TT01 Rally Spec Project - M1R

[andymac1981 2]

Hi All and welcome to my TT01 Rally car build. For any who don't know I have a thread already going that will hopefully document my 1st steps into RC racing and can be found at the link below. I also have a few other build threads and can be seen at the links below also.

So here it is as and when I bought it, a standard Tamiya TT01 with a Ford Focus Body Shell. This was my 1st RC car in quite a few years and has served to re-ignite my passion for the hobby again. As I said I do plan to race with a local club but this one will not be for racing and is more a project just for fun and experimentation.

So the plans for the car are to raise the ride height and put on some rally tyres to have some off road fun on gravel/loose surfaces and hopefully equip it so it will take a few small jumps ect. When I bought the car all the kit was standard including the motor and ESC. As of writing I have an HPI 15T motor for it. The car is 100% and the only fault is the ESC seems to have lost reverse probably due to age and being stored in a damp roofspace for a while.I have no plans to change the ESC at the minute as funds will be concentrated on other projects for a while although I may eventually get round to this.

Aside from the motor, tyres and ride height modifications I plan to try and seal up some of the holes on the underside if I am going to be going off road and also possible waterproof the electrics to a degree. I also plan on keeping the same shell but will modify it to something slightly different looking.

[SteveU30 1011]

Ooo we like rally car build threads, looking forward to this!

[XV Pilot 1936]

Sounds like a good project!

The TT-01 isn't the most obvious choice for a rally conversion, but it can work really well in this role with a bit of work. This is mine:

I started off with a used chassis in rather good condition, which had originally been built with parking lot racing in mind. In preparation for the conversion I disassembled the car completely and gave everything a good cleaning, so that I had what amounted to an unbuilt kit of parts.

The first modification I made was to cut away small sections of both front and rear B6 parts (the braces that go under the gearboxes, keeping the bulkheads in place). This allows the suspension to deflect further downwards. I didn't need to cut away much - I just trimmed where the lower suspension arms contacted the parts, until I had enough droop.

The second mod I did was to take the four SB4 outdrives and remove the protruding flanges. This I did by putting them in a drill press and holding a file to the spinning parts until the flanges were filed flush with the rest of the part. This was done to stop the flanges hitting the wishbones when the suspension is at full droop. Incidentally, this mod also removes some rotating mass from the drivetrain, improving performance. (If you don't fancy trimming the outdrives, you could simply replace them with DF02 outdrives which are supplied flange-free.)

The shocks were next to receive some attention. I decided to use Tamiya plastic Mini CVA shocks on the car, as they can be built quite long and give a nice smooth ride without costing a fortune. They also don't show scratches, unlike anodised alloy shocks that start to look a bit tatty after a while.

I built the shocks with small internal spacers, and used Yokomo ends on the shafts. The shock length is the means by which one sets the cars ride height, so they are pretty much a case of personal preference. More ride height = softer landings, but it makes the car easier to roll when cornering. It is just a case of experimenting to find the best setting for your driving style.

The extra travel that one gets from the mods described above means that the stock plastic steering links (part B1) are not up to the job by any means, as they limit your suspension travel. If you haven't done so already, now is the time to make up some adjustable ones using a bit of 3mm threaded rod (a bolt with the head cut off works well) and the four spare shock shaft ends that came with the Mini CVA shocks. These clip onto ball links that you screw into parts A7 and A1.

The diffs in my car were originally built to run very free, and only had a little thin oil in them for lubrication. However for rallying on gravel and sand, something a bit tighter is recommended, so that you dont lose out on performance when one wheel loses traction and all your drive suddenly gets transferred to it. The old drifter trick of using fuel tubing on part MA11 makes them a bit too stiff, but packing them full of AW grease seems to work well.

At this point I added my usual selection of TT01 go-faster goodies to the mix. These are again a matter of personal preference, and depend on how mild or wild you want your car to be. I chose to use the following, for the following reasons:

· Sealed bearing kit, for ease of maintenance and less drive train friction, resulting in more speed and longer runtimes.

· Aluminium prop shaft, as the standard one tends to vibrate at speed if you use anything faster than a standard Johnson 540 motor.

· Motor heat sink, to keep the motor cooler and prolong its life.

· Metal motor mount, to further help with cooling and to overcome the classic TT01 wobbly motor syndrome.

· Carbon chassis brace, for added rigidity and robustness.

