Ford Focus RS WRC 2001

I was looking for a rally chassis since I'm a fan of this sport, but until now, I was using my Citroën Xsara WRC based on the TT-01 chassis. Though, even with a chassis cover adapted to it, peebles and dust could get inside: cleaning was long and boring after each run. On the other side, I decided to setup this chassis for pure on-road usage and no longer for rally. So I needed something else to play "Loeb".

The TB-01 chassis familly

Surprisingly, this chassis is used by a limited number of models, the only difference being the body. But this leisure intended chassis revealed to be gifted for competition. Tamiya noticed that and created a pure competition chassis lineage based on the TB-01.

58257 Mitsubishi Lancer Evolution VI WRC	58259 Subaru Impreza German Rally '99	58262 Raybrig NSX 2000	58270 Subaru Impreza WRC Arai Version
58271 Subaru Impreza Rally Car Prototype	58281 Ford Focus RS WRC 2001	58286 Mitsubishi Lancer Evo VII WRC	58298 Enzo Ferrari

You can notice that 6 out of 8 models are rally vehicles. The way the chassis is made, its gearboxes, steering tie-rods and the chassis cover do protect the inside of the chassis in a very efficent manner. It's the best chassis ever made for this use, even if it is not dust or waterproof.

You can also notice the very good relationship between Tamiya and Subaru. Like all on-road chassis', the TB-01 features several versions of the Impreza WRC. Including a version which is the early prototype of the Subaru Impreza WRC 2001 that appeared a few months before the "official" presentation of the 2001 rally championship car (released on the TL-01 chassis, kit 58273). The TB-01 chassis will then evolve into TB-02 version (2003) and the recent TB-03 version (2008).

Based on this short lineage chassis (compared to the TL-01 and TT-01 chassis), Tamiya developped on-road competition versions. The first evolution of the TB-01 chassis was a stock chassis fully hopped up with any available option. The following evolutions will then progressively modify the original design.

58267 - TB Evolution	58284 - TB Evolution II	58299 - TB Evolution III
58331 - TB Evolution IV	58371 - TB Evolution 5	The TB Evolution next to the TB Evolution 5

The TB series chassis design goes as far back as 1994 with the TGX nitro chassis. The TGX pioneered the center shaft, the gearbox and drive trains for model cars. This shaft drive design was soon applied to the TB-01 electric chassis and its evolutions. Used on-road (tarmac or carpet), it soon proved to be a serious competitor even if it was originally built for off-roading. Built for competition, the TB Evolution was equipped with performance options such as a double deck carbon fiber chassis, carbon shock towers, aluminium motor mount and ball bearing differentials. Data collected from competition was applied to improve the chassis performance and gave birth to the TB Evolution II. The TB Evolution II mainly gained weight (differential, aluminum bulkheads) and better adjustable suspension setups for more precise suspension angle changes.

The TB Evolution III will bring a huge modification to the chassis by inverting the motor and stick pack locations for a better weight distribution. This new arrangement will be used by the next evolutions that will even lower the gravity center of the chassis. The last photo above shows all the evolutions between the first and the last generation of the TB Evolution chassis (TB Evolution 5 on the left, TB Evolution on the right).

The chassis when it arrived

What I received is in fact a second hand 58281 Ford Focus RS WRC 2001 kit, but without body, tires and motor (the body will get here a few weeks later).

The chassis I got

Chassis view

Many parts came along with the chassis, including a complete gear set and several spare parts. Sadly, the chassis cover has been cut in the front part (but I have a new one in stock), the rear body mount anchor is cracked which means the whole gearbox housing needs replacement (which I also have in stock). The good side is that it is fully ballraced, and the hydraulic dampers are there.

As usual, I stripped it down to check it and rebuilt it. Apart from verifying, this is a good way to learn how the chassis is made.

All the transmission part (shafts, bulkheads, uprights), motor mount, front and rear differential gears are very similar to the TT-01 chassis. Same thing concerning the steering part. Main differences with the TT-01 are on the chassis tub, espacially where the front and rear gear housing link to it. On the TB-01, they are protected from peebles and dust which not the case of the TT-01. The counterpart is a tidier access that can be a problem to quickly make changes like you may need it in competition. For leisure, there's no big deal.

Last, the great advantage of this chassis is its cover for outdoor use. It provides a good protection for the inside of the chassis and the electronic that is installed. The counterpart is a more critical heat dissipation for the motor and the electronic speed controller. Motor choice should be conservative, but the gear ratio also needs attention not to make the motor too hot.

The gear ratios

For this, the TB-01 is pretty generous: from 9.91:1 to 5.72:1. These figures are easy to understand: they are the number of turns the motor needs to do to gear a complete revolution of the wheels. When the figure is high, the vehicle will pull out strong at start up or at low speed. When the figure gets lower, the top speed gets higher. Of course, you need to find the correct balance between top speed and acceleration as these two values exclude each other. To make it simple, the first gear of your real car makes it accelerate a lot but you don't get any top speed. On the contrary, the top speed is great with the 5th gear, but you'll need a lot of time and distance to accelerate and get it. The gear ratio is short in 1st gear (so the figure is high) and long in 5th gear (low gear ratio). The problem is that a real car has a gearbox that lets you change the ratio while driving: RC models don't have (apart some rare exceptions).

