Smoke! Heat! Fun... (for a while)

[flipwils11]

I feel like such a hack with this car. My priorities are run time, reliability, and speed in that order, but it seems like I can't get much (other than speed lately).

This morning running my gold pan beater with a motor I got from Jeff civilguy on this forum, smoke started coming out the back and that not-so-great burnt electrical smell! Took it in, pulled the motor and put another one from Jeff in, and ran for a few minutes and then smoke again! Damn. I'm in no way saying Jeff sent me something bad, on the contrary, I'm obviously screwing something up.

ESC is an older Novak (early 90's maybe?). Car is fast as hell I'll say so I'm happy with that. Batteries are nicd 5000mh and two 1800mh packs (which don't last for crap). I have this MRC charger I bought which has all these adjustable settings. I've been trying some overnight charges at 1amp but have gone 2-2.5 amps for quicker charges? Sometimes the battery pack that is freshly charged acts like it never charged and takes a dump in the first 30 seconds of driving. This morning the 5000mh pack was running great and the car was a rocket, until the smoke started coming out. Maybe I have the speed setting on the ESC cranked too much?

The nimh packs that we got for my son's RC18MT seem to be very consistent and he gets crazy long run times with that little truck, like over 20 minutes of fooling around in the parking lot or driving through the grass (4wd is nice for a beginner).

For the batteries I guess I'd really like a set it and forget it configuration for charging these things with some consistent run times, and smoke not coming out of the motor would be nice as well. Someone sit me down for battery and charging 101 and esc and motor setup 101 please!

[tulsa]

what tooth spur and pinion? batts dumping quick and motors up in smoke usually add up to the wrong gearing.

[civilguy]

Either that or you're Erich at the VONats.
Adam- tulsa is right. I never thought to ask you what you ended up finding for a pinion. Post up what you have for pinion and spur size. And it's a 6 gear tranny, right?
Sorry you're having such a hard time btw. Both those motors were 27turn and shouldn't be this much hassle.

[flipwils11]

what tooth spur and pinion? batts dumping quick and motors up in smoke usually add up to the wrong gearing.

Just checked, 15t pinion, stock spur I think.

Stock 6 gear tranny.

[civilguy]

I think I had a 12tooth (stock spur) in mine at the VONats, but that was a small track. ygpm coming.

[civilguy]

Adam- here's a really good write-up on gearing ratios: http://www.rcuniverse.com/forum/m_2587132/mpage_1/key_/tm.htm

You just put new tires on, right? So you increased the diameter of the tires over your old worn slicks.
Basically the article says 1-to-1, running circumference of your tires to final drive ratio. People can argue about this method, but it does at least give you a starting point of speed vs torque.
You had 54t spur / 15t pinion (from your pic) = 3.6 drive ratio X 1.9 (internal ratio for the 6-gear) = 6.84 final drive ratio
That means you need about 6.84" circumference tire... which means a 2.2" diameter tire. I bet your new ones are over 3" across, which means you have tons of speed... but at an extreme cost.
You should be more in the 10-11t pinion area-- unless you change spur gears.

[flipwils11]

Pretty much right on. Old tires are about 2.75, new tires slightly over 3". Still don't understand the smoke. Is the 15T pinion a lot of work/load for the motor to keep accelerating? I should maybe weigh the car as well.

[civilguy]

2.75" tires would be 8.6" circ. That's closer to your 6.84 FDR than 9.4" circ. for 3" tires. You probably JUST crossed the line for efficiency with that gearing when you installed the new tires. There's so many things to consider when you change motors, gearing and tires.... most of us learned the same way you did: a cloud of smoke and an acrid stench.
11t pinion/54t spur = 9.3 FDR.... would be a perfect match for your 3" new tires.

[Charlie don't surf]

This might sound dumb, but did you have the motors sitting on/in something that may have had say a few e clips lying around? Diff balls, e clips and small screws love to get as close to the magnets as they can, binding the motor ( or something in the tranny may be binding )

[flipwils11]

This might sound dumb, but did you have the motors sitting on/in something that may have had say a few e clips lying around? Diff balls, e clips and small screws love to get as close to the magnets as they can, binding the motor ( or something in the tranny may be binding )

It's a good question. I'm reasonably confident that nothing is in there because I had them in ziplock bags in my tool box, but maybe I can peak inside.

[flipwils11]

Update on this thread: After some great advice from Jharris and civilguy (including some free pinions civilguy sent to me in the mail, very good guy in the community), she's running great. I'm using an 11t pinion and the stock spur, but as I discovered the motors I had were still toast.

I stopped at the local hobby shop and bought something to get me going, a 12T Traxxas 550 can brushed stock motor. Got it for $26. I explained to the guy that it was an old gold pan RC10 with the 6 gear trans and he swore it would be ok as it's a very torquey motor but doesn't rev as high.

So far so good. The car is a rocket and tons of fun. Best part is this seems to have also cured the short battery life issues I was having. Maybe the old motors were drawing a lot of current? Anyway with my 4500 nicd pack the car runs forever, like 20 minutes of runtime. I've also noticed it's faster with the 4500 than my 1800 packs, even though the 1800 packs run a decent amount of time now with the new motor. The 4500 is just more fun and fast. Something to do with the amount of juice in the 4500 pack (trying to remember my highschool electronics, E=I*R, voltage or "push" as my teacher called it)?

Anyway, no smoke, long runtimes (adjusted my charging settings from civilguy's recommendations so all has been good, 4amps on 4500 packs and 10mv on the peak detection), and just hard on tires!