Tamiya Mazda Eunos - Off Road Edition

[SnøMotion]

The first of several 'in progress' projects I'll post and the most recent one I started. It's the Tamiya Mazda Eunos Roadster, or MK1 MX5, or Miata...

 

 

Anyway, I bought this because it was cheap and I thought I might lower it and chuck some little fat wheels on. But then I thought that's what happens to most MK1 MX5s, so maybe I'll make a dune buggy because the tyres should be fairly easy to model. So I need to model a lift kit and some wheels, maybe a roll cage and new exhaust.

 

First thing I did was wheels and tyres - because it's fun! I decided to recreate the original 14in wheel centres but as though they'd been machined from the original wheel and converted to split rims. Then I went with a 17in front rim and 15in rear to keep the overall diameters similar. The wheel centres are the same front and rear (because they're modelled on the originals) and I made separate valves that push in from the outside.

 

 

After printing a set of these and mucking about with them for a while, and making a start on the front suspension, I decided I'd quite like to do a set of off-road wheels, too. Then I could make a trophy truck or rock crawler type vehicle as an alternative. Because the off-road wheels would be a square set-up (same diameter, width, offset front and rear, not actually square!), I thought my rear offset on the sand wheels was a bit too aggressive for the suspension to work with both sets of wheels and keep a similar front and rear track. I re-modelled the rear rims and re-printed them. As you can see in the photo below, it's not a massive difference (1.4mm actually). The left is the original and the right is the new version.

 

 

Below is the final set of sand wheels and tyres with an original wheel and tyre for comparison.

 

In order to create the off-road wheel set I needed to up my tyre modelling game and picked the Yokohama Geolandar X-AT as my inspiration. This wasn't too bad to model as it turned out and I'm really happy with the result. For the wheel, I went with a Fuel Zephyr as my starting point but made them a 4x100 bolt pattern to match the original MX5. I went for a 17in wheel and I can't remember what size tyre I picked but it comes out at about a 32in.  The wheel comprises a Tamiya style locator that is also the wheel nuts, the wheel, a centre cap, a valve and a lock ring. I did this mainly for ease of painting  Although, the separate centre locator does mean I can create an Aoshima/Fujimi style one in the future. I'll probably model some 5 and 6 bolt versions of the wheel, too.

 

 

Once I'd printed the wheels and tyres, I thought it'd be much better if I gave the tyres a bit of 'sag' so they look like they've been aired down for off-road use. I use Fusion 360 for my modelling but it isn't really made for deforming stuff. As it happens, I also have a copy of Blender installed, so I used the mesh deformer in that to squash the bottom of the tyre and I'm really happy with the results. Below is a photo of the full set of wheels and also a comparison between round and sagged tyres.

 

 

Whilst I'd been messing with wheels and tyres, I'd also been working on the front suspension mods. These components basically replace the kit originals directly with the removal of the anti-roll bar and addition of a sump guard/skid plate. I didn't want to have to cut or modify any of the original kit parts, so the front and rear track are vastly wider that original for tyre clearance. In fact, the wheels are entirely outside of the original bodywork!

 

Although this doesn't articulate, I did check that it was "useable" in terms of camber and steering. It has a crazy amount of lift and I wanted to give as much ground clearance as possible, so the track rod angles are ridiculous. Through the full "movement" of the suspension, though, the hub would remain the same distance from the steering rack, so it shouldn't be a nightmare to drive. The track would actually alter dramatically, though, and I guess that's not ideal. Here are some shots of the front suspension so far, with comparisons to the original kit parts. Everything is beefed up for off-road use.

 

 

I'm now working on modelling the rear suspension and am pretty much there. I still need to work out the propshaft, differential and half shafts, as I'm keeping to independent suspension. I think I'm going to attempt to model a Mazda RX7 diff and use it upside down for extra ground clearance. Here's a render of where I'm upto so far

 

Wow! I think it's taken me almost as long to create this post as it has to model everything! 

 

I was thinking I could actually create a full exo cage for this and make a military version so I'd fit in more 

 

Anyway, if you've managed to make it this far down, I hope you've enjoyed it!

 

Cheers

 

Martin

[Potsie]

This is truly exciting to see. I recall seeing photos of some real NAs up on big wheels - mostly from America - and yours is going a long way to capturing that look. I think yours maybe even more extreme.

