Mamba Max Tweaks and Mods Continued

[DrKnow65]

(first post here, I will try now to be too lengthy with follow ups)
I recently purchased a used Mamba Max 5700KV system intended for my also newly purchased used Losi XXXT (ebay goodies). The XXXT was in almost new condition, the MM was just the opposite... and needed imediate attention.

I have been reading for hours on end about the different brushless ESC's and settled on the MM. I found huge volumes of information here at MRC, so I was prepared for some of the issues with this system. I was hoping by buying a used (older) MM I might get a better quality unit as I have heard the manufacturing hasd gotten poor in recent times. (I have read that) This is the second generation controller (newer style FET's).

The unit I received would have been a severe disappointment had I not read and pondered the original "Mamba Max Tweaks and Mods" that is I believe in the temporary site? That thread prepared me for opening up the unit, seperating the boards, and dealing with the (extremely) poorly mounted heat sink. ( I could see gaps between the FET's and heat sink with the ESC still assembled )

So now we are here--- pic's to follow when I figure that out...

I have seperated and cleaned the boards, last owner must have driven (or submerged?) the car in mud. I did make sure it functioned befor tearing down.
Removed the factory 13awg wires in preperation for new 10awg's. Removed the original caps. Removed the heat sink and adhesive. And prepared the boards for re-assembly.

Here is where the new thread comes into play.

I would like you opinions of where to go from here with what I would like to have when this project is complete. The goal for the XXXT/MM combo I will run is fairly simple. I want a reliable, glitch free, efficient, yet powerful 1/10 scale truck to run at the local track (no ROAR BS) in multiple classes (stock, mod-6 cell brushed, and lipo brushless), and general make my budies look bad bashing when it's too quiet to run nitro. Yes I still run nitro, I started electric then when to nitro and now I'm back to electric...

I have a MaxAmps 8000mah 7.4v on the way, new Imax B6 charger, my 3PM-2.4Ghz fasst radio, a JR Z9100S servo for steering, and the already mentioned MM 5700KV system (that I will run 7.4v and 11.1v lipo's and IB4200 nimh 6-cell packs with 24degree stock brushed, 19T brushed, and of course the 5700KV brushless with the possibility of other brushless cans later).

I plan on configuring the MM differently in a new enclosure (original looks like it was used for a motor guard). I will mount boards vertically, extend the bus wires between the boards so I can run 6.5mm copper heat sinks on both sides of the power board (cool all the fets's equally). and run 25mm fans in a pusher/ puller setup vertically. I think the combo will come out roughly 89 grams, 75mm long, 29mm tall, and 27mm wide). Basically it will look like a brick with fans at both ends and the part of the power board that the motor/ battery wires connect to coming out the top (like a mohawk) front to rear.

Now the questions...

1) Is there a way to move/extend the data port to get it to point up (or out the same side at the motor leads, thinking of the original unit)?

2) When upgrading the 3 caps on the power board is it necessary to keep them 330uF? or can I go larger or more? will that help heat, efficiency, or RFI?
(refer to MM tweaks and mods)

3) Will extending the bus wires between boards have a negative effect?

4) Can I use 3 6800uF caps on the opposite side of the chassis on the battery circuit to help with supply voltage/weight balance?
(also refer to MM tweaks and mods)

5) I plan on using a CC BEC, shielded wires for signals from receiver, and a FMA 4s DPM... Can I shield the "3 motor wire group" (common ground for all shielding) also, or will that inductive current turn the rest of the shielded wire into an antenna increasing the glitch potential as opposed to decreasing it?

More questions later as they come up. I will try to get pictures up soon.

I would like to thank all of the guys here at RCM and especiaaly those of you who posted in the original MM tweaks and mods thread...

GriffenRU being at the top of the thanks list!

[DrKnow65]

6) forgot to ask, will using caps that are closer to the battery voltage (7.4v-11.1v) be more efficient than higher rated caps with the same volts? say 16v caps vs. 35v caps...

[brijar]

About the only thing I can answer is the question 6. Using caps with a smaller voltage doesn't really help electronicaly, but will just make them smaller. I think it would be safe to use smaller voltage caps, not sure about more UF, but I can't really see why it would hurt the ESC if the caps could hold the voltage longer.
I'm not a complete expert, so don't do anything untill you hear from BrianG. He should know a lot about the caps and interference etc.

Brijar!!!

[GriffinRU]

Originally Posted by DrKnow65

6) forgot to ask, will using caps that are closer to the battery voltage (7.4v-11.1v) be more efficient than higher rated caps with the same volts? say 16v caps vs. 35v caps...

In general caps must be rated at list 25% over max operational voltage. In case with BL motors you need to add BackEMF...

With proper technique you can reduce 25% margin to 5%.

