Brushless Associated Monster GT

[RC-Monster Mike]

7xl gets my vote. I have done a backflip or so with my e-maxx, but haven't caught it on video. Perhaps I will give it a whirl(no pun intened) this weekend!
Welcome to the forums!

[MaxxBashers]

Thanks guys. Well I have sold off $220 worth of nitro stuff with some more going, hyper 7 pro roller and a RB C5 w/pullstart. I am thinking about keeping the hyper and making it BL as well.

I stripped the Monster GT down and am getting it ready to go. Do you think the RC Solutions cage and the all the FT upgrades will make it to heavy for the 7xl?

I am still debating using the stock tranny versus the ofna ultra center diff.

Mike as soon as the 9920's get in I'm ordering one. I can't wait to get this project along a little further.

[Batfish]

I got the parts from Mike today and it looks like I have enough to get the MGT going with the center diff. I'm hoping to have it together between tomorrow night and Sunday.

I'll be sure to update here.

[coolhandcountry]

What center shafts did you get there batfish?

[Batfish]

Originally posted by coolhandcountry
What center shafts did you get there batfish?

Although I don't think Mike knows exactly where they originally came from (he had them laying around the shop for/from various projects :) ), one is a UE dogbone at 113mm (I think) and the other is an OFNA dogbone at 88mm. I'll definitely be using the 113mm and will either use the 92mm I already had or the 88mm, depending on which fits better once I have the diff mounted. Then I'll send back what I don't use and compensate him for what I keep :)

[coolhandcountry]

cool. Let us know how that center diff works out there. I know the mgt is a long truck. That is what I like about it.

[Batfish]

Well it's up and operational.
As usual, my projects aren't pretty, just functional :)

Here are the latest specs, pics, and a short video:

MGT Stock pieces are the chassis and suspension.
BlueBird (BMS) 621MG Steering Servo
(2) 3s 3200 FMA/Kokam Lipo packs in parallel (3s2p)
MGM 12012 Speed Controller
Feigao 8L Motor (15T Hardened Steel Pinion)
OFNA Ultra Center Diff (51T Nylon Spur)
(2) 12v CPU Fans






http://www.rcpics.net/view_single.php?medid=64321

I'll be soldering up a 10L and seeing how that handles it compared to the 8L. The speed control got up to 130 pretty quick with the 8L, so I'm hoping for lower temps with the 10L.

[MaxxBashers]

Great Job Batfish!!! I am still trying to decide between stock tranny, center diff or modd'n an Emaxx tranny into it. Is the diff on its side?

[RC-Monster Mike]

Sweeeeet, Joe! I am very curious how this performs on a track with this center diff. Looks pretty good for the hack job you described!

[Dafni]

Nice! How do you like the handling on the center diff compared to before?

Now you have no slipper in your driveline, correct?

Lookin' good! From the vid, it looks to have about the same power as my MT2.

[Dafni]

Joe, may I ask what's your Final Gear Ratio? I guess the MGT has some kind of 8th scale buggy diffs.

Just curious.

[Batfish]

Thanks for the nice words :)

Now some answers and more details.

Yes, the diff is laying on it's side. Since the diff mounts are indented on the sides I figured that would be the best way to mount so I could put the motor overhead. I wanted the motor in-line in the center of the chassis, not off to one side. I would have had to mount the motor on the side if I stood the diff up normal.

There is no slipper mechanism in the drivetrain now; correct. This should be offset by the diffs overall (I hope).

The handling feels more stable to me. I think it's a result of a lower CG now. In the video I tried to get it to flip sideways and I'm very pleased that it showed no signs of doing so :)

As far as the gear ratios, hopefully one of you math-magicians can get the final stuff based on this:
A - According to AE, the MGT diffs are a 3.31 ratio.
B - According to info at Tower, the OFNA diff has (2) 18T gears and (4) 10T gears.
C - 51T spur and 15T pinion.

Here's a marked-up pic. There are descriptions of each number below the picture.


1 - Three parts that show how I mounted the diff.
*The arrows on the bottom point to underneath where I used the original OFNA center diff top plate as a template for drilling two holes to mount the diff.
*The two circles in the middle show where I cut/filed the top posts to allow the diff to fit a little better. I cut/filed about 4-5mm off and ended up putting washers in to get some of it back and even the front and back so the diff would be square with the motor.
*The drawn part on top is a piece of aluminum I had previously drilled to be my template when I was going to mount the Ultra diff in my Hyper 7. I used half of it to keep the diff from pulling the mounts apart during running.
(As a note on the diff mounting, It's currently held in by only 2 screws because I don't feel that the diff needs to be mounted as securely as in a buggy because it only serves to turn the dogbones and not as a platform for brakes or anything else.)

2 - Shows where I filed and dremelled about 2mm from the chassis to allow the spur to fit.

3 - Shows the ESC. The drawn purple is showing the foam under the ESC. I used part of a 2.2 truck tire foam shoved underneath. The zipties are run through the holes for the nitro engine mount. I'm very happy with this setup and will only change it if I have a need to mount the ESC somewhere else.

4 - Shows the fan setup. I raised the rear body posts to the second hole, which allowed for the two CPU fans to stand and be ziptied to the rear tower and post mount. I wired the two CPU fans into the battery leads on the speed controller (another great thing about PowerPoles; I just pushed the wire into the connector and taped it there :) ). The fans put out a very nice airflow on the 11-12v from 3s lipo.

5 - Shows the motor mount attachment. I used two of the original tranny mount holes on each side. The screws are long screws from my XXX-T screw kit and the 'spacers' are 8 E-Maxx wheel nuts from my E-Maxx screw kit. Using different spacers can get the mount higher or lower, plus I cut the mount to allow for moving the motor up and down about 1cm for different gearing options.

6 - Shows where I cut away the original battery box. I needed the room to mount the lipo pack. I left the plastic "wall" from the battery box as a possible mounting location if I do end up using a receiver pack at some point. I can just attach the pack to the wall via zipties or velcro.

I'll be bringing it with me when I race this coming Thursday night. I hope to get a run on the outdoor track before the indoor racing begins.

Let me know if there are any other questions :)

[RC-Monster Mike]

You may want a couple more screws holding the diff. "only turns the dogbones" is true, but this means power and brakes for a heavy/large truck. You have until Thursday to address this! :).
Also, rather than spacing the entire motor mount, you could remove the material at the motor mount itself(where the screws go through) in stright lines (up and down), so the motor itself could slide upward or downward instead of the whole mount. This would be easier to adjust, as well as allow the flat section of the angled aluminum to rest flat on the chassis-more stable as well. :)

[Dafni]

Nice write up. I enjoyed this post! Thanks for sharing.

I thought similar things as Mike. The diff mount has to hold up against quite a bit of torque. A few more screws wont hurt.
I would suggest mounting the fans closer to the motor and ESC. One on the motor, one on the ESC, for example.

Still, I like your work. Must be an awesome RC.
btw, Joe, you're quick! I suggested this Centerdiff like 2 weeks ago, and now you have it running!