Monster Humvee - Episode 2

Buzzbait · Post by **Buzzbait** » Wed Jun 25, 2003 9:04 pm

Here’s my next episode of the ongoing Buzzbait Monster Hummer project. If you remember my last thread on the subject, I was toying with a Motorworks chassis, H1 Micro hummer body, and Lego wheels. It just didn’t work out. While the Motorworks steering was stronger than normal Bit steering, it still wasn’t strong enough. Even with dual steering springs, the wheels carried an undesirable amount of wobble. The truck was barely maneuverable, and prone to skidding out of control.

So I skipped out to TRU and picked up a couple of Micro Blast RCs. If you don’t know about Micro Blast RCs, they’re about the worst clone on the market. They are VERY slow, have no torque and lousy bodies. The controller even sucks. MY one and only reason for buying these cars was the steering. Micro Blast RCs have motor and gear driven steering, which is pretty much a must for monster truck building.

Mounting my Lego wheels onto the existing wheels only took a few minutes. I also had to grind down the front wheel well area of the chassis so the tires didn’t rub when turning. This experiment immediately proved to be worthwhile. While the car was dead slow, steering was absolutely perfect with the Lego wheels.

Now for the speed. My first speed mod was to add a second battery. The result was a hefty payoff in speed, but not quite enough. Torque was still quite bad. Shortly after adding this second battery, I found a 1/43 scale pullback diecast pickup truck at Rite-Aid pharmacy. It had the most glorious set of monster truck wheels and tires. So I modded my second Micro Blast body with the new pullback wheels and tires, and made it into a tri-cell vehicle. The wheel mod took quite a bit of Dremel work. A real challenge. Speed was even better than the dual cell Lego project, and the looks were much improved. The new tires also provided a tighter turning radius.

Unfortunately, the torque was still very bad for a monster truck. It was even less than on a normal Bit. The problem was the gearing. The gear ratio was VERY low, with gears similar to a Kit Racer. The truck was far too heavy for a single motor chassis and such a low gear ratio. There was no torque, and the vehicle took about 20 feet of straight running to reach full speed. Replacing the pinion gear with a Bit gear was a piece of cake. The idler gear was much more problematic, as the outside diameter of the gear was significantly smaller than the original, and the idler gear axle was non-removable. A Dremel tool and a pair of needlenose pliers got the gear axle out. It turned out that the axle hole of a Bit gear was too small for this axle, so the gear had to be drilled out to size. Once the new 12:1 Bit idler gear was on, to my dismay, the pinion gear did not make contact with the idler gear. After some dremeling of the chassis and pcb/motor cover, and a little shimming of the motor bay, the fit was perfect. While I was at it, I yanked out the drive motor, and soldered in a 21.5 Zip Zap motor for some extra speed and torque.

On to the body. As luck would have, my Bensu Hummer body was the perfect size for a Micro Blast chassis. The original front and rear chassis tabs had to be removed, and replaced with new tabs to fit the Hummer body. The tabs were made extra high to clear the front wheels, and add that high riding monster truck look. The operation was a piece of cake with an old Dick’s gift card, a pair of scissors and some Krazy Glue.

My only minor problem now was that the Hummer had a tendency to tip over on high speed turns. I had originally mounted the two extra batteries on top of the pcb, which wildly threw off the trucks center of gravity. A little soldering and some extra wire brought one battery over the steering compartment, and the other battery over the motor compartment. The truck tips over much less now.

Overall, I now have a perfectly functional Monster Hummer. The speed and torque is about equal to a Bit with a 3.4 motor in it. The steering is absolutely perfect. There is no wheel wobble whatsoever, and turns are nice and tight. Carpet running is a piece of cake. Ground clearance is about double that of a standard Bit. I just have to secure my external batteries a little better, paint my body mount tabs, and add some headlights. I may try popping in a second motor for that extra bit of monster truck torque. Then this baby is finished!!!

Post by **CaboWabo** » Wed Jun 25, 2003 9:37 pm

and then what?

jus messin wit ya man!

that's cool, live and learn about the lego tires.
sounds like you got a nice monster truck there, I'd say go for the extra motor so you can ramp another bit and keep on truckin

crazydave · Post by **crazydave** » Wed Jun 25, 2003 11:53 pm

That looks really nice, but that's really cool that spent all that extra time to make it work properly.

I've been thinking about my childhood dream of making a RC Stomper, but haven't quite figured what approach I'm going to take yet.

payaso · Post by **payaso** » Thu Jun 26, 2003 1:33 pm

crazydave wrote:I've been thinking about my childhood dream of making a RC Stomper, but haven't quite figured what approach I'm going to take yet.

That would be so awesome.. I still bust out the stomper every now and again..

That truck is outstanding buzzbait..

silla

maximan · Post by **maximan** » Sat Jun 28, 2003 3:11 pm

buzzbait when you add the second motor put a removable weight inside the rear of the body and it should do giant wheelies also when the weight is out jump the truck over other bits and race it and when someone passes you just run their car over
it would be funny lets see some videos please