KB-45 Heat
 

Hey guys,

I'm pretty new to all this electric stuff after converting my Monster GT to a brushless truck, and I've learned to make sure the stuff I put into the truck is up to challenge of moving it.

So far I've burnt up a Turnigy 100a Plush ESC, and a KB-45 8L 2300kv motor... That's way over $100 up in smoke.


So I now have an MMM in the truck, with the V3 case on the way and the new 1.20 software installed. But I've noticed that my new KB-45 8XL (XL not an L this time) seems to get warm even without a load. When I spool the motor up without the pinion gear on it, after about 15-20sec of just seeing how fast it's gonna go compared to the 2300kv motor, it touch it and it seems warm. Maybe 100-110ºF (not that warm I know, but with no load I expected 0 heat). Is this normal? I'm afraid that with the 14lb truck the motor will overheat like the last one and will demagnetize. The gearing will be 14/58 if anyone cares, don't know the gear ratios of the tranny and diffs...

Thanks in advance

BL motors do heat up with no load on them, it's actually not good to run them without a load as they can over rev and shatter the magnet. A Monster GT is a big heavy truck and IMO that motor will most likely not be up to the challenge. When this motor dies you may want to consider a Neu 1515 or bigger or a 70-80mm Medusa with a kv value near 1600-1700. For your wallet's sake I hope your new motor hold up, good luck!

Brushless motors shouldn't be run too much without a load. They do heat up quickly this way. It seems strange, but they run more efficiently when there is a proper load on them. I've read several recommendations from company reps that say not to run without a load other than to briefly test/check rotation.


edit: oops, you were too quick for me e-revonut

The KB45 will be up to the task. I've got a spare KB45 10XL and some 6mm scetyl pinions if you're interested. :wink:

really?

The kb45 is bigger than the neu 1515.

are you sure you didnt mix this motor up with something else?

these motors are beastly.

kb45 will push it no problem. on 5s you'll be fine, I'm going to run mine on 6s in an e-maxx

that's nothing dude, tip of the iceberg.

I run the kb45 8l in my gtp and it is geared for 50mph. No issues at all with that load. With the 8xl you will have plenty of power. It will run warm, but I do not see you having any issues with it. No load revving a motor is a bad idea. Even a little throttle can push an unloaded motor past its max rpm. All bl motors will heat up fast if run unloaded.

Alright. Hopefully the 15sec I ran it for, actually, maybe around 5-7, didn't do too much harm. I like to exagurate I guess...

And just for everyone's info:

KB-45 8XL
1600kv (some say1700kv)
45x77mm
6mm shaft
It's a beast!

I have the pinions down, but thanks for the offer above. If this motor dies, the 10XL may be the next step, or a Medusa. I'm scared, but somewhat confident.

Thanks guys! Tons of replies in just a hour or so!

No prob, but pics are required. If you do not post them, BrianG will most likely flood your PM box with pics of himself in ladies undergarments. Watch out for him...very strange.

Tomorrow I get a new pinion gear to bore out for the new motor (last pinion's set screw stripped, couldn't get it out...) so I'll take updated pics then. All the pics I have now are of a truck with a smaller motor and way weaker ESC.

kershawdesigns.com sells 6mm bore pinions.

Sorry wasn't sure, I was thinking this was the even cheaper version of a Feigao.:whistle:

Very different. KB45s aren't "spinning toasters of death" -SuicideNeil

I've seen them, but unfortunately, they only sell like 19-20t pinions. I need a 14-15t. So I've been boring out RRP Extra Hard 5mm Pinions. Last one worked great! Until I used my old tools to try and take out the set screw... I need a new 2mm hexdriver, just a few bucks I guess.

Typically what I do is cut off an allen wrench, and put it in my drill chuck so I have a hex screwdriver. Be sure you cut it straight though, it's very easy to cut it crooked and then it spins wildly in a cone-formation. :lol:

Losi hex drivers all the way. Best that I have tried, but I hear the hudy drivers are nice too.

I prefer Meg's hex drivers myself. :lol:

Kb 45xl is about the same size as an lehner 2250 just that it's no where nearly as efficient.

A 557g 80% efficient motor should heat up as much as an 280g 90% efficient motor (neu 1512) while doing the same work.

While they could sustain the same kind of load by their thermal design, the kb45 would feel much more powerful as well it is because of it's extra winding and magnet mass...

I believe that you should treat a kb45xl as a rougher neu 1512...

I donno ... I think the torque/power of a kb45 will exceed a neu1512.

they are rated at over 3500w

even my 1515/1y is only rated to 2500w

HAHAHA, funny...

I'm on the outside, let me in! I dont get it.

video of monster gt w/ kb45 8xl on 8s!

http://www.youtube.com/watch?v=kXG1bYLe4H8

I thought those were only rated to 40K rpms

you have to to 47000+

how are the temps? is it still alive?

AWESOME vid BTW.

Well my assumption started by if the kb45 is 80% efficient. If it's more efficient than that then of course i would be wrong and of course i don't know for sure.

I never denied the radical torque advantage of the kb45 though. I only said that it's efficiency might not allow it to put out more power to the wheels than a neu 1512 without demag as it's much more the heat that the motor reach that limit them than anything else.

Also keep in mind that different manufacturers might have different idea to what is an acceptable use. Maybe Kb constructor said those spec with the airflow from a propeller in mind while castle did it with a 5 mph airflow...

Linc had said, "Lois hex drivers all the way," when he obviously meant Losi.

I made a poor attempt at humor by referencing another member of Family Guy.

I think I'm hilarious, but I tend to laugh alone more often than not. I'm not quite sure what that means. :lol:

that was aqwuts video, hes not on here much anymore, busy mushroom farming I guess, but he's got all kinds of big trucks with crazy hv setups, like a Lincpimp but from cananada. He said it got warm but not hot, and bought two more kbs after that

ok, i thought family guy, but wasn't sure. What the deuce!

Resistance is futile!