Project: Kyosho Ultima 1991 World´s Stealth Car

Kyosho Ultima 1991 World´s Stealth Car – The World Champion Car from an alternate universe

We write the year 1991. The young japanese Kyosho driver Satoshi Maezumi surprisingly wins the 2WD IFMAR World Champion title over the top drivers Masami Hirosaka, Mark Pavidis and Craig Drescher. He won this race with a top secret prototype buggy from the japanese company, what was special designed for this rough track conditions in Detroit/Michigan. The team of the favorite US manufacturer Team Associated has no chance for the win with the RC10, what has big issues with handling over the bumps of the crater-like Detroit track.

This really happend – but in a alternate universe. Everything in this parallel universe was same as here. Ok – apart oft he fact, that the earth was flat, has three moons, the grass was blue and a stick transmitter never was invented.

The Optima Pro is the perfect choice for this project.

Front view.

Some months ago I asked me the question, what if Kyosho has made a Stealth Car, instead oft he iconic Team Associated Stealth Car from 1991? Please don´t ask me why! It simply happend. We can´t change history. But I was keen to find out, how this car would look, feel and perform, when it was made on the same way as the Team Associated Stealth Car – just with Kyosho parts. So I started to redesign the key parts from the Kyosho Ultima MK1 to make the unthinkable. The Kyosho Ultima World`s Stealth Car from 1991.

I designed all parts on a way, what would be possible for Kyosho to produce back in the days. But I also integrated my „Neo-Vintage“ Design in this project, what means, I adjusted the suspension geometry to the latest modern buggies geometry. I adjusted toe-in, anti dive, roll center and steering geometry, what we have today on our buggies, what are made for high traction tracks – and especially for vintage races in Europe – for carpet tracks. And as on all of my projects – with modern electrics. So some details are pretty different to the old design, but helps to race today on vintage meetings.

The design process

Tob e honest, it was much easier than expected. Thanks to the clean design from the Kyosho designer Akira Kogowa it was a quick job the rebuild the Kyosho parts with my 3D CAD system.

Front suspension old vs. new design

Rear suspension comparism. 3 degrees toe-in per side. 1.5 degrees anti dive.

So it comes together

Fits perfectly. I use set screws everywhere to hold the hinge pins in place.

The front bulkhead

To make life easier at vintage meetings I decided to use modern hex adapters to fit the JConcepts rims

Steering assembly. A little bit redesigned and with ball bearings.

the assembly of the rear bulkhead and gear box.

After drawing all parts I started to redesign them to make them fit into the new chassis. I adapted the typically Kyosho design language from Akira and mixed it with the Team Associated Stealth Car Design. Basically much longer arms, narrow bulkheads and the carbon sandwich chassis. So if you look at the new parts I made, they really look like Kyosho parts!

The good thing with 3D CAD drawings is, that you can (or must) simulate motion on your drawing assembly to check, if there is any issue with the design. So you can simulate the suspension and what is most important – the steering geometry. That is, what I always do in my job! Only with simulation you can design the „perfect“ steering geometry with zero bumpsteer and the correct rate of camber gain, etc..

Same thing for adjusting the suspension geometry, hight of axles and geometry of the suspension arms, etc.. That´s, what you have to do as RC Car designer.

Because this car is so simple it took me 3 days to finish the drawings. That was quick.

The parts

I have put all plastic parts into one bulk and send it to shapeways. Since Shapeways offers the new HP printer material I am in love with it! The surface is pretty smooth, but the best things are the fantastic resolution and precision oft he prints! The tolerance are so small, that holes are nearly real – round holes and even bigger parts are super precise! If you put a ball bearing in it´s seat, it fits simply perfect! Crazy! And the best thing is maybe the strenght of this material. It is so strong! It comes very close to injected plastic material and it is pretty stiff. Perfect for RC Car parts!

The only dowside is the price. The bulk with the plastic parts costs more, than you pay for a kit (!)

270 Euros for this piece of parts. Shapeways loves me.

Shapewas offers the same material with a much smoother surface, what doubles the price. Yep, it is expensive fun.