· FXX long axles and hexes all round, to widen the track slightly for better cornering stability.

· 2 degree toe-in rear hub carriers, for improved straight-line stability.

· 58-tooth spur and 25-tooth pinion for taller gearing.

With regards to the gearing, one can go all the way to 55/25, but as the courses for rallying are typically quite tight and technical, I thought it better to sacrifice a bit of top end for the sake of punchy acceleration. Gear ratios are easily adjusted though, and also depend on the motor you choose for your car. For example, a Johnson-equipped rally car seems to work well with around a 61/20 ratio.

I considered putting adjustable upper wishbones on the car, but decided to stick with the stock items as they are stronger, and cheaper to replace if they do break. Rally cars have to be tough, and also cheap and easy to fix, as they are probably going to take a bit of a hammering on the course. As a clubmate said, "A basic guideline for a rally car is to keep it simple. The wear and tear is extreme, so dont put expensive components into the car."

The final step on the chassis was to stone-proof it. The TT01 already has all the gears sealed, so the main areas that need protection are the driveshaft and steering mechanism. It is also a good idea to find a way to keep stones and other debris from collecting in the tub and weighing the car down, and some protection on the underside might also be wise if you want to keep it looking neat.

To stone-proof the driveshaft, I initially made it a cover out of transparent plastic overhead projector sheet. This I secured with double-sided tape. It worked satisfactorily, but when a stone did manage to work its way in there, it was a real pain to get it out again. I have since removed this cover, as it was more hassle than it was worth.

To stop debris from getting into the tub, I first tried a set of lexan mudguards. These didnt work at all, so I instead opted for a cotton fabric cover that fits over the entire tub. The cover is elasticised front and rear and attaches to the tub sides with Velcro. A piece of foam cut to fit around the front driveshaft cup and steering mechanism keeps debris clear of this area.

This solution works really well. The fabric is breathable to facilitate motor and ESC cooling, but it keeps stones and dust at bay. I find it works even better if I dampen it with water before running the car, as this lets it trap more dust, and further helps with cooling.

To protect the underside, I first covered it in a layer of fibreglass tape, which I followed with a layer of black duct tape, doubling up on the front over the area where the three screws attach part B6 to part A2. I know from experience with off-road buggies that it is important to protect screw heads that might otherwise be worn down or clogged with debris, making disassembly of the car rather tricky.

To finish off the chassis I added a waterproof LRP ESC, a 19-turn rebuildable LRP Rally Special motor (rebuildability being important in rallying as motors can get a bit mucky and need regular cleaning of their innards) and a water-resistant Spektrum receiver.

I then fitted that car with appropriate wheels and tyres. I used Tamiya Rally Blocks, which are easy to find, not ridiculously expensive, and provide a good compromise between grip on tar and gravel. These were mounted on a set of 2mm offset rims. The less offset you can get away with, the less bending stress is placed on your axles when you land after a jump, although more offset = wider track = less chance of rolling. Compromises, compromises...

I think a rally chassis deserves a bodyshell that represents a full-size rally car, and my LHS happened to have HPIs Mitsubishi Lancer Evo VI bodyshell in stock at a reasonable price, so thats what is covering my chassis at the moment. Your Ford Focus shell also sounds quite fitting.

I look forward to reading more about your project as it progresses. Good luck, and be sure to keep us posted!

[andymac1981 2]

Thanks for the reply's and thanks for the guide XV Pilot. It seems you have done wuite a lot to your TT01! At the minute I have 4 on going projects and most of my money at the minute is being concentrated on my M05 Race car (I'll get a thread up soon) as I plan to enter my 1st Race in 2 Saturdays time. The rally car will be completed with either cheap parts or stuff robbed from the parts bin at home. I do have a an update from working at the car last night but will post from home as my work PC won't allow me to upload pics to the thread. I like the Evo 6 shell and think it looks smart and I actually have one in the house but that is set aside as a possibility for my TT02 race project. For this one I think I will stick with the focus shell but it will be different (still white though).

I love your idea of the fabric cover and looks very useful, my auntie is quite useful with a sewing machine so might need to test the water see if she can get something together for me!

One question, did you strengthen any parts of the shell with the likes of fibreglass tape or the like?

[XV Pilot 1936]

I found it useful to reinforce the front end and wheelarches with fibreglass tape, and to add some foam tape to the inside of the front bumper to help it transfer impacts to the chassis foam bumper without cracking.