My brushless HPI Nitro MT Project
 

Well my first real brushless project has begun with me winning a used HPI MT roller with radio for $60. :eek: My only BL experience is with an RC10T2 with a Novak SS5800. I liked the power but needed more and needed it to be 4WD. I was thinking a 1/8 buggy, but figured a 1/10 would be cheaper and easier. I saw Camel's MT18SS and liked it, but didn't want to spend that much, so I picked up this MT.

I'm thinking a Feigao 380c 6L or 8S (8T here at RCM?) with a Warrior 9920 and 8 cells. My max is 8 cells due to my charger limit, and I'd rather not split it into 2 packs as this makes charging very long. Which is the better choice, the 6L or 8S? What size pinion should I look at? Any other recommendations for a controller? This will be strictly for bashing.

I'll update this as it progresses...wish me luck! :dft003:

I would go for a 8S since it will have more torque and shouldnt heat up as much.

I thought the L series would have more torque?

*edit* Or do you mean that a 6 turn L will have less torque than an 8 turn S? I can't find any numbers from Feigao for torque.

The 8s won't necessarily have more torque, since it has to do with the number of amps the motors will pull. Unfortunately, Feigao doesn't publish the kt ratings (torque constants) for their motors, so we can't tell which motor will put out the most torque at the same number of amps.
It's relatively tough to decide without actual numbers which motor has the highest kt. The 380C 6L is longer, but the 540 8s is larger in diameter. They have similar kv ratings (by several hundred). If it were my decision, I would pick the 380C 6L. The can of this motor is a heatsink, so it can dissiapate heat well, and it has removable endbells that won't pop off like the 8s's endbells will. This also makes motor maintenance (bearing maintenance) easier. Besides those things, the 380C 6L is less expensive.

Thanks for the reply. I actually meant the 380c 8S, not the 540. The 6L pulls 69 amps and the 8S 52 if that helps.

Actually, they call them a 8T instead of a S. But yes, out of those 2 I would also choose the 6L.

Metalman, in theory, wouldn't the 540 8S have more torque than a 380C 6L?

kt in oz/inch/amp is 1352/kv. Kt is always proportional to kv. So a higher kv motor will always have less kt. The total torque depends on the number of amps times the kt. In theory, a 540s will have slightly more torque than a 380c 6l. They both will draw about the same amount of amps, but the 8s having ~4400 kv verses the 6l having 4900 kv will have slightly more kt. Once you gear the 8s higher to compensate, both motors should theoretically have the same power output, although the 6l spools up faster in real life.

Hmm, good info. I'll probably go with the 6L. Hell they're cheap enough now that I can just buy another one to play with if I want to.

Well I went with the 6L and Mtroniks Truck. Here's a few pics:

How I got it. It looked cleaner it person:

http://img.photobucket.com/albums/v2...irty1Small.jpg

http://img.photobucket.com/albums/v2...irty2Small.jpg

http://img.photobucket.com/albums/v2...irty3Small.jpg


Cleaned up:

http://img.photobucket.com/albums/v2...lean1Small.jpg

http://img.photobucket.com/albums/v2...lean2Small.jpg

http://img.photobucket.com/albums/v2...lean3Small.jpg

First attempt at a mount….lol

http://img.photobucket.com/albums/v2...MountSmall.jpg


That’s better:

http://img.photobucket.com/albums/v2...ount1Small.jpg

Not the sturdiest thing in the world but we’ll see how it holds up. I just bent a stock mount for a Tamiya MaxClimber.


http://img.photobucket.com/albums/v2...g/ESCSmall.jpg


And the modified radio/servo tray:

http://img.photobucket.com/albums/v2.../TraySmall.jpg

Nice! Let us know how it runs.

You may get a lot of flex from that motor mount, which will affect the gear mesh. The mount may need more than two screws holding it to the chassis. Check out this thread to see my motor mount. It's overkill really, but there sure isn't any flex.

http://www.rc-monster.com/forum/show...&highlight=mt2

Yeah I saw your MT2 thread. I know the mount isn't great, it's temporary until it causes a problem. I liked cold fusion's but I didn't like people sending money and not having a mount months later. I don't know anyone with a machine shop and e-machine wants $60-$80 and a month to make one so I'm kindof stuck at the moment.

Yeah, I'm lucky that I've got access to a machine shop at work (plus a lipo charger). :)

I think adding a brace would make it strong enough. I would use something like a Hyper 7 rear chassis brace.

I was actually thinking about that or maybe something going to the spur gear housing. I don't do 20 ft backflips like a lot of people here that I've seen so it may just be ok, but I'll probably end up with a brace of some sort.

*edited* I DON'T do backflips lol

*UPDATE*

Well it's finally together....or was.

