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Two motors, one plane, one motor starts slower than the other.

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Old 09-05-2018, 10:19 AM
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cracker39
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Default Two motors, one plane, one motor starts slower than the other.

Have a problem. I am new to electrics and am building a twin motor plane. The wiring is as shown below, one battery powering two identical ESCs, each going to one motor. I have two new Exceed RC Rocket 3010-1700KV Brushless Motors. I set up a test using identical HobbyKing Skywalker 40A ESCs. One motor (#1) hesitates to start, but does start after the other motor (#2) has started. If I switch ESC #1 to motor #2 and vice versa, then motor #2 is the slow starting motor. I can switch the cables to the RX and nothing changes. So, it is in the ESCs, not the wiring.

OK. I now try an identical pair of Simon Emax 40A ESCs from my newly converted to electric seaplane and get the same results, escept that the slow starting motor hesitates longer than it did with the Skywalker ESCs. (I don't recall this problem happening with the seaplane). Again, swapping the ESCs on the motors, the slow motor follows the ESC.

Is it common for two identical brand/model ESCs to put out different amounts of power…or rather, at different rates? I have not yet put props on the motors and checked the RPMs of each to see if at a given speed they are turning the same RPMs. I guess that will be my next test if i can find my tach. If this is a know occurrence, then ordering another of either ESC to try to get matching results is probably a waste of time and money.

I am not concerned with one motor starting slower than the other, because if I push the stick up to at least half throttle, both motors respond, though I can’t guarantee right now if they are running at the same speed. That in my opinion would be a problem causing the plane to veer in the direction of the slower motor.

Any ideas or opinions?

Note: The clipped red wire so only one ESC provides power, is on the wire Y harness, not the ESC wire as shown in the diagram.
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Old 09-05-2018, 04:17 PM
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Dale -

Some ESCs program quite a bit from the transmitter. One common(?) feature I’ve seen is a slow start that ramps up the motor gradually so hitting the throttle all at once does draw lots o’ watts. Any chance you accidentally program this in one of the ESCs, or perhaps it just came that way? Checking the current draw on each motor with the prop on, and/or the rpm would show whether each side is pulling it’s weight at full throttle. If you don’t have a tach or current meter, you could run each side independently while the plane is tied to a suitable luggage scale (Brookstone type) and compare the measured static thrust.

Last edited by Gyrodog; 09-05-2018 at 04:23 PM.
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Old 09-05-2018, 04:36 PM
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did you do the throttle calibration for the escs?
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Old 09-06-2018, 02:33 AM
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On another forum, it was suggested that i do the the throttle calibration, which i didn't know about. I will do that. also, it was suggested that i might have a bad solder joint which is very possible as i am not very good at soldering. Today i will try the throttle calibration and if that doesn't work, i'll redo the soldering on the connectors on the ESC. I know the motor connections are good as the problem moves with the ESC from one motor to the other.
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