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-   -   Cutting a motor commutator & motor tweaks (http://www.rccrawler.com/forum/electronics/223989-cutting-motor-commutator-motor-tweaks.html)

EeePee 01-14-2010 04:11 PM

Cutting a motor commutator & motor tweaks
 
9 Attachment(s)
What up yall. :mrgreen:

Been working over some motors on a Cobra lathe. Learning some motor tweakin too, like brush hood alignment done right, and shimming, and whatever else. Doing a friend's motor I snapped some pictures of the passes and felt like sharing, and so he could see what it looked like.

I don't know what this motor is, maybe a Reedy 70 turn? Never heard of it and it's not new. Big commutator and laydown brushes too.

First thing I noticed was where the wear marks from the brushes were on the comm. Not in the middle.

Then the last picture shows a groove worn into the comm from the top of the brushes I guess, so a few more passes and it will be done.

I could and should have kept taking pictures, but I didn't. Next time.

8)

Robbob 01-14-2010 05:15 PM

I love seeing the ones that come out of scalers with the arms all rusted up from playing submarine.

Nice lathe :mrgreen:

http://www.rccrawler.com/forum/electronics/165187-importance-motor-maintenance.html

EeePee 01-14-2010 05:44 PM

Quote:

Originally Posted by Robbob (Post 2228488)
Nice lathe :mrgreen:

I know. 8)

It's borrowed. :mrgreen:

I remember your thread, and I even remember my post in your thread!

I redid an Integy 45 turn motor the other week and tried to do a real good job with brush hood alignment. Doing/bending whatever I had to so the comm hits right in the center of the brush and the difference in power and pep is amazing.

Robbob 01-14-2010 05:49 PM

after you cut the comm have you tried measuring the thickness at the top and the bottom to see how straight the lathe cuts? thats a big help with brush seating and wear too.

you running stand up or laydown on that arm?

EeePee 01-14-2010 06:01 PM

Nope, and I have a small feeling it's not exactly right. Just asked to borrow a pair.

Laydown brushes on that thing.

Top_Ramen 01-14-2010 08:07 PM

Did you use a hood alignment tool like this? http://www.integy.com/st_prod.html?p...27&p_catid=168

KBrog 01-14-2010 09:20 PM

Great pictures!!! Ive been wanting to learn a little about rebuilding a brushed motor, since Im using a trinity Monster 550 Emaxx motor on one of my LCC's. Im just lazy and like a fast lesson using pictures instead of reading a loooooooooooooooooooooooooooooong thread about it. This one is still short, like my attention span :mrgreen: So Please sir, spare me from having to use the search button and answer a few questions.

About how many times can you mill a comm?
What is a hood alignment tool?
Im guessing a hood is the guide for the brushes?
And you would just run that tool through the end bell, and make little tweaks or bends to the hoods to line up the two?
And thanks for any answers you might give...

EeePee 01-15-2010 11:57 AM

Quote:

Originally Posted by SicksAreR (Post 2229030)
Did you use a hood alignment tool like this? http://www.integy.com/st_prod.html?p...27&p_catid=168

I use one that came with a Team Cobra Brush Serrator/Cutter thing. More or less the same thing though. Though there's more to it than just sticking the tool through the hoods and lining it up.

Quote:

Originally Posted by KBrog (Post 2229215)

About how many times can you mill a comm?
What is a hood alignment tool?
Im guessing a hood is the guide for the brushes?
And you would just run that tool through the end bell, and make little tweaks or bends to the hoods to line up the two?
And thanks for any answers you might give...


Thanks.

There's a minimum diameter you can cut down to, and I don't know exactly what it is. EddieO (brood) says 0.270, which is just under 7 millimeters.

A hood alignment tool is used to "aim" the brush hoods (holders/guides) as perpendicular and square against the commutator as possible.

Yes, you're pretty much right, little tweaks to get everything in line.

The next step is to see where the comm touches the brushes, ideally dead smack in the middle. Using a clean brush I give the motor some voltage for a few seconds and check where the comm hits the brush. Then make adjustments to get it dead center (if possible).

EeePee 02-06-2010 01:35 PM

2 Attachment(s)
Hey hey! Had the chance to take some more pictures of another cut. Nothing special to see, it's a 55 turn Integy motor that was run in a Losi Comp Crawler and smoked. I wanted to see what it looked like, and what I could do.

I mentioned some other tweaks I do to the motors before, this time I'll grab some pictures of that also.

Firstly, I notice the brushes aren't in the center of the comm. Adjusting the shims will change that. I was expecting a way out of round commutator like these Integy motors are known for, and was pleasantly surprised actually. It wasn't all that bad.