Choosing the gear ratio needs to be done when building the model, even if you can lately change it by disasemblying part of the chassis. The TB-01 is provided with a stock gear ratio of 9.91 which is very short. The box contains 3 different spur gears (61T, 58T and 55T) that allow you to change the gear ratio. But you'll need other motor pinions as the kit only provides a 16T.

Choosing the gear ratio is complex and mainly depends on 2 parameters: the surface on which you drive, and the motor. For surface, it can also be the track: when it is a low speed one with lots of sharp curves, the gear ratio needs to be short. If it is a high speed track with long straight lines and smooth curves, you should set the chassis for a high top speed. Still for surface, the more grip the faster you reach the top speed as there is no grip loss: you need a high top speed. Again, always compare to a real car: you won't climb a hill in 5th gear, and won't drive in 1st gear on the highway. And you don't drive the same way on ground, tarmac, snow or wet tracks.

The motor is also very important: to make it easy, the faster a motor can turn the less power it has at low speed. Power at low speed is needed to make a good start. So use a short ratio with a fast motor, and a long ratio with a slow motor (like the Mabuchi 540). With a short ratio, the fast motor will make a good start and will also get a good top speed since it can take higher turns. With a long ratio, an entry level motor will have enought power at low speed to make a good start and the top speed will be correct since it doesn't take high turns.

Bascically, this is the theory. Practically, you have to try to find the best gear ratio based on the surface, the track and the motor. One thing you can count on: a long ratio with a high turn motor or a very short ratio with a low turn motor are the choices to avoid.

For my TB-01, I will drive it on ground and the motor will be the stock Mabuchi. So I need power at low spped and the best possible top speed. Being an "average" situation, I chose an average ratio I calculated in a very scientific manner because I'm so gifted in maths: (short ration + long ratio) / 2. I told you . The short and long ratio values are those allowed on the TB-01 chassis (9.91 and 5.72). So my "average" gear ratio is 7.81, and the closest on the chassis is 7.94: theoretically, it the best compromise between power at low speed and top speed.. On the right is a capture from my TB-01 manual with the available gear ratio table and how to get them. The gear ratio is the combination of a motor pignon (lines) and a spur gear (columns). The "T" values (16T, 61T...) stand for the number of theeth on the gear. The stock gear ratio is 9.91 which means a 16T motor pinion used with the 61T spur gear. To get my 7.94 ratio, I will need to use a 19T motor pinion (optionnal) and the 58T spur gear (including in the kit together with the 61T and 55T spur gears). The letter between brackets along each gear ratio shows how the motor need to be mounted to perfectly fit the spur gear. That's it. I just now need to mount the 58T spur gear on the central shaft, the 19T pinion on the motor and fit the motor on its mount respecting the alignment. Finish rebuilding the chassis and we go for a test run.

The body

At first, I decided to swap between the Ford Focus RS WRC 2001 body and the Lancia Delta HF Integrale's (58117 kit). Afterwards, this was a bad idea: the Lancia body is way too fragile to be used in rally. So swapping between bodies implied to constantly modify the chassis setup from off-road to on-road, especially the damper settings. This is the reason why, after a few months, I decided to dedicate this TB-01 chassis only for rally and to get a TA-01 chassis dedicated to on-road use for the Lancia Delta HF Integrale body (which would then be a 58117 kit.

So the Ford Focus RS WRC 2001 body arrived a few weeks after the chassis, but it was already painted, decorated and in excellent shape. So I just had nothing to work on it, except some paint on the cockpit set (which is pretty much a reduced version compared to the Lancia Delta HF Integrale's).

First runs

The track is made of hard gravel with poor grip, which is great fine for controlling slides. The first impression is that the 7.94 gear ratio is still too short: my scientific method to guess it was not that reliable. This chassis general behavior is excellent and it is easy to control it. For this first run, the suspension was too soft: I changed the springs for stiffer ones but keeping the soft setting for the piston rod.

For the second run on the same track, I had changed the gear ratio to 7.18 (21T motor pinion): it provides a clear top speed boost keeping and still a strong traction needed for rallying due to the poor grip of the track. I also mounted urethane bumpers at the front and the rear to preserve the body. Unfortunately, nothing exists for this chassis, the only solution is to adapt TG-10 urethane bumpers (reference 53353) and to replace the TB-01 bumpers with TG-10 (reference 50803).

These are the last changes I made to this model wich was made for rally: it is very well protected against projections inherent to this kind of driving and proves to be reliable. Since 2008 and the 58417 kit release on the DF-03Ra chassis, Tamiya gave a new boost to the rally category by fitting short arms to the Dark Impact chassis. Unfortunately, the rally version shares its buggy counterpart problem: the gearbox is not waterproof and you can easily find comments of fans who made they motor pinion and spur gears bald due to dust and peebles getting in. Moreover, only a few models include a chassis cover, even if you can easily make your own by fitting a Dark Impact body on the chassis tub and then fit you rally bodyshell.

Even if it tends to become rare and its design is not the most recent, in my opinion the TB-01 chassis still remains Tamiya's best ever rally chassis.

More photos on the gallery.

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First publication: february 26, 2009 Last modified: june 07, 2010

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