Uneven RPM

Hello, Admin Bill ------  I know this is a very old thread, but I'm wondering if you figured out the problem here?  I'm asking because I've recently experienced this intermittently, and I'd like to know the cause.  When it happens, I usually just very slightly adjust the throttle, and the "hunting" stops.  It's more of an irritant than a real problem, but I'd like to resolve it, if possible.

Thanks for any information you can provide!

Please advise if you isolated the cause and resolved the issue?

DUF21

EMAIL duffy4sale@att.net

@robhouston 

Hi Rob 

Im experiencing similar issues including shut downs underway. Thought it was a motor issue, but it restarts and runs midspeed, but misses now i. Full speed.

Did you replace your throttle to resolve??

DUF21

email  duffy4sale@att.net

@duf21 Yes, I resolved it, but I had to change some controller parameters to smooth out operation of the throttle.  I have the Zapi FS5050 controller, and I bought a handheld programmer from China to change the controller parameters.  It worked fine.

However, based on your other post, I don't think this is your problem.

Good luck,

Rob

The problem described in this thread sounds a lot like what I observed when my motor brushes were seizing. My motor eventually stopped running altogether. These motors seem a bit prone to this problem, particularly when they sit for a while. Fortunately the fix is quite simple. In Power Rudder models, you don't even have to take the motor out to repair it.  Fix is as follows:

Materials:

- Brass or steel wire brush

- High temperature antiseize, e.g. Permatex

- Ratchet with 10mm (IIRC) socket

- Nitrile gloves recommended

Steps for Power Rudder models:

0. Take key out to prevent any current from going into your motor!

1. Remove motor noise shield.

2. Remove upper motor housing clamp (single latch on side).

3. Remove two bolts on top of motor. Lift upper housing up and off of motor. Don't lose the metal disc in the center that rests in place.

4. On upper housing, you will see four spring-loaded graphite brushes, each wired on its own phase. Take a photo of how everything is arranged. It's a little tricky, but remove the springs and then the graphite brushes, keeping the wires attached. Chances are good that one or more of them are seized in place. You may need to knock it free -- if so, use a rubber mallet. Don't use anything hard, as it may break the graphite.

5. Clean each brass brush housing with the wire brush. Apply a small of antiseize dab to your finger (nitrile gloves recommended) and spread around the inside of each brass housing. Apply antiseize conservatively -- you don't want it getting on the commutator and acting as a conductor between phases or an insulator from the brushes.

6. Put each graphite brush and spring back as they were. Wiggle the brushes. They should slide freely now.

7. This is the hardest part, but a little patience and you'll be done soon. Place the metal disc from step 3 back on top of the commutator. Now you need to push out all the graphite brushes as you put the top back on so that it seats properly. A combination of holding them out and wiggling the top is what worked for me. It may take a few tries. You'll know when you have it, as the top won't go on until you do.

8. Rebolt the top of the motor. Don't overtighten.

9. Test motor, verify it works properly.

10. Reapply upper motor housing clamp.

11. Reapply noise shield.

Robby,

I just looked at this post.  I still have an occasional hiccup with the RPM as described, so I'm going to check out my motor brushes when I have the chance.  

Thanks for posting this solution!

Rob

Posted by: @robhouston

Robby,

I just looked at this post.  I still have an occasional hiccup with the RPM as described, so I'm going to check out my motor brushes when I have the chance.  

Thanks for posting this solution!

Rob

Happy to help. I tried to post photos as well but it didn't work on the forum. If anything is unclear I can email them or publish an illustrated writeup elsewhere.

Robby,

I've been corresponding with Admin Bill about the inability to post photos.  He found that WordPress had done an update that broke that ability, and he's working with them to get it restored.

In the meantime, if you have photos, could you send them to me at rahouston at gm....com?

Thanks again for your very useful post!

Rob