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Old Dec 18, 2005, 07:34 AM
Registered User
United States, NY, Queens
Joined Oct 2005
2,627 Posts
Bad motor or bad speed control?

How do you determine if the motor went bad or if the speed controller went bad. I've had about 50 flights with my plane, and now it doesn't have enough power to take off. I have tried two different battery packs with the same results. The batteries work fine in my other plane.
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Old Dec 18, 2005, 08:43 AM
Italian Member
lombafly's Avatar
Dalmine , Bergamo , Italy , Europe
Joined Feb 2004
64 Posts
Motor brushless or brushed?
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Old Dec 18, 2005, 08:51 AM
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Howland, Ohio
Joined Jun 2004
729 Posts
If its a brushed motor it's probably the motor.
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Old Dec 18, 2005, 08:52 AM
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Jeremy Z's Avatar
Northern IL
Joined Oct 2005
2,380 Posts
It is most likely a brushed motor, right?

The ESCs are solid-state; no moving parts, hardly EVER wear out unless abused.

Brushed motors on the other hand... They have carbon brushes which transport current to a rotating commutator into the armature. There is friction & arcing, which wear the brushes down. There are springs which feed the brushes into the commutator, but they can only make the brushes so long. So a point comes when the spring has fed the brushes as far as it is able, a gap between the commutator & brushes opens, there is more arcing, and less efficiency & power.

If it's a brushed motor, replace it. It'll probably cost you around $10. If that doesn't fix it, buy a new ESC, make sure it can handle the current the motor draws while running full throttle. Make sure the plane is not over-propped, so to speak.

Brushless motors would tend NOT to go bad, unless it is a bearing problem. There is no physical or electrical contact in a brushless motor to wear out. It works through pure electromagnetic induction. This means a longer life, and much higher efficiency due to lower friction. If you have a brushless motor, it is most likely the ESC.

Jeremy
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Old Dec 18, 2005, 09:20 AM
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Tres Wright's Avatar
Forney, TX
Joined Mar 2002
15,165 Posts
Usually when an ESC goes, it dies completely and you lose all motor control AND servo control. You probably just need to replace your motor. Or upgrade to a brushless and never worry about wearing out a motor again
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Old Dec 18, 2005, 11:01 AM
lawn darts r' us
Joined Sep 2005
171 Posts
probably the motor. easisest way would be to swap motors with a known good speed control or vice versa, this way you can rule out the faulty component.

Speed controls are typically an all or nothing deal, they either work or they dont, In all my years in R/C (used to do high perf electric boats), ive never seen one 'loose power'.
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Old Dec 18, 2005, 07:16 PM
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United States, NY, Queens
Joined Oct 2005
2,627 Posts
Thanks for all of the replies. The plane is a stock PZ Cub that I bought used on e-bay. A replacement motor is $10, while a replacement ESC/RX is $28. I took a chance and ordered a motor. Looks like I made the correct choice.
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Old Dec 18, 2005, 07:53 PM
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Media, Pa/Blacksburg Va
Joined Oct 2004
1,238 Posts
yup, and a motor is usually cheaper to replace, at least if it's brushed. So if you have problems, changing the motor is usually the best bet.
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Old Dec 19, 2005, 06:32 PM
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Purvis, Mississippi
Joined Sep 2005
977 Posts
I've had two cheap ESC/RX boards go bad after a crash...each one would run the motor wide open when a battery was attached.

Anyone ever heard of that?
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