Before the first battery pack...

http://img.photobucket.com/albums/v2...6419Medium.jpg


http://img.photobucket.com/albums/v2...6420Medium.jpg


http://img.photobucket.com/albums/v2...6421Medium.jpg


http://img.photobucket.com/albums/v2...6422Medium.jpg


Aaaand this is after the first pack...

http://img.photobucket.com/albums/v2...6424Medium.jpg

Full throttle + Water pipe thing sticking out of the lawn = that

First impressions:

Well, it's FAST. This is my first real brushless other than my SS5800 in my T2. I was going to put the gps on it tomorrow but now I can't. From a dead stop if I nail it it'll veer to the left and I can't keep it straight.

It handles pretty well and seems to jump ok off of the tiny jump I had. I'm pretty happy so far. The controller was getting pretty warm though with not even a full pack ~135-140, the motor was maybe 130. I'll probably add fans eventually. It's geared 52/15 right now with the Road Rages.

Oh and it's pretty noisy, is that just the sound of mod1 gears? The mesh is good so I think that's just how it is.

It needs a few tweaks but overall I think it was a success! :dft012:

A question about the veering, I filled the front and rear diffs with 3 or 5000 wt silicon. Would that cause it? Or is it just the torque?

It shouldn't be the torque causing it to veer. My MT2 doesn't veer, and my 540c-9L has a lot more torque than your 380c-6L. I'm not sure about the diff fluid. I just use grease in mine. How did you seal the diffs?

Btw, the gears are noisy on these, and not just the spur/pinion. A lot of the noise comes from the front and rear diffs.

I didn't seal them, but they haven't leaked as far as I know. I'll have to do more testing when I get it fixed.

It probably veers because your camber, toe-in/out is off or something of the sort.

That could be it, but it doesn't look off. Like I said, I'll have to do some more testing. Does anyone know of any place to still get the aluminum parts from? I only know one place and most of the parts are out of stock:

http://www.powerlineracing.com/index...S&Category=215

ya im also coverting but brushed,

Try messing around with your radio trim settings and the like on camber and such, thats usually where any abnormal veering would come from.

Ebay usually has some aluminum parts.

I'll try messing with it.

Yeah I found a good place on eBay that has most of them except the front arms and diff cases.

Another update:

Well it wasn't as successful as I orignally thought. Apparently going to full brakes from a fast speed causes the pinion/spur to grind, so it chewed up the spur a little. It looks fine but makes a terrible noise now. The problem is there's no slipper, it's just a gear that transfers to the front and rear diffs, so I'm thinking about switching to a slipper or maybe some kind of center diff from a buggy?

Even worse is now it's glitching no matter what I do. I've moved things, wrapped the receiver in foil, changed radios and batteries and it still does it. I'm using a Futaba 3PM FM and I tried an old Futaba PCM. The worst part is it started for no reason, it was fine one day and now this. The only thing I haven't done is try it in another location to see if something around here is interfering.

Oh well. :031:

Sorry to hear about the glitching. That's always a pita. As for the spur, maybe you could use an MT2 slipper clutch? I'm not sure about the MT design, but it might be a direct fit.

That's what I was thinking so I'm trying to piece together the whole assembly by parts on Tower. If I can't fix this glitching though, the whole thing is a 5lb purple paper weight.

nice truck...

Thanks but it's about to go in the garbage. It won't stop glitching. I've changed radios, the batteries, I've put the esc and motor in another car and it works fine. I've moved every component around on the chassis, I've wrapped the receiver in foil. I thought maybe it was the motor mount with the metal chassis acting like a big antenna into the system. I disconnected the motor from the mount and it still does it. I get about 75 feet away and it starts. The worst part is it WORKED FINE before. It's just plain interference because I don't need to touch the controls for it to happen, so it's not like the motor is causing a problem when running or anything like that. I just don't know what to do anymore.

Does anyone have ANY ideas?

Have you checked your servos? I have heard of them causing some glitching and such.

Yeah, it does it without the servo even plugged in.

Have your tried a different esc?

Well this is the only sensorless ESC I have and the system works fine in another truck so I don't know what to think. Unless there is something wrong with it that only affects it when it's in this particular truck, which I doubt.

TRy a reciever pack and an antenna tube and not running the antenna across the esc.

I would try something like removing all the electronic components (except the motor of course) while still hooked up and try to run it and then just add components to see which causes the problem.

I tried a receiver pack and tube with the antenna in different locations. Thanks though.

I'm going to try just a servo with a receiver pack with the esc unplugged and see what happens.

Check around for any metal to metal rubbing as well. It can cause you headaches.

Yeah I checked all of the screws and other than that there isn't much metal-metal. I think I'm going to take the whole system and sit it on the ground and see if it does it, then put each one in until something happens, like squee said.

Well I tried laying everything out next to the car and putting things in one by one. I can't get it to consistently not work so I don't know what's causing it. It has to be the controller in some form or another. The question is do I send it to Mtroniks or try (buy :mad: ) another controller first to see if it does it?