mm + 4600 motor temp near 200 with rustler

Is there any reason the cms4600 motor should approach 200 degrees on a rustler with 13/90 gearing and stock 2.2 tires running a123 3s batteries. The esc stays around 120 tops I believe. Batteries barely warm.

I've asked on other forums and even talked with Thomas at Castle a few times on the subject and nothing has brought down the temps. The old 4600 was just replaced with a brand new one by Castle (excellent support I gotta say), gearing was changed to 16/90 and 20/90 to see if the 13/90 was simply undergeared, but the temps rose even quicker than using 13/90. I have the stock plastic transmission housing and no heat sink to help spread the heat. I drive it at the clay rc track almost non stop except for battery changes and some other delays. After the first 15 minutes temps get to 160 then every pack afterwards is in the 180 - 200 range. There is no binding in the transmission since the car easily rolls down even the slightest incline.

I have another mm with vxl motor on the way from an ebay purchase so I plan to try out the vxl with my current esc first. Then will swap out the esc if the vxl runs hot. Any other suggestions?

[MetalMan]

Have you by chance tried a different battery combination? If not, it seemse it's the only thing you haven't listed.

13/90 is quite undergeared - that's a theoretical 26mph, and the motor's going to want to push out at least 35mph on that voltage, which would be with an 18t pinion. But since you tried pinions around that size, I just don't know.

How about timing on the ESC?

And welcome to RC-Monster!

[pullinteef]

I also think you are undergeared. I was running a MM/5700 in my B44 geared 14/84 for a while, and things ran hot. I tried going to a 16 pinion and as you noted, things got relatively hot even faster, but I did not really test for long enough to see if the temps continued to rise. Finally I did some testing and went to a 19 pinion and everything ran much cooler, and had nicer top end. Turned out I was way undergeared (about 30% too low on the pinion. I would just try even higher pinions for a short time, testing the temps every minute or so just in case.

[DwightSchrute]

yeah, definately ungeared. my 5700 ran hot on 90/16, in the 185-190 temp range, and at 86/19, ran about 145.

after you gear up, you might look into a motor fan as well...they work great on the mamba and feigao motors.

I like this forum already - you guys are quick! I haven't tried any other batteries for an extended time because I get lazy and don't want to swap the pinions around when I stick the 2s lipo pack in there. I've stuck to the 3s a123 because that is what I want to use long term due to ability to quick charge. If I were just racing at the track with two 7 min qualifiers and a 10 minute main with an hour between each session I'd be ok with 2s lipo. But when I get out to the track I usually run for a couple hours solid and need the 3s a123 ability to quick charge using a standard 12v supply.

I can run the car onroad with top speeds around 40 (not sure if that is with 13t or 16t, forgot what is in there at the moment), but it was clocked by someone with a radar. Onroad the motor will not get nearly as hot as it does at the track.

20/86 is the tallest combo I've got to try I believe. Thats got to be well over 50 mph at 10v. I'll have to set my epa at 70% if I am going to use the full trigger.

Is there a motor heat sink without a fan that is going to fit with the rustler transmission... and actually work to bring the temps down? I like the 16t speed and feel - just don't want to ruin my motor or have to constantly check the temp.

Oh, timing is set to minimum, punch control at 50%, no drag braking.

Thanks - Chad

Is there a motor heat sink without a fan that is going to fit with the rustler transmission... and actually work to bring the temps down?

Wow, surprised nobody recommended the fastlane transmission case. It's not a heatsink, but it is solid aluminum that will dissipate heat, and open up the motor area to let it breathe. Only problem with that is it leaves your motor out in the open and prone to getting beat up on unless you get yourself a swami bar or like what I did before my swami bar arrived. I got an rc-monster motor heatsink which is aluminum finned and looks cool as all hell, until you use it as a motor guard. BTW try disabling your punch control if you can stand it, and put your start power to high. See if your temps come down after a pack or two.

[pullinteef]

oops, I missed the 3S part. If you're running at ~10V, then that might change things a bit. Maybe you're not undergeared. I'm stumped then.

