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Pumpkin drop event

HELP PLEASE for issues with a TWIN ENGINE BUILD

C210LUV

Junior Member
#1
Hello all,

New to the site, please be kind!

I am having throttle issues with my twin engine build. I am doing a foam-build replica of ExperimentalAirlines RC-69 Cargo Dropper. As for the throttle issue, all was working perfectly until now, where one motor has instant throttle response, and the other takes one-quarter throw before responding. As you would guess, the instant responder reaches full throttle, the other does not.

My trouble-shooting has narrowed it down to a bad ESC, but I wanted a second opinion before ordering another set of ESCs. Many times with me it is user error!

The specs:

2826/10 1400kva motors
8x8.8 slow-flight props
30A ESCs
2 x 2200 Mah batteries in parallel
HobbyKing T6 radio and HobbyKing receiver
Programmed with T6 Config
V-tail mixer mixing rudder and throttle at 30% rudder travel

How did I arrive at the bad ESC theory? Swapping the ESCs to opposite motors transfers the throttle lag to the other motor as well. I've done this with the servo mixer in use as well as sending the ESCs into the receiver straight through a Y-Harness (no mixing). Throttle trim is just below centered on the transmitter. I've made sure that all receiver wires and ESC cables are clear of battery cables.

When did the problem start? As best I can guess is when I zip-tied (tight enough to hold but hopefully not crimp) wires and cables to keep things neat, and hopefully to keep things away from those they might interfere with, but I am no expert on the subject.

If it is an ESC problem, would you suggest buying a new SET as opposed to a replacement? I'd hate to have one peter out like this in the air on my first twin.

Thank you all for the help!

C210LUV
 
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Foam Addict

Squirrel member
#2
Welcome to the forum!

To start, have you calibrated the throttle ranges on each esc separately? The problem you're describing sounds very much like the lagging ESC is mis-calibrated.

On a side note, you say you have 8x8.8 props, those are way too big for a 28-26 1400kv motor. You would be much better off dropping down to 7X6s or 8x4s, if you don't you will probably burn out a motor within a flight or 2.

I hope this helps!
 
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C210LUV

Junior Member
#4
To start, have you calibrated the throttle ranges on each esc separately? The problem you're describing sounds very much like the lagging ESC is mis-calibrated.
I will learn how to calibrate ESCs and give that a try. Thanks for the suggestion! Also, I may have misinterpreted what Ed was saying about the prop size in his YouTube breakdown of the Cargo Dropper, and will adjust the props down to 8x4. Good catch!
 

C210LUV

Junior Member
#5
Welcome to the forum!

To start, have you calibrated the throttle ranges on each esc separately? The problem you're describing sounds very much like the lagging ESC is mis-calibrated.
I calibrated both ESCs and they are matched beautifully, with one hitch: They are only matched when they are paired via y-cord to the receiver. ExperimentalAirlines' design incorporates a V-Tail mixer to add throttle as the rudder reaches a certain travel amount. (i.e. left turn, left rudder, right engine increases RPM slightly at 30% rudder travel). When I run the motors through the V-Tail Mixer, the lag returns to one motor. Mind you this was not the problem before calibration, one ESC was lagging even without the mixer input.

So to re-cap: Motors now matched in throttle without mixer, one motor lags when routed through the mixer. Swapping ESC radio cables on the mixer causes the lag to switch with it.

Again, thanks so much for your help! It's just nice to get the motors re-matched in one form.
 

Foam Addict

Squirrel member
#6
I'm glad to help! The Synced motor sound is awesome isn't it? :D

Actually, I just built my first twin too! I was lucky, my ESC's came synced from the factory.

Sorry the V-tail mixer isn't working out. I think you can mix rudder and throttle in t-6 config to get the same result, but I haven't tried it.

I found these threads over on RC groups, I hope they can help. The first one has some limited instructions on how to mix rudder and throttle in T-6 config.

http://www.rcgroups.com/forums/show...ight=T6A+differential+thrust+mix#post31704948

http://www.rcgroups.com/forums/show...ight=T6A+differential+thrust+mix#post31848785