Sluggish Gremlin

[sprintwrench36]

Hey guys. Got a new to forum posting, new to multi-rotor, but not so new to Flite Test guy from Iowa here. I've been flying Ft planes for about 2 years now but I'm currently stumped. I recently built a gremlin (TJ frame), and had a blast building and flying at first. Flew on 2S and 3S for aprox. 10 flights and all was fine. About mid way through the second day of flying, i landed to change out batteries, and when i started flying again my gremlin has very little power. It now on 3S it behaves like it used to on 2S. This is most noticeable on punch outs and takeoff. Battery life seems to be the the same as always, about 6 mins on a 550mah. When i give roll or pitch input it seems to perk up and fly fast again, but on a straight up or recovery from a drop it doesn't have hardly enough power to lift itself. I have tried 4 different batteries, including two 2S and two 3S and it is the same on all batteries. So i think i have ruled that out? I have re soldered all esc and power connections to no avail. I was thinking about getting some higher rated esc's that are really rated for 3S but don't want to if i don't need to. Also wondered if i cooked the FC with 3S (i found out afterwords that the gremlin isn't supposed to handle 3S, not sure if it is the esc's or the FC or both that are that way). Im not really sure what to do next, but was hoping that someone else has experienced this or could help me out. This thing was awesome to start with and i want to get back to that. Grateful for any help that i can get.

 

[PsyBorg]

I fly mine all the time on 3s. I have had the weight on mine as high as 180 g and it flys great. Now I am down to 157g (still lardy for a Gremlin ) and it flys great.

How hot have your motors been getting? If you fly 3s on stock pids you are more then likely cooking them and may have changed the electrical properties of the motors. It is also possible the bearings may be drying out a bit. Maybe a half a drop of light machine oil would help them out.

I have a build thread about everything I have done with and too mine. Including the pids, rates, and horizon leveling mode settings I fly on mine. Take a peek in there and maybe you will see something that helps.

 

[sprintwrench36]

PsyBorg, thanks for the reply. Funny that you are the first to speak up, ive been following your build since it started.

When this cropped up i went to your thread and adjusted my settings to what you have suggested and there is no change in the acceleration problem. i didnt notice the motors heating up excessively before but since this problem has started they do get quite warm, even on 2S. I will try a little oil on the bearings in the morning and see what happens. if i hadnt tried other batteries i would almost suspect that they dont have enough burst rating, (supposed to be 50c) but switching to others doesnt change things if that helps discribe it at all. A few short bursts of throttle does get it to accelerate better, but still not like it did at first.

 

[PsyBorg]

Another thing to do is check for bent shaft or crimped cans. Turn the quad sideways so you can see between the bell and the frame and spin the motor by hand. If the shaft is bent that gap will open and close as it rotates. Then while you are turning pay attention for any binding where the magnets may be rubbing the stator because the can is now egg shaped.

 

[sprintwrench36]

Well, looks like its back to the drawing board on this one. I double checked everything i could and did the things that were suggested with no avail.
I have 4 new 20a emax lightning esc's on the wall for something else that look like they will fit, albiet tight. Think im going to try that to rule out an esc problem. First im thinking of reverting back to default setup in betaflight just to make sure i didnt screw something up in there, as i am new to this.
If an esc switch doesnt fix it and points to overheated motors, is there a better replacement to look for or are the stock ones a good choice if i take care of them?

 

[PsyBorg]

There are other 1104- 1106 range motors that would work with these easily enough. I believe DIY and brother hobby make the more quad copter looking ones and not just the can style of the Emax motors.

 

[sprintwrench36]

Well, after a bit of life to get in the way, i finally got time this weekend to put new esc's on the gremlin. It now flies like it did when new, fairly crazy on 2s and borderline out of control on 3s. I ordered some 12a emax nano's and received 20a lightning esc's as a supposed upgrade-rolleyes. the 12's would have fit nicely but the 20's just barely squeeze on the frame. they will do the job until this frame meets its expiration date i suppose.
i have learned alot about the setup and calibrating of these things along the way, thanks to psyborg's advice and build thread and the main gremlin thread. Through a mistake of my own in betaflight i learned much on how that works and the ins and outs of flashing firmware and such.
One remaining question that i have is if there is any way that i can test my 6a esc's to see if they are all bad (unlikely in my opinion) or if it is just one. I just ordered another gremlin kit to build as a gift for my brother and thought that if only one is bad that will give me a few extra parts in the bin.
To psyborg. Thanks for the help, and i enjoyed the flite fest debrief on the FTCC podcast the other day, it was interesting to hear all of the stories and opinions on the event
Thanks again
J