1350kv...Why did I buy this?

[Havoc]

Before I damage anything else, I figured I would ask for some advice here. I hate my first post to be "Hi, I did something stupid.." but I have no choice.

My old Novak HV (it's a 6.5, but this was before they labeled them as such) was in my old 14.4 Emaxx. I decided to put it into my new Emaxx 16.8, but the factory heatsink won't let it happen. So, I went with a new Tekin solution, the RX8 combo w/1350kv motor.

My goal here was to make my Emaxx bullet-proof, maintenance free and something that would rarely need to be on the bench. I went with the lowest kv motor so I could gear it just high enough to get okay speeds, long run times and cool running electronics. Well, so far that is not the case at all.

What happens is the truck runs okay for about 2-3 minutes, then there is no power at all. It feels like a stock Emaxx running on a single battery. I am using two 7 cell trinity 4600mah nimh. I have 5 of these batteries and have tried a different set with the same outcome. I have tried a 15t, 17t and 21t pinion, all came out with the same results.

I just got some lipos recently, but haven't tried them yet. My concern is that this motor requires some serious battery power and I don't want to detonate my truck by smoking two Lipo's because I don't understand what this motor wants from me.

I have a new 2250kv sitting on my bench, waiting to be swapped with the 1350kv, but what could I even use this 1350 for? Do I need a 6s? I hear all these stories about people going to lower kv for more torque and control on a smaller track, but have I gone too far?

Thanks!!

[nitrostarter]

That 1350 will definitely need 6s to be responsive! On 6s, thats still only 29970 rpms, which is pretty conservative! You could run that motor on 8s no problems!

And Nimh packs just dont cut it either.

Swapping in that 2250 motor will really wake it up tho! But gear conservatively with those NimH packs otherwise, you'll fry those packs in no time from the massive amp draws. Or use the Lipo's you have and hold on!

[brushlessboy16]

According to mike at rc-m, the t8 motors like being driven at lower rpm.


Bump up to 6s lipo... makes all the difference.

Hobbycity.com <<<<

---

Benjamin White
R/c Monster Team Driver
Jq the car, LST, Sportweks turmoil pro
Unconventional Techniques, Superior Results

[bruce750i]

Is anything getting hot after running the 1350kv with the NiMh? What kv is the Novak6.5?

[What's_nitro?]

I bet the nimh are hot.... The T8 is gonna want a ton more juice than the novak system..

[redshift]

"My goal here was to make my Emaxx bullet-proof, maintenance free and something that would rarely need to be on the bench."

Welcome to the forum. A bulletproof Maxx is a tall order, especially the 3906. The 3905 is much better in some respects, but about the same in a few other areas.

The 1350 is definitely too low, but you'll have no issues with "overpulling" your lipos with that motor, if I had to guess, that motor will pull a maximum of 50-60 amps, well within almost any decent lipo's discharge capabilities. A bl motor will only use what it 'needs', whereas a brushed motor will try to take whatever you throw at it in most cases.

The 2250 is too high for use on 4S IMO, (not sure what you have for lipos) but proper gearing will make it useable.

Don't feel bad, you can unload whatever you don't end up using here.

See my 3906 mute in my sig for some ideas.

[aqwut]

You could still be geared too low.... I run a 1390 12XL with a 24T pinion on my old FLM maxx....

as said above, i would go lipo before anything else!


6s would be a good combo

[Havoc]

Thanks for all the responses, I guess I will try the Lipo's first. I am not done with my Lipo bunker yet, but I will give it a shot soon regardless.

Those nimh batteries may be on their last leg anyway, I had 6 of them until one of them blew a cell in those oven-type battery holders in my Erevo. Sorry Traxxas, that was a crappy design. I will run them with the 2250kv in the Emaxx after I try the Lipo's with the 1350kv.

With the 1350kv, the nimh's were getting pretty warm. Since they are getting old, the cells are way out of sync now. Will be breaking them apart soon to cycle each cell and rebuild them as side-by-sides. If the 2250kv hurts them, well, they had a good run.

bruce750i: The Novak 6.5 HV is a 3400kv. It made my old Emaxx fly (standing back flips) and never had any heat issues. I just put the 5mm rotor in it, which was a pain, but it doesn't have a home right now. May go back to my old Emaxx when it is running again.

redshift: The Emaxx I am using is a 3905. I have a 3906 as well, but its in the middle of a never ending project. It doesn't even look like a monster truck anymore. I will take some picks when I get done...whenever that may be. The "bullet-proof" remark was meant to, more or less, just mean a truck I don't have to jack with too often. Just throw in 2 charged batteries, get some modest speed out of it and chase my dogs.

aqwut: I have a roll-cage on it, the motor is sitting in between two plates, I may be able to get a 22 or 23 in there at the most. I may try doing that.

[sabongi]

I can´t be sure, but for me looks like a too small pinion. I´d go with a hobbycity 6S 30C lipo and a larger pinion. Ever tried brian´s calculator?

[redshift]

"I am not done with my Lipo bunker yet"

listen, forget the horror stories. If you have a decent charger, and are charging at the right rate, you have nothing to be concerned about. As soon as you run the lipos you will forget Nimhs ever existed.

"I have a 3906 as well, but its in the middle of a never ending project. It doesn't even look like a monster truck anymore. I will take some picks when I get done...whenever that may be."

Well now that has me (and a few others I'm sure) very interested......

[redshift]

BTW if you need charging info, post up your equipment.

[GO-RIDE.com]

Havoc,

The rotor in your motor may be unbonding from the shaft. It is a very common problem with Tekin T8 motors and Tekin will send you a new improved rotor ASAP. If you can still hear the motor spinning, but the truck is barely moving, then the rotor is going bad.

[emaxxnitro]

+1 if you need to have a battery bunker you are not doing something right.
all the youtube stories are scare tactics. the people with fires and lipo explosions dont know what they are doing. Let us help out.

Originally Posted by emaxxnitro

+1 if you need to have a battery bunker you are not doing something right.
all the youtube stories are scare tactics. the people with fires and lipo explosions dont know what they are doing. Let us help out.

+1 those people are dead shorting and charging on insane rates on a lead acid battery charger for a long time before anything happens