Tamiya TRF201 Project

Page 1: Building the TRF201

Considering the content of this box, it is really small. If you look closely, you'll see that it is only labeled as an XR Aluminum Upper Deck Set, not the 42167XR number under which it was sold. In the picture on the right you see the contents after the body and wing were already removed, and it still pretty much full. The parts you see in individual packaging are the big bore shock upgrades. If I'd had to pay full MSRP, this box would have cost ~$1100.

This is quite a complex set so it comes with a lot of parts. It even comes with 3 different kinds of grease as shown on the right. Beyond the large number of parts trees, the hardware bags are stuffed full with aluminum parts and high quality hex hardware. There are no tapping screws, only machine screws.

It is interesting to note the quality of the plastics in this kit. Pretty much everything is reinforced in some way or another. If you can read the molding codes you can see how. The gearbox housing on the left is a carbon filled polyamide, probably Nylon. The body tub on the right is a glass fiber filled polyamide manufactured in May of 2010. All other things being equal, the carbon filled will be stronger and stiffer and the glass filled will be more resilient. The carbon fiber parts are so hard that the manual recommends tapping the threads into the holes before installing any screws.

Step 1 is assembly of the ball differential. The picture on the left shows the parts for this step. One unusual feature of this kit is that it uses Imperial sized balls (like its builder). The diff balls are 3/32" in diameter and the thrust bearing balls are 1/16". Presumably this is to make them compatible with American racing buggies, though I'm not sure why it matters whether or not the balls match. Perhaps racers are crazy enough to rebuild their diffs between races and need to stock a consistent size of balls. The diff uses nice hard steel drive cups and a Nylon gear. There are a number of spacers and shims used to make everything fit perfectly with no slop. The diff uses 12 main balls.

The thrust bearing needs to be carefully assembled from 8 balls and a pair of thrust washers. The clamping nut is blue anodized aluminum. The completed ball differential is shown on the right with the 15x10mm support bearings installed.

Step 2 builds the idler gear and counter gear. The idler gear is Nylon and just sits on a pair of bearings and a solid shaft. The counter gear assembly uses a steel shaft, a steel gear held with a cross pin and retained with an o-ring, and some spacers and bearings. I've always found the name "counter gear" odd, but I guess it makes some sense. Because the spur gear will sit on the other end of this shaft, it rotates in a direction counter to that of the motor.

Step 3 assembles the gearbox. My 3mm tap was required to thread some holes for this step. Some 36mm length 3mm screws were also used to pass all the way through the gearbox to the motor mount. These may be the longest Tamiya screws I've seen. The picture on the right shows the differential, the idler gear, and the counter gear installed in one half of the gearbox housing.

Once the gearbox is closed up the aluminum motor mount / heat sink can be installed. Thread lock is required at this point but was oddly not included in the kit. This is surprising given how otherwise complete the kits seems to be.

Step 4 builds and installs the slipper clutch. This kit uses a 48 pitch, 79 tooth spur gear to be compatible with American racers. There are two slipper plates and two hexagonal pads. The spring uses square wire, a type I've not seen in another Tamiya kit before. The completed gearbox assembly is shown on the right.

Step 5 builds the rear upper and lower decks. The upper deck will support the shock tower and turnbuckles and the lower deck will support the lower suspension arms and gearbox. On the right you can see that some ball joints were added to the upper deck and protected from contamination by foam rings. The lower deck has had the front suspension mount installed. The spacing of the holes on this mount along with the matching mount on the rear will determine the rear toe angle.

Here in Step 6 the rear decks are attached to the chassis tub with a pile of countersunk hex screws as shown. This is a very simple step.

Step 7 builds much of the rear suspension. The lower arms are angled slightly back. They can be switched left to right to alter the wheelbase. The vertical hubs are installed backward. By that I mean they are labeled with L for Left and R for Right but they are installed opposite that. The hubs install to the arms with 2.6x27mm shafts with spacers on either side of the hub for a perfect fit. There are no E-clips to install. Instead the shaft is retained with a tiny screw whose head overlaps it. An exploded view of the assembly is shown on the right.

