Brushless MGT - pics and details (long)

[10kman]

Hey all -

I took a pretty lengthy layoff from the hobby, I was lurking around the boards still, just keeping up to date on new parts, mods, and just waiting until I got the bug back.
One thing I had always wanted to do was an electric MGT. Like most people probably have done, I started on electric years ago, got some nitro trucks, then pretty much just ran nitro (except for the RC18T I had). Then I took the layoff and sold everything off, even my built from the ground up MGT that was awesome.

So, the bug bit me a couple months ago and I started planning for an electric MGT conversion. Why? Honestly I don't like nitro. For someone that lives in a city, it is just too messy, a pain to get fuel, draws attention from people that end up not letting me just play with my truck in peace, etc. Also, fuel prices are going up. I also think that electric technology has way more room to advance. LiPo batteries are almost to the point that everyone knows about them (they aren't quite the standard yet though, due to safety issues and people just not doing their homework), motors are brushless and super effecient, lighter weight for all of those parts, and it's honestly easier.

Plus, I have always loved the torque of an electric setup, especially in a truck where power rules.

Anyway, back to the truck rather than my personal theories.

The hardest thing for me was figuring out the mount for the motor. It has to be an "L" shape, and I initially thought that aluminum would be great, but it's hard for me to work with since I am an apartment guy without huge equipment to mill down parts. I tried it with some 2" x 2" stock I picked up at Lowes, but wasn't happy with it.

I then decided to try something out of Lexan (polycarbonate), and loved it. It was easier to work with, and I think stronger, which is key for holding up that big electric motor. I made up a few designs in Visio and cut out templates from paper, and after 2 tries I got one that was good. All I used was a jig saw and a cordless drill, so I had a hard time lining up holes and getting things perfect.



Next thing I had to tackle was figuring out how to brake. I can either do it with the motor/esc, like a normal electric vehicle, or I can use the mechanical disk on the truck in stock form. Well, stopping a 13 pound truck over and over is rough on an ESC, even one rated to 300 amp surges, so to keep heat down and stress on the expensive electronics, I am using the stock disk. What this also does is let me use the stock tranny (I did install a FOC like most do), so I still have a 2-speed. Otherwise, if you choose to use the electronics to brake, you need to lock your tranny somehow so it is singlespeed, and turns the wheels both forward, and reverse, so the motor can stop the truck (otherwise, if you try to stop, the spur gear will just spin backwards, and you'll coast, but not brake). Some have done it by using an E-Maxx tranny, and some have made center diffs, like on a buggy, but I wanted to keep the MGT close to stock, with electric power.



You'll notice if you look closely that under my motor, I have a brace. This lets me rest the motor right on there, so it is fully supported, and bolted to the "L" I made, so for landing, hopefully I won't have any issues. I may put a Velcro strap around the whole thing just to be extra safe, but it is super stiff how it is now.



I adjust gear mesh by moving the whole mount on the chassis and bolting it tight. That's a little bit of a pain to do, I have to remove the spur, then the motor, then move the mount, then reinstall and hope the mesh is right, but I'm pretty good at getting it right. I honestly don't move it though, I have a 16 tooth pinion with the stock 52t spur and it is fine.
I also had to do some Dremel work on the bracket to let me get the gears close, the MGT tranny has some pieces that stick out, and rather than ruin the tranny, I ruined the mount (always ruin the cheapest/easiest to fix). Also had to Dremel the base of the mount to allow for room for the center driveshaft to spin. No biggie.



So, that's it in a nutshell. The only other thing someone may notice is that I'm using a Quark 125 Air Master controller, rather than the 125 Monster Pro that is designed for trucks (so they say). However, if you look at the specs of each, they are identical. I called Quark to ask and they confirmed that they are indeed pretty much the same, differences being with software obviously since the Air Master is for helis/planes. They said they would support me trying it out and help me out if it fails, and I've been in contacts with them a few times to let them know status. So far so good. Why not use the Monster Pro? It's considerably more expensive for some reason.

I'm using a Neu 1515 1/y brushless motor with 2200 k/v rating, the Quark Air Master ESC, an external BEC rather than a hump pack to save weight (it is in the hump pack compartment of the truck), Airtronics 94358 for the steering, and the stock steering was moved to the braking duties. Other upgrades are a FT steering kit, FT shock caps with gold/red springs (50wt in the gold, 40wt in the red), FOC in the tranny, and I think that was it. I am going to order some Maximizer beadlocks with some Losi Zombie Maxx tires to drop some weight on the wheels, and then some aluminum diff housings just for kicks, and then the truck is just going to be run until something breaks. I shimmed the stock diffs when I had the truck all apart, but I'm waiting to embezzle another 100 bucks from my monthly budget to get the diff housings.

I have run the truck on junk 9.6v packs for testing, and it wheelies when the pack is fresh, then drops off. I can't get it to shift with those packs though, but I did run the truck a few times with 2 9.6v packs in series, and it shifted fine and is super quick. Also has so much torque it'll flip right onto it's lid with a blip. I have a 4s2p LiPo pack coming, but it was backordered so I have to wait until 6/15 (hopefully) for it to get built up. I'm peeved about that, because it was not noted on the site and having a 2 week wait as a "gotcha" isn't making me happy. But, with a 9.6v pack, it was quick enough for backyard fun by far. So, having a 4s setup, I should be MORE than happy.

I will get a video after the LiPo gets here and I have that all figured out. I need a better mounting option for the battery, and wanted to wait until I had the actual battery I was going to use before I cut away some of the chassis guards for another Velcro strap.
I really want the layout different, but am not sure where to move the electronics. If I could move the ESC to the rear of the truck, and the BEC/Receiver to the right side, I'd be happier. I just want a cleaner setup. I'll have to set it on my table and have a good look at it for a while, and see what comes to me.

I'll end my post here. After I get the battery and have it mounted, I'll get a follow-up picture for final layout, but you can see where it goes (left side of the chassis). Any questions post back here, I will try to check regularly.

10k