MMM V3 safe on 1717?
 

Have a 1717 in a 5T conversion, am looking at either 4s Lipo (High speed Idler) and geared for 30mph or 6s Lipo geared for 35-40mph but worried the stock esc wouldn't handle it, ripple current, MMM 6s = fire etc. Any thoughts? Should I go the MMM XL route? Is that esc safe now?

Did they ever find a way to stop the spark on connection thing? An inconvenience for some, but for ppl with an implantable defib or pacemaker, isn't it potentially hazardous? (or do we have to give up the hobby?)

Ive seen people put the mmm and 1717 combo in buggies truggys and big mts without problem.. id imagine youd be able to run it without problems

If you used castle caps and a bec that would help the esc.

I take it you don't like Brian's no spark idea?

And mechanical brakes! that helps.

Brian says that CC says not to use a resistor on a Mamba esc. If I remember correctly, it's been stated that it's Ok to use it on a Mamba if the esc is turned off when you charge the caps through the resistor - then turn the esc on.

That's correct -- you MUST have the switch in the "off" position when powering up the caps through the resistor.

Otherwise the motor beeping THROUGH the resistor can damage the ESC over the long-term.

Is the No-Spark resistor safe to use on the Mamba XL2? Reason I ask is because obvoiusly there is no switch...and the large spark you get plugging in the bullets damages them over time. And the large spark form the caps charging is quite un-nerving! I prefer the nice quiet No Spark resistor vs the large "CRACK" I get without using it. But if it is damaging my XL2, I will quit using it. The longest I leave the no-spark resistor plugged in before pluggin in the power wire is probably 1 second. I plug the power wire in right away. Let me know. Thanks Patrick. -Kirk

XL2 is OK for use with a resistor - -just not Mamba Max Pro or Mamba Monster.

What ohm resistor are you guys using...placed in series with the positive side or parallel? I think XPS sells one...

1 ohm. 5 watts minimum.

Series or parallel?

series

Ok so I can use a no spark thing on the XL, that's good to know, so am I to take it that the consensus is that the 1717 on 4s Lipo using the high speed idler is less than ideal and I should go 6s, gear more conservatively (say 35-40mph) to keep the amps down? Won't I then perhaps have the issue of an undergeared brushless motor running hot?

I guess I'm going to have to amend that page. I knew about using the resistor as long as the switch is off, but didn't say that on my page because I thought it was a "secret", and didn't want Patrick mad at me. :lol:

fastbaja5b: The 1717 is pretty low kv for 4s. To get any kind of speed, it has to be geared up, which does draw more current. So yeah, I would run 6s and gear more conservatively. And undergeared motor doesn't necessarily run hot - I find it's more about running the motor at WOT for extended time at any voltage. It just seems motors "like" more partial throttle running with limited top speed running. Probably something to do with how the PWM signal plays with the motor coils...

Ok, silly q time, we say the esc has to be in switch off to use the no spark (makes sense) but my XL2 has no power switch (that I can see) so how does that work? Can I therefore not use a no spark resistor?

Check out post #7

Ok so I know the sequence to plug is connect neg, connect non spark, connect positive but then do we disconnect the non spark resistor or do we leave it plugged in?

You can safely remove the non-spark after you have charged the caps up and plugged in both the neg & pos battery connectors.

Would it be easier to just get a small switch of some sort.
Mount the switch on the R/C and plug the hot wire side into the switch.
Plug battery on other side of switch.
When ready just throw the switch and no spark ready action.
Just a crazy idea.

If I'm reading that right, it's not a good idea. For one, you would one very large and robust switch to be able to handle the current requirements. Second, there is still a spark, it's just happening inside the switch.

here's the info I found on spark arrestor resistors

http://scriptasylum.com/rc_speed/nospark.html

http://rc.runryder.com/helicopter/t547501p1/

They seem to suggest keeping it hooked up and say that electricity like water will take the route of least resistance and therefore the resistor hooked up doesn't matter.

