MM/Lehner Challenge
 

Hey guys. As many of you know, I have a brushless CRT that is running a 1940/10 hi-amp motor with the MM ESC. I currently have a Hyperion 4s 4350, 6v/5v BEC, and a nice Airtronics steering servo.

Here's my "challenge" . . . . this weekend I went to our track and was running it. It hand'es awesome, but would cogg or glitch sometimes. I noticed that it seemed to happen mostly when I was accellerating slowly and turning at the same time. However, there were one or two times where it looked like it would lock up the brakes for a split second. By the way, I have a Spektrum DX3 radio.

I don't remember what my settings on the MM are, except for the lipo cutoff.

Any ideas guys?

Oh yeah, I have a 12t pinion with the 44t Kyosho spur. Thanks.

I would try it with a reciever pack to rule out the BEC being affected by any interference,and if that works then try moving the BEC around the truck and/or shielding it.

Do you have the internal BEC disconnected on the MM esc?

Hmmm, good points. Right now the external BEC is not shielded, and it's immediately next to the ESC and the motor. That might have quite a bit of interference actually.

And about the MM BEC . . . . I'm not sure I have that disabled. How do you do that? :002:

take the little red wire out of the signal plug.

Yeah i was just off checking which color it was.Remove the red wire (+ve)that comes from the MM to the reciever plug,lift the little tab on the plug and slide it out,and insulate it with some electrical tape.

Ok, I'll give that a try. Thanks guys. Do I need to insulate the external BEC somehow also? Like a little plastic box or something?

There is a thread on the castle section involving this, according to castle you solder the wires together (eliminate plugson motor) and the problem is better if not eliminated, I have just had it happen to me for the first time so i intend to do it soon

edit; here is the link; http://rc-monster.com/forum/showthread.php?t=3952

Not usually,sometimes they pick up some interference from somewhere and moving it elsewhere on the truck helps,like i have mine under the chassis on one of my trucks so the chassis shields it from the other electrics.you can rule out the external BEC as a source of glitching by trying with a reciever pack to see if the problem goes away.I'd just try disconnecting the internal BEC first,one thing at a time,then you know what the problem was for future reference/problem solving.

Thanks crazyjr, but I went through that whole thread and only seemed to see the UBEC mentioned. Nothing about soldering wires together or anything. I would really like to see a photo of the application. You know what they say . . . a picture's worth a thousand words! :027:

Anyone have a photo of the wire to remove, and the look of the finished product? Thanks.

I just re-read the first page and it does mention the Castle blamed the plugs. Basically solder the ESC wires directly to the motor wires.

I don't know about all of this. It was not long ago that everyone was praising the MM controller because they were capable of so much more than they were rated for.

As time has past and these controllers are being used more widely in applications for which they were never designed, I believe that we may just be discovering the limitations of the MM controller.

I've exchanged emails and have had conversations with the guys at Castle. I've asked many questions and have gotten answers ranging from "the MM was never designed for that application" to "it must be something else because it couldn't be our controller." On my last contact with them, I was told that my cogging problems were due to my battery not being able to supply the needed current to the esc. He told me that before he asked me what batteries I was running. I happened to be running a Kokam 4S 4.8Ah pack, and I think that I'm pretty safe in saying that the battery wasn't the problem. I've also heard the connector bit too. I was direct soldering for a short time too. This did help with the cogging, or it seemed that it did anyway (I was using 4mm connectors). Since then, I've gotten some of the 6mm connectors from Neu. When measuring the resistance across a piece of wire and then comparing that to a piece of wire with a 6mm connector in it, I got no measurable increase in resistance. I've gone and re-wired all of my setups with the 6mm connectors and haven't seen or noticed an increase in cogging.

Things that I have seen that I know will cause problematic cogging is running the MM in a heavy vehicle or a vehicle with large diameter tires. I have a Muggy that I converted and the Muggy seems to be heavier than other truggies by a pound or two. It is a beast of a truck if you compare it to a real truggy, like an 8ight. When I first got the muggy I put a 7XL into it and with the 40 series tires, I had to run a 9T pinion just to be able to get it to go at all. I'm now running it with an 8XL and a 10T pinion with 40 series mashers, which are very big tires and it's doing ok, but I really can't gear for any speed. If I go up to a 12T pinion, I start getting the cogging problem again.

On the other side of the spectrum, a friend of mine had a MM 5700 system in his 1/10th scale dragster a few weeks ago. He was running with a matched pack of GP3700 cells (I think they were 3700s) and when the light turned green, his car lept backwards. This only happened once that day, but it did happen. He subsequently called Castle and told them what he was doing and they said that they would send him a new controller without any other questions. I wonder if there is something particular that is causing this that castle is aware of.

If you are having a cogging issue, try dropping your pinion by two teeth and see if it gets better. If it does get better, perhaps your setup has the esc on the ragged edge of what it can comfortably handle. I don't know, it's just a suggestion. I know that after all of the issues that I've had with my MM controllers and the lack of support for them (with the understanding that we are running them out of spec), all five of mine are going to be retired at some time in the near future, in favor of something that can comfortably handle the 1/8 scale conversions.

I know that the Compro that I got recently wasn't what I expected. I believe that I got a defective unit, but I can say this. On 4S or 5S lipo with either a 7XL or an 8XL motor, no matter what gearing I used, it never cogged or ran hot.

AAngel, while most of what you said is true and very logical, I have to disagree with the whole dragster leaping back part.

That is no problem, but a common symptom of any sensorless system that get punched from a low speed. My 18T does it pretty often, it will go backwards a few inches and they shoot off like no tomorrow.

At a stop, the contoller has no way of telling where the rotor is. The motor isn't spinning, and therefore is not creating any EMF backpulses for the controller to read. When you punch it, the controller is simply guessing where the rotor is. Its usually right, or close enough where it will at the very least still move forward, but sometimes its wrong, which is why it rolls back a bit.

The rolling backwards that the MM causes is actually related to only the CC controllers. The MGM and Mtroniks controllers I have do not do this at all, and I don't remember ever seeing it with the BK Warrior 9918.

As I said in my previous post, Castle sent him a new controller. The new controller hasn't done it. I don't know anything about electronics and can only make observations or relay what others have represented to me.

Oh well, either way. My 18T has always had that "problem" where it rolls back a few inches or so if you punch it from a standstill. It only happens say, 1 out of every 50 times you floor it from a stop. It hasn't affected performance or given me any problems, unless you count delayed throttle response as a problem.