Tamiya Avante Project

Page 2: Building the Suspension

Time to get started on the rather unusual suspension. The links you see on the left are radius arms which are intended primarily to carry thrust loads (power and braking). The vertical hubs are on the right and include the wheel bearings. Note that the nice CVD style axles are new for the 2011 re-release; the original used dog bones. First the radius arms are connected to the rear links we installed earlier and to the mid chassis plate.

After that the vertical hubs are pinned in place, the axles are installed. Installation of the upper rod completes the rear suspension geometry. Altering the length of the upper rod will change the camber while altering the length of the radius arm will change the toe. The sway bars have been attached to clips on the upper arms.

Here the front bumper has been attached along with the sway bar and pivots. You can also see the little silver attachments for the radius arms which pivot in a clear plastic tube. This plastic tube serves as a load relief for front tire impacts.

Very unusual front horizontal c-hubs here. These act as lower control arms and the wide stance allows excellent thrust rigidity.

Time for the first cool gold anodized parts. The original cast aluminum uprights were among the most fragile parts of the model and were a real durability problem. The new gold uprights are machined and are greatly strengthened. Here we them as part of the highly complex front steering assembly. In the previous step we saw the horizontal c-hub. The gold upright pins into it and controls the camber pivot. Yet a third part, this time a plastic knuckle, pins into that one and controls the steering (and toe) pivot. Front CV drives are also installed at this point in contrast to universal axles on the original.

I'm not sure what the logic was behind what to make gold and what to make silver. All the rod ends are silver and and so are all the plate components. If all the machined parts were gold, that would make sense but the rear shock tower supports are silver. Somehow it all works and the model ends up looking coherent.

Now the upper arms are connected to the hubs completing the front suspension. Continuing with the trend of being non-traditional comes the steering. A lateral link connects the steering tie rods. That link floats on a 4-bar linkage which pivots at two points on the chassis plate. An L-shaped crank completes a right angle turn allowing the servo attachment to drive longitudinally. It all works fine, but there are a lot of joints and therefore many places for friction or looseness.

The assembly method of the shocks is pretty standard. There's a volume compensation bladder in the head end and the piston is retained with E-clips. The unusual part is the tapered diameter of the cylinder and matching tapered springs. The kit comes with Tamiya "medium" 600 weight damper oil which seems about right.

At first glance these shocks appear the same as those used on the 1988 original, but there is an important difference. In the original, the rod end seals were swaged into the cylinder and could not be accessed or removed. In the 2011 version, the guide ring and seals are installed with a plastic threaded retainer. The assembly details can be seen in the exploded view above.

The rear shocks are installed in a pretty standard fashion, but the front shocks face almost totally inboard. This is very good from the point of view of having small frontal area and is also very strong compared to a tall cantilever. This design avoids the tall front shock tower that dominates the look of many buggies and makes the Avante look different. The rear shock tower has been strengthened from the original with a lateral gusset.

Update: I discovered much later that I had the rear arms installed upside down. You can see how the shocks attach above the wheel axis but they should be below. The result is that the rear end sits much lower when built correctly.

This model is so special that I couldn't just use any old generic servo. I was searching for something with an aluminum case, ideally gold anodized to match. I couldn't find anything that matched, but the Protek 160SS looks really nice and has impressive specs (127 oz-in at 0.05s). After installing it, I also found it to be the quietest servo I have ever used. It is nearly silent. Sadly, once installed it is totally hidden. I actually wish you could see it because it looks so cool.

The last step of chassis assembly is installation of the radio gear. I've got a 2 channel Spektrum receiver and a Tamiya TLBE-02s ESC. The battery is installed between the two chassis plates next to the steering servo.

The final touch is the unique cam-loc wheel system. The wheels have a traditional drive hex on the back, but instead of a wheel nut the entire wheel cover is the nut. A pair of links fold out from the cover to be used as levers to tighten the wheel, then you simply fold them into the grooves in the wheel to lock. No tools required. Works really well. I also took the opportunity to use a paint pen to make the tire sidewall lettering white which I think adds a lot of extra character. Unlike many Tamiya cars, this one actually come with tire foams.

In addition to the clear body and wing, the model comes with a bottom tray. This does a good job of protecting the carbon chassis plates. It swivels down for battery access, but sadly you cannot reach the connector without also removing the upper body. The upper body is hard to remove because the lateral links which connect the shock tower balls are in the way. You need to remove them every time you remove the body.

I painted the model per the box instructions with Metallic Blue. The wing is a little difficult to paint because of the very thin vertical sections. Would be easier with an airbrush that you could get in closer.

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