motor skips at low throttle

[doctormike]

The motor on my Dynam GeeBee stops and starts rapidly at the lowest throttle setting. It didn't do this before the crash. I'm pretty sure it's an ESC problem. I tried the full throttle and plug in the battery trick...doesn't work. It works fine once the throttle is advanced. Any advice would be greatly appreciated. Doc

[Grossman56]

hey Doc, have you tried increasing the throttle trim, I can get my planes to do that by decreasing it, see what happens if you increase it a couple of clicks

Grossman56

[fhhuber]

Check the connections between esc and motor. Might be some arcing causing the ESC to lose sync with the motor.

I usually go in and put heat shrink over the bullet connections to lock them together and prevent the tiny insulation gap from just plugging them in.

[doctormike]

Thanks, I'll try it. Doc

[doctormike]

It worked! Thanks Gman! Now, I have to make a note in my GeeBee to change the throttle trim when I fly it. Doc

[xviper]

The throttle trim thing may only be a "bandaid" solution to a very specific problem. Your Dynam ESC may also have the known problem with altered programming. MotionRC (Ryan) has a video detailing what needs to be done to address a hidden problem. You may also need to do the throttle calibration again after a crash.

https://www.youtube.com/watch?v=aX5E***2G4M

[ryramZ]

The throttle trim thing may only be a "bandaid" solution to a very specific problem. Your Dynam ESC may also have the known problem with altered programming. MotionRC (Ryan) has a video detailing what needs to be done to address a hidden problem. You may also need to do the throttle calibration again after a crash.
https://www.youtube.com/watch?v=aX5E***2G4M

If that doesn't work sometimes its a bad solder joint on the bullets.

[doctormike]

Throttle calibration is the first thing I tried. Didn't work. I'm going to check all the solder joints and connections. Thanks, Doc

[WintrSol]

Do you know whether that is a delta or Y configuration motor? If its a Y, it is possible the common point, for the windings, needs attention.

[OV10]

Hello Doc,
The throttle pulsation at low throttle is a well documented problem out their on the various forums.
Here's a link that might provide some indepth insight for you.

http://www.rcgroups.com/forums/showthread.php?t=2225185

The little unmarked circuit card that they refer to being provided with the ARF of which I had a couple but were never installed initially because I was like "what the hell is this about" when I got my Waco and then followed by the FW190. Well the Waco had no pulsing but the FW190 did, that is until I put that little circuit in between the ESC and the Rx on the throttle line for the FW190 and no more pulsing. As xviper suggested, it looks like Dynam knows of the problem with the 40A ESC and the little circuit is a Band-Aid.
Best regards,

[Konrad]

Fantastic info. I'll link this to the Dynam ESC thread where I asked much the same question.

http://www.hobbysquawk.com/forum/electronics-and-rc-accessories/electronic-speed-controls-escs-and-becs/1933-dynam-esc-s

So that device looks to be a buffer to address the poor stability of the pulse coming out of some recievers. So it is Dynam's Band Aid to poor signal clarity from the receiver. As a general rule we want an ESC to respond to any change in the pulse width (signal) as fast as possible. This is a great property for 3D type ships where the throttle is constantly manipulated in hover.

Poor signal stability shows up as a surge at low power setting as the pulse is going between the on and off threshold.

So by read of this the issue really is in the Rx. But in the real world Dynam is trying to address this with the buffer.

I think I'll actually remove this add on in the hopes of adding more reliability (less parts to fail).

[OV10]

Fantastic info. I'll link this to the Dynam ESC thread where I asked much the same question.
[url]So by read of this the issue really is in the Rx. But in the real world Dynam is trying to address this with the buffer.

Always two sides to the pancake though, or the real world is that they are not willing to address the more expensive fix of dealing with the thousands of defective ESC warranty claims and found it easier to put the inexpensive non-descript circuit card on the ESC throttle lead provided with the ARF. Never have had this issue occur with other brand ESC's and of the Dynam's product line it appears to be the 40A is the culprit which is a high usage device for them. Glad I was able to impart some light on the subject of the mystery card.

[Konrad]

Always two sides to the pancake though, or the real world is that they are not willing to address the more expensive fix of dealing with the thousands of defective ESC warranty claims and found it easier to put the inexpensive non-descript circuit card on the ESC throttle lead provided with the ARF. Never have had this issue occur with other brand ESC's and of the Dynam's product line it appears to be the 40A is the culprit which is a high usage device for them. Glad I was able to impart some light on the subject of the mystery card.

Don't know about nondescript, just not well documented. Pulse width stability has raised its head in our radios on and off for years. I have a few 60 amp ESCs they look to be the same PCB as the 40 amp ESC just with different MOSFETs (numbers).


To bringing this on to the PCB would cost resources and might introduce other unforeseen issues. As Dynam has a fix with this "add on" I see little benefit to making it integral with the PCB "mother board".

Now that I think I know what that add on is I actually like the idea as the end user being able to remove it in applications where I want the fast throttle response like in a hover. If I want to taxi around I have the option of adding it back at the cost of some delay. For most user this delay is of no consequence, so the buffer looks to me to be an appropriate fix for what really is an economy vendor of foam models. If one wants a higher end ESC look towards the ZTW, Hobby Wing and Castle Creation brands. But for low entry cost sport models little can beat the Dynam product line.

Again thanks for lifting one more veil of ignorance from my eyes.

All the best,
Konrad

[apmech1]

I would also check the timing of the esc. I have seen what you are describing when the timing is too high.

[Gatorjohn]

I had this problem with all my Dynam planes. I bought the Dynam ESC programming card from Motion RC, hooked up and pushed DEFAULT on the bottom of the card, lights (settings) will change. Then pressed OK and the problem was solved.

[Michael60.mpv@gmail.com]

What will be the right

[OV10]

Hello Michael60 and welcome to the Squawk.
"What will be the right" what??? Can't help you if we are unsure of what your question is. :Confused:

[champdavid96]

Maiden flight on FT P-38 went perfectly. Second flight, after about a minute into flight, I lost throttle on both motors at the same time and had to dead-stick land it. When I got to the plane the motors would spin up like normal. Launched it again and It did the same thing. I was able to pump the throttle stick and get the motors to kick in a couple times but still ended up losing the bird. Took it home and replaced the Y power harness and used different battery. Went to the field today and the same thing happened but crashed this time. Got to the plane and the motors would still spin up. Using an Admiral Gyro receiver and programming differential thrust. Have several Admiral receivers and they all work fine. I'm also not losing my other channels when the motors quit. Please help guys!!!

[OV10]

Need to start with a simple process of elimination. Try removing the differential thrust from the equation and see if the power system continues to exhibit the characteristics.