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Thread OP
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Help!
ESCs on twin electric - this is driving me nuts!
I thought I had half an idea about all this.......
So I have an old Lanyu Do335, foamie warbird, 2 motors, one at each end. I pranged it a few months back, the fault being traced back to a dry solder on the main power Y harness (it runs 2 x 28mm brushless outrunners off the one 1800/2200 3S). Airframe is straight enough again to try and get it back in the air. The original outrunner up front was bent in the crash so I am playing with both a 28mm Eflite Park 370 or an Eflite Park 480 (1020 to 1250 KV). Props are only 8x4’s The original ESC’s are only 18A so I thought I would try something a bit beefier up front and current set up is the original 18A on the rear motor and a Tower Pro 40A ESC up front (the one with the external perforated heat sink – purple in colour). ESCs plug into the Spektrum AR600 RX via a Y lead. Now I know running 2 different ESC’s and 2 different motors is not ideal BUT, they SHOULD run..... Simple issue is everytime the front ESC is run through the Y to the RX the motor wont run? If I plug the ESC directly into the RX it runs fine but as soon as it is plugged in via the Y to the RX it wont? I have tried 3 different Y leads all the same symptom...have even tested the leads with a DMM, no issues, all low resistance and no continuity problems?? I have not pulled the power wire from one ESC yet . Some recommend this but Eflite even recommended leaving them both in place in the old P38 foamie I had which was essentially the same wiring set up. I still have another P38 twin with the same configuration(although motors and ESC’s are all matched) and it runs fine? Any ideas from the gurus? This is driving me nuts? Cheers Shaun B |
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With two dissimilar ESC's I would definitely pull one of the BEC leads. I am sure this is your problem unless you are somehow plugging the plug in backwards into the Wye.
https://www.rcgroups.com/forums/show...0#post21403989 Scroll down to post #7. |
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The Y should work but I would pull the BEC power lead (middle) on one of the ESC's. The two BEC's may not be compatible. Use the better BEC.
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Thread OP
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So......In frustration I wound up re fitting the original ESC to the front motor. These are only rated to 18A but the front motor was only an Eflite park 370 turning an 8 x 4 prop so should be well within its limits.
On the bench it spun up fine (both motors), however on a test flight today the front motor quit about 10 seconds in. No problem, the thing flies fine on one , so around we went and got down OK. Next test I pulled the red (power) wire from the front ESC, close it all up again, no change, front motor still wont run. Upon arming it does the “twitch” when the esc counts the cells etc but it just does not run........ I am wondering if the original motor required some weird timing setting that the ESC is set up with ? I have no way to program the original ESC's, they are brand X from China. Going to spend some more bench time on it later this week, gotta be a lesson in this for me somewhere.... Shaun B |
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I'd try re calibrating each ESC individually - one at a time. Disconnect one and calibrate the other. Spin up the motor to make sure that one works. Disconnect that ESC and reconnect the other one, and re calibrate it. Spin up that motor to be sure. Then connect both ESCs as you origonally had them, but with one of the red wires pulled. . See what happens...
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Agreed. It sounds as though the throttle learn is off on the one esc. The original is arming as normal, but the second one is not recognising the off throttle position and not arming.
Also unless both motors are the same kv, you may end up with some weird flights, as one motor is delivering more power then the other. And with two dissimilar esc's they could cause one to shut down before the other. Lucky for you it will fly on one. With twins I've always matched systems. Twins are twice the fun, and double the trouble. |
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It is possible that your battery pack is unable to cope with the current draw of both motors and one of your speed controls goes into low voltage cutoff (LVC)and it's motor quits, the other motor now gets full power until the battery runs down or you land before the second speed control goes into LVC. This is disastrous on a twin engine model like my EDF ME-262 which will go out of control with one motor quitting, unless you can shut off throttle quickly and land dead stick. What I learned is that both motors and speed controls must be well matched , speed controls must be set for soft cutoff and you must land well before the battery runs down, so that the one motor quitting thing doesn't happen. Make sure that your battery pack is able to cope with two motor current draw.
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Thread OP
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Gents a quick thank you for the replies. I am going to re calibrate the ESC's again as a first step but also swap the battery leads around to make sure I have not got a dud solder joint somewhere.
Its not a battery capacity thing, the original was designed to fly on an 3S 1800 20c battery and did so well. Also there should not be an issue with different KV motors, I have flown the plane with only the rear motor running and it slight flies acceptably. Some Do335 tragics only run the front motor and let the rear freewheel. I will post a note when I have done another round of testing. Cheers and thanks all again. Shaun B |
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