why are my temps so high???

[mk351e]

so brushless is really fun, but NO ONE EVER said that I would literally be glueing tires EVERY NIGHT!! Seriously, thanks guys.

But what i don't get is this: how is everyone running these setups at such low temps all the time, and I'm almost frying things here? My MMM thermalled today(!), but took off again when it cooled. For the trillionth time, here's my setup:

Losi muggy (~12lbs 1/8 4wd)
Tekno Neu 1515 1Y (2200kv)
MMMv2
Hyperion 6S 4800 20C
12 or 18T pinion

Temps today reached: motor: 185, MMM: thermalled @ ~185ish, battery: 133. These temps are too hot for me! I want to be like everyone else who runs a MMM and never even sees the fan turn on! Why am I so hot? I was doing mixed driving today (speed runs, fast turns, stop and go, jumps, and tearing up the grass), and the temp outside was ~80ish, but the body was off the truck the whole time!!! And these temps were not reached at the end of a charge, no, more like after 10 min or so.

Also, I don't see much, if any difference between 12T and 18T pinions. So, what am i doing wrong?

Finally, why is it that I have my MMM LVC set to 18V, and yet when I plug the battery in to charge (and balance at the same time), the charger says the battery is ~20V?? What's wrong? and am I getting robbed of 2V?

[lincpimp]

you are currently geared for about 60 mph. The 1y is a bit much on 6s, IMO.

I would try a larger spur with the 12t pinion, if you can fit that.

Here is your setup with the 12t pinion

Differential Ratio: 4.09
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 12
Total Voltage: 22.2
Motor KV: 2200
Tire Diameter (inches): 6.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.006
Spur/Pinion Ratio: 3.83 : 1
Total Ratio: 15.67833 : 1
Tire Circumference (inches): 20.42 inches (518.68 mm)
Total Motor Speed: 48840 RPM
Vehicle Speed: 60.24 mph

Not sure if you can fit a larger spur... Something like the 62t spur off the crt truggy... 12/62 gearing will definately help, and get you around 45mph.

I have a feeling that the current draw is well over 125amps... That would explain the battery temps...

[BL_RV0]

You stole thw words right out of my mouth... 1y is a 4s motor, 6s for speed runs only in a light truck.

[lincpimp]

Originally Posted by BL_RV0

You stole thw words right out of my mouth... 1y is a 4s motor, 6s for speed runs only in a light truck.

If he gears it down that will lower the load quite a bit, and then the batteries should be able to keep up. I would use a 5s lipo with that motor myself, but gearing will be the cheapest way to get good temps...

Here is the spur.. I meant to type 62 tooth, that with the 12t pinion will work...

http://www3.towerhobbies.com/cgi-bin...?&I=LXLMY5&P=7

[lincpimp]

A 5s 5000 neu or flightpower lipo would be a good choice with the motor and esc setup. The excessive motor and esc temps are more than likely caused by overdrawing the battery, thus lowering the voltage and drawing even more amps... Vicious circle...

i run the 1y on 4s, gear it for 45 and i cant break 140 on anything, amazing torque and everything, granted my jammin truggy is a bit lighter than your pig lol

[jhautz]

Like everyone else has already said....

too much battery for that motor. period. Get yourself a 5s pack or a lower kv motor.

with the setup you have run it for a few mintutes and let it cool. Thats a speed run setup, not a general running/bashing/racing setup.

[BrianG]

It's already been said, but I too think that 6s on that motor is fine as long as it is geared appropriately. It's maybe a tad higher voltage than I'd go for general use though. Gear down to shoot for 40mph max speed and it should be fine.

The reason why you don't notice a difference in speed between 12T and 18T is because on 12T there is very little voltage drop. On 18T, the increase in load (and therefore current) is causing the battery voltage to drop. Since motor rpm is a function of kv and voltage, if voltage drops, so does top rpm.

[lincpimp]

Originally Posted by mk351e

Finally, why is it that I have my MMM LVC set to 18V, and yet when I plug the battery in to charge (and balance at the same time), the charger says the battery is ~20V?? What's wrong? and am I getting robbed of 2V?

First, 3v per cell cutoff is too low. You need to set it to at least 3.1v per cell, and 3.2v per cell is preferable. Under load the battery is hitting the lvc. When you let it rest and it is not under load the voltage will rise a bit. Most likely it is rising quite a bit due to the very heavy load on the lipo.

[DRIFT_BUGGY]

What about that last part he was asking about with the voltage difference?

[George16]

I never thermalled my V1 when I was running 6S Neuenergy 25C 5000mah lipos with my 1515 1Y on my Gmaxx.

I'm using 51T Ofna spur with 20T pinion along with 43/13 buggy diff gears. I think it's geared for 47-50mph. No temp problem until the MMM quit working a month ago.

I am amazed at how many super high rpm set ups I see...mike always tells me 30-35,000 rpm's are perfect.

[Finnster]

Originally Posted by coolrunnings

I am amazed at how many super high rpm set ups I see...mike always tells me 30-35,000 rpm's are perfect.

Yeah, but they do seem to correlate well with the "why is my setup a molten chunk of lava?"

lol

30-30K is perfect. I even really run mine less (28K). Plently of power and great reliability.

If people really want huge amts of power they need to go to HV setups really.

[BrianG]

Originally Posted by coolrunnings

I am amazed at how many super high rpm set ups I see...mike always tells me 30-35,000 rpm's are perfect.

You have to remember that just because a setup is theoretically capable of high rpms doesn't mean it WILL run that high - at least very often. For general track/bashing use, top speed is not hit very often, and if it is, it's pretty short in duration. The majority of the time is spent in stop-and-go and acceleration, which obviously is not the max rpm. 30-35k rpm is about as high as you want to go with a Feigao, but Neus (and other hi quality motors) can still run efficiently with higher rpm. 30-35 is a good range to work with, especially with conversions as that is about how fast nitros can spin. I shoot for 35-40k when possible and things run perfect. And higher rpm, but geared for reasonable speeds, is smoother on startups with less chance of cogging.

[mk351e]

a little more info is in order I think:

1st - and this may be odd, but the battery is always dead last to get hot; in fact, it normally doesn't. It's usually, MMM, Neu, then battery gets hot. My MMM fan seems to be on almost all the time, but castle says it's ok. As for the motor selection, here's some interesting info: a VERY trusted source told me that this setup would be ideal, as Neu motors love to spin, and running mine at nearly 50k is a non issue. While they're rated to go to 60k, they can typically function up to about 100k(!). I just wanted to add a little fuel to my pending lipo fire here

Also, I didn't make my point right; i certainly notice a difference in performance between my 2 pinions: the 18T obviously has more top end, but it also seems to pull wheelies easier! What I meant was that there isn't much difference in temps between the 2 pinions.

Does this change anything? And does anyone know where I can get tires that can stand this horribly painful abuse?