Tamiya TB evolution: Tamiya takes its shaft chassis from basic to ballistic

Tamiya takes its shaft chassis from basic to ballistic by Greg Vogel

If you've been into the hobby a while, you'll remember that, with the TA series, Tamiya' pioneered touring cars and their shaft-drive technology. As belt-drive cars became popular, Tamiya responded with the TA-03 and its latest top-of-the-line competition tourer, the TA-04 Pro. Tamiya never gave up on shafts, however, and the system remains the drive train of choice for its 4WD vehicles. This is evident in the company's latest (and very competitive) super-scale nitro car, the TGR and the wellestablished TGX, TG-10, TL-01 and TB-01 platforms. The TB-01 is particularly interesting; it was initially offered as a rally car, but dedicated Tamiyaphiles soon discovered it had real racing potential, and Tamiya now offers a full line of race-oriented hop-ups for it.

It seems Tamiya wasn't satisfied with merely hopping up the TB-01 and has designed an all-new car-- the TB Evolution-around its shaft-drive system. The limited-release Evo is much more than a TB-01 with some optional parts; it has some TGR in its bloodline and obviously seems competitive. But as good as a car looks, the racetrack is always the real test. So let's check it out.
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KIT FEATURES

Chassis. The TB Evo has a double-deck chassis with both plates cut from woven carbon-fiber. The lower chassis plate is slotted to hold all 6 cells low on the right side, and molded battery cups with a carbonfiber hold-down strap keep the cells in place (there are also small slots for strapping tape if you want to save weight by omitting the battery hold-down). The left side of the chassis is home to the motor and all the electronics, and the area under the motor has been cut away, so the motor sits almost flush with the chassis' bottom. Even the gearboxes get the low-- CG treatment; small openings allow them to poke through the chassis and, of course, the holes on the bottom plate have been countersunk.

The top deck spans the chassis' length, and it's bolted to the front and rear bulkheads, the motor mount, the steering posts and an aluminum center post. By bolting the plate to these areas, Tamiya provides a very rigid platform with almost no noticeable flexing.

A foam bumper is captured between an upper and a lower plate. This prevents the bumper from folding over in a crash and allows it to do its job.

* Drive train. Although the Evo is shaft-driven like its TB-01 precursor, the drive train is almost totally new. The rear end is equipped with a ball differential like the one used on the TG-10, but a lightweight plastic bevel-diff gear replaces the TG-10's cast-- aluminum gear. To reduce rotating mass, the differential halves are made of light machined aluminum instead of cast aluminum. A plastic bevel pinion is mated with the diff inside the gear case, which is borrowed from the TGR. Up front, a torque splitter (also known as a one-way diff) is used in place of a conventional diff. It's built into a TB-01 cliff case held in another TGR gearbox. The TGR case is unique in that its halves aren't bolted together; instead, a ring slides over the area that encloses the bevel pinion gear bearings and prevents the case from splitting. To hold the case's outdrive portions together, they are wedged between the bulkheads.

An aluminum shaft with a steel rear tip sends power to the front and rear gearboxes. The steel tip is on the spur gear end where the pin slides through the shaft to hold the gear; the steel construction prevents the pin from stretching the hole. The spur is a 0.4 module (metric 64-pitch) and a kit-specific part; no standard gear adapter is offered, so only Tamiya spur gears and metric pinions can be used. I'm glad to say Tamiya has you covered: three 88-tooth and three 72-tooth spurs are supplied.

The drive assembly runs on rubber-sealed ball bearings, and universal axles drive the front and rear wheels. The axles aren't drilled for Tamiya's usual crosspins; instead, they are splined for metal drive hexes.

The motor plate is machined from lightweight aluminum that's anodized in a light gray and has a washer plate that the motor screws go through to hold the motor. Although the plate looks badass, it's very hard to reach the screws unless you have a ballhex driver. Even with the ball driver, it's hard to get to the screws after the car has been assembled. Tamiya supplies a black heatsink to cool the motor, and a 35-tooth pinion is also standard equipment.

* Suspension. The Evo's chassis is wider than the standard TB-01's, and its arms are longer than the standard car's, too. The arms run deeper into the wheels to improve the car's stability and handling; they are very stiff and have a matte finish that looks more raceworthy than the shiny gloss of other Tamiya kits' parts. Believe it or not, I had to drill holes in the arms for down-stop screws. I don't think I've ever had to do any hand-fitting on a Tamiya car before. You'll find stout rear hubs, hub carriers and steering knuckles at the ends of the arms, but you won't find any screw-in hinge pins. Like Tamiya's previous pro-car offerings, the Evo uses E-clip hinge pins to hold the suspension pieces together.