 

If you do not mind me asking, what 3D printer do you use? I have an old thermo-plastic one and am considering updating to the UV curing resin type.

[SnøMotion]

4 hours ago, Potsie said:

This is truly exciting to see. I recall seeing photos of some real NAs up on big wheels - mostly from America - and yours is going a long way to capturing that look. I think yours maybe even more extreme.

 

If you do not mind me asking, what 3D printer do you use? I have an old thermo-plastic one and am considering updating to the UV curing resin type.

Ah, thanks Potsie! Yeah, I think I’ve seen some in the US. I’ve spent an intense couple of days modelling the diff and carriers and hopefully I’ll get a low res test print off this week 🤞

 

I’ve got an Elegoo Saturn S that I picked up in 2022. I think it’s been superseded now, but it’s a great printer!

 

Martin

[Potsie]

Thanks for the reply Martin. I was looking at the Elegoo printers, and am sorely tempted. My major hurdle is whether I will ever make the time to learn the associated software to a level such as yourself. "All the gear and no idea" springs to mind!

[SnøMotion]

2 hours ago, Potsie said:

Thanks for the reply Martin. I was looking at the Elegoo printers, and am sorely tempted. My major hurdle is whether I will ever make the time to learn the associated software to a level such as yourself. "All the gear and no idea" springs to mind!

 

This is my first printer and it was really intuitive to set-up and get started. I reckon I had a print out within about 3 hours of the boxes being delivered 

 

The software for creating the print files is, again, pretty self explanatory and there's an internet full of info about it. As for the models, there are loads of people out there selling files to download at very reasonable prices, so you can probably get away with never needing to know to create them yourself.

 

For me, the 3D modelling is the bit I like most! Not like this painting nonsense when so many tings can go wrong and ruin all your hard work . I come from a motion graphics/video/animation background and I've played about with 3D software since the mid 90s, but not to any great degree. I tried using Blender at first (because it's free and I first used it in 2004), but it became apparent that CAD software was definitely the better option. The last time I used CAD was in 1990 (in an earlier mechanical engineering life) and I think I had to code my requirements in Pascal!  That said, I've found Fusion 360 to be pretty intuitive, too, and there are loads of videos on You Tube to help out when I need to do something new.

 

I think, if you like to add detail or modify your models, a 3D resin printer is an absolute game changer for being able knock out highly details components 

[Potsie]

I just spent a good hour on the Elegoo website trying hard not to buy one of the new Saturn 4 Ultra. I canot believe how cheap they have become; at least, relative to what they were. I have an old Dremel branded - made by Bosch - filament printer that cost nearly double, and more likely three times as much if one accounts for inflation in the last 6 or so years! Mind you, Christmas is not that far away......

 

Thanks for the information on the software packages. I actually work in engineering education - though not mechanical - and I have been thinking of ways to get students using rapid prototyping and makerspace style infrastructure to create solutions to design problems. I guess I really should know what I am doing before I try to teach it!!

[SnøMotion]

 

Yeah, the prices have really come down - even in the two years I've had mine. If I was getting a new one, it would be a Saturn [current number] Ultra. I could do with the extra volume at times.

 

37 minutes ago, Potsie said:

I actually work in engineering education - though not mechanical - and I have been thinking of ways to get students using rapid prototyping and makerspace style infrastructure to create solutions to design problems. I guess I really should know what I am doing before I try to teach it!!

 

Ah, you should definitely get one then! It's the perfect excuse!

 

[SnøMotion]

Okay, a quick update of my weekend's work. Nothing physical to show yet, so I've knocked out a few renders of the rear suspension and driveline. I've broken this into roughly the same components as the original kit, except that I've cross braced the lower arms so they're now a single piece.

 

I started trying to accurately model a Mazda FD RX7 rear diff but, because I've flipped it over, the drive comes in on the wrong side for the MX5 gearbox and so it was never going to work. Once I'd ruled this out, I omitted a number of mounting points and the like to clean it up and I moved the upper (originally lower) mounting point further back so it would nicely line up with the original cast mount on the car. I've recreated a 'fabricated' version of that, too, as the diff sits much lower now.