Step 8 installs the rear suspension to the chassis using only the rear suspension mount and a temporary 3x5mm screw. When the bumper is installed later this screw will be replaced with longer versions that go through both parts.

Step 9 mounts the gearbox to the chassis. Two screws are installed from the bottom through the chassis plate and another 2 are installed from the top into the rear upper deck. This split support allows the whole gearbox to act as a stiffener for the rear chassis.

Step 10 builds the rear universal axles and upper links. The axles consist of a swing shaft, a cross joint, an axle a pin, and a grub screw. The links use blue anodized titanium and they look really nice. The ball cups are a special type that fit very tightly.

Step 11 installs the parts from Step 10 onto the chassis which completes the rear suspension. It is a real pleasure to run this suspension through its range of motion and feel the absence of slop or lost motion. Setting the link length to exactly 23.5mm was not that easy with my dial caliper.

Step 12 is the rear shock tower, a huge cross braced plastic part. The wing support brackets connect directly to the shock tower. In the right hand picture you can see the unusual horizontal body posts sticking out at rearward diagonals. You can also see that two of the countersunk holes between the rear upper deck and the chassis are empty. The manual never asks you to fill these holes.

Step 13 installs the rear motor guard which also acts as a bumper and wraps around from the bottom of the chassis to the top of the gearbox housing making it nice and stiff. There is also a diagonal link which connects the gearbox to the shock tower. I really like this detail. It adds so much strength to the suspension.

Step 14 builds the steering mechanism including dual bellcranks with servo saver. These are hard carbon filled plastic parts with tiny ball bearings (7x3mm). The fit and motion is very precise with very little backlash. More titanium turnbuckles are used as steering links.

Step 15 installs the steering mechanism into the chassis using even smaller bearings (6x3mm) and 3x33.4mm posts. Note how the whole steering mechanism is tilted back to match the kick-up angle of the chassis. While the bottom end of the pivots bolts directly to the chassis, the upper end is somewhat floating in space, retained only by a single countersunk screw on a post. The upper deck, once installed, will grab the little conical pin forward of the screw, but I'm surprised to see that this whole upper end of the mechanism wasn't retained more firmly.

Step 16 attaches the C-hubs and steering knuckles to the front lower suspension arms using quite a few parts as you can see on the left. The steel axles are separate parts which fit into the knuckles and are fastened from the back side. The axles have a very slight asymmetry which it is easy to miss (and in fact I did miss it). The effect of this asymmetry is movement of the front wheel very slightly forward from the center of the knuckle. If you look very closely at the right hand axle in the right hand picture you can detect that the long end is not perfectly aligned with the short end.

Now the knuckles can be installed into the C-hubs. Instead of using separate upper and lower kingpins, this kit uses a single vertical 2.6x22mm shaft which provides a very smooth steering axis. The hub then connects to the arm with a 2.6x25mm shaft and a couple of spacers for centering. The wheelbase could be altered slightly by changing the configuration of these spacers.

Step 17 attaches the front arms to a center bulkhead. It is interesting that this bulkhead is a separate part which means the arms do not pivot directly from the chassis. The arms are attached to the bulkhead with 3x35mm shafts and retained by an aluminum front plate.

Step 18 bolts the self contained front suspension assembly to the chassis plate with a single countersunk screw installed from below. This is as simple as steps get.

Step 19 builds and installs the front shock tower (which Tamiya calls a damper stay) and upper deck. The deck includes a bit of support for the steering cranks, a front body post, and structural support for the shock tower. These are both very hard carbon filled parts. We even get a little Tamiya logo visible from the front. We start by installing some spacers, ball connectors, and dust covers to the shock tower along with some long 3x23mm screws for the shocks.

Now the shock tower can be bolted to the upper deck with 4 screws. Finally, this entire assembly is connected to the chassis to complete the front suspension. At this point both the upper suspension links and the steering links are connected. There is also a tiny (almost invisible) front bumper protecting the bottom of the chassis tub.