For the rest:

1. No
2. No ( I provided the link for the proper replacement, what's wrong with that part? )
3. Yes, very bad
4. Yes, as long as wires are short, and caps connected on ESC side of power connector.
5. Can you draw (schematic or smth) of what you planning to do?

[DrKnow65]

GriffenRU, thanks for the reply

1) bummer, guess I'll be removing the ESC when I change the settings

2) nothing wrong with the part you listed, just thoughtif I was changing the case size I could go to bigger caps (got the impression this was somthing you wanted to do but decided to keep the original size (different spec's) caps to fit the case. I was hoping bigger fets would help with efficiency

3) an additional 6mm too much? I'd like to be able to heat sink both sides... How do you do it on your mod with 2 boards?

4) cool

5) will draw something to post asap, I don't think my "idea book" is quality enough to help someone else see what I'm thinking...

[GriffinRU]

Originally Posted by DrKnow65

GriffenRU, thanks for the reply

1) bummer, guess I'll be removing the ESC when I change the settings

2) nothing wrong with the part you listed, just thoughtif I was changing the case size I could go to bigger caps (got the impression this was somthing you wanted to do but decided to keep the original size (different spec's) caps to fit the case. I was hoping bigger fets would help with efficiency

3) an additional 6mm too much? I'd like to be able to heat sink both sides... How do you do it on your mod with 2 boards?

4) cool

5) will draw something to post asap, I don't think my "idea book" is quality enough to help someone else see what I'm thinking...

3. 6-10mm would be Ok, it wasn't clear how far you want to move brains board from FET's. :)
I have the same brass plate as with mod 1, but to improve heatsinking, I do polish FET's and brass plate on sand paper. Do not try too hard on FET's...

Originally Posted by DrKnow65

1) Is there a way to move/extend the data port to get it to point up (or out the same side at the motor leads, thinking of the original unit)?

Well you can't move it but you can program with the Castle link.
http://www.castlecreations.com/produ...stle_link.html

[DrKnow65]

3) basically like your double decker setup but with a sink in between.

[suicideneil]

How big (or small I should say) is the gap between the two boards 'stock'? I think when doing thermal mods to the Quark125b it was decided that so long as one fet board is cooled efficiently, the other will be okay (knock-on effect?). That, and your 'wind-tunnel' cooling/case idea sounds rather wicked, should have a big impact on temps by itself.

[DrKnow65]

Almost no gap. There's a peice of paper that just seperates the brain from the fet's... I would be good with the brass plate sink GriffenRU used, but they cut the bus wires off too close.

[suicideneil]

The swines....

[DrKnow65]

well, would I expect more of my kids? wounder how long IS acceptable?

[DrKnow65]

Awesome! Now just fo find the perfect copper finned heat sinks (6mm tall, 24mm wide, and 32mm long- with the fins running along the length). What grit sand paper are you using? I do plan on using the new arctic MX-2 since the the whole esc will be held togeather by the case. Then I could open it back up and mod it more later without dealing with the thermal adhesive...

P.S. why use brass as apposed to copper? copper is a better conducter right?

I was also thinking about stacking copper tubing 2 high (like a honeycomb) and gluing them togeather with the arctic silver then MX-2 to the fet's. would that be effective or should I continue the persuit of somthing finned? Not sure of the purity of copper tubing...

[GriffinRU]

Originally Posted by DrKnow65

Awesome! Now just fo find the perfect copper finned heat sinks (6mm tall, 24mm wide, and 32mm long- with the fins running along the length). What grit sand paper are you using? I do plan on using the new arctic MX-2 since the the whole esc will be held togeather by the case. Then I could open it back up and mod it more later without dealing with the thermal adhesive...

P.S. why use brass as apposed to copper? copper is a better conducter right?

I was also thinking about stacking copper tubing 2 high (like a honeycomb) and gluing them togeather with the arctic silver then MX-2 to the fet's. would that be effective or should I continue the persuit of somthing finned? Not sure of the purity of copper tubing...

Start with 220 grit, finish with 500.
Brass is easy to find.
I don't think that finned copper heatsink required for our application. Just copper/brass plate on the bottom and stock heatsink on top, with FAN should be good up to 150W of dissipating power ~80 Degrees C. You can stick brass plate in between top FET's and Alum heatsink, but that would be just a caviar :)
You need to make entire sandwich work for your heat spreading needs - brass/copper plates/FET's/PCB/FET's/Top heatsink. Brass/Copper for speed and Alum/PCB for mass (Cp).
And, yes you can ran FAN from internal power, just keep it under 100mA and solder on capacitor.

[squeeforever]

I'm certainly no expert, and may be wrong, but I don't think conductivity has to do with heat dissipation.