed from the com to restore the surface finish. In such cases and assuming that the brushes are to be reused this creates a situation where very little difference in the arcs of each exist thus little material need be removed under water to mate them. Would you still recommend 45 seconds at 3 to 4 volts? Also as you know some lower powered motors spark very little at the lower end of the voltage scale in free air. Is it required that enough voltage be used to force sparking in free air to assure cavitation under water? I've always favored the lower end but perhaps a rethink?

I get the impression that once you remove the motor from the water bath that you blow out the motor with compressed air, oil the bearings and do the naphtha finish and never disassemble the motor for the entire process. Do I understand that correctly? I've always did a disassembly between each step, drying it out and used a #11 Exacto to clear the slots. This raised the question then that perhaps disassembly "upsets" the brush to com interface. Expand please as removal of com slot sludge, bearing moisture in shielded bearings and the mud the builds between the brushes and hoods seems quite difficult to extricate without disassembly.

The water dip itself. Do you find a difference between tap water and demineralized or distilled water? Tap water leaves Mineral deposits?

Lastly, how does one determine the "end" of the naphtha cycle? When is enough, enough? and why the higher 4 to 6 volt cycle?

Thanks

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Marty,

Most of your concerns can be covered by the notation that one should use "clean" water. I typically use a 32oz. tumbler three-fourths full, and rotate the water after 4 or 5 motors. You will see some discoloration from the brush dust. I use tap water, but I don't have a 'hard water' problem here in Victorville, and have not noticed appreciable deposits of any kind.

Yes, when re-using a brush on a motor that needs only a mild retrue, you can probably use less time, I just try to be thorough. I do leave the motor assembled through the whole process (especially a shunted motor!!), but have looked at brushes at the end of the water only phase. You'll notice they are NOT glazed, thats the purpose of the naptha drip. If this process works as its supposed to, there won't be anything in the slots to scrape out. The water carries the brush particulates away. I am rather thorough with the compressed air, especially at the bearings. I use some shielded bearings, but never sealed. They dry out OK with the air.

I'm pretty sure that actual voltage is not an issue, I use the quoted voltages as a reference to be consistant. The final spin at 6 volts is when I take note of the current draw, so I try to set that fairly accurately. The naptha cycle is done when the naptha has evaporated and the current is relatively stable. If inspected at this time, a full glaze should be found at the brush end.

[Phil I.]

I trued one and did it at about 6V. I used to make contact lenses and our lathes turned at 20,000 RPM and was thinking the faster the better!! I recovered it in black marker and turned the dial the width of one mark and turned at about 2V. I got two shadows on each segment and looking at the arm turning very slowly. They were at when the O-ring hit and left the lamanitions. I put another fine coat of color on the comm, went the width of the line and did another cut and it was smooth. The higher voltage, I could cut the comm faster. Leaving no ridges and sometimes leaving ridges at the lower RPMs. I just wonder how much the harmonics of the O-ring hitting the laminations hurt or if they do?. The TOTAL cuts on the comm equaled .0007 using a digital micrometer.

When reusing brushes. I have always done a slight scraping with an exacto knife to get to vergin material thinking that the arcing left burned meterial behind. Is my thinking working overtime or just to :eek: ....

Some times I wonder if i'm spending too much time on my little toys?
PHIL I.

[Martyn]

Monty, thanks. I understand and yes I've made some minor errors in my set up which are now corrected, thank you agian and you have just saved me a couple of hours per motor. How good it all that :)

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Phil,

I use a Hudy with the plastic hold down clamps. I adjust them VERY tight, use good oil (Kiwi-Pee, of course!), and feed it enough voltage to overcome the drag. This cuts down on the microscopic out of round condition you noted, which I believe to be a result of bouncing in the Vee blocks with a less than rigid setup. Otherwise, the cut should come out at least as round as the shaft! Before I had the Hudy, I used finger pressure to augment the belt tension. This led to a few minor injuries and curses about the geeks who couldn't do a neat job of cutting a shaft short or who didn't de-burr the cut ends. The other lathe (cobra) also had aluminum uprights without the steel inserts, like the Hudy has, and I wore out several sets of them.

Marty,

Thanks... but really, several HOURS? Whatever else were you doing? I spend 5 minutes to do the entire break-in process, and the motors perform just fine thank you, according to the customers. Dang... I can do the entire blueprint in a couple of hours! Now, finding a couple of hours CAN be a trick!!

P.S. Phil - I also scrape the glaze off to reuse the brush. Might help, hurts only in losing a few thousandths of an inch in brush length.

[Martyn]

I have mentioned poor eye sight even with magnification and a hand tremor, right? ;) Creepy fastidious by nature and let's see. I've done maybe a hundred motors total in my life you about what, a zillion? No surprise you can do in minutes what takes me hours. Besides Monty, if I've told you once I told you a million times not to exaggerate LOL Okay not hours, but a solid hour.