 

On the original car there's a torque 'channel': a c-section piece that runs down the transmission tunnel and connects the gearbox to the diff. Because my diff is now lower and a different shape I can't use that part, so I'm going to create a propshaft (driveshaft) guard/chassis stiffener that runs from the sump guard (skid plate) to the rear subframe and ties into the chassis rails. I'm also going to extend parts of this out beyond the sills (rockers) to make rock sliders. Hopefully that'll be a quick job and I can get a low res test print out before the weekend.

 

Anyway, those renders...

Edited September 10, 2024 by SnøMotion
typo

[Potsie]

Amazing work.

[SnøMotion]

Another quick one...

 

Sorted the underbody structure and I'm ready to do a test print. I'll set that running in about an hour and it'll hopefully be done in about 3 hours 🤞

 

In the meantime, here are some renders of the structure and its tie-ins with the front and rear assemblies and the chassis rails. Once I've had a look at it IRL and checked the fit, I might add some plates to the rock sliders to act as 'steps'. Not sure about that yet, but here are the renders...

 

Martin

 

[SnøMotion]

So... the print wasn't 100% successful. I used some really old settings to get a 0.05mm slice height and there were a few issues with layer adhesion. BUT... it was enough for me to see that most of what I've done will work. There are a couple of details I've forgotten to add, which I'll sort before the next print, but the most glaring mistake was the propshaft (driveshaft) length!! Don't know how I got that so wrong.

 

Main takeaways are: the mounting point with the original kit are all in the right place (except for the UJ at the gearbox) and the understructure meets the subframes and the chassis rails as planned 👍

 

Here are some bad photos to show you (all printed parts were poorly washed, approximately cured, haphazardly chopped from their supports and not finished in any way)

 

Edited September 12, 2024 by SnøMotion
Typo, as usual

[Potsie]

This is looking so very good. Are you intending to add some sort of external "cage" for the cabin? I have seen some quite bad MX-5 roll-over crashes where people remarkably walked away, but this would be something else!

[SnøMotion]

Yes, I'm going to model a full cabin cage and also a spare wheel carrier that, as this would probably not qualify to be road registered, will mount from the rear number(license) plate locators up onto the boot(trunk/deck) lid. This is going to have to have some sort of hinge and locking detail as the plate mount doesn't lift when you open the lid.

 

I have also thought about modelling a full external cage that ties into the rock sliders, cabin, includes a wheel/jerry can holder over the back and protects the front and rear bumpers. Maybe also a winch. I think this would be a phase 2 type undertaking, though. I'd like to create it as a single component, but I think it would be very large and difficult to print and very fragile when handling. But the base model kit is pretty cheap, so I might build another one in this style.

 

I'll see how this one comes out first 

[SnøMotion]

Just a quick update.

 

I shortened the propshaft (twice!) and reprinted the rear subframe, coilovers, driveline and rock sliders at maximum resolution. More on this in the next episode!

 

While the above was getting sorted, I realised the original exhaust wouldn’t fit and so created a short one that dumps under the floor (again, more

later) and I also modelled the spare tyre rack. I did a low res test, made some tweaks and have just finished a max res print.

 

I’m still going to amend a couple of details but here’s a sneak preview!

Note: had a really strange anomaly on the upper rear bend of both ‘tubes’ that created perfectly matching 0.1mm (approx) gaps from the inner to almost the outer radii. I quickly superbodged the bits together for the photo, but need to re-check the geometry to make sure it’s a print error.

 

Martin

 

Edited September 21, 2024 by SnøMotion
Added note

[Potsie]

Love the rear wheel rack. We have a 1:1 NB SE turbo (Mazdaspeed in the US) and the factory bigger wheels do not fit in the boot without removing all the inner lining. Not good when you get a flat tyre on a week away... This would be a great solution for wheel storage!

[SnøMotion]

5 hours ago, Potsie said:

Love the rear wheel rack. We have a 1:1 NB SE turbo (Mazdaspeed in the US) and the factory bigger wheels do not fit in the boot without removing all the inner lining. Not good when you get a flat tyre on a week away...

Thanks, Grant!

 

Yeah, I’m pretty pleased with how it’s come out. I’m going to add a handle/lever above each of the front mounting points so they can be detached, and the rack pivoted back, to allow for boot opening.

