Over the past few months I've been slowly piecing together an APM2 3DR quad as parts come in the mail and I'm finally up to the pre-flight configuration checks before my first test flight. The latest bump in the road has me a bit stumped and I'd like some advice/suggestions before moving forward to try and fix it. Here's the situation:
After calibrating and arming the ESCs, I throttle up to test the motors. Three of them run beautifully but the front left motor "twitches" as if it's not getting a good signal or power is repeatedly cutting out. It'll spin around once and then spin right back in the other direction again, over and over, while the other motors keep going. At highest throttle it cuts out completely and doesn't respond again at low throttle until I throttle all the way down and start over again.
I took the quad apart to inspect for bad/broken solder joints but see nothing. Upon testing again after inspection, the back-right (directly across from the first bad motor) now exhibits the same symptoms! It's like it's spreading or something, but it's probably just me...
So, is this normal behavior and I'm missing something or is something clearly wrong? And if the latter, what might it be? I could re-solder half my quad, but if I could get some suggestions before I go all out that would be awesome.
Are you using the bullet connectors between the ESC and motor? If so, one of them is the problem. Try hard-soldering those connections.
Yes I am, will do.
Thanks a bunch!
I had to replace all my bullets from the kit, due to that the male bullets swiveled in the female bullets when assembled, I found some replacements that looked identical, but they had a tight/firm fitting.
Chris was correct. After taking off the bullet connectors from the problematic motors and soldering them directly to the ESC wires all motors operate as desired.
I suspect I may be doing some flying this afternoon! Thanks again for the help.
Although not likely, if you have an intermittent motor winding connection internal to the motor it would be a similar symptom.
As your motors are likely new, I would hope this is not the case. Trent of My Geeek Show actually had a video of this exact problem.. Trent's Twitchy Motor
ALL electrical connections should be extremely rigid/firm and not loose or able to move easily (a poor solder job counts as loose).
I am at the same point with my project. My plan is to use a servo tester/driver to run the ESCs up and down to confirm correct direction and operation. Then the radio/APM2 would be a later phase.