MT4 G3 / ST1 Pro Bash Truggy conversion

[CerberusVI]

Looks good, I want to see some vids when you get it all done with the 1717 combo in there! I almost jumped on the MT4-G3 band wagon when they 1st came out, but instead i built a Mugen Mbx5t. Still tempting to make it more into a Monster truggy like the G3

[Lizard]

I almost jumped on the MT4-G3 band wagon when they 1st came out

hehe, "bandwagen" that describes it well. Couldn't really understand why that MT4 G3 got hyped so much. I mean, it's a nice car, but not indestructible, like everybody says. I only got it because it was cheap and I already have a ST-1 Pro, this way I have a nice truggy for bashing with lots of spare parts.

Well, yesterday I finished the diff top-plate prototype made from acrylic glass. I will redo it later with alloy or carbon fiber.

Also weighed everything, final weight with 6s 5300mAh packs will probably be around 5.4 kg (12lbs). Castle 1717 motor with Savage diff is about 200grams heavier than stock motor.

[CerberusVI]

Looks good! i took my Mbx5t out with some 40 series road rages with a castle 1515 on 6s geared for around 64. I think that's around the fastest i've run any of my kits. What kinda speeds are you going for in your setup?

I don't want to say im a hater of the Mt4-G3 but i hate seeing all the OMFG its the BEST BASHER EVUR! When in reality it has weaknesses just like any other rc. It's probably a really good kit, the price point for a rtr is good, but in my eyes it's not the end all be all. I have to stay away from RCU and the wonder tiger forums now because of all the favoritism, loyalty and one sided assumptions about other kits.

Anywho...I like how your going outside the box with this build and not the normal brace the chassis, buy a bunch of digi-dem parts, buy better hinge pins, add a summit bumper stuff

[Lizard]

I'm not sure yet on the gearing, I hope I can use the 46/22 combo without the motor getting too hot.

46/22 with 6s and 3.7v per cell would calculate to 70mph (without tire balooning factored in).

[Lizard]

Well, the car is almost done.

The steering servo posts are the original ones I cut out of the MT4 G3 plastic cage. RC Box is from a Traxxas XO-1.
The ESC is mounted to the chassis plate as on the XO-1, but I'm not really happy with all that plastic, I think I will put everything in some Epoxy later.

Weight with 6s 5300mah battery, Body and HPI Phaltlines is 5303g, with Traxxas XO-1 wheels 4879g.

Gearing is 46/21, with XO-1 wheels and 6s with 3.7V that's 80km/h or 102km/h with Phaltlines.

Did a testrun yesterday, well, what can I say, the wheels take 0.5 seconds to accelerate from zero to 50mph, just the car has problems keeping up with that . Total driftmachine, but drives very well and controllable.

Motor was about 60 degress celsius after 15 minutes, I need to put a fan on it ...

[Lizard]

Took it out for a run on a big grass area yesterday, this time with Badlands and geared for 108 km/h (67 mph).

Seems like 500.000 cps diff fluid is not enough, front tires still try to baloon, could not reach topspeed because of that.
The center diff also got quite hot, I think I will replace it with a CEN limited slip diff and maybe put thicker fluid in it.

Apart from that, it was real fun, a Castle 1717 in a Truggy is definitely recommended.

[Lizard]

1/8 scale tires only last 10-20 packs for me, so got myself some 1/5 scale tires.


1) From a Carson Dirtattack 1/5 scale buggy.
They are already glued and with 280g reasably lightweight. Foams are soft enough for the 5-6Kg of an 1/8 scale car. Diameter is a little bigger than Maxx size but smaller than HPI GT2 tires, I really like it that way. What's not so nice is, that they have very little offset, so I needed wider squares. Took 17mm wide ones, vehicle width seems okay now. They seem quite sturdy, rubber is thicker also. I hope they'll hold up better than 1/8 tires that I always shred within 10 to 20 packs or so.

2) Carson FG wheels and FG Marder Buggy tires. Problem with them is, that the foam is too hard for 1/8 scale vehicles, but I have already ordered some softer ones. I also decided to turn down the part of the wheel where the tires are glued to (see pictures) because with softer foams I think the tire would "bottom out", not good. With FG foams and turned down wheels they only weigh 250gram now, nice.

3) PMT Supreme V2 touringcar onroad tires. Very good traction (wheelies with those small tires, yeah) but foams are a little to hard for 1/8 scale weight, I think I need to get some unglued ones and replace foams.


Center diff is still the Savage Nova diff, but with 2.000.000 cst Oil in it. I am almost not able to turn the diff by hand now :). If I grab the car by the rear wheels and push it over the ground with the front wheels the tires will skid, only if I press the car to the ground in a 45 degree angle the tires will move.
Driving was very good, all 4 tires now always have the same diameter, no front-balooning anymore. In general the tires baloon only very little. Interestingly, the center diff still got quite warm (but not hot anymore) so it's still doing it's job of protecting the drivetrain, very good.

Gearing was changed to 18/46, that's 97km/h with the Carson tires. Also fitted a small 50mm fan on the motor, temps are much better now, after running two packs, max temp was 47C, but most of the time it stayed around 37C. Ambient temp 20C.
But I must say, it feels a little slow now, it stops doing wheelis at about (estimated) 60-70km/h now, with the old gearing (108km/h) it would still do them at 80-90 estimated. Now it's somehow missing that nice "there's still plenty of oomph left" feeling at high speeds.

Seems like I have to improve motor cooling, so that I can run higher gearing again. Unfortunately I couldn't find a motormount that has good heat transfer to the chassis, seems like most manufacturers don't use their brain when designing motor mounts :(