Mamba Max Tweaks and Mods Continued
 

(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!

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...

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!!!

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?

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

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.

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.

The swines....

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

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...

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...

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

Yah, I just read somewhere that thermal cunductivity and electrical seem to hand in hand (rule of thumb). I guess gold is a real good thermal conducter too but that's a little too much *bling* to sneak past the wife....

Truthfully, these ESCs don't dissipate THAT much power where a degree or two of cooling won't make too much difference. Aluminum is cheap, easy to work with, light, and easy to get. Works fine for this application. Things like CPU cores where thermal concentration and high temps are present can benefit from any increase in cooling performance. Depends on application really.

Cool (literally :) it should be easy enough to find an aluminum heatsink for my setup. Of course I have found some promising copper PC heatsinks I would just have to cut to size... and the e-mail I sent to a heatsink mfg to inquire about cost for something custom. Guess I'll give it a few days.

Speaking of heatsinks I have hopes for a replacement end bell (MM 5700kv) that would cool the motor too but I suppose I should go start another thread for that so we can keep to the "MM tweaks and mods" here.

Yeah, if I don't have a heatsink I can hack, I usually look around for something that will work. Sometimes, computer liquidation stores will have P2 heatsinks which usually cut up kinda nice and are fairly low-profile. Also, electronics surplus places usually have sinks as well.

Cooling the motor would be better done by using a heatsink that goes on the can part. Fairly cheap clip-on styles can be found on eBay.

Opened an new thread for the motor cooling... fit issues with the xxxt tranny.
I'll start looking for a p2 heatsink, no surplus around here but I have ebay open in another window right now ;)

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

I've got the castle link. It;s just that if I turn the boards vertical with the motor leads coming out the top the data port will be pointing straight down. No big loss realy, it will stay dirt free that way.

Right but the Castle link uses the servo plug to program. I think all the brushless Castle creations products and BEC can be programed with the link. I've never tried in on a Mamba but it should work.

Ohhhh.... now I get it, like my CC BEC. that cable I do not have yet but it's not expensive. Thanks a bunch, I'll look into it.

Here are the photo's of the boards. I will post more as the project progresses.

http://photos.imageevent.com/drknow6...;20640x480.jpg
http://photos.imageevent.com/drknow6...%20640x480.jpg
http://photos.imageevent.com/drknow6...%20640x480.jpg
http://photos.imageevent.com/drknow6...%20640x480.jpg

You can see better photo's at http://imageevent.com/drknow65/rccarstuff

About the programming port; you should be able to move to to any place you want; just use shielded cable and a chassis mountable USB port. That should not be a problem. But since it works with the old-school programmer, why bother?

btw; for some odd reason the images aren't working. The link to your site does work however.

I don't get it with the pictures, they worked for a few hours then stopped.

I'll use the castle link to tune the esc as I have to get one to set the voltage on the CC BEC anyway. Besides it's a good oppertunity to buy something I need from the RCM store to support this site, which in my opinion has a value all it's own.

I was pondering the "wind tunnel" setup for the esc boards (actually made a 3d model out of folded paper to set in the car--- I'm how old? hehe) it occured to me that I wouldn't get any cooling air flow on the channels of the heat sink that are pointed directly at the hub of the fan.

Do you think a mesh screen say 4mm from the fan would difuse the flow enough to keep the coverage even?
Mabe if it was concaved (funnel shaped) with the center cut out- say the same diameter as the fan hub? Any ideas on how to difuse a 25x25x10mm fan in the shortest length possible without excessivley restricting flow would be welcome at this point.

Also are there caps available that will do the same job as the 3 330uF 35v caps but take up less space? I could also see the caps restricting flow but I don't think it would keep the "wind tunnel" from working. Just curious...

Don't know about the other questions, but the caps are pretty much standard size. You don't want to go down in either voltage or capacitance value. As a matter of fact, some people add more caps (usually on the power input wires as close to the ESC as possible) to improve performance and to reduce stress on the existing caps.

There's no super porcelin capacitor gizmo's? I understand about the capacity and voltage ( as per GriffenRU's posts) and the solution I have in mind now is to run 3 220uF caps on both sides of the power board (440uF per leg) laid back to parallel the heat sinks. Just figured if there were more options...

