Tamiya Juggernaut 2

Tamiya Juggernaut 2

Hetmanski, Kevin

We tried to break it!

Ah; the Juggernaut. Even before Tamiya’s* Clod Buster replacement hit the shelves, it was the most talked about truck of 1999. When at last it debuted to instant sales Success, it remained a hot topic-for all the wrong reasons, unfortunately. A wellpublicized drive-train durability problem sidelined the Jug, and despite Tamiya’s generous free factory fixes, a satisfactory solution to the problem required drastic measures. Big T decided to pull the Juggernaut and tool up a bunch of new parts for a “sequel.” and that brings us to the Juggernaut 2. Tamiya’s engineers went all out to make the truck unbreakable, so I went all out to break it. I think you (and Tamiya) would expect nothing less.

DATA CENTER

VEHICLE TYPE 1/10-scale 4WD/4WS electric monster truck

BEST BUYER Monster truck lovers; serious backyard bashers

KIT RATINGS (poor, satisfactory, good, very good, excellent)

Instructions Excellent

Parts fit/finish Very good

Durability Good

Overall Performance Good

SPECIFICATIONS

SCALE 1/10

STREET PRICE 5350

DIMENSIONS

Wheelbase 11.02 in. (280mm)

Width 14.75 in. (375mm)

WEIGHT

Total, as tested 179 oz.(5,074g)

CHASSIS

Type Ladder

Material Aluminum/ABS

DRIVE TRAIN

Type Shaft

Primary Pinion/spur

Drive shaft Telescoping universal joint

Differential(s) Metal bevel gear

Bearing type Combination of bearings and bushings

SUSPENSION (F/R)

Type Solid axle/leaf-sprng/coil-over

Damping None

WHEELS

Type One-piece chromeplated plastic

Dimensions-do (DxW) 2.91×3.7 in. (74x94mm)

TIRES

Type Rubber Terra tread

ELECTRONICS

Motors Mabuchi 540 (2)

Battery Not included

Speed control 3-speed mechanical with reverse

Top speed 16mph with 14T modified motors

LIKES

Big scale looks.

No more drive-train problems.

Awesome scale Ford body.

DISLIKES

Tips easily when steering.

Bouncy ride.

Steering is a bit touchy.

How Tamiya Built it Better

TRANSMISSION HEAT SINKS. There are two heat sinks on the outside of the center gearbox. They keep the temperature of the gear shafts down, and this, in turn, prevents the gears from heating up. This is not as much of an issue when you run bearings instead of bushings, but it shows Tamiya is taking no chances.

HEX-MOUNTED LOWER DRIVE GEAR. The lower drive gear now uses a large aluminum hex hub that is pressed into the gear. The gear/hex unit fits over a splined shaft. Everything is held in place with an E-clip on both sides. The old setup used a gear that fit over a small hex piece. The hex and output shaft were one unit; this was also held in place with E-clips.

PRECISION UNIVERSALS. The universal joints on the drive shafts are rebuildable, and they have been manufactured with greater tolerances for less slop.

BEEFIER AXLE PARTS. The bevel gears are now twice the size of the old gears. The bevel-gear shafts run straight through the gear and are supported on both sides by bearings. The old bevel gears had a ratio of 1:1; the new set has a ratio of 1.2:1. This slightly lowers the overall gear ratio of the truck, which eases the load on the drive parts.

building & setup tips

I know what you’re thinking: how can there be any setup tips for this truck? It’s a monster truck; there’s nothing to adjust. True, but here are a few tips to make your building experience a little easier.

Step 3. Liberally apply a coat of thick grease to the shaft that the main drive gear spins on, even if you install bearings. The grease prevents the main gear from vibrating on its shaft, and that keeps the transmission operating smoothly. If you can, substitute thick grease for the relatively “thin” kit lube; thicker grease will be displaced less easily and will last longer.

Steps 24-29. Pay close attention to the number-and the positionof screws installed in the chassis sides. Some screws are supposed to be left out.

Step 43. The tires fit tightly, but if they aren’t glued to the rims with CA, they will slip-especially if you run mad motors. Before you do any gluing, you must scrape the chrome plating off the rims where the tires will seat. Don’t skip this step! if you don’t remove the chrome first, the glue will just pull the chrome off the wheel.

