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Juddering Brushless

#1
Thanks to all of you who helped me on my control rod issue - a few tubes donated by my equally locked down neighbour (and RT nut) allowed me to use 0.5mm wire perfectly successfully. I'm enjoying my first forays into RC flight although it's quite scary!

I have the Power Pack A radial kit and the brushless motor is amazingly powerful - I'm still trying to build a Firewall it doesn't wrench loose from but that's another matter. If I accelerate the motor too quickly from stationary, it judders (back and forth I'm led to believe but it's hard to tell) but if I accelerate more smoothly it seems ok. Googling it, it seems that it's not unusual with brushless motors but I'm wondering whether you people have any experience/advice on this. I just want to know if the motor is likely to be damaged or maybe I'm being too heavy handed on the throttle. Many thanks.
 

Hai-Lee

Old and Bold RC PILOT
#2
I have experienced the same issue in the past and I fixed it by changing the timing on the ESC from Auto to a fixed setting. You will need to consult the ESC manual and following the appropriate signalling sequences ot beeps from the ESC in programming mode.

Just what I had to do!

Have fun!
 
#3
Thanks very much. I have the FliteTest 20A ESC that came with the Power Pack A and there were no programming instructions. Does anyone have a link to a manual? Am I correct in thinking the FT ESCs are re-badged Emax components? Sorry for all the questions!
 

Hai-Lee

Old and Bold RC PILOT
#4
Thanks very much. I have the FliteTest 20A ESC that came with the Power Pack A and there were no programming instructions. Does anyone have a link to a manual? Am I correct in thinking the FT ESCs are re-badged Emax components? Sorry for all the questions!
Sadly I cannot answer your question on what ESC FT uses.
Perhaps you could contact the FT store and enquire of them if a manual is available or where one could be obtained.

Have fun!
 

FDS

Well-known member
#5
Also be sure there’s no motor screws touching the windings. I would also check there’s no exposed wiring on the motor plugs, you might be getting arcing between them if so.
If you want a tough firewall then aluminium sheet, thicker sheet plastics and DIY plywood can all be used. It’s only a square with a hole in the middle, plus mounting holes for the motor. Lay it all out and drill the holes, then cut the firewall.
 
#6
Also be sure there’s no motor screws touching the windings. I would also check there’s no exposed wiring on the motor plugs, you might be getting arcing between them if so.
If you want a tough firewall then aluminium sheet, thicker sheet plastics and DIY plywood can all be used. It’s only a square with a hole in the middle, plus mounting holes for the motor. Lay it all out and drill the holes, then cut the firewall.
I did consider that possibility. I think my cautiousness in not having the screws protruding too far into the motor back plate may have cause some of the problems when the firewalls failed (or at least the screws worked loose). They definitely aren't now and the three leads are well shielded where they connect to the ESC tag leads. My latest firewall is thicker and I can now tighten the screws really quite firmly with only the very slightest sign of the ends of the screws - well clear of the windings - not tested it yet.

I did wonder whether expired credit cards might not be a bad material - maybe a double thickness to cope with the screw length.

Thanks
 

cranialrectosis

Well-Known Member
Mentor
#7
In my personal experience, most often, jittery motors are caused by a poor solder connection between the ESC and the motor.

Pre-soldered bullet connections are notorious for poor solder connections. This is especially true on new builds or motors that act up after a crash.

The simplest thing to check, fix or break are the solder connections between the ESC and the motor.

@Hai-Lee is very experienced and very possibly correct. However, I suspect he checks the solder connections first just by default and I would do the same.
 
#8
In my personal experience, most often, jittery motors are caused by a poor solder connection between the ESC and the motor.

Pre-soldered bullet connections are notorious for poor solder connections. This is especially true on new builds or motors that act up after a crash.

The simplest thing to check, fix or break are the solder connections between the ESC and the motor.

@Hai-Lee is very experienced and very possibly correct. However, I suspect he checks the solder connections first just by default and I would do the same.
Actually I did have a crash where the motor broke free and slipped the bullet connectors so that's quite a possibility. Thanks for that.
 

Hai-Lee

Old and Bold RC PILOT
#9
In my personal experience, most often, jittery motors are caused by a poor solder connection between the ESC and the motor.

Pre-soldered bullet connections are notorious for poor solder connections. This is especially true on new builds or motors that act up after a crash.

The simplest thing to check, fix or break are the solder connections between the ESC and the motor.

@Hai-Lee is very experienced and very possibly correct. However, I suspect he checks the solder connections first just by default and I would do the same.
You would be very correct. I not only check for poor solder joints but I also check the individual windings for resistance and any possible intermittent breaks in every winding.

