Brushed motor odd behavior

[dabigboy]

Hi all, I decided to go brushless with my RC10 build, which means the motors and ESC that came with my RC10 are suddenly available for hopping up my old-school Bandit basher. There are two motors, I've tried both in the Bandit with a Novak 610, and both are acting wonky. The one I really want to get going is a Diamond 12t. It really woke up the old Bandit, but after a few minutes, it stopped working. I took it partially apart tonight for inspection, stuck it back together, and it started working again. I'm assuming the problem will return, since I didn't really fix anything.

The other motor I tried is a Reedy Mr Outlaw. It got to where it would slow down and stop, but for a while it would start working again if I just gave the back of the motor a light tap. It's like something is just not making a good connection, on both motors.

I hadn't oiled the Diamond, but did put some oil on the Outlaw. Hopefully I'm just making a noob mistake....these are the first rebuildable brushed motors I've worked with.

Matt

[radioactivity]

Hi dabigboy
From the last pic one brush looks to be at a different depth than the other.
Were the springs still on the brushes?
Do the brushes slide easily in the brush hoods?

Chuck

[dabigboy]

Good catch! I noticed that but assumed the brushes would be under enough pressure once reassembled. That brush was almost stuck in the hood, very dry and a bit dirty. I cleaned and lubed both brushes and they move freely now, they spring in until they hit each other.

Now my problem is how to hold the brushes back so I can reassemble. What's the trick?

Matt

[radioactivity]

Great!

Pictures can really be a great help.
No real trick, just release the spring, pull the brushes back and reassemble. Then reinstall the spring
The only thing to consider is that the brushes should be placed back in the hoods the same way they came out.
Brushes wear more on the leading enge than on the trailing edge.
If put in backwards they will tend to dig into the comm. They will spark and contact will be quite bad.

Chuck

[radioactivity]

Matt

Also check into how to wet clean/break in an rc motor.
Several youtube videos and references here as to how.
It does work and was regular maintainance on all my brushed motors when I raced.
We used trichloretnane but plain water works and is probably a lot safer. Remember to dry completely and lube with 1 drop of oil on each bearing.

Chuck

[dabigboy]

Well now I see when I took it apart that a small brown washer (bakelite?) fell out, not sure where it goes....spare parts bin?

Matt

[radioactivity]

Matt

My guess would be that it was pulled off the armature by the brush that was still under spring tension. (BTW, should probably release tension on brushes if you decide to take any brushed motor apart again.)
It is probably the shim that goes on the armature up against the commutator.
Shims are important. They can keep the armature from drifting about and causing the brushes to wander on the commutator.
Ideally you should only have a few thousandths of end play.

Chuck

[dabigboy]

Good thought, the washer is just the right size to fit over the main shaft. So it would go on the very end of the shaft, after the brushes?

I can push on the output shaft from the front and move it about 1/8" or so, but the washer is probably less than 1/16" so even with it installed I'd have some play. It does take a fair amount of pressure to push the shaft back.

Matt

[radioactivity]

Matt

The washer (shim) should go on the commutator end of the shaft snug against the commutator.
1/16" or alittle less is OK for endplay. It is best to keep with the original spacing so the brushes ride the same as they did before dissassembly.
It is a little worrisome that you find it tight when re-assembling.
When the motor is assembled and the brush springs are unclipped ( the brushes do not have pressure against the comm ) the only resistance should be the magnets.
Even with the brushes fully installed with the spring pressure pushing the brushes on the comm , the motor should not be in any bind.

Chuck

[dabigboy]

It's not binding, I believe it's just the force of the magnets I'm feeling. Got it back together and gonna try it in the Bandit. Thanks for all your help!

Matt

[dabigboy]

Well the motor runs GREAT! No problems with it at all. Except the Novak 610 seems to be a little overwhelmed, it overheats after a few minutes....guess I need to put a fan on it!

The ol' Bandit is a little more peppy now, great fun!

Matt

[radioactivity]

Matt

Glad to hear you had success
A fan is not a bad idea. You might also want to go a tooth or two less on the pinion or up a few on the spur.
A little slower on the top speed but a little easier on the ESC.
Keep her clean/oiled and it should last a good long time.

Chuck

[SteveMax]

You're also running the hottest wind recommended for that ESC. It *should* be ok, but more cooling is definitely a good idea