One week later I recieved the Shapeways parts and 2 weeks later the carbon fibre parts. Meanwhile I made parts, like aluminium posts for the chassis, hinge pins from piano wire and other small parts, what was needed. As on all my cars I use Lunsford titanium turnbuckles, Xray ball ends and (now) titanium ball studs. As I wrote before, they are simply the best! And if you drive your final on a vintage meetings, you don´t want a popped off ball end on your suspension.

Because the bad experience with the Hong Kong Option House Shock copies, I started to equip all my Kyosho cars with the new original Kyosho Turbo Optima Re-release shocks. They are complete different to the originals. First, I was not a fan of the new design. But after building them I know, they are working fantastic! Much better than the original ones! Easy to fill and a super smooth operation. And no leaking! I only changed the ball ends and the shock spring retainer to Team Associated B4 parts to fit AE springs. That´s, what I did on all my Kyosho cars to make them identical equipped.

The assembly

Do you know the old strong emotions from your childhood, when you got your first RC Car kit? And you lost it a little over the years, because you buy each year the latest car to go racing? I lost it a lot! You order your new car, you assemble it as you always did in the past and you go to the track to race it. I can´t remeber when I was so excited to build a car like this one – since many years! All the feelings and emotions are there, when I was a young boy and had to save money from birthday, christmas and all the pocket money over many months to finally get your kit in your hands! The shaking hands and all the loaded excitement when open the bags and the hours of building your dream car where you have waited for a long time? This feelings was there again! We are always kids, no matter how old we are. We always want this warm feelings from our childhood experience. And I feed my inner child with a lot of stuff, because real life today is not an easy job in this crazy stupid world.

The assembly was pretty quick and there was zero issues. I used a reamer for all holes for the hinge pins for perfekt fit, but apart of this, all fits together perfectly, thanks tot he great 3D print quality from Shapeways. And the result looks absolutely stunning! I love this look! After installing the electronics I put the car on a scale to check the total weight – it weights 1230 grams race ready (!). For our high grip carpet tracks much too light!

The 3mm stainless steel plate weights 100 grams.

Reedy 13.5T motor as usual for 2WD vintage races.

So I installed a 3.0mm under lipo steel plate from stainless steel, what I ordered from a laser cutting company to my dimensions. It weights exactly 100 grams – so 1330 grams total weight. I know, I need a weight of at least 1500 grams to race on carpet. So I have put more weights in the chassis to get 1400 grams in total. Still not heavy enough. If your Buggy is too light, the handling on high grip carpet is a nightmare.

I like, what I see!

Especially on EOS/ETS carpet, what is popular at this moment around the world. Your car will roll over in every single corner and is super hard to drive. No matter, how low your setup is. It will roll over and it will drives you crazy! The only help is adding weight. Much weight! Make your car weight at least 1500, or 1600 grams. The next problem is, you have to find proper springs and oil. If your springs are too hard, you will roll over in sharp corners – no matter, if your car is heavy or not.

If your setup is too soft, your car is very hard to drive and it will roll over again! Generally you need medium hard springs and relatively hard oil. So harder your oil so easier your car is to drive on high grip tracks. But if your oil is too hard, your car will roll over again! For me, this ist he most important thing! Springs and oil! I have several sets of Team Associated B4 springs for all my Kyosho cars. And you can still buy them everywhere!

I have spend a full day with oily fingers to find the right spring/oil combination for a basic setup. This is so important if you are a serious racer. You spend so much time and effort in your vintage car, go to vintage meetings with a lot of costs for flight, hotel, etc. and you get a nightmare, if your dream car is always with the wrong side up the whole weekend. Invest enough time for a basic setup to enjoy a race weekend with great driving and fun! It is hard to believe how fast some guys (Hello British team from the Oldschool Euro Masters!) can drive their 30 years old cars around the track. Those guys simply made their homework with setup.

At the end I think, I found a good basic setup for my Ultima Stealth Car. Can´t wait to run it the first time! It looks sooo neat! Feels so great! It must be a rocket.

The only questions is, is this still vintage? Did I go too far this time? To be honest, I can´t answer this question. The idea behind is so stupid, that I would understand, if race officials would not allow something like this on a vintