Sounds like Rocks - RC Groups
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Oct 18, 2009, 04:30 PM
Registered User

Sounds like Rocks

A couple days ago my plane made a horrible sound and quit. Apon landing I ran the motor. It sounded horrible, like rocks in the motor. It will run about a second then make that bad sound and quit.
I have changed batteries, and inspected the magnets.
Any ideas what the problem is?
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Oct 18, 2009, 05:08 PM
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raz's Avatar
Is it a brushed motor or brush less? What kind of a horrible noise did it make?
Oct 18, 2009, 05:11 PM
Registered User
its a brushless park 400 out runner.

Sounds ruff, like rocks tumbing. Just makes sound really quick before motor dies. Then i can do it again over and over.
Checked prop and nose cone for rubbing as well as motor rubbing fues. All looks good.
Oct 18, 2009, 05:18 PM
Registered User
I just took the prop off and it still makes noise.
I have only had about 5 flights on the equipment since new.
Kinda thinking it might be a problem with the ESC. What do yall think?
Oct 18, 2009, 05:26 PM
Xpress..'s Avatar
Possibly loose motor wires, or incorrect ESC timing.
Oct 18, 2009, 07:58 PM
Registered User
Does it use a gearbox? (Broken gear?)
If no gearbox, bad/dirt in bearing(s)?
Bent shaft?
Motor wire broken/open circuit?
Out of balance prop?

Oct 18, 2009, 08:48 PM
Suspended Account
I would re-solder the wires on both the ESC and motor. I've had a few occasions where the wire is mostly broken but hasn't fallen out yet.
Oct 18, 2009, 10:19 PM
Registered User
Thank you for the advice.
I will check all the connections. That may be it because i have been tugging real hard to disconnect the battery from the ESC each time. The deans connectors that I have are tight !
Oct 18, 2009, 10:46 PM
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Murocflyer's Avatar
Bad bearings is my guess. Does the prop shaft move fwd and aft or have more than the expected amount of play in it?

Oct 18, 2009, 11:15 PM
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Mark Wood's Avatar
Sounds like the motor dropped a phase and is single-phasing.
Check your motor connections very carefully. Redo if there is any question.

What does it sound like when turning the motor by hand?

Oct 19, 2009, 12:16 AM
Registered User
Just tried turning by hand fast. It sounds a little ruff maybe. Its my first motor, but from what I remember it was super smooth.
Oct 19, 2009, 01:43 AM
Registered User
If it was smooth then and rough now, it's probably the bearings.

What motor is it?

If it's a bell-type get your bearings from $1.50 per bearing with $2.00 shipping. Get 3 or 4 of each size (2 for each motor. Larger bearing in front, smaller bearing in back).

Oct 19, 2009, 12:24 PM
Registered User
Sounds like a good idea to order some bearings and of course have spares.

How do I replace them?

I have the EFLM1305 Park 400 Brushless Outrunner Motor, 920 Kv.

Thanks to all for your help !
Oct 19, 2009, 04:11 PM
Registered User
Oh, and get a couple of new prop shafts while you're at it.

Oct 20, 2009, 11:43 AM
Registered User
I also have a Park 400 that needs repair.

Any advie here in dismantlling the motor would be helpful

My motor has a screw broken off in the mounting holes, there is a bit of screw on the inside that I could get too if I could get the stator off of the motor chassis.

I have the circlip and retaining ring off, (and therefore the Rotor and shaft), but cannot see if the stator is pressed on or ????? I don't want to ally too much force as the chassis seems flexible.

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