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M04RR Project - Rear motor M04M Miata

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I want to share with you all my Tamiya M04RR project. I have posted about it before in my TC showroom, but it has evolved a lot since.
You can find my old showroom entries here: http://tamiyaclub.com/showroom_model.asp?cid=96268&id=19827

The M04 has always been the black sheep of the M-chassis family in my experience. That makes it all the more fun to be quick with one. I had been racing my bodged RR conversion since early 2011, and every year it proved to be really quick and easy to drive on our track. I originally build the M04RR before Tamiya came out with the M06. The new M06 proved I was on to something with the rear motor layout. Since our club was growing a lot in 2013, and our annual big race weekend was coming up I had to step up my game and rebuild my poor worn out M04RR.

I started from scratch with a brand new M04 kit I got cheap of a friend. I also had another friend draw up some 3D drawings for a simple adapter to convert the M04 to RR without the need of modifying any part. Just add some screws and spacers, and it works. The new car would be build using every single bit I had always wanted on my old M04RR but never bought. I will skip all the evolution of the old car, and go straight into the build of the new car.
I already had a body which I barely used and handled great. I have reused it for the new car. Its a Tamiya Miata with a Kamtec spoiler on HPI stands.
Here you can see it when it was brand new, next to my FWD Sakura D3 touringcar project. I took more pictures that night, but I can't find them anywhere...

I bought a bunch of hopups and special parts for this build, and I will try to explain why I used those specific parts so you guys have an idea of what this chassis is build for.

When I started the build I was still waiting on some parts including the screws. The entire car is build with M3 hex screws instead of the standard self tapping screws, because I like working with hex screws much more. Plus is also looks great! All plastic parts have been pre-threaded so the build would be quicker and more precise. The screws I am using are Hiro Seiko stainless steel blue plated screws, so they are much stronger than the usual coloured screws that are anodized aluminium. Hiro Seiko is one of my sponsors, so I got a good deal on the screws :)
Because I knew the M04 of the top of my head already, I did not follow the manual. I started with the front end of the car, as I had most of the parts in stock already.
- Inside the bulkhead there's 25gr. of weights for a bit more front grip. The chassis is very light in the front so this is needed or it will lift the front wheels to much.
- It is fitted with one-piece reinforced plastic lower arms from Cross Racing. This makes it easier to work on the car, its stronger and simply looks better.
- On the inside of the arm I used Tamiya gold coated kingpins, and I shimmed most of the slop out of it.
- The dampers are a mix of 3Racing TRF copies and old pink TRF dampercaps. I wanted to keep the pink colour of the old dampers, but with adjustable preload and full length cilinders. Now I can adjust the rideheight and preload much better than before. I used 2-hole TRF pistons, soft (blue) TRF O-rings and Yokomo medium bladders. Its filled with MuchMore #350 oil and set to full rebound. The springs are ltd.ed. metallic black TRF Medium (yellow dot) springs but will be replaced later on in this build thread.
- Just for the looks I added 3Racing pink aluminium ball connectors.

On the inside the gearbox is fitted with
- Hollow carbon shafts
- Ballbearings, cleaned out and re-oiled with my superb Hot Racing bearing oil
- Tamiya reinforced gears
- Standard geardiff filled with lots of AW grease to keep it from spinning one wheel in the corners.

On the outside the gearbox is fitted with
- Cross lower arms with Tamiya gold coated kingpins. Slop removed by shimming again
- Tamiya M06/M05golded. kingpins with ball connectors. This places the damper more outward on the lower arm, but also increases the damper angle to give the car a bit more sideways grip and keep it from spinning out. I ordered the gold coated kingpins but got the normal silver ones instead, bummer!
- Yeah Racing 3* toe-in hubs. I need the maximum amount of toe-in on the hubs to compensate for the toe-out you get from the gearbox suspensionmounts. On a normal M04 this gives you 0,5* or 1* toe-in, but because I flipped the gearbox around it is toe-out. It works out as around 2* toe-in on my car. Another advantage of these hubs is that you can play with the rollcenter. I used the outer hole on the hubs to get minimal camber change on the rear wheels.
- 3Racing 6mm wheel adaptors on standard M04 shafts. I also shimmed out all the slop here. I had to use 3x0.2mm and 1x0.1mm shims per side!!
- Ballbearings offcourse, with the same oil threatment as the others.

