Mamba Max vs Quark Observations - RC-Monster Forums

BrianG · **Mamba Max vs Quark Observations -** 01.03.2007, 05:09 PM

I was playing around with my Quark 125B and the MambaMax a couple days ago and thought I'd share an interesting observation.

I hooked up batteries to both ESCs, hooked the ESC to a BK Wanderer 10XL and set the transmitter throttle trim so the motor spins slowly. Then, I applied a load (my hand holding the tires) to stop the motor.

On the Quark, it understandably cogs until I let go. Even after a couple minutes, nothing heats up to any noticeable degree.

On the Mamba max, an interesting thing happens. When I first hold the tires, the ESC cogs. However, once the ESC realizes that the rotor isn't moving, it applies more and more power until the tires are ripped from my hands. Once the motor is in motion, the ESC slows back down to whatever throttle level applied by the transmitter. After doing this a few times, the ESC gets noticeably warmer. The motor temperature does not seem to increase much, if at all.

To make sure this wasn't a fluke, I did the same test using the 4600 motor and got the same results, except the MM ESC didn't heat up quite as much.

This is both good and bad. It is good because the Mamba ESC appears smarter and assumes a higher load and increases the power to compensate. But it could be bad if the motor is somehow locked/stalled, or if you are using a large motor. A larger motor could naturally pull more current, and if it is locked/stalled, it could pull way more than is safe for the ESC.

After thinking about this for a while, this phenomenon could be what is causing issues with larger motors in larger vehicles. Maybe even explains why it doesn't seem to like 4 pole motors. The higher load from the weight of the vehicle coupled with the larger motor could be causing strange things in the firmware.

Thoughts?

Serum · 01.03.2007, 05:15 PM

Yeah, i noticed the very same.

You can see it in my movie of the crawling revo.

The mamba maxx seems to do this to act smoother. and it works.

the mamba-maxx doesn't start at 2 rpm, it has a limit of several rpm's per minute. (to produce the needed EMF for sensorless) after it reached the starting RPM range, it can go lower. it's a neat trick to prevent cogging IMO..

BrianG · 01.03.2007, 05:35 PM

Yeah, it is a neat trick, but only if you are using 2-pole motors. Even then, that feature sounds like it would be most useful for smaller motors (like their bundled solutions) since they don't quite have the torque of a larger motor.

I suspect that if Castle releases a firmware update to use 4 pole motors, we'll find the ESC acts more like a normal ESC.

neweuser · 01.03.2007, 06:50 PM

That is pretty cool stuff. What made you think of doing the test? But, at the same time, if a motor was locked or whatever, it could be damaging. But then again, things usually go, and when they do, it's seems it's always more than just one!

Serum · 01.03.2007, 07:10 PM

Brian, i used it on a 6poler, i don't think the amount of poles have got anything to do with it, it simple runs on a lower RPM at the same amount of pulses

jhautz · 01.03.2007, 08:06 PM

Brian,

Really interesting find there... I'm not sure Im underatanding exactly why a 4 pole motor makes a difference over the 2 pole though. Whats your thinking on that???

I can see how a locked rotor can cause a big heat issue for the MM if the motor is too large. though. Probably why I had mine fail whill cogging on a large motor. It cogged so bad it acted like a locked rotor and just pulled to many amps.

danverz · 01.03.2007, 08:09 PM

Brian, I am experiencing the same behaviour.

Ciao,
Daniele

BrianG · 01.03.2007, 08:41 PM

Well, it seems people running more than 2 poles (like the Neu) seem to have more problems than people running 2 polers...

jhautz · 01.03.2007, 08:44 PM

Oh.. I tought that there was some electrical reason for the difference. Being the electrical guy around here and all.

See what you did... Now not only am I getting used to long fact filled explanations, I'm starting to expect them. :D

crazyjr · 01.03.2007, 08:49 PM

Could this possibly fall into my theory that the mamba max anticipates and trys to match load and timing

BrianG · 01.03.2007, 09:14 PM

@jhautz: Lol. This time the answer was simple. :)

@crazyjr: I really don't know. That might be part of it.

It's like the MM ESC is saying: "Hmm, the rotor didn't turn. I'll just give it more power! Hey, it still didn't turn?! Well, I'll give it all I have!". And if the rotor still doesn't turn, the ESC heats up like crazy and possibly blows.

Don't forget, when a motor's rotor isn't turning, the only thing limiting current is the DC resistance of the coils, which is quite low. A rotor turning through the magnetic field generates back EMF in the coils, which increases the resistance (actually "impedance" when you start getting into AC).

01.04.2007, 01:22 AM

thats wierd, and i have noticed this a litlle bit, but i have no other speend controols to test it with...

thanks for posting

MetalMan · 01.04.2007, 01:29 AM

When I first noticed this with the Mamba Max, I thought "cool!". I have to agree with Serum, it is a neat feature.

hyperasus · 01.04.2007, 03:28 PM

I was curious why my MM controllers feel so much smoother then my BK and MGM controllers. Now I know. Personally, I like the feature. Really hate when my brushless setups cog.

BrianG · 01.04.2007, 03:40 PM

I agree; it is a nice feature, provided the motor isn't loaded way too much or locks for some reason. Then, the ESC simply tries to kill itself to get the motor moving. For this reason alone I like the Quark better simply for better protection during those what-if times. Although, I would have thought the MM would have some type of current limiting feature, but maybe it is set to kick in too late...

I'm curious to see if this action will change if/when Castle releases a firmware revision for different motors.