Night Vapor engine/prop squeals then looses thrust - RC Groups
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Jan 05, 2013, 04:48 PM
Registered User

Night Vapor engine/prop squeals then looses thrust

I'm a noob here and have just dipped my toe into the hobby for the first time in about 30 years. On day two of my return I have run into a problem with my new Night Vapor. After flying it quite a bit today, I started to hear a chirping sound that varied with throttle setting. While flying it back to where I was standing, the chirp turned into a squeal and then the a/c lost power (still squealing) and descended into the grass. I retrieved it and then slowly advanced the throttle to start troubleshooting. When it just starts to turn, the prop/gears/engine sound fine. At about 10% throw on the throttle, the squeal starts to build and if any more power is added, the airframe shudders and there is a noticeable loss in engine power.

Can anyone point me in the right direction to start replacing parts?
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Jan 05, 2013, 05:30 PM
Registered User
Digital Don's Avatar
Is the prop tight on the shaft? If not, it may be cracked or stripped.

If the prop is good, check the gear on the prop shaft for a crack. If it's cracked, it It might work OK up to a point, then start slipping with increased power.

It's also possible that the motor is on the way out.

Hope it's something simple!

Jan 05, 2013, 06:36 PM
Or current resident
glewis's Avatar
Sounds like maybe the nut on the back of the prop shaft is too tight and caused the gear to come loose on the shaft as Don suggested.
Could also be the prop shaft and motor bushings just need some oil.
I've had both of those things happen.

Jan 06, 2013, 12:37 AM
Micro enthusiast
Groovechampion's Avatar
My umx spitfire motor did the same thing recently. I noticed degraded performance on her after only 20 or so flights. The motor let out a loud squeal and the plane glided towards the ground. RC Babbel calls this the scream of death! Anyways my solution was to buy a new motor from RC Babbel.

Regards Nath
Jan 06, 2013, 05:00 AM
Have fun
airpower's Avatar
Sometimes the motor slides back in the mount and disengages, sometimes the crash pushes it back into place.
Jan 06, 2013, 10:39 AM
Registered User
Thanks for all the feedback. I took a look at the prop and gears this morning. There was no visible evidence of breakage to I did a static power test. I ran the throttle up slowly until I was at full power and left it there for several minutes. There was no squealing so I'll take it out in a while to do an inflight eval.
Jan 06, 2013, 11:57 AM
Registered User
Terry Rigden's Avatar
Add just a tiny drop of light oil to the shaft and gears - don't over do it

Jan 06, 2013, 03:09 PM
Have fun
airpower's Avatar
Add a litte glue to the motor so it doesn't slide back. This would happen to me, in the middle of the flight it would squeal and go to zero power. It was the sounds of the motor being unloaded from sliding back. With the night vapor I just shifted the wing right up against the motor to hold it there.
Jan 07, 2013, 06:29 PM
This has happened to me several times and frequently was difficult to diagnose.

Each time the prop or one of the gears was slipping or the motor had moved so that the gears no longer meshed well.

Fred Rash
Jan 14, 2013, 07:59 PM
Registered User
Thanks for all the advice. I haven't had the symptoms return since last week. I guess I over flew it. My new rule is only 2-3 batteries before giving the motor/gears a break.
Feb 13, 2013, 12:16 AM
Registered User
Originally Posted by tasksaturated
Thanks for all the advice. I haven't had the symptoms return since last week. I guess I over flew it. My new rule is only 2-3 batteries before giving the motor/gears a break.
If it happens again, call Parkzone. Bob

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