I haven't messed with a resistor yet...will be a while as my XL2 crapped out

A quote from the no-spark page on my site:

In replying to your first question, i have the same query as you do (MMM + 1717 = safe?), although i have run it on 5S in an extended Savage Flux to XL length just recently (in my separate build thread), maybe couple of runs only. I would really like to go to 6S although have my fears. Done my homework and searched a lot, and only got mixed opinions. Essentially i firmly believe that it all come down to the gearing and the weight of the truck/car; may try to gear down a tooth or two om my pinion and try 6S.

Given the same setup would going from 5S to 6S add more amp draw? or the increased voltage would give the more power at roughly the same amp draw?
If I recall correctly the 1717 was offered as a package with the Mamba Monster on the same page, does it mean anything, i dunno. also searching for the answer.

Might do as others have done and get myself a MMXL.

Well got a resistor, this one do the job for 6s?

Will use a 2mm bullet plug to hook it up between the positive leads on the esc and the battery next to the 8mm bullet plugs I am using to connect the ESC to my 6s Lipo.

The Mamba Monster will do fine, it is just crucial to have quality lipos and connectors.

10 watts is a little large, but won't hurt anything, just be more difficult to install. 1 ohm is perfect for 6s though...

Sorry to bring up an old thread, but I figured it was better than just starting a new one that basically is related.

Anyway, just some background info I am hopeful will help.

I have been toying with with the idea of doing one of those 5SC Flux style conversions (though in buggy form) using a TCS or Alza Racing conversion to an HPI Savage Flux. I am thinking right now of using 6S setup, possibly with the MMM and 1717 motor combo, maybe even that new traxxas MMM and the XO-1 1717.

Anyway, I wanted to know a few things first:

- I have heard of people running external BECs, however, if that for some reason fails, does it usually send all the voltage to the servos, receiver, etc? Would it be better to run an external receiver pack in that case instead if you have this concern? If so, has anyone done this and what did you need to do to get your wiring correct?

- Sorry if this is really easy info here, but I am still trying to wrap my head around it. So, for 3S dual lipo use in series with the MMM, do I need to worry much about the whole spark thing or is it more so when you have greater than 4S going through one connector?

- For dual 3S lipo use to total 6S in series, are the deans connectors still useful or are they out of there element and should a different one be used? (I am assuming they are based on what HPI is doing with there 5SC Flux)

- What is different between the traxxas XO-1717 and the original 1717 motor and can you use the traxxas one fine in offroad?

- Any thoughts on the new "extreme" MMM? Is it worth looking into or is the MMM sufficient for what I am looking to do.

- Lastly, would a 1520 motor be a better selection than a 1717 in your opinion in a 1/5 "Flux" style vehicle? If you feel so, can you state why?

Thank you everyone before hand for any help you can provide. I really appreciate it.

1: Yes, ANY switching BEC can fail like you describe, although it happens more if you are pulling larger currents which stresses it more. A receiver pack is obviously better in this regard, but is just one more thing to charge up, and I would personally use a 2s LiFE pack instead for flatter discharge curve and higher capacity.

To use an external receiver power source, you'd simply remove the red wire from the ESC's throttle cable. This will keep the ESC's BEC from powering the servo/receiver.

2: No matter how you arrange it (1x6s, 2x3s, 3x2s, etc), a 6s pack will have the same amount of spark. And whatever connector type you use, the spark will happen on the last connection you make.

3: According to Patrick (Castle pres) the Traxxas 1717 has slight design changes for faster spool up and higher efficiency at higher currents. Kinda makes sense in an on-road vehicle that is geared stupid high.

4: By "extreme MMM", do you mean the MMM included with the Traxxas XO-1 or the one for 5th scale? The XO-1 ESC has two main differences: has the speed lock-out firmware which requires the iDevice to unlock and has an additional capacitor bank. Personally, I would just use a regular MMM and add some capacitors to the power leads.

5: Not sure really but the 1717 does have a slightly higher continuous power rating. Either motor would probably work well.

Thanks for the info Brian I appreciate it!

Definitely give a regular MMM a look again then.