Cutting a motor commutator & motor tweaks

[TEDROCKZ]

Now you are getting the point of a dyno! Not by comparing motor to motor but subtle changes to one motor IE tuning.

Only enjoyment I ever got from it was taking an almost dead motor and dynoing it then doing all the "love" to it then rerunning it.

Originally Posted by EeePee

Spring testing with the beater Fantom after a comm skim. I've confirmed I have the Lemans brushes in it. They leave a pretty color on the comm.

I Fiddlestick'd and swapped around tens of thousands of springs til I got fairly solid consistent numbers and hit it on the dyno.

The left was more or less black springs, the middle two were a mix of purple, red and green, and the rightmost one is with gold springs. All were handpicked and Fiddlesticked. Great tool. Unlike the iPod Touch's camera. Terrible tool.

[schiesz]

I got a nice donor from the bay to rebuild for a friend's scaler. This little lathe is a lot of fun.



I wish I had a dyno to show the improvements. Love seeing the stuff you guys are putting on here!

[Charlie-III]

Nice finish on the comm.
I would guess that's a great "go-fast" motor, probably not great for crawling though.

[Manning]

Yeah, "stock" class race motors are not so good for a crawlers. Terrible overall efficiency (will run hot), and the start up control is also bad.

But they can be made to perform a bit better by de-timing the endbell. Grind new flats on the endbell so the brushes are parallel to the flats on the can. You'll have to super glue the endbell back on since the bolts won't work anymore. Yes, it's ghetto. But it'll make the motor more usable for crawling.

[EeePee]

Originally Posted by schiesz

I wish I had a dyno to show the improvements. Love seeing the stuff you guys are putting on here!

The dyno RULES! It makes it all come together. It's like a nice rug; it really ties the whole room together.

[Cordwood]

You can cut the end bell on the flat side stock motors to adjust the timing. I did it on a green machine and it's in my kids wheelie king. The timing is at 6 degrees and it runs descent. The end bell folds down a little but it's secured good enough.

[schiesz]

Originally Posted by Cordwood

You can cut the end bell on the flat side stock motors to adjust the timing. ]

Nice! I didn't even think of that, I just delivered that motor to my friend today. I picked up a few more arms today as well. He wanted a fast motor for his scaler, so we'll see how this one does.

[binaryterror]

Wow this thread tapered off.

Just picked up a new lathe and need help setting it up. Problem is the cutting seems wonky and I can't seem to set its level. I'll get some detail pics up tonight to try to show you guys where I am lost on this damn thing.

[EeePee]

Originally Posted by binaryterror

I'll get some detail pics up tonight to try to show you guys where I am lost on this damn thing.

Well then, hurry UP!

Take a picture of the side view of the bit very close to the comm, and add in which way the thing is spinning in relation to the bit.

[Charlie-III]

Originally Posted by EeePee

Well then, hurry UP!

Take a picture of the side view of the bit very close to the comm, and add in which way the thing is spinning in relation to the bit.

+1.

Until more info, you "can't" cut too slow. Most issues (outside of the drive motor spinning the wrong way) are from:

Too much of a cut/pass in terms of depth of cut
Feeding across too fast
Broken/chipped/dull cutter

If it's a new rig, it "should be square" meaning the comm diameter is the same at each end.

[TEDROCKZ]

^ I believe Jake is referring to shimming the bit up or down. Which should be slightly above centerline of the comm. Depending on what lathe he has some are more finicky than others.

[JohnRobHolmes]

Depends on the bit used too. A bit with less rake will need to be farther above center on copper to prevent smearing and promote proper chipping. Copper likes a lot of back rake so the bit can sit even or below the center line

[TEDROCKZ]

About any typical bit that is used with a pit lathe, especially one that comes with it, will be used above the centerline. I see no need to complicate it with using any other bit that would set up otherwise. Between 2 Fantoms, 3 cobras, 2 Hudys and 1 Orion quickset errone of them is above.

EDIT: I see John changed his wording..;)

[TEDROCKZ]

I am glad this thread was brought back up. Reminded me that I had 3 Carter bits I was planning to send back to them for relapping before I loose them. Been in an envelope for months

[binaryterror]

Originally Posted by TEDROCKZ

^ I believe Jake is referring to shimming the bit up or down. Which should be slightly above centerline of the comm. Depending on what lathe he has some are more finicky than others.

This is part of the issue, bit height is weird on this lathe. Also this bit is different than the one on my old worn out Trinity lathe. (would help if i remember to post the pics sitting in my camera at home)

Originally Posted by JohnRobHolmes

Depends on the bit used too. A bit with less rake will need to be farther above center on copper to prevent smearing and promote proper chipping. Copper likes a lot of back rake so the bit can sit even or below the center line

Here is another part of the equation that has me scratching my head. (would help if i remember to post the pics sitting in my camera at home)

Originally Posted by EeePee

Well then, hurry UP!

Take a picture of the side view of the bit very close to the comm, and add in which way the thing is spinning in relation to the bit.

Would help if i remember to post the pics sitting in my camera at home. Pics tonight for sure...sorry guys. I'll make sure I have all the shots and close ups and stuff.

[JohnRobHolmes]

lol, got those pics yet?


I guess we should define what below and above is, because many of the lathes have the bit upside down and so "bit above center" would really be "cutting below center" like normally done. At any rate almost all hobby lathes have the bit on center or above the centerline because of the bit direction.

[binaryterror]

Pictures. On this 17x2 arm it seems to have worked much better after tearing it down and resetting it some. Still want to be sure this is the proper method. My old Trinity is different in the bit and how it needs shims everywhere to even cut somewhat true, hence it being no longer used.




Cutter height to comm stack


Bit, was originally set on the lower darker flat and that has chips missing.



In the middle of a cut photo, early pass:


Results:

[TEDROCKZ]

Looks if you are on the right path. Look on Ebay or some of the other RC forums for cheap motor lots. Old mods or rebuildable stockers to practice with. You usually can find a good deal. I give $42 bucks for my last find that consisted of 20+ decent motors. Good for practice and parts.

[EeePee]

What's up with them bearings on the right? And I don't think you can turn a tip like that. I'm under the assumption the black part is the actual bit.

[4xFord]

Originally Posted by EeePee

What's up with them bearings on the right? And I don't think you can turn a tip like that. I'm under the assumption the black part is the actual bit.

X2 that was my first thought, bit is rotated in the wrong position. I would definitely order some new ones and try it again.