[DwightSchrute]

Originally Posted by 1maxdude

Is there a motor heat sink without a fan that is going to fit with the rustler transmission... and actually work to bring the temps down?

unfortunately, the way the rustler is designed, the rear shock tower really blocks any airflow over the motor to help with cooling.

some people use this one, but i saw no benefit...

http://www3.towerhobbies.com/cgi-bin...?&I=LXRJP1&P=7

i had to resort to a motor fan, but that's not a popular choice when you're running offroad.

Originally Posted by 1maxdude

try disabling your punch control if you can stand it, and put your start power to high. See if your temps come down after a pack or two.

I would think both of these would run more amps to the motor why should it bring down the temps?

Today I tried a few different gears at the track to see which one would get to 200 the quickest. All testing done with 90t spur and motor starting temp was 130 after my warmup laps.

19t - got to 195 within about 10 minutes. Seemed easier to pull the wheels up on the straight away when not really trying. Plenty of acceleration and speed. esc got to 145

16t - took a bit longer, but still got close to 200 in under 15 minutes. Still plenty fast for the track, feels perfect. This gearing gets me about 40 mph on the street. esc at 130+

13t - didn't get above 180 after 10 minutes then I called it a day. Fast enough but yet slow enough for easy control on the straight. The 16t and 19t are just enough speed to make it a bit difficult for full throttle. esc at 130 or less

I like the aluminum transmission option so maybe will try to get a deal on one of those. Today I got the vxl motor and installed the 19t so it should be just a tad faster than the 4600.

3500 * 9.9 * 19 = 658350 teeth per minute
4600 * 9.9 * 13 = 592020 teeth per minute

I hope the temps stay down so I don't need to spend $40 on an aluminum transmission case.

My bad, those recommendations are to keep the esc cool, not the motor. I've had pretty much the opposite problems. My motor temps have usually been ok, but my esc would heat up like nobody's business. I don't think my motor has ever been over 160 that I'm aware of. The esc has been in the 240s once and slightly in the 200s a couple of other times, never once did it "thermal" on me though. My guess is you got one in 5,000 motors that heat up really bad. The vxl should be much cooler.

BTW, is this an xl-5 rustler? If so, are you still using the bushings in the wheels? If so, you will NEED the 5X11 bearings, not the 5X8s. If you do have bearings, make sure they are all free and smooth.

Originally Posted by 1maxdude

BTW, is this an xl-5 rustler? If so, are you still using the bushings in the wheels? If so, you will NEED the 5X11 bearings, not the 5X8s. If you do have bearings, make sure they are all free and smooth.

Thanks - this rustler is older than an xl-5, but I installed vxl carriers and bearings, and also used ball bearings throughout the transmission. The car rolls easily down the slightest incline so resistance is minimum.

Well, if you got the velineon already, I'd go with that, and if it heats up more than you'd like, consider getting the FLM transmission case. Not sure if a faulty ESC can cause the motor to heat up or not. My rustler has been doing nothing but speed runs and on road driving lately. I haven't actually been to a track and ran it off road, it'd probably heat up like crazy as well after 5-10 minutes. Check out the Medusa afterburner motors and try and sell the castle motor. The Castles do have a reputation of being an inefficient motor that runs hotter than most others.

I ran the vxl motor today for about 45 minutes with only a short battery change every 15 min and I could only get it to 160 with gearing at 19/90. Esc was less than 110. Today outside temps were probably 30 degrees cooler than the other day but I don't think that should mean my motor temps will be much higher when the weather warms up. I really couldn't tell a difference in runtime between the two motors. We'll see how it holds up as outside temps rise.

Thats pretty good. Did you notice a difference in power or speed? Glad you got it worked out. I've been having major headaches with my stampede project. 2-3 months worth of sending speed controllers and motors back and forth. Just when I get it goin and it seems to be working right. I sheared the motor shaft clean off.

Based on my what I could tell the speed is very close to 13/90 with the 4600. Maybe the car is little faster with the vxl like the calculations should indicate but not much difference.