Cutting a motor commutator & motor tweaks

[EddieO]

Now if we could just get the other 99.999% of crawler guys to read this thread and rebuild their motors!

Some of the motors I have gotten in for rebuilds over the last few weeks have been nuts!...

Later EddieO

 

[Duuuuuuuude]

Now if we could just get the other 99.999% of crawler guys to read this thread and rebuild their motors!

Then you'd be out of a job, wouldn't you? :ror:

 

[Duuuuuuuude]

A magnetic "prop blade balancer", like this.... http://www3.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=prop+balancer (top of the page, although there are some nice alternatives to utility knife blades as well)."thumbsup""thumbsup"

Does that work pretty well? I can't seem to get anything level enough to work properly. Its hard to tell if its out of balance or just running down hill... :lmao:

 

[Charlie-III]

Does that work pretty well? I can't seem to get anything level enough to work properly. Its hard to tell if its out of balance or just running down hill... :lmao:

The magnetic one is a bit better, depending on how heavy the arm is. It is not picky about how level the table is.

The "blade" types work if the table surface is off a tiny bit (out of level), but not much. If the arm has a heavy side it will always tend to stop rolling with the heavy side down. If it's fairly well balanced, it may continue to roll.

Dynamic balancing is ALWAYS better, especially with higher arm speeds.

 

[EddieO]

I personally think the razor blade method is better for static balancing.....the prop balancer can do weird stuff....most of the home winder slot guys use the razor blades. You really need to be a 100% level for it to work right though. You can make a cool little balancer out of a piece of aluminum, a couple of razor blades, some nuts and bolts and a small level if you have access to a mill.

There is a bit of misconception, balance is balance. Higher winds don't benefit any less performance wise from balancing. Lower winds its critical, because at higher RPM, things can go boom if the balance is bad. A correctly balanced motor will always run better than a non-balanced motor.....one of these days I will do a full dyno run up the ladder from 30-65t of balanced vs non-balanced.....


I wouldn't be out of job, your motors would last a little longer but it all works out to the same really.....


Later EddieO

 

[Onebdgti]

Now if we could just get the other 99.999% of crawler guys to read this thread and rebuild their motors!

Some of the motors I have gotten in for rebuilds over the last few weeks have been nuts!...

Later EddieO

I will be one of the dumb ass that sent 2 motors back to him that were junk. Im a newb to the whole electric side of the rc world. But thanks to this thread and the help of Eddie and killswitch i am ready to tackle my first rebuild on one this weekend. Wish me luck.

 

[EddieO]

Believe it or not, your motors were more on the tame side of things.....more of a product of the water than anything. I got some others that made yours look fairly normal.

Later EddieO

I will be one of the dumb ass that sent 2 motors back to him that were junk. Im a newb to the whole electric side of the rc world. But thanks to this thread and the help of Eddie and killswitch i am ready to tackle my first rebuild on one this weekend. Wish me luck.

 

[Duuuuuuuude]

There is a bit of misconception, balance is balance. Higher winds don't benefit any less performance wise from balancing. Lower winds its critical, because at higher RPM, things can go boom if the balance is bad. A correctly balanced motor will always run better than a non-balanced motor....

Certainly, but I previously wasn't too terribly worried about balance in my motors for two reasons.

1) I was just happy that a motor I rewound didn't go up in smoke. :ror:

2) 95% of the time I'm not approaching anything near full throttle where a vibration would be more deadly to a motor.

A balanced arm is certainly a more efficient arm. Now that my winds are looking better, and I'm playing with things that'll see higher rpm's, I'm going to be paying greater attention to it.

I made a trip to Lowe's today and picked up some supplies. Gonna see if I can build a balancer. :mrgreen:

 

[JohnRobHolmes]

I saw somebody ask about epoxy, but now I can't seem to find the post...

For the epoxy, a good penetrating, encapsulating, or impregnating epoxy that is thermally conductive will work best. Unfortunately it is not easy to buy it in small quantities, and some of the better resins are not available for non commercial uses because of EPA regulations. Ideally it will be a one part with elevated cure temps highest thermal properties, but two part epoxies can work well too. Epic Resins is a fairly easy company to work with if you know what you are buying when you call.