 

5 hours ago, Potsie said:

This would be a great solution for wheel storage!

It would, if you didn’t need a rear number/licence plate! 

[SnøMotion]

Another quick update (not the aforementioned next episode).

 

I've lengthened the rack to move the spare another 1mm forward and added some 'quarter turn' release pins to detach the front of the rack from the boot lid. Here are a few renders as I think the details are more apparent than in my photos!

 

Martin

 

[SnøMotion]

Okay, THIS is the aforementioned next episode! Sorry its been a while, I went on holiday 🏖️

 

I mentioned earlier that I’d had an anomaly when printing the spare wheel rack. It turns out it was my own doing! I’d added a strut into the inner radius of each of the rear upper bends, even though I knew they were fully supported from both sides, and this was actually causing the subsequent layers to detach from the existing ones! Lesson learnt.

 

So I have high res prints of all the under floor components now and I’ve painted them all! I’ve even painted the floor pan in what I am calling Mazda Mariner Blue (and ProScale Paints call Porsche Shark Blue). I painted the various ‘details’ in semi-gloss black and a couple of shades of silver.
 

I didn’t want any of this to be glossy but I wanted to protect it, so I used ProScale’s 2K clear with their relatively new matting agent. The guidelines gave the following clear/matt ratios:

Matt: 50/50

Satin: 60/40

Semi-gloss: 70/30

 

I mixed a batch at 60/40 and gave it all a good dousing. To my surprise it dried gloss! Not mirror finish, because there was a fair bit of texture under there anyway, but certainly shiny. I was going to leave this but, after having a weeks holiday in Dumfries and Galloway, I just didn’t like it. So I overreacted and mixed a 40/60 batch and this came out great!

 

Here's a photo of all the components from the gearbox back with the original components they’re replacing.

 

 

As you can see, some of the new components bear little resemblance to their forebears  I also chose to use the kit supplied brake rotors and calipers to avoid any clearance issues with the dune buggy wheels. You can just about make out the stubby little exhaust up in the top right, next to the massive original! I’m not sure this would pass emissions 

 

Here are a couple of shots, with entirely too much depth of field, that attempt to show everything in its approximate location. Nothing is glued, so the coilovers were falling all over the place! You can, again, just about make out the exhaust dumping out in the middle. I guess this location could cause an amount of light headedness, also.

 

 

And, finally, a shot of the painted spare wheel rack in situ!

 

 

Thanks for looking!

 

Martin

[othertales]

A really intriguing modification build! Really enjoyable to see your progress so far. Can't wait to see how it will look like when finished.

[SnøMotion]

Thanks, @othertales!

 

All I have to do now is model the interior components. I’m planning a full roll cage, some fixed back seats (which should help me with clearance for the side bars of the cage) and a steering wheel. Hopefully I’ll get this done in the next week 🤞

 

Martin

[HK-500]

Reminds me of these incredible photos of Daytona Beach in custom magazines when I was a teenage boy ! 👍

Your build is just bonkers !!  Throttle open ! 🤪

[SnøMotion]

Thanks, @HK-500! I was inspired by an episode of the greatly missed Motor Trend show Dirt Every Day, where Fred and Dave made a ‘sand buggy’ out of a four door Dodge station wagon. It was terrible, but it looked insane 

 

Alas, Motor Trend blocked their channel from the UK, and probably the rest of Europe, so I could only get a link to a short clip on YouTube.

[SnøMotion]

Just a tiny little update today. Even though I've been mucking about with other things, I've been plodding on with interior mods. Hopefully I'll have a rollcage and seats by the end of the week but, in the meantime, here's a steering wheel I've modelled ready to fit this. Obviously, this is just a render. I hoping that the weekend might see all the remaining parts printed and then I can get the interior and body painted.

 

Thanks for looking!

 

Martin

 

[Potsie]

I somehow missed some of these updates and ... wow! If you ever consider selling this as a full conversion kit, let me know. I want one!!

[SnøMotion]

Thanks @Potsie!

 

5 minutes ago, Potsie said:

If you ever consider selling this as a full conversion kit, let me know. I want one!!

 

Yep, that's the plan 

 

As I'm working through it, I've realised the seats, steering wheel, rollcage and road wheels that ended up happening would also make a great 'track package' if I knock out some lowering components, too.