KIT FEATURES

The Jug 2 has the same features as the original but with beefier drive-train components (for details, see “How Tamiya Built it Better”). In case you missed our original Juggernaut review (July 1999), here are the truck’s highlights:

Aluminum/ABS chassis. Four pieces of stamped aluminum and a pair of ABS plastic rails are joined by plastic bulkheads in the front and rear of the truck. Aluminum bash plates are also provided. Right out of the box, the aluminum chassis parts give the Jug an “aftermarket” look.

Four-link suspension. Molded links tie the frontand rear axle assemblies to the chassis via large-diameter pivot balls. Authentic-looking (and stiff) leaf springs are attached to the axles with miniature shackles and keep the floating axles centered under the chassis. Each axle is also sprung by four coil-over “shocks” that are undamped and more decorative than functional.

Dual-motor drive train. Unlike the Clod Buster’s one-motor-per-axle setup that required the rear motor to operate in reverse, the Jug uses two standard motors bolted into a central gearbox held between the frame rails. The two motors straddle a single drive gear to spool up the gearbox. Power is transferred from the center transmission to the axles through telescoping universal drive shafts. Bevel gears spin the differentials, and they, in turn, drive outside hubs and drive the axles-units borrowed from the Clod Buster. A combination of bearings and bushings keeps the rotating parts turning smoothly.

* Four-wheel steering. Like full-scale monster trucks, the Jug uses a four-wheel-steering system. A single servo is mounted between the chassis rails, next to the center gearbox. The servo is connected via linkage to a fully adjustable servo-saver system on each axle.

Ford F-350 “hard” body. A beautifully detailed ABS Ford F-350 Super Duty body tops off the Jug and features a detailed grill, bumpers and roll bar with lights (they aren’t functional, but Tamiya offers a light kit, including bulbs, for the headlamps and light bar). The bed of the truck is hinged to allow easy access to the battery; it’s held down by body mounts, and the cab is attached to the chassis with screws. Unlike clear bodies, the Jug’s white shell must be painted on the outside. The “glass” is separately molded in smoked plastic.

PERFORMANCE

After I had fixed a transmission-chatter problem that marred my first run with the Jug 2 (see “Not Again!”), I was ready to give the truck a thorough thrashing. With the first tug of the trigger, the truck pulled an explosive wheelie and refused to lower its wheels until I chopped the throttle. The two 14-turn Reedy motors moved the Jug along at an impressive speed, but the stiff suspension caused it to bounce uncontrollably over bumps, and either a wide arc or much deceleration was required to turn the truck; otherwise, the Jug would roll onto its roof. When I drove it hard, the truck flipped over a lot, and the hard plastic body quickly deteriorated. Eventually, the rear body mounts completely poked through the bed area of the body, and the body suffered many cracks in the roof and hood panels. Given the time required to finish the body and the cost of replacing it, it’s best to use a Lexan body for hard running and save the kit body for cruising and static display.

To test the durability of the drive train, I ran the truck full throttle forward then dumped into reverse and vice versa. I also landed jumps on pavement without letting off the throttle, and then I hopped the front wheels up and down the RC Car Action parking lot by stabbing the throttle repeatedly. No breakdowns or funny noises occurred during four packs’ worth of such abuse, but I decided to pull the transmission apart to be sure everything really was OK.

With the tranny and axles disassembled, I saw a little wear on the universal joints that caused them to develop some backlash, but otherwise, the parts looked as fresh as the day I installed them. As I reassembled the drive train, I decided to try running the Jug with a single motor; in my opinion, having two was overkill, and I welcomed the thought of increasing the Jug’s run time. One motor was plenty! The truck still wheelied on command, and I gained an extra two or three minutes of fun (depending on the pack).

THE VERDICT

The Juggernaut 2 retains the scale appeal that caught our eye the first time around, and Tamiya has fixed the drive-train gremlins. That leaves us with an attractive machine that’s fun to tool around with but, like its predecessor the Clod Buster, the Jug 2 needs some modification before it can tackle real off-road terrain without getting bounced off course (or upside-down). That will come later; in the meantime, don’t shy away from the Jug 2 because you’re worried about durability (with the exception of the body, patch). I put my truck through its paces, and it kept coming back for more. You can bet there will be plenty of Jug 2 tips in upcoming editions of my “4×4” column, so stay tuned! If you have any hopup/setup/tuning tips of your own, shoot me an email at kevinh@airage.com, or write to me at “4×4,” c/oRC Car Action, 100 East Ridge, Ridgefield CT 06877-4606 USA.

* Addresses are listed alphabetically in “Featured Manufacturers” on page 216.

Copyright Air Age Publishing Aug 2000

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