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Electric Motor Doing Something Strange

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Electric Motor Doing Something Strange

Old 04-03-2023, 12:44 PM
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ohnow
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Question Electric Motor Doing Something Strange

I flew a plane on 4S, like usual, then flew it on 5S without issues. I went to fly it again on 5S and the motor turns but sounds like a car that misfires. The motor wires are heat shrunk and I don't see any issues with them. Here's a vid of the issue. The plane specs are in the description. What's going on?

Old 04-05-2023, 05:45 PM
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model14
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How much play (forward and back) do you have in your motor shaft. If it is more than usual the thrust bearing is shot and timing is thrown off. I experienced the exact thing on one of my motors. Is your motor rated for 5S? My problem occurred when running a 3S motor on 4S.
Old 04-06-2023, 09:03 AM
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ohnow
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Originally Posted by model14
How much play (forward and back) do you have in your motor shaft. If it is more than usual the thrust bearing is shot and timing is thrown off. I experienced the exact thing on one of my motors. Is your motor rated for 5S? My problem occurred when running a 3S motor on 4S.
Great, I'll check that. Thank you. It's rated for 5S
Old 04-08-2023, 03:22 AM
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ron_van_sommeren
 
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Originally Posted by model14
... My problem occurred when running a 3S motor on 4S.
Timing may help alleviate your problem a bit but I don't think timing itself changes through axial play. Timing is a tangential effect, hence the (shaft)degrees. It's the e-motor analogy of ic-engine ignition timing.

TS's problem, and probably yours too, described/solved in his RCG thread
Electric Motor Doing Something Strange - RCG

Just let me know if you want me to do those calculations for your case, going from 3s to 4s. A more disproportional effect than in TS's case, going from 4s to 5s.

My advice, ad nauseam:
Always check/measure current and power drawn in a new or changed setup.
A watt-meter will more than pay for itself, several times over, if you don't already have one.

Note that motors don't have a voltage rating, it is merely a suggestion.
(Winding)wire insulation lacquer/resin/coating can withstand several hundred volt.
Highest voltage with min. load prop, to keep current in bounds. Not highest voltage with highest load, motor will burn. Lowest voltage with lowest load is no problem of course, will give result in lowest current and temperature.
It is not possible to overrev an e-motor with a low load prop, max rpm = voltage x velocity_konstant_Kv)

Also note that Kv (expressed/measured in rpm/volt) says nothing about a motors max. continuous power and current, or max. torque, or rpm.
Both the motor in your toothbrush and the motor in a 1:1 train can have the same Kv.

Prettig weekend Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
E-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC
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Last edited by ron_van_sommeren; 04-08-2023 at 05:26 AM.

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