Well, you can use smaller ones, just more of them. Capacitance value is additive. Two 330uF caps (660uF total) is the same as three 220uF caps. It's actually better to use more caps as it spreads the heat out a bit and each cap doesn't have to work as hard. As long as you meet or exceed the original total capacitance value, you're ok. Unless you are like ZeroPointBug who decides to solder a bazillion caps on his ESC. :na: :wink:

I do plan to solder two 470uF caps to the steering and esc power wires, but that's to help keep voltage and EMI in check.

Then there's the three 1800uF caps I'm putting on the esc power wires on the opposite side of the chassis (more as something useful to help balance out the weight of the esc, extra heatsink, and fan combo). I'm going to mount the reciever, CC BEC, and 4S DPM opposite the esc too... Starting to think I may need to get 1/8th scale springs for my XXXT.
Mabey me and ZPB need to go to a caps anaymous meeting ;)

WTF?!?!?:diablo: my pic's are working again???:intello: wish I knew how to keep them going.:neutral:

I'm looking into thermally conductive padding right now to protect the MaxAmps 8000hv that finally showed up today.

OK overkill, waaaaayyyyy to expensive to go with the whole thermal pad idea.

Ok, heres some update photos. I found some heatsinks when it clicked to talk to the gal who does my computer stuff for work. She had a few to choose from.
All of the cpu coolers were way to thick at the base even if I did cut down the fins, but I did find a nice on off a vidoe card.
The copper was too heavy and I ended up with an aluminum unit. After being cut in half and trimmed a bit it's a PERFECT fit... so pleased.
It is a little tall at 10mm but that's also a fix for my fan flow/dead spot concern as with the 3.5mm board between it's 23.5mm so the fan should blow directly into all the fins fairly equally.
http://photos.imageevent.com/drknow6...4449%20640.jpg
http://photos.imageevent.com/drknow6...4451%20640.jpg
http://photos.imageevent.com/drknow6...4452%20640.jpg
http://photos.imageevent.com/drknow6...4455%20640.jpg
http://photos.imageevent.com/drknow6...4458%20640.jpg

As always you can also view the pic's at http://imageevent.com/drknow65/rccarstuff
now I just need to order the caps, fans, diode, shrinkwrap, and wire...

to be contunued...

sounds good, what caps did you decide on?

I'm going to keep the 330uf 35v caps for the board like GriffunRU suggested, would have gone with bigger caps or doubled up a 220uf for each leg but I think it would restrict the air flow too much. The 3-330uf caps are going to get mounted parallel with the center-line of the board horizontally, that will let the air flow straight from the front fan (blowing in) thru the heat sinks and straight into the back fan (pulling out). I am going to run 4 1800uf caps in parallel for the power supply of the board on the opposite side of the chassis- more for balance than actual function as GruffenRU thought 1 would be enough.

I have reconsidered only using thermal grease and no adhesive as I am concerned movement in the sink/board/sink/board pack might slowly displace the grease. So I'm going to go ahead and put adhesive on 1/2 of the outboard fet's to keep a good mechanical bond between the board and sinks. like Griffen did on the bottom plate style sink on his modded MM.

The total forcast cost of the esc mod (not including the $11 solder sucker i bought for this project) is $54 save the wire and deans connectors.

MM esc/5700kv combo $130 (used ebay)
XXXT roller $67 (used ebay)
Maxamps 8000hv 2s2p batt $147 (new)
CC Bec $24 (new)
Z9100S jr servo $114 (new)
Esc mod parts $54
Wire and connectors $57 +/-

Total cost to spank the neighbors PRICELESS hahaha ($600)

not bad considering almost half that is the battery and servo.

Gotta love the fact that you paid almost as much for the servo as the esc/motor. Not sure why you opted for a servo with that much power, a futaba 3050 or hitec 645 would work just as good on a 2wd vehicle. I actually have run a futaba 3003 ($10) on my stampede and cannot tell the difference to a 645. The only benefit is the metal gears as they can take a hit better than the plastic.

