Mamba Max 5700 in my T2 - RC-Monster Forums

GeeReg · **Mamba Max 5700 in my T2 -** 08.15.2006, 10:30 PM

Just thought I would start off the new subforum. This thing on 3s is amazing. I went from 8 cells to 3s and it's not even close. You can lift the front end at any speed up to almost top speed just by squeezing the trigger. It's very dangerous if you're not careful.

Anyway, I have no idea how to gear something like this other than trial and error. Right now I'm running 84/17 with the T2's 2.6 tranny and Speed Hawgs and I GPS'd it at 52. Everything gets hot after a few minutes but I'm not sure if that's just the voltage.

Every now and then it will cut out though and I'm not sure what that is. For example, I'll take off and ease into full throttle, and it will cut out for a second then kick back in. The only thing I've heard is this, which doesn't apply because it's about 4s:

Shawn from Castle at RCZ

BEC on 4s:
The BEC is a linear regulator, meaning it's taking the battery pack voltage and knocking it down to 5v for the radio system. This "knocking down" of the voltage has a price: the higher the voltage, the more heat the linear regulator chip has to vent off in order to get it down to 5v. Now the chip itself is in no danger - it's designed to thermally shut down (provide no voltage to the radio), cool off (takes about a 20th of a second) and come right back on if things are out of whack. Or even continually cycle in "shut down and come back on" mode if things are REALLY bad with no damage. The issue is obvious - each shutdown is turning off power to the Rx and servo (bad thing) and can look like anything from just a glitch, to totally erratic radio behavior, so the car may be undrivable immediately, or may become so at any time if you haven't disabled that circuit when using 4s. (Again - not covered under warranty and beyond spec at this time!)

RC-Monster Mike · 08.15.2006, 10:52 PM

On 3s Lipo when freshly peaked, it is concievable that you are actually exceeding the rated rpm limit of the motor.
the heat scenario Shawn described is still possible with 3s Lipo as well - if the steering servo is bound for example, it will increase current draw and generate more heat.

GeeReg · 08.16.2006, 08:27 AM

The heat is the only thing I can think of. I don't think it's rpm related because it will do it about 2 seconds after I take off from a stop, so the motor isn't wound up all of the way yet. This is on the street so with all of the grip, maybe it's drawing a lot of amps and having the heat issue? It's no big deal, I'd just like to know what it is.

RC-Monster Mike · 08.16.2006, 08:42 AM

The slight rpm excess won't typically affect anything operationally really - higher rpms are generally going to draw more juice, though. The cutout could be a couple things. If you suspect it is the BEC, disable the controllers BEC and use a receiver pack for a run - if it happens in the beginning of the run, I suspect it isn't heat related(if it happens after running for a bit, it is more likely). Depending on your batteries, it could be voltage drop in the cells, as well. It could also be a servo causing the glitch or a crystal from your radio equipment even. The only way to truly track it down is trial and error.

GeeReg · 08.16.2006, 10:22 AM

Thanks mike. Like I said, the problem is only every now and then and I haven't had the system long enough to work it out. I will try those suggestions though.

Serum · 08.16.2006, 11:34 AM

What cells are you using? it can be the lipo saver that takes hand.

GeeReg · 08.16.2006, 12:14 PM

I am using a Maxamps 6000 3s.

crazyjr · 08.18.2006, 09:13 AM

I had a similar problem with a Novak ss5800, what i ended up doing was to get all wires away from the reciever, all esc wires on the esc side, even the battery wires. I also drilled a small hole in the antenna so i could run tie reciever antena wire into the antena tube without going through the chassis. it worked great till one day i put the battery in the opposite way as described earlier and the interference came back. Not sure how it will work on you're alumnium chassis, but hope it helps

GeeReg · 08.18.2006, 12:46 PM

Hmm, I didn't think it was a radio glitch though because it shows no other symptoms really. I'll try rerouting some wire though. I'm just waiting for a replacement cvd for the universal I bent somehow while driving in a parking lot...:032:

crazyjr · 08.18.2006, 12:59 PM

Also, What radio are you using? I found that JR's don't like brushless, at least Novaks, haven't tried a mamba yet, but tryed different recievers, transmitters and nothing worked till i put a Futaba in it

GeeReg · 08.18.2006, 10:27 PM

I'm using a Futaba 3PM FM.

BrianG · 08.18.2006, 11:11 PM

Quote:

Originally Posted by crazyjr

Also, What radio are you using? I found that JR's don't like brushless, at least Novaks, haven't tried a mamba yet, but tryed different recievers, transmitters and nothing worked till i put a Futaba in it

I'm using a Spektrum DX3 on both my brushless systems, Mamba included, with no problems. I know the servos are actually made by JR, so maybe the Tx/Rx is too? Anyway, just my $0.02...

RC-Monster Mike · 08.19.2006, 05:44 AM

I have a JR radio and just about everything I run is brushless - never had any troubles with it. About the only radio issue I have noticed is a short range when using an Airtronics tx and the UBEC for some reason. My KO transmitter with the Airtronics Rx works flawlessly, though.

crazyjr · 08.19.2006, 09:05 PM

ok, just a thought, maybe my stuff is old. Good thing i'm going nomadio

squeeforever · 08.19.2006, 09:39 PM

I often wonder if I should just save up for a Nomadio or just get a damn Spektrum for my M8 and maybe upgrade to a M11 later since the Spektrum would work with that aswell. Hate to buy the Spektrum and then later get a Nomadio...