In a pinch, hardware store epoxy certainly works if you don't push the motor temp too high. Two part epoxies or resins generally have a low temperature rating, but you can pick through them and find the highest temp versions. Many can be thinned with alcohol after mixing for lower viscosity and better penetration if you are not willing to use a vacuum table to really impregnate the windings right.


Hope that helps somebody out, whoever you are.

 

[Duuuuuuuude]

Hope that helps somebody out, whoever you are.

That was me, thanks. For now I'll have to do the best I can with store bought stuff.

 

[JohnRobHolmes]

Try thinning a batch with alcohol and see if it sets up right. It will really help the epoxy penetrate and keep it from laying too thick.

 

[Duuuuuuuude]

So I thought I'd test my balancer idea out before I actually started to build a dedicated rig. I took some $2 1" ceramic magnets and stuck them to the inside of the jaws on my drill press vice. They come 6 in a package, so I put 3 on each side. Here's the results on one of my crummy armatures...

http://www.youtube.com/watch?v=LKVEVY9aOlg

I found its works best if only one end is actually touching the magnets (the comm end works best) . Get the other end close enough, and it'll float. A little dab of lightweight oil on the comm end of the shaft and it spins nicely.

There were three arms tested (two 540's and a 5t puller arm), and once you figure out how to spin it without bouncing it around too much it seems to work quite well. I could get them to stop with the heavy side down fairly consistently.

 

[EeePee]

Looks like it stops whenever it feels like it? Seemed inconsistent?

 

[killswitch]

I've tried numerous times to balance arms using magnets and never have been able to get it right. The razor blade method is WAY better IMO because it's more consistant. It's nothing like the machine Eddie uses, but I really agree with Eddie that it's better than magnets. Plus, it's how my dad showed me to balance slot car arms when I was a kid, so it gets a bonus point for that "thumbsup"

 

[Duuuuuuuude]

Looks like it stops whenever it feels like it? Seemed inconsistent?

A little. If you keep spinning it eventually you'll find that one side comes up on top more than the others. It takes a bit of feel to spin it right without it bobbing up and down really badly, and once you get that down it gets more consistent. The puller arm stopped in the same position nearly every time, but its bigger and heavier and more apt to do so. It would even rock back and forth a little until the heavy side rolled under.

 

[Duuuuuuuude]

The razor blade method is WAY better IMO because it's more consistant.

I'd like to see a pic of how thats set up if you've got one.

 

[Robbob]

http://www.niftech.com/catalog.php?mode=3000



you use to be able to get just the sleeves for the arms seperately.

 

[Duuuuuuuude]

Uploading some vids of a puller arm, a reedy 15t arm, and a random junky arm that I use to practice winding on. Should be up shortly.

The puller lands in the same place nearly every time, the reedy is a little hit and miss, and so it the junky one though its a little more consistant.

I have yet to test any that I know for sure are out of balance, but its a good guess that anything I've rewound is.

Its surprising that the puller is doing what it is, I never had any vibration issues with it. If someone could post up a pic of the razor blade method, I'd like to double check it...make sure I'm not getting any kind of weird magnetic interference or anything...

 

[Duuuuuuuude]

Here's the puller. Watch the putty dots...

5t puller test

After watching it again, the reedy was a bit more consistent than I thought.

reedy 15t test

And the crummy one. Its got a point machined into the comm end of the shaft, so it spins pretty nicely.

junk arm test


Any thoughts?

 

[EddieO]

I'll check your videos tonight after my sons practice....been a long day of 40+ motors and another 40 I still gotta get done, on top of the two Limited Editions I gotta finish up.....

The Niftech thing is junk and over priced. You can just get a prop balancer for $25 to do the same thing....

The magnets will never work right. They do weird stuff as the arm spins....if it worked worth a crap, all the slot guys would use it....none of them really do.

I've attached a homemade unit from a slot car guy. Could be built for $25 or less if you had access to a mill.

Vacuum Table? All Vacuum Impregnated Epoxy is designed for vacuum chambers....

For a useable epxoy, PM me....I'll send you a link, but be prepared to spend about $80.....stuff is pretty awesome stuff.

Later EddieO