- Rear dampers are build up the same way as the fronts. But here I used #300 MuchMore oil and soft springs (red dot).
For the steering of the car I used the following
- RC OMG brushless lowpro servo. This is the old prototype servo I had in my competition drift car, which I don't need because I'm testing a new aluminium housing RC OMG servo now. These RC OMG servo's are fantastic quality, better than anything I've owned before including Savox, Sanwa, Futaba and Hitecs. If you are in the market for a new servo, you should definatly check RC OMG out. Their stuff is amazing!
- Tamiya high-torque servosaver with the hopup aluminium arm for M03/TL01/M04.
- Tamiya aluminium servomounts to reduce the chassis flex around the servo.

And here you can see the 3D printed adapter I had made by Shapeways. It replaced the aluminium angle bits I used before. This is much more solid and is a direct fit. All I needed to do was M3 thread the holes in the front. For those of you who would like to build a M04RR, the adapter is for sale on Shapeways. You can find it here: http://shpws.me/rwdG

In addition you will need 4x 18mm or 20mm screws and 4x 5mm spacers to attach the adapter to the gearbox. I used 3* toe-in hubs, so if you are using the standard hubs, 4mm spacers might work too. Either way you can adjust the wheelbase by changing the length of the spacers so you can always make it fit your specific chassis and bodyshell combination.

I chose Strong&Flexible Pink Polished, but you can buy it in different colours too.

And that is what all of the above looks like together. I will post another update soon, as the car is already finished but I need to translate the build thread from my local forum :) Hope you like it so far!
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I don't understand one thing: why make two sections (or adapters) when you can make only one?

Now you have a pink section and a black section. Why not a single longer pink section?



And here you can see the 3D printed adapter I had made by Shapeways. It replaced the aluminium angle bits I used before. This is much more solid and is a direct fit. All I needed to do was M3 thread the holes in the front. For those of you who would like to build a M04RR, the adapter is for sale on Shapeways. You can find it here: http://shpws.me/rwdG

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The black adapter is the original M04L spacer. Without the spacer I can run short wheelbase (210), and with the spacer I have medium wheelbase (225). 2 spacers should get me almost right for long wheelbase (239). So now it works like a factory Tamiya part. Making it all in one piece would be a lot more expensive to print at Shapeways, and also would not allow me to change the wheelbase without having to make a different length spacer.