EeePee 02-06-2010 01:38 PM

6 Attachment(s)
And here we go...

EeePee 02-06-2010 01:45 PM

5 Attachment(s)
And here's a shot of the set up.

And the brush cutter.

And then at this point I use the 3 cell battery pack to check where the brushes hit on the commutator, and where the comm rubs on the brushes. A short count to ten while the motor is running should show me what I want to see.

Duuuuuuuude 02-06-2010 01:52 PM

Hey I've got the same lathe! Did you do like I did and turn the comm on every motor within reach? :ror:

I've done a couple of really bad Integy's. One was so bad I had to make 5-6 passes just to get one section down to the same level as the other two. The brushes were definately getting a workout following that egg shape. :roll:

RcBro 02-06-2010 01:56 PM

Interesting, I was spoiled and went brushless almost from the get go, but now been playing with lathe motors again..

EeePee 02-06-2010 02:18 PM

Quote:

Originally Posted by Duuuuuuuude (Post 2283282)
Hey I've got the same lathe! Did you do like I did and turn the comm on every motor within reach?

I'm borrowing this from a buddy, so yeah I did all of mine, and offered to cut everyone's motor for some more practice. Gives me something to do, too. :mrgreen:

Yeah, I've dome some Integy motors that were that bad too, it's really amazing how out of round they can be. I really want to do my Fantom Rhino motor, but I'm hesitant thinking I'll screw up their awesome job.

EeePee 02-06-2010 02:19 PM

1 Attachment(s)
Originally there were two shims on the front of the motor and one on the endbell. I swapped one over so there's two on the endbell side and hit the motor with a 10 count and you can see where the brushes hit now. Not perfect, but better.

EeePee 02-06-2010 02:36 PM

3 Attachment(s)
Now for the brushes. I usually don't use a marker, but I think it'll help show what I'm trying to accomplish. Though it's still hard to see.

I run the motor for a 10 count and check to see where the comm rubs against the serrated edges.

Then I barely loosen the screw that's holding the brush wire eyelet and the spring post for the initial adjustment with a brush hood alignment tool, then lock one down tight and test a couple times, and do the final couple adjustments that way, then lock down the other one. Usually about 5 or 6 total adjustments.



First shot is the marker line. Hard to see, but the first wear marks are way off to the bottom, they're the shiny part.

Second is where I got the comm to hit the brush after a small adjustment. Closer to the center.

Third shows a second marker line, and a little more tweaking of the brush hood with a little extra bending and you can see I went a hair too far. Perfect. So then I go back and hit dead center.

Sharkey 02-06-2010 02:45 PM

Quote:

Originally Posted by EeePee (Post 2283321)
Originally there were two shims on the front of the motor and one on the endbell. I swapped one over so there's two on the endbell side and hit the motor with a 10 count and you can see where the brushes hit now. Not perfect, but better.

i always thought you shimmed the armature to center it in the magnetic field, not to center the brushes on the comm

EeePee 02-06-2010 03:04 PM

Every time I pull a motor apart it's not right. The arm is against the shims forced magnetically towards the pinion side. No float.

When I put them back together and you can float the arm a little each way, and the brushes hit more in the middle of the comm. I have a bunch of shims I use, but for this one, I used what was already on there.

To check, I just took all the shims out of the motor. The brushes would hit just about dead center, if not a little high. This motor was way off from the factory.

Sharkey 02-06-2010 03:15 PM

it is amazing how far out the motors can be. my first motor i had in my old touring car many years ago had a bearing failure quite early as it was shimmed extremly tight for some reason, to the point were the endbell had to be sucked down tight to sit flush with the can. after that, i started soaking in all the info about building motors right. its amazing how much of a difference it can make. a lot of it is overkill for a crawler, however none of it hurts.

good to see people still know how to do all this, it seems with brushless in everything but crawlers all these tricks are rapidly being forgotten.

EeePee 02-06-2010 03:28 PM

Quote:

Originally Posted by Sharkey (Post 2283398)
to the point were the endbell had to be sucked down tight to sit flush with the can.

good to see people still know how to do all this, it seems with brushless in everything but crawlers all these tricks are rapidly being forgotten.

:shock: Jeez! Magnets weren't glued in right I guess huh?

I'm learning, I always am. Simply from reading what the master motor builders have shared with us on the internet I can give it a shot myself. It's fun. I've had one motor, a simple Integy 45 turn, simply go above and beyond all my expectations. I must have hit every nail on the head or something because it's a beast and really made me think I might know what I'm actually doing. Keeps me going.

This stuff also makes me realize how sweet brushless motors are. "thumbsup"


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