I also have a number of old and retired ESCs that I programmed ages ago that I test motors on if they are subject to timing problems.

Often I find that changing the ESC for one of greater amperage than the motor requires actually calms down a twitchy motor.

Just what works for me!

Have fun!
 
#11
No I didn't. Not even sure how I do that - so many sources of info and as a novice it's quite surprising how much you are assumed to already know with this stuff!

I presume that's done with the transmitter?
 

Aireal Anarchist

Well-known member
#12
I would direct solder the esc to motor I have had this issue MANY times...it happens frequently on fast electric race boats the esc gets real hot from the amount of power we demand and the ESC actually needs water cooling so if not setup proper it gets so hot the we melt the solder connections at the esc bullet connectors creating a a poor solder joint and we get the stuttering motor issue....Im not saying you melted the connections, Im merley pointing out just how often RC race boats experience the stuttering motor phenomenon and that a poor connection between the ESC and motor is almost expected to be the cause....
given you experienced a crash that pulled the bullets apart....I would certainly resolder the bullets or as I suggested eliminate them and direct sloder the wires from ESC to motor
 

shadeyB

Well-known member
#13
No I didn't. Not even sure how I do that - so many sources of info and as a novice it's quite surprising how much you are assumed to already know with this stuff!

I presume that's done with the transmitter?
I feel your pain ,with expecting to know more than we do when starting out😂😂😂
any time I build plane , change motor or ESC , after crazy crash landings (not ever my fault) I always calibrate - recalibrate ESC
simple - use video below
 

cranialrectosis

Well-Known Member
Mentor
#14
Yeah the learning curve here is steep. :)

Posting on the forums will help a ton. Just, be ready to experience failure, smoke and crashes. We all do. It is part of the game. You will learn more about yourself than about RC flight in the next month if you keep at it. And IMO, that is the greatest gift we get from this hobby.

I presume that's done with the transmitter?
And with the props OFF!!! :)

Lots of video on the web for how to do this:

The basics are:
PROPS OFF No foolin'. Leaving the props on and getting injured is the biggest mistake you can make here. Take the prop off and save the trip to ER.

With the ESC connected to the throttle channel on your RX and connected to the motor but NOTHING connected to the lipo set throttle on your TX to max.
Connect the Lipo to the ESC and wait for beeps.
During the beeps, set throttle on TX to minimum.


None of this will function correctly if you have broken or loose or cold solder joints.

Note: Murphey's law dictates that even if you have a broken connection it will still spin the motor and BITE you if you leave the prop on! ;)

If you are new to soldering or just don't like it when mistakes smoke your parts and cost money, use a smokestopper to test after a bad crash or after any soldering is done.
 
#15
None of the manuals I’ve read cover the symphony of beeps I get when calibrating! I’ve made a small video illustrating what happens. Not sure whether anyone would advise.

By the way I really appreciate how helpful everyone is. Thanks.

 

Aireal Anarchist

Well-known member
#16
Im sure you have considered this..... but just incase.........do you have a second motor or ESC that you can swap parts around to ensure the parts are not defective
 
#17
Im sure you have considered this..... but just incase.........do you have a second motor or ESC that you can swap parts around to ensure the parts are not defective
Sadly not. Just beginning so bought enough gear for one aircraft. And it’s not quite as easy getting stuff when we’re in lockdown here in the UK as I’m sure all of you are.
 

FDS

Well-known member
#18
Buy a Hobbywing Skywalker ESC, plenty on EBay, I use them for all my FT builds. Any brushless motor will be fine for a tester.
 

Andrew

G'day Mate
#19
.....If I accelerate the motor too quickly from stationary, it judders (back and forth I'm led to believe but it's hard to tell) but if I accelerate more smoothly it seems ok......
This is why I agree with Hai-Lee that it could be a esc timing issue.
If it's working fine if you move the throttle stick very slowly and plays up when moving the throttle stick quickly it's usually the timing, with 50+ models I've came across this problem 3 times and was lucky to have the program cards to easily change the timing (low to medium).
It's also possible that a intermittent wire/plug contact somewhere when the motors spinning and vibrating causing problems.
 

Bricks

Well-known member
#20
No I didn't. Not even sure how I do that - so many sources of info and as a novice it's quite surprising how much you are assumed to already know with this stuff!

I presume that's done with the transmitter?

To calibrate the ESC plug battery to the receiver put your throttle all the way up turn on radio wait for beep then lower throttle, done deal..