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Old Sep 19, 2014, 06:21 PM
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Help!
Champ RTF motor problem?

Hey, I'm new to the RC Airplane Hobby, and I have recently discovered a problem on my Champ. When I finish charging I fly it around fine, but occasionally when I try to take off, the motor just revs. It's like you push the throttle stick up and down very quickly. Anyone know what the problem is?
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Old Sep 19, 2014, 10:17 PM
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a video would help.

do you mean it has a spurt of power and then stops even though you have the throttle up? this is on a fully charged battery?

also, how long are your typical flights?
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Old Sep 20, 2014, 04:26 PM
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Slip, slipping away?

Sounds like something is slipping in your drive system.

Easiest to check is whether your prop is slipping on its threaded shaft? (if so, the prop's hub has stripped threads.) Second would be is the motor's pinion gear fully engaged with the spur gear on the reduction box? You will have to take your fuselage halves apart to troubleshoot. No big deal, just cut through the tape with a razor blade or Xacto knife. When you are done simply put new Scotch tape over the old.

Dick
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Last edited by Dick Adams; Sep 20, 2014 at 04:34 PM.
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Old Sep 20, 2014, 05:52 PM
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Quote:
Originally Posted by cmdl View Post
a video would help.

do you mean it has a spurt of power and then stops even though you have the throttle up? this is on a fully charged battery?

also, how long are your typical flights?
No not on a fully charged. I fly it for some time and then it starts acting up. I usually fly it for about 10-15 mins.
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Old Sep 20, 2014, 07:37 PM
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Quote:
Originally Posted by Dick Adams View Post
Sounds like something is slipping in your drive system.

Easiest to check is whether your prop is slipping on its threaded shaft? (if so, the prop's hub has stripped threads.) Second would be is the motor's pinion gear fully engaged with the spur gear on the reduction box? You will have to take your fuselage halves apart to troubleshoot. No big deal, just cut through the tape with a razor blade or Xacto knife. When you are done simply put new Scotch tape over the old.

Dick
Well, I took your advice, and none of the gears seem to be slipping. But one thing; after I took off the cover, the gear on the propeller seems to be grinding onto the top of the body. Would that be a problem?
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Old Sep 20, 2014, 08:03 PM
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Doubt it, unless that is a sign the whole assembly has become loose. Try the wiggle test and you can use a knife to cut the foam from around where it appears to be rubbing. If it's solid and the knife trick doesn't solve your problem, it sounds like you have something else going on.

Try describing in more detail what you are experiencing. If it is fluctuating power when you are asking for full throttle on your Tx stick, check your batteries and your battery connector.

Dick
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Old Sep 21, 2014, 12:28 AM
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you wrote this doesn't happen when fully charged. i assume you flew for 10-15 min and landed and then this happens when you try to take off again?

as Dick wrote, we need you to describe this with a bit more detail. a video would be very useful.

the Champ manual recommends landing after 6-9 minutes (page 13: http://www.horizonhobby.com/pdf/HBZ4900-Manual.pdf). if the situation is as i described above, then its likely you are running your cell too low.
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Old Sep 21, 2014, 07:52 AM
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Troubleshooting

The part of your description that doesn't make sense is the "revs." Center on describing that better.

Two things could be happening if we eliminate the "revs," and just concentrate on fluctuating or on/off power:

1. The Champ will turn off its motor if you fly it out of range or if the transmitter's signal is lost for another reason. If it regains the signal, the motor will not turn back on until you "rearm" it by moving the throttle stick all the way down and then reapply power.

2. The Champ has an LVC, low voltage cutoff, where to protect the battery the motor throttles back. This is called a "soft" LVC, as it does not turn the motor off all of the way. If I recall correctly, it will sound as though the motor is pulsing. Is that what you are describing?

If it is the LVC, you are running your batteries too low and will end up shortening their lives considerably. That is CMDL's point. Fly less and your batteries will fly longer. (Unlike our old bullet proof NiCads, LiPo batteries die easily if not treated with TLC.)

Welcome to the hobby. You picked an excellent first airplane. Even old timers, like myself, thoroughly enjoy flying it.

Dick
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Last edited by Dick Adams; Sep 21, 2014 at 08:02 AM.
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