Heat?!? - RC-Monster Forums

10:04 PM

Castle Creations Mamba Max & 5700 CMS Engine installed 2 weeks ago, didn't run it til I got a 3s lipo from maxamps today... put it on the truck and took a couple quick cruises up and down the block... after about 5 mins or so... truck started sputtering a tad during accelerations from stops... and eventually stopped making attempts to move at all.

I took it down to the shed figuring the pack might not have been fully charged when sent to me... put it on the charger and when charged took it out again. Couple cruises up and down the block... still have yet to hit full throttle... when I goosed it and wheelied the truck.. when the front tires landed... I could hear the ESC beep at me... then had little jerky movements from the truck. I remember these movements from when I had first hooked up the engine and when re-aligning the wires forgot to connect the white wire... it needs all three or it jerks a little... figured a wire came loose...

I picked the truck up... engine kinda hot... burned my hand a little and on returning to the work bench and lifting the body off... noticed the male banana clip on the black wire must have heated to the point that it melted the solder... a splash of solder was put on the body when the wire jolted loose.

Engine runs fine after resoldering the connector... haven't done any damage that I can tell. But I assume this heat isn't normal. I have timing set at it's lowest setting... 19 or 21 tooth pinion, 86 tooth spur with slipper clutch (that's another thing I noticed... the smell of burning brakes/clutch when I picked it up this afternoon after the first run)...

what else can I do to keep this heat down? I have yet to reach full throttle... and have only had 2 5-7 min runs...

skellyo · 11.06.2006, 11:10 PM

19:86 is probably a bit too much for a 5700 on 3S. I'd start with a 15 or 16T if it were me.

MetalMan · 11:20 PM

"Burning" is a relative term when it comes to these motors. To your hand, burning hot might only be 130 deg. F. These motors can be taken to ~180 deg. F before damage is done. So, your motor could be running at a temperature that is fine. You could get a temp gun so that you know the actual temp.

EDIT:
I agree with skellyo, 19/86 is quite high (the estimated speed would be ~53mph, a bit high for normal driving). Taking it down to a 15t pinion would still make the truck run at about 44mph, but should drop the temps a lot.

BrianG · 11.06.2006, 11:25 PM

If you're melting solder from the current draw, there is probably a bad solder joint. This creates a resistance, which drops a voltage, which creates heat. Not to mention your system is not getting the voltage it wants due to this voltage drop...

glassdoctor · 11.06.2006, 11:52 PM

I think the only way to get wires hot enough to splatter solder like that is a short of some kind... whether in the external wiring or inside the motor/esc.

When/if the esc cogs from a dead stop and just sits there clicking... this is like a short and wires will heat up very very fast. I have seen this before.

Something is not right... even with tall gearing, etc it should not heat up to the point of desoldering wires. Maybe the motor is bad or has been damaged by a short, like when you had one of the wires unplugged. If the bare wire touches the wrong thing it can damage the motor or esc. I have seen that once too....

Solder melts in the 400+ degree range..... well beyond what we "should" see under any use. Although I've seen brushed stock motors come unsoldered...........

11.06.2006, 11:48 PM

because of the slip clutch traxxas has in the truck... I have a pile of 32 pitch pinions that would be perfect... problem is... the spur gear is 48 pitch.

I don't know if I can find any smaller then the 19 I have on it... have to do some looking around.

Quote:

Originally Posted by MetalMan

EDIT:
I agree with skellyo, 19/86 is quite high (the estimated speed would be ~53mph, a bit high for normal driving). Taking it down to a 15t pinion would still make the truck run at about 44mph, but should drop the temps a lot.

11.07.2006, 12:19 AM

my ESC is surrounded by a wooden box and plate I made for my truck. The fastlane machine chassis I have had too many open spaces for any type of securing of the ESC, so I made a wooden plate for over it. Kinda stupid to cover up that beautiful aluminum, but I bought it mainly for strength... plus with the mamba and motor in there... it moves to fast to be seen LOL!

I will double check tho where my wires run threw the aluminum shock tower, make sure there is no contact there... might line those holes with shrink wrap or possibly some foam insulation where they pass threw.

Tazz · 11.07.2006, 10:08 AM

Robinson Racing has them from 12t-35t. Go to the second page of the link for the RR pinions.
http://www2.towerhobbies.com/cgi-bin...on&FVPROFIL=++

rchippie · 12.10.2006, 07:06 PM

I just ran my MBX5 with the MM for the first time today. The motor is a 7xl with 14 cells. The gearing is a 46t spur with a 13t pinion, the temps were 95- 100 for the motor the speedo got a bit hotter around 180 +, with out a fan. Is this a good gear or should i change the pinion & add a fan ?.

crazyjr · 12.10.2006, 07:51 PM

Quote:

Originally Posted by rchippie

I just ran my MBX5 with the MM for the first time today. The motor is a 7xl with 14 cells. The gearing is a 46t spur with a 13t pinion, the temps were 95- 100 for the motor the speedo got a bit hotter around 180 +, with out a fan. Is this a good gear or should i change the pinion & add a fan ?.

Glad to see you got it going

rchippie · 12.10.2006, 07:53 PM

Quote:

Originally Posted by crazyjr

Glad to see you got it going

Thank's larry i took the switch off the ubec & it started working.

crazyjr · 12.10.2006, 10:15 PM

Quote:

Originally Posted by rchippie

Thank's larry i took the switch off the ubec & it started working.

I hate power switches, I take them off any racer i got

MetalMan · 12.10.2006, 07:20 PM

That gearing sounds great! If the motor stayed so cool, I wouldn't touch it. A fan certainly would help the ESC, though.

rchippie · 12.10.2006, 07:33 PM

What is the normal operaiting temp range for the ESC ?.

MetalMan · 12.10.2006, 08:27 PM

Quote:

Originally Posted by rchippie

What is the normal operaiting temp range for the ESC ?.

I think the thermal protection kicks in at 200-220 deg. F, so pretty much anything below that is okay. However, it will operate better when cooler, as the resistance of the FETs increases as the temp. increases (decreases performance). Also, heat generally is not good for these components when it can be helped.