MambaMax ESC quirk
 

I was goofing off with my Mamba powered jato tonight when I noticed an odd thing. If I go forward, brake, and then go backwards, it works fine. However, if I go backwards, brake gently, and then try to go forward with medium gradual throttle, I get tons of cogging. I have to go to neutral, then add the throttle and it goes fine with no cogging. Also, it does not do this all the time, just once in a while. At first I thought it was just a matter of the ESC not being able to read the rotor position, but how would that be different from when it first starts out? Has anyone else seen this?

For those who don't know; This is on a Jato: spur=54T, pinion=22T, total gear ratio=9.63, 8.4v 2S2P 5.8Ah emoli pack, 4.7lb truck fully loaded.

Is it still going backwards when you pull foreward on the throttle?

Nope.

Have you tried adjusting the startup power at all, Brian? It is odd that it does it intermittently - I will have to try to duplicate the phenomenon on my truck.

I've tried to reduce all the settings on the ESC for the least amount of startup power as possible to tame the spinouts while still giving me decent punch. Below is the output of my saved settings file (it's cool that it outputs plain text rather than compiled code, makes it easier to post):
The throttle curve is actually two linear lines. From 0 to 75 throttle (X axis), the slope is linear to 5.5 lines on the Y axis. Then, from 75 to 100 on the throttle, the line's slope is steeper from 5.5 to 10 on the Y axis. I have no idea why the brake/reverse curve is so complex. I never messed with that one at all.

Update on this.

I haven't had this happen much lately, but I was talking to a guy at my LHS today and asked him why he doesn't carry the CC stuff. Well, he said several people were having trouble with them during racing. If they jammed on the brakes so the tires would lock (stopping the rotor), then try to go again, there would be large amounts of cogging-like action. At first I said I didn't have that problem at all, but then got to thinking about this thread again and remembered that it sounds very familiar after all. During races, I tend to slide around corners more than stop so it makes sense I wouldn't see it very much.

Glassdoctor, he said you had this problem too during races. What are your thoughts? Did you do anything to alleviate it?

If enough people report this, maybe CC will release some type of firmware revision...

On a rare occasion i would get a slight hesitation after hitting the brakes, but i rarely ever fully lock the brakes

If you have it programmed from forward to reverse, the truck all of a sudden brakes (well brake, it's more of going into reverse) hard and throws itself in reverse, this is the same with the mamba 25.. Perhaps the guys from your LHS missed this setting..?

What is your forward to reverse setting?

my mamba doesn't like to start from a stand still... i've tried all the different combos of start power but i haven't been able to resolve it yet... i'm hesitant to contact castle as i'm using it on a g2r revo on 4s with a plettenberg maximum w/fan... gearing is 16/51... i think the fact that the motor is 4 pole has something to do with it... once it gets rolling, i mean even just for a couple of inches, its silky smooth... but from a stand still it just cogs... i found that if i give it full throttle it actually doesn't cog... only problem is if there is any sort of grip, instant backflip... lol... btw i've got a fan on the esc and it doesn't even get warm after 15 min of hard running in a parking lot... the motor feels warm to the touch i would get around 80-90 F and batts are cool... i'm using apogee limn 5800's...

those plettenberg have got a nasty startup.. What you can do is set your gas-curve to start at 5 percent or something, so it's starting a bit more aggressive. Did you tried changing the timing?

and did you programmed it to your setup?

i will try the curve idea... i played around with all the timingh setting along with the startup setting and they didn't seem to make a difference... once i've tried the changing the curve i will post the setup file

I hesitate to get into this too much because there are a lot of unknowns and it's difficult to get on the same page... what I "see" you might "see" a little different.

First off I can say I have talked to Castle about some issue I have noticed... I don't know what can and will be done to address certain things. Some things they (Castle) don't "see" so it's hard to say what they can do about it.

The cogging from a dead stop is a problem with the big cars/big motors. I'm sure certain motors do this more than others. I have run my 1/8 and barely saw this at all and other times it happened a lot and was a big problem.

If you ever have this cogging on initial startup definitely don't keep on the throttle. Let off immediately and try giving just a little throttle to get the motor to start. If you just jam on the throttle when it's sitting there stuttering it basicly is shorting out the esc and it will get very hot very fast... wiring and all.

I actually smoked my datalogger one day when I was getting cogging and decided to see what would happen if I stayed in the throttle a lot etc... bad experiment. The wires got hot.. the plugs on the eagle tree actually desoldered. The MM still works fine btw... just had to let it cool off.

Did you programmed it to your receiver/transmitter?

and what is your forward/reverse setting?

Another thing; the plettenberg is a rather stiff 4 poler.. The stator 'grabs' the rotor pretty hard. Most controllers don't like the plettenbergs because of this.

You can feel a large resistance when turning the shaft by hand. (for those who know the Neu's and who turned it's shaft; it's about 5 times more resitance to turn a plettenberg)

The glitch BrianG describes doesn't sound like the same issue I have seen.

Here's the issue we are having while racing:

This is in 1/10 offroad buggy, 4wd, and truck, running good 6 cell packs, forward only or reverse lockout, two different high end radio systems, five different cars and rx's, differnet electronics layouts, two different drivers, etc etc etc

It appears as if the MM can "misfire" in certain situations, when there is just a small amount of throttle input. What happens to us is when coming through a sweeper we let off the throttle and let the car coast a bit (with the drag brake activated) and then gently roll back on throttle.... sometimes the car will "glitch": the rear wheels lock up just for a split second and then back on power. We belive what is happening is that the MM gets a misreading on the rotor position/direction and it "fires" backwards once... then immediately goes back to the correct sequence. It is just enough to make the car loop out sideways... just like a quick stab of the brakes in the middle of a turn.

This happens to me about once per race on average... sometimes I have seen it several times in one race. I didn't notice the problem until I started racing on the smooth indoor tracks recently, where this behavior is obviously not just a bump or rut in the track messing with the car.....

We have the brakes dialed way out... the brakes are not strong enough to even make the car do what it does. And we have the drag brake set to around 30%... pretty strong... so we only need a little more brake available when we want it.

Setting the exponential on the radio to "soften" initial throttle response seems to make the problem worse, as well as setting the drake brag higher may make it happen more.

Castle's response so far is that they are blaming the connectors... they said that one guy reported a similar issue and that the problem went away when he direct soldered the motor. They think possibly the very small low voltage pulses that the MM uses to get info from the motor may not "like" the connectors. I tried putting a little solder "jumper" on my connectors to see if that would help and my buddy replaced his connectors with Corally style gold plugs that are similar to the 4mm stock ones but are a different (we think superior) design and quality. But we still see the issue.

This week I plan to direct solder my motor and see what happens.