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Here's the next update
I finished building the chassis in the 2 nights before out annual big race weekend, so I had no time to take pictures before racing the chassis. Here you can see it with two succesfull race days under its belt.
The car ran good, but not as good as the years before. This was mostly because of the lack of grip, as we ran out of sugarwater to spray the track with so the entire track was less sticky then we were used to. Near the end of the second day I switched to a softer compound tires (33 to 25) and that made it a lot better.
My package with the Hiro Seiko screws and shims I needed to finish the car arrived just in time so I could finish my car on thursday and friday night with the help of one of my friends' endless supply of M-chassis parts.
The M04RR as it sat back then. Not completely finished, but ready to race and pretty quick.
The chassis has been cut to fit 4200mAh shorty lipo's which are held in place with glassfiber tape.
The rear suspension as it sits now
- Back to standard lower arms, as the Cross arms are not the same shape and are useless. They shorten the wheelbase a lot.
- HPI purple turnbuckle on the upperarm as I needed a longer one plus this is much easier to set up than just a long grubscrew. I spaced the ballconnector on the chassis backward to reduce the angle of the upperarms so it can move more freely.
- Raised the rideheight a bit
- 5mm spacers behind the 3D printed adapter to get the right wheelbase. The spacers are from Hiro Seiko. I did have to change the holes in the body for the bodyposts a little bit.
- Hiro Seiko serrated wheelnuts
The front suspension in temporary form
- M03M Swift c-hubs and knuckles. These will be replaced by M05 c-hubs and knuckles to remove the bump steer. The M03M Swift knuckles are already better than standard.
- Lightweight kingpins in the c-hub/lowerarm. These will also be replaced by gold coated ones when I get the M05 stuff
- Standard upperarm. I would like to get an adjustable one, but I'm not sure what to use as its so **** short.
- Front toe set to about 1 - 1.5* toe-out.
- 100 gram of weight on the front bumper. This seems excessive, but it works. Might play with it a bit more in the future.
- Short white TRF spring for M-chassis, as I could not get the front rideheight low enough with a full length spring. This is also a medium (yellow dot) spring.
In this picture you can see the nice low profile of the chassis
- RC OMG HDT045070B Lowprofile servo sits a bit to high in the chassis, so I spaced it down by 3mm on the servomounts.
- The Tamiya servomounts are to short surprisingly, being an official listed hopup for the M04. Even with the supplied spacers it still sits to one side a bit. I have used another spacer to get it closer to the center. It does reduce the chassisflex around the servo now, so it works as I intended.
- Reciever mounted on the side of the chassis for a low profile and lower c.o.g. I might move it to the other side of the chassis to balance it out.
- Mesh sleeves around the ESC and servo wires for a cleaner look. Both wires have been cut to the right length.
- Castle Sidewinder V3 ESC with pink wires. I removed the third motor wire as I only intend to use this ESC for brushed. The ESC is great to set up! Much needed for a RWD car with relatively low grip.
- Blue stainless screws from Hiro Seiko throughout the entire chassis. These screws are amazing quality! I have been using them for a long time in my competition drift car, and they are super strong and the colourplating will last a long time. I have rebuild my car many times, and driven it on asphalt and concrete many times but I don't have a single screw that is even scratched. Most of the spacers and nuts used in the chassis are also from Hiro Seiko and match the Tamiya blue colour very well (better than the screws).
- Carson Cupmachine motor with a 21t pinion. This thing has a bit to much power for the M04RR sometimes, but on carpet tracks I can use all of it B)
- Tamiya M04 motorcooler on the opposite side to balance out the weight of the motor a bit.
And lastly the body of my M04RR. I should've taken more pictures when it was new, as right now a lot of the paint is flaking. Tamiya PS paint is not what it used to be at all, and the fluo colours are the worst! :(

One more update to come!
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That is pretty neat.

I feel inspired to build one with TL01 arms and driveshafts and run a proper Porsche bodyshell, as they are in real life. As if I don't have enough projects to finish already!

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That is my next project, an M04RR-XL. TL01 arms and a 260mm wheelbase to run one of my Kawada 2000GT bodyshells on. I still have my old M04RR, as I build this one from all new parts, so I can rebuild that one.

It would also be cool to have a short wheelbase M04RR with the HPI Porsche Cupracer bodyshell on it :)

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nice work :) , is it any faster in the turns ? ,

i ask as the last thing thing my m04's need is to loose front end grip , especially on power , with your m06 style rear end i get the impression that the car will push (understeer)even more when powering out of corners ,


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It pushes a lot actually, but never ever loses the rear traction. You can get on the throttle very early coming out of a corner and along with the 1 teeth bigger pinion you can get a lot of speed going already before any other car on the track can. Its definatly not the fastest car. I'm slowly building an M05 at the moment to see if I can go faster (pretty confident it will be) but its not as much fun as racing with an underdog chassis. Because of the understeer/pushing it is very predictable, something that can not be said for a normal M04. It is also really stable with a pretty low COG, so you can run the kerbstones very hard. A FWD M-chassis would just tip over on its side if you try doing that.

So its not really much faster, but with the right drivingstyle you can keep up very well and even overtake most of the field. I race it in a field with mostly amateur drivers and I can beat all of them so far

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