Step 20 opens hardware bag C which contains the parts for the standard TRF buggy shocks. The all aluminum shocks have a 10mm bore and a lot of parts as you can see. The complete assortment of parts is shown on the left. On the right you can see three completed shocks along with an exploded view of the fourth. The kits comes with two sets of pistons, one with 1.3mm holes and one with 1.4mm holes. I certainly wouldn't be able to discern the difference between these two, but I tend to like softer suspension so I chose the larger holes. Note that these are emulsion shocks which don't use a bladder. Instead, air is removed through a bleed screw in the head end cap with the shock retracted. The results in a void when the shock is extended. Shock assembly continues into Step 21 which adds the oil and bleed procedures.

Step 22 installs the completed rear dampers behind the rear shock tower but ahead of the rear suspension as shown. Special joints are used at the top to allow spherical rotation without a ball joint. There's also a plastic retention nut here. I assume this is to prevent over tightening which would crush the joint.

The shorter front shocks are installed in Step 23 using the same procedure as the rear. There is a difference in lower attachment point as shown on the right. The rod end sits in a slot in the middle of the lower suspension arm.

I had a Tamiya brushless system saved for just this occasion. At one point I had a pair of TBLE-03s controllers in my TXT-2 but they don't work well in pairs and I burned one out. I saved the good one for a worthy cause and this was it. I combined it with a TBLM-02s 10.5 turn sensored motor and a 25 tooth steel pinion gear. Step 24 installs the motor onto the chassis. As previously mentioned, this chassis uses 48p drive gears.

The gear cover is soft plastic and includes a removable cap to access the adjustment nut for the slipper clutch. Many brushless motors have tabs onto which you must solder the wires which requires that the motor be oriented in a specific way to avoid interference with other parts. Tamiya brushless motors have colored 4mm bullet taps in the end face so orientation isn't important.

Step 25 does no more than attach a servo horn to the steering servo. The kit comes with two servo horns: one with 24 teeth and one with 25 teeth. The cheap Futaba servo you see here is just a placeholder until the correct servo arrives. I got a low profile Savox servo that would work well with all three chassis variations.

Step 26 installs the steering servo in the chassis. Most Tamiya kits use only two screws to mount the servo to the attach brackets, but this kit uses four. Another two countersunk screws attach the brackets to the chassis tub. The steering link is very short and requires you to cut two ball ends to make them short enough to work.

These pictures combine Steps 27 and 30. Step 27 shows you how to install the electronics. I put the ESC on the left and the receiver on the right. There is plenty of room to spare. The battery area runs down the center of the chassis and will accept a NiMH stick pack or a hard racing LiPo pack. Step 30 builds the battery holder from the parts shown on the left. A pair of thumbscrews hold it in place. There is a transponder mount as well.

Both the front and rear wheels attach in unusual ways. These pictures show the installation of the rear wheels. There is no 12mm hex, instead the drive pin mates directly with the inside of the wheel as shown. There are also some spacers and washers which sit behind the wheel to make it fit tightly with no lateral slop.

It is not unusual for the front wheels on 2WD cars to have the bearings housed in the wheels, but usually they are installed with a 4mm nut. In this case the hub actually has an internal thread so the wheel is installed with a screw instead. The screw is not self locking like a nut so thread lock is required. Both the front and rear tires need to be glued to the wheels. I chose competition compound dual block tires. Front are 25mm and rear are 35mm wide.

With the wheels installed, the rolling chassis is done. This is a great looking and well balanced chassis. From the bottom you can see the clean, smooth lines. You can also see the standard toe out in front and toe in in the rear.

The body and wing came back from the painter better than I could have hoped for. Hats off to SKG RC Painting for his stellar work here. The kit does not come with the correct stickers to decorate the car like the box art, but judicious application of the TRF stickers looks pretty good. I kept them minimal so as not to hide too much of the paint.

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