Brushless Associated Monster GT

[Nick]

Very nice Batfish, actually looks rather similar to the T-Maxx. Except is it belt?

Keep it up. :D

[Batfish]

It's shaft-driven.
I'll snap a picture or two of the underside, and even put it next to my E-Maxx for comparison. I'll add those pictures to the gallery later tonight.

[Batfish]

I've put a few pictures up in the gallery tonight:
http://www.rc-monster.com/coppermine...s.php?album=38

Mike - the gallery is limited to 1MB for pictures? It wouldn't let me upload any more.

I actually got the brushless MGT running tonight :)
I first ran it on six GP3300 (the pack you see in the pics) to make sure I had everything set up right, then switched to one 8-cell IB3600 pack. With 6 cells it moved at about 10-15 MPH, I'd say. with the 8-cell pack, I'm sure it was over 20, but not by much. At the end of the 8-cell 3600 pack (10 minutes or so) the MGM 12012 was 115F and the Feigao 8L was 120F.
The truck didn't get enough RPM on the ground to auto-shift into second gear, but it would do it while I had it in the air. I've got to get into the tranny and adjust when it shifts, or see about getting it stuck into second.
As far as my braking concern, it turns out that the MGM uses the double-pump brake method, which means it won't go into reverse until you let the throttle back into neutral and push reverse again. So, as long as I go right from forward to brake, the motor just stops and the brake servo does it's job. If I'm coasting in neutral, the motor will spin in reverse when I push on the controller. I'm sure this isn't good for the motor since there's no real load with the tranny just spinning freely, so I'll just have to be conscious of that while I'm running.
I was using my 15 tooth pinion, so I'm thinking of going with the 16 next since the temps were so stable. I don't recall what the stock spur is on the MGT, but I know there are delrin replacements from 47 to 52, that I've seen.

Now I just have to come up with a permanent motor mount and a good system for mounting the batteries. It looks like velcro around the rock guards will work great, at least for now.

[RC-Monster Mike]

Add some more cells and get the party started(although you should mount the motor with something besides zip-ties first!). Have to thought about trying an emaxx tranny in there? Perhaps a single speed would work quite well and allow you to drop the brake servo (although mechanical brakes make the controller/motor life easier). With the mechanical brakes, a forward only controller would be the way to go. I am looking forward to seeing this project through completion. The MGT is a nice, stable and easy to drive monster truck that should perform excellent with a nice brushless setup. Perhaps I can see it in person some day (you aren't terribly far from me, after all).

[Batfish]

Small amount of progress tonight.

I got into the tranny and adjusted the two-speed shift. It now shifts at about 1/4 throttle and was easily as fast as my stock E-Maxx on 12 cells. This was with the 8-cell IB3600 pack.
Just for kicks, I finally plugged in one of my Kokam 3s 3200 packs...wow... I only ran it for about one solid minute since I didn't re-program the MGM for the 3s lipos, but it was a WOW difference. The peak voltage on the 8-cell is only about 1 volt less than the 3s, but I got my first glimpse of the way lipos don't drop voltage under load. If I didn't already say it; Wow! :)
Time to get a secure battery mounting system so I can put those packs to good use!
If I had to guess the difference, I'd have to say that the 3s lipo was about a 30% faster "feel". If I was running high 20s with the 8-cell, I'd easily say mid-30s with the 3s lipo. I really gotta get a GPS.

Also, the temps after 6 solid minutes of about 3/4 throttle on the 8-cell pack were: ESC - 125F, motor - 135F. The 8-cell pack started dumping right around 6 minutes of relatively hard running. Also, just about all my home testing is done in my back yard in the grass. At the track, I expect that it would have barely made a 5-minute race with hard driving. I think I have to cycle my packs a couple times since they haven't gotten much use over the past couple weeks.

[RC-Monster Mike]

A good 3s Lipo "feels" as punchy as 12 nimh cells, but the top speed isn't quite as fast. The MGT is a nice candidate for Lipo too, since the batteries will be up out of harms way. Sounds like you are having some fun with this, Joe!

