Teeeeejirrrrr

This is Mammoet, a six wheel drive, six wheel steering monster mutant truck.

It was built from a Tamiya Juggernaut 2 and TXT-1 truck kits, both of which were originally 4WD vehicles.

So without further ado, some answers to frequently asked questions…

How big is this thing?
The truck is about three feet long, 20″ wide, and closes in at 24lbs.

How fast does it go?
It is meant to be a scale truck, and has a top speed limited to 21MPH.

What powers this thing?
This is an electric powered truck. The ‘standard’ for electric are 6-cell rechargable battery packs that usually come in a stick form factor.
The average car model takes one stick pack. This truck consumes three at a time.
Two stick packs drive the motor, and one stick pack is dedicated just to run the electronics and radio gear.

The current trend of new trucks is to go with nitromethane and alcohol powered ‘glow fuel’ engines.
However they are much louder, definitely get messier, and require more maintenance to get running.
Don’t get me wrong, i love nitro power too, but it does not fit well on a scale-type rig like this.

How long do the batteries last?
It depends. On a standard 2400mAH ‘sport’ pack, the truck gets about 10-12 minutes of full driving per set of packs. The electronics battery lasts about 30 minutes.
Yes, i do own bowling ball bags, filled with batteries 🙂

What is this rig based on/inspired by?
Well… honestly Mammoet is not entirely to scale, as the body is 1/14th from the Tamiya Ford Aeromax kit, while the rest of the drivetrain comes from the 1/10th Tamiya TXT-1 and Juggernaut 2 kits. It’s sort of a fantasy mishmash of things.

In terms of inspiration, the long discontinued (and now highly valuable) Tamiya Toyota 4×4 Pickup Bruiser kit is what got me going. The Bruiser featured a variety of goodies such as:

• Three speed manual shifting transmission with 2WD and 4WD modes.
• Steel chassis, and many metal parts for scale realism.
• A hard plastic body, with further scale realism amenities.
• Authentic leaf spring suspension.
• Large RS-750SH motor (most kits that time had the smaller RS-540 sized motors).

Although the Bruiser and its predecessors were legendary, they had a number of shortcomings too.

• Despite being largely metal, the bulk of the metals were diecast pot alloys. They were somewhat delicate!
  • The trucks of this design did not have rear differentials.
  • Front differentials were just a ‘slip’ design using a failure-prone one-way bearing.
• The transmissions shifted with gears in motion, as opposed to gears always in contact shifting via nubs or synchromeshes.
  • This meant the opportunity to grind gears during misfired shifts was a dangerous thing.
  • The stock transmission did not come outfitted with ball bearings.
• The steering linkages were less than desirable on most models.

But all of that having been said, Bruisers were really fun trucks to drive around.

Their leaf sprung suspensions gave them a really scale ride which simply has to be witnessed. Their shortcomings are among the things that made them interesting.

I tried to address some of these with this project. The name Mammoet sort of stuck, after i thought about a good name for the truck, and couldn’t come up with anything that sounded cheesy. Mammoet features the following:

• Three-speed manual shifting, with Tamiya’s more modern transmission from the Tamiya Big Rig series of trucks.
• Leaf sprung suspension, in the form of long travel, dual-ellipitical leaves facing one another. This design was inspired by Amish horse-drawn buggies of all things!
• A brushless electric motor. Just one would be needed to move this truck around with authority.
• An adjustable slipper clutch, to keep the driveline from melting.
• Six wheel crab-type steering, for ‘agility’, since this thing is going to need any help it can in that department!

Are you insane?
Well, i really hope so.

How long did it take to build this?
I started this in late summer of 2003. It was structurally complete about four weeks later.
The truck then sat around for a while and i had resumed work in summer of 2005.

Why not build the real thing?
Because i don’t have the estimated $200,000 in cash lying around, nor the storage space or garage to house this thing. Forget about the support equipment like one hell of a flatbed to transport it on, and the space to actually drive it.
Yup, this version of the hobby is much cheaper.

What’s the turning radius?
Surprisingly… about three and a half feet. For a truck of this size, and without using high-torque servos on the axles, it steers rather well.

You spelled ‘Mammoth’ wrong.
Well, the name comes from Dutch for ‘Mammoth’. Too many things are named ‘Mammoth’ so i figured it would mix it up to do something different yet recognizable.
Mammoet is also the name of a Dutch-owned heavy lifting and transport company.

This section is just for the hardcore R/C crowd. Newcomers, please feel free to skip over, or just let your eyeballs glaze 🙂

• ESC – Jeti Master Car Sport, 12 cells. These days, i would go for Schulze or Castle Creations instead.
• Motor – Hacker C50L, 11 turn. A nice beast of a brushless motor.
• Wheelbases
  • Front to mid axle – 16″
  • Mid to rear axle – 8″
• Radio – Futaba T9CAP surface, with analog servos.
• Lights – Tamiya Tractor Trailer (generation 1) kit.
• Sounds – Tamiya Tractor Sound (generation 1) kit.
• Suspension – dual-facing elliptical leaf springs, stayed with 4-links, dampened with coilless HPI Savage oil units, 80 weight oil.
• Steering – Claw type, 6WS. Front axle moves opposing the rear and middle axles.
• Balance – Almost 50/50, CoG about 1″ above the tires.

Links and Resources

• http://www.scale4x4rc.us/ – An excellent bulletin board catering to scale 4×4 radio control enthusiasts.
• http://www.tamiyatrucks.com/ – Tamiya’s official bulletin R/C truck bulletin board.
• http://www.tamiyaclub.com/ – A commercial site, but an excellent resource where builders can display their older (and newer) Tamiya models.
• http://www.sherline.com/ – Sherline, a maker of excellent tabletop machining tools.