Tamiya Avante Project

Page 1: Building the Frame

The Avante comes in a large, beautifully illustrated box. Inside the contents are divided into three sections. On the left and right are blister packs with some of the notable parts including the carbon chassis plate, the gold anodized shock bodies, ball bearings, special motor, and other metal parts. The center section has the polycarbonate body and under tray. Beneath these are the plastic part trees and hardware bags.

The assembly begins with the motor mount and rear gearbox. This is not just your standard Mabuchi 540 motor, this is a custom labelled, 25 turn, rebuildable brushed motor. It looks really nice. We'll see if it has an increased performance proportional to its looks. The model uses a 22 tooth aluminum pinion gear which I immediately replaced with a Robinson Racing steel gear of the same size. This is the only upgrade I made to the model.

Here's the beautiful carbon chassis plate with the motor and aft gearbox housing attached to it. The use of a carbon chassis is the biggest and most obvious change from the original model which used an FRP (fiberglass) chassis.

The front gearbox housing comes next. At this point, only a single bevel gear has been installed which rides on a floating axle. The end of this axle protrudes and will connect to the center drive shaft.

The front gearbox is cantileverd off the front of the chassis plate. At this stage in the build, the thin center is obviously the weak point between the thick ends.

The front and rear differentials are internally identical but the front has a longer housing. The model uses gear differentials, but not your standard bevel gear type. These are planetary differentials using only spur gears. The first layer is an output sun mating with 2 planets. The planet axles are locked to the housing making it the planet carrier. The second layer is another set of planets and the opposite side sun gear. The two layers connect together with the planet gear teeth which rotate in opposite directions. The sun gears are splined to the axles. Note that the diff ring gear is not a bevel, which means the 90 degree turn will have to happen in another gear stage.

The rear differential drops into place from the bottom of the chassis and is then enclosed with a cover plate. This makes access easy for greasing, but you still need to pull the axles to actually remove it. Note the super wide face width on the spur gears.

Now we do the same thing for the front differential. The installation is similar to the rear except that the second stage is a bevel set instead of a spur set. The axle supporting the idler gear is inserted from the side and needs to be restrained with some tape until a part holds it in later.

Step 10 begins the installation of the suspension arms much earlier than the rest of the suspension. These are the rear lower arms which need to be installed now because they will be locked by the mid-plane chassis plate. In this case, the inside ball ends are aluminum and the outside are plastic. The outer ends are not balls but just sleeves. The thread between them is not a turnbuckle so the length can only be adjusted by removing one end and this means you need to get the lengths right now. A jam nut against the aluminum end locks everything in place.

Unlike many 4WD buggies, this one actually has a center differential. This is a ball differential which is integral to the motor spur gear. This does not use a coil spring to adjust the tightness, instead it uses a stack of 5 Belleville springs. The right image shows the center diff installed in the rear gearbox, but at this point there is still no gear to connect to the rear differential. The center drive shaft is just a steel rod with the ends flattened. It is not a hollow tube and it does not have any splines.

The addition of another carbon plate at the mid-plane completely changes the stiffness of the chassis. Now it is a brick. A really light brick. This plate has plenty of cutouts to accommodate the motor, the center drive shaft, and the later installation of wires.

Time to finish the rear gearbox. One more idler gear completes the rather complex path to the rear axle. There is the pinion:spur stage, a bevel stage, 2 spur stages, and then the differential. Since the rear has one more stage than the front, you'd think this would result in them rotating opposite directions. I was actually a bit worried about this until I saw that they mirrored the direction of the bevel gears to compensate.

Now we can close out the rear gearbox from above and also install the shock tower and rear bumper. The shock tower is also a carbon plate. You can also see the fine wire sway bar clipped to the chassis.

Up to Index | Go to Page 2