Tamiya Formula E Project

Page 1: Chassis Assembly

The image on the left shows the entire pile of stuff that was gifted to me. It is hard to think of all the things which will be needed to build a model including all electronics, paint, and bearings but my friends did an excellent job and I didn't have to buy a single thing. The picture on the right shows the contents of the box don't look like anything. A lot of work is needed to turn this into a racing car.

Here are the contents of the box. A large part of the overall parts volume consists of body parts which are still in the box. Even so, this model has a vast number of parts. This is a complicated chassis that should be a joy to build. There are four labelled hardware bags which are used sequentially (only one open at a time).

Did you notice that there are two sizes of ball joint here? I didn't. They have different part numbers in the manual but it still did not jump out at me that they were different. Make sure you pay attention and use the two shorter ones in the right place. On the right you can see that I broke my ball joint pliers (center tool), though I don't think it had anything to do with my failure to distinguish between the two sizes. The fracture gave me the opportunity to buy better tools which I do not lament.

The build starts with the chassis tub and the fittings for the front lower suspension arms. This models uses a lot of shims and spacers to control part locations. The track width can be changed slightly by altering the number and location of the washers shown on the left. From what I can tell, pretty much every plastic part in this model is glass filled so they should be pretty strong. It is not a great idea to tap directly into GF plastic because it is brittle. Tamiya got around this by using nuts almost everywhere. On the right you cans see multiple slots for nuts viewed from the bottom of the chassis. This kind of assembly is tricky since they tend to fall out while trying to assemble the mating part.

The lower wishbone arms assemble as shown in the exploded view. The wheelbase can be adjusted using the shims which sit ahead and behind the arms. A set screw which protrudes from the bottom acts as a bump stop and sets ride height. A metal ball is pressed into the end to support the uprights. The other two ball joints are for the shock pushrod and the anti-sway bar. The rear suspension goes together exactly the same way using the same parts. The rear toe angle is also adjustable by differentially varying the number of washers on the front and back arm mounts.

There is very little room for electronics in this model so your choices are very important. A low profile steering servo must be used. I've got a fast Savox racing servo here. The kit does come with Tamiya's high torque servo saver which uses metal springs. I'm pretty sure the bracket outboard of the servo is for a transponder. I used the small Hobbywing ESC shown on the right, but I had to later remove the cooling fan since it simply wouldn't fit. They don't say so in the manual, but chances are that the Tamiya TBLE-03s would be the best fit.

Time to get the motor mounted. The motor mount is an aluminum plate supported by a plastic bracket which houses an aluminum main shaft supported by included ball bearings. I used a 10.5T Tamiya TBLM-02s sensored brushless motor which is about as powerful as you would want to put in this chassis. I replaced the stock 24T aluminum pinion with a steel version from Robinson Racing as shown. The spur is 63T and does not use a slipper clutch. Gear pitch is 0.6 mod (metric). The stock ratio is 6.56:1 but can be adjusted anywhere from 5.25:1 to 7.5:1 using pinions from 21T to 30T. No optional spurs are listed because everything is so tight I don't think anything else would fit.

Now I'm trying to cram all those electronics into the chassis. The Tamiya TBLM motors don't use solder tabs, they use bullet connectors inserted into the end. I trimmed all the wires to length and soldered them to the connectors as shown. A bracket then mashes all the wires down against the chassis because the front drive shaft will sit right above and needs to be clear of obstacles. On the right you can see that I've also hidden the motor wires as much as possible. My ESC came with a capacitor pack for which it was hard to find a home. I ended up sticking it to the outside of the chassis, but still within the body lines.

Time to start working on the suspension. The front cover is assembled by adding 90° crank arms to it supported by ball bearings. The other 6 ball joints seen will be for the upper arms and shocks. There are a lot of ball joints on this model. The rear cover is shown on the right and works exactly like the front though the outer profile is a bit different. These covers will enclose the differentials.

This picture shows the only metal bushings which came with the model and these are intended to be used for the steering mechanism. Bushings can arguably provide tighter action than bearings because there are fewer clearances, but I switched to bearings anyway.

Here the steering linkages have been installed and you can see how little clearance they have to adjacent wires. Wire routing and tie downs are very important on this model. The steering rods are intended to be fixed length, though spacers can be added to adjust the toe angle.

The front and rear differentials are identical so two are built at this point. The diffs are open but oil filled so resistance can be adjusted by using different viscosity oils. Tamiya clear shock oil comes with the kit and is used to fill the diffs. The internal spider gears are plastic as is the cross bar. Steel optional parts are available. The differential pinion gears are shown on the right.

Here you see the installation of the front driveline. The differential is installed into the chassis along with the front drive shaft. You can see that there is an angle between the shaft and the drive cup which is not ideal for efficiency. These can be replaced with universals. Once the gears are greased, the front cover can be installed which completely obscures the steering linkage. You can see how little clearance there is above the ESC.

The back driveline installation works exactly like the front. The battery will sit laterally in that slot underneath. The rear toe angle is controlled by the fixed length links shown.

The upper suspension arms are true wishbones with ball joints at all three corners. Plastic caps are installed on top of the outer joints to prevent from being contaminated on the track. The same arms and uprights are used in the front and back, but of course the rear steering angle is fixed. The stubby pushrods for the shocks have also been installed at this point connecting the lower arms to the cranks. The outdrives are dogbone type.

Now we'll build the unusual oil shocks. The assembly sequence isn't odd, but the very short stroke combined with the very long rod ends makes these look really odd. The springs are quite stiff which makes sense with that short stroke. These inboard, pushrod type shocks allow for a very low body. At the time I was building, no aluminum upgrade shocks were available. The exploded view on the left shows how the shocks are assembled and the view on the right shows them all installed. The shocks are filled with the same fluid used in the differentials, Tamiya's second heaviest weight.

The kit includes plastic wheels and directional tires with foams. The tires must be glued or they will come off immediately. These photos show the wheels and tires as well as the aerodynamic aids in the front and rear. There is a huge splitter in front which also serves to protect the fragile body and a diffuser in back.

Here is the completed chassis. It is completely driveable at this point. I had no trouble fitting my standard 2s LiPo in this chassis as shown.

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