Lincpimp,
I wanted a fast jr metal gear servo (have had good luck with them) the z9000s has .06/128oz.in at 6v and found a few for $114, then found the z9100s .06/188oz.in for the same price. Figured it was overkill but there aren't that many MG servo's that will do .06sec. If I find that it's too quick or too strong I can always slow it down and adjust the end points with the 3pm-2.4ghz radio.

GriffenRU,
I finally got around to drawing up the wiring setup for the electronis. I did it by hand and you'll have to look at the website photo to desipher it. Sorry for the sloppy writing but if you note my signiture I have issues with the quality difference between what I invision in my head and what I can actually get onto paper... I have a good drawing program and a turbocad mechanical program but it would take quite a bit longer.

Anyone is welcome to look at it and let me know if I'm missing somthing or have a better way of keeping out RFI/EMI?

I am still flip/flopping on wether I will "tee" off the red power supply as illustrated, or run the batt power straight to the ESC then loop back to the 1800uF caps, BEC, ect...

Also I'm going to power the ESC fans with the ESC's internal BEC, I know when guys use the MM over 3s (11.1v) they disconnect the ESC-BEC from the receiver. Do you think it would still work for the fans at 4s? Or do you think it should be run by the CC BEC? I'd like to keep all the ESC (and fan) circuits isolated from the radio/servo items.

Too small version,
http://photos.imageevent.com/drknow6...0001%20640.jpg

Good version, you'll have to click on "original" when you get there to see it clearly...photo #17... then click "original"
http://imageevent.com/drknow65/rccarstuff

By using the internal BEC on 4s, youre probably going to create more heat than the fans are removing. Theres no reason your external cc bec couldnt handle the fans along with the radio/ servos.
But now Im confused, I thought you were planning on running 2s? And now Im also confused as to why you need to do all this cooling work to run a mm/ 5700 on 2s.

The cooling stuff is preemptive (spelling?). I will be running 2s regularly, then when I've got a handle on that I would like to step up to 3s, then when I've got that down (way down the road), I'd like to step up to a better motor (neu or the like) and run 4s... but I'd like to not have to make any more mods from one step to the next. I'm also likley going to copy most of this work when I start converting some of my nitro 1/8th scale RC's later.

The CC BEC would handle the fans and the steering servo no problem, I was just hoping to keep the CC BEC power circuit entirely away from the esc/motor leads.

I had planned on doing the small plate sinks on the "brain" board anyway, suppose I could get a cheap 4s battery on ebay now to test the heat output of the ESC BEC running the two fans (not running the motor of course) just to see if it get's very hot. They have some really cheap 1200mah 4s lipo's on ebay all the time.

The only problem with running a switching BEC for 2s and 4s is the drop-out voltage. Switching BECs can require up to 1.5-2v higher than the BEC voltage. 2s is pushing it and the system won't be getting a solid 6v. It will still operate though. A UBEC is required for anything above 2s though.

The castle creations battery eliminator circuit (CC-BEC) is a switching unit right? Does this mean I won't be able to run the servo at 6volts when I'm using a 2s battery, as the internal ESC-BEC puts out 5volts and the CC-BEC could drop as much as 1.5volts? And it's not ok to run the radio and servo at 7.4volts correct?

Is there a ubec that will provide a constant 6.2volts while running a 7.4volt 2s battery (the voltage cutoff will be set for no less than 6.4volts to protect my lipo battery investment)

I think I also spoke too soon about running the fans on the ESC-BEC, for the cost of a pair of fans $22 to go to 12vdc fans and a voltage regulator that wouldn't work at 7.4volts v.s. a second CC-BEC $24 I think it would be more universal (2s,3s,4s) to keep 5vdc fans and add the second CC-BEC inside the ESC pack, that way if I wanted to run a third fan (motor cooling) I could just put a third pair of CC-BEC power output wires going to a connector outside the ESC pack. {read dedicated CC-BEC mounted inside the esc to run all 5vdc fans at all pack voltages}

I'm starting to feel like I'm straying from the MM tweaks and mods a bit but since these components go inside the esc it's not too much of a strech right? Or should I start a different thread about BEC stuff?