[Batfish]

Originally posted by RC-Monster Mike
Add some more cells and get the party started(although you should mount the motor with something besides zip-ties first!). Have to thought about trying an emaxx tranny in there? Perhaps a single speed would work quite well and allow you to drop the brake servo (although mechanical brakes make the controller/motor life easier). With the mechanical brakes, a forward only controller would be the way to go. I am looking forward to seeing this project through completion. The MGT is a nice, stable and easy to drive monster truck that should perform excellent with a nice brushless setup. Perhaps I can see it in person some day (you aren't terribly far from me, after all).

We discussed the E-Maxx tranny earlier in this thread. I'm torn about using my existing stuff cause I have been wanting to sell the E-maxx as an RTR, but I've always got the option of stealing from it if I don't sell it.
I imagine it would run me well over $100 to get another E-Maxx tranny and do the right modifications to it, plus whatever it would take to mount it in the MGT. As it is now, I'm just puttering along with what I've already got and finding ways to make it work. I really don't want to spend too much money on it at this point. Of course, once the MGT tranny dies, that'll be another story ;)
I already have the Associated battery cups and am thinking about doing a stacked config with the lipos like I saw by Promod in another thread. 3s2p 6400 mAh should do me just fine at the track, but I'm sure it won't win any speed competitions.
Right now the brake servo is working out good. The one thing I may buy is the FOC kit for the MGT tranny since I've seen it on ebay for about $11. Is that something you can get, Mike?

[RC-Monster Mike]

I can get that pretty easily actually. I will pick one up for you the next time I am at my distributors. 3s2p should be pretty quick with the right gearing.

[Batfish]

We should try to get together sometime. Google maps says our cities are 3.5 hours apart...that's not prohibitive.

[RC-Monster Mike]

Do you race at all(at a track)? I go to RC-Madness every year for the car action monster madness race. Enfield is just below Springfield I believe. I also get upstate sometime to visit my family. I used to work in Lee, Mass(western Mass) many years ago and i grew up in upstate NY on the Mass border (jiminy Peak/Brodie Mountain if you ski). I would love to hook up one day!

[Batfish]

I was born and spent the first 24 years of my life in the Springfield area.
Madness may be a good place to meet up, since I might actually be able to make it there this year :)
Let's keep in touch on this via email as it gets closer.

[RC-Monster Mike]

Will do. I hope to meet you there!

[Batfish]

After removing the carry handle I can easily fit the Associated battery cups. Here's a quick view of how it may look.
I have to decide if I'm going to remove all the stuff from the front of the chassis (receiver pack box, receiver box, forward/reverse servo). The two boxes are molded together, from what I can tell. I may cut the receiver pack box out and slide the batteries forward.
With the tranny, motor, and steering servo set to one side, two 3s lipo packs may be just the right thing to offset that weight. Decisions, decisions....

[RC-Monster Mike]

1 3s pack will probably offset the weight.

[Batfish]

Originally posted by RC-Monster Mike
1 3s pack will probably offset the weight.

I'll be running 2 in parallel, so I'm hoping that the 2 doesn't put too much weight on that side. I think my only other option in order to put a pack on the opposite side (with the stock tranny) is to try and re-locate the steering servo so I can move the pack forward. I'm pretty sure that's beyond my current skill and equipment, at least if it's to be done with any accuracy or reliability.
I've seen a couple ebay buy it nows (the folks that part out new vehicles) that have the stock chassis and rock guards for about $15, and I'm seriously considering getting one so I can hack up what I have and still have something to fall back on.
My buddy at the track/shop is really looking forward to seeing it in action this Saturday because he's been wanting an electric MT, but doesn't want to spend the money to make an E-Maxx brushless-worthy.
All things considered, if I can take a used MGT and have such a relatively drop-in brushless solution (and if the stock hardware holds up for a while) this could be a great brushless MT platform.

I've regularly wondered when Traxxas will come out with a brushless electric truck, but now that I see how relatively easy things fit on the MGT, why not Associated as the first ones on the brushless MT front?