Tamiya TRF421 Official Product Info

Tamiya have published the product details of the production TRF421 chassis kit, with official photos and description.

Here follows the full detailed description of the new TRF421 (alternative texts in cursive are translated from Japanese presentation as it contains more info).

42384 TRF421 CHASSIS KIT

This R/C model assembly kit creates the 2 belt-driven 4WD TRF421, the latest model in the line of TRF chassis; its newly designed carbon fiber upper and lower decks move the motor 22.7mm further forward than on the TRF420X, while the center shaft is in the chassis center and drive belts are of equal size; pulleys are also a new design. The upshot of this is greater pitching stability on the throttle. Bulkheads have a new design for a lower center of gravity, and new USBB (ultra-short big bore) dampers are mounted via aluminum stays: they can be fine-tuned with spacers. The suspension uses upper and lower A-arms for superior rigidity, with identical lower arms front and rear that have a longer span for more linear roll that translates into more control.

The 2-belt drive 4WD touring chassis bearing the name “TRF”, the pinnacle of Tamiya R/C, has been fully remodelled for the first time in 2 years. The newly shaped carbon lower and upper deck moves the motor position forward 22.7mm compared to the previous TRF420X. The centre shaft is positioned in the centre of the chassis and the drive belts are of equal length front and rear. The front and rear pulleys also have a new shape. This change reduces pitching during throttle operation for a more stable drive. The front and rear bulkheads have also been reshaped for a lower centre of gravity, and new USBB (Ultra Short Big Bore) dampers are mounted with aluminium stays. Fine angle adjustment is now possible using spacers. The suspension uses highly rigid A-arms top and bottom. The lower arms are the same front and rear, with a longer span for a more linear roll posture when cornering and improved stability when controlling the car. With an optimised drivetrain, chassis flex and low centre of gravity, the TRF421 chassis is set to reach new heights of performance.

The center shaft is moved into the middle of the chassis, and belts are of equal size, while pulleys are new: the result is less pitching on the throttle, and greater stability.

The centre shaft is positioned in the centre of the chassis and the drive belts are of equal length front and rear. The front and rear pulleys also have a new shape. This change reduces pitching during throttle operation for a more stable drive.

Front and rear bulkheads contribute to a lower center of gravity. Ultra-short big bore dampers are mounted via aluminum stays.

The front and rear bulkheads have also been reshaped for a lower centre of gravity, and new USBB (Ultra Short Big Bore) dampers are mounted with aluminium stays.

Front and rear bulkheads contribute to a lower center of gravity. Ultra-short big bore dampers are mounted via aluminum stays.

All new damper: the USBB damper is 5.5 mm shorter than the SSBB damper, resulting in a lower centre of gravity and reduced weight. This dramatically improves dynamic performance. Two types of shock ends are available, one for the front and one for the rear, with a 0.5 mm difference between the front and rear to allow the piston height to be adjusted to the same level according to vehicle height.

With the motor 22.7mm further forward than on the TRF420X, the center shaft is now in the chassis middle. The spur gear is affixed using a single nut for easier pit-work.

The centre shaft is positioned in the centre of the chassis by moving the motor position forward by 22.7 mm compared to TRF420X. Equal-length belts front and rear reduce pitching moments during throttle operation, resulting in stable drivability. The spur gear can be fixed with a single dedicated nut, greatly improving workability when removing and installing the spur gear.

Stabilizers have had an overhaul, and now feature a common design front and rear, and are positioned lower than the drive shafts. The kit includes one each of 1.0mm and 1.2mm rods, and two 1.1mm parts.

High-precision stabilisers with a common design for front and rear, based on a review of the materials and hardened parts. The mounting position is lower than the driveshaft for a lower centre of gravity and easier maintenance. The kit includes 1 x 1.0 mm, 2 x 1.1 mm and 1 x 1.2 mm sets, allowing for setting changes.

The revamped suspension employs A-arms; lower arms are ball-attached. The lower pivot is positioned on the inside of the bulkhead to keep chassis width the same while allowing the long span lower arms. Lower arms have neutral toe on the inside, and toe angle is applied on the upright side.

Suspension is a highly rigid A-arm with each part newly designed. The lower arm has a longer span and the mounting has been changed from a block type to a ball type. By placing the lower pivots inside the bulkhead, a 7 mm longer span was achieved without changing the overall width of the body. Lower arm toe angle set to 0° on the inside and toe angle adjusted on the upright side.

1-piece and 2-piece upper decks are included; use them to adjust flex. Using more or less screws to affix it to the motor mount lets you further fine-tune your setup.

Upper deck available in one-piece and two-piece versions for chassis flex settings. Multiple dedicated mounting screw holes for fixing to the motor mount allow a variety of chassis rigidity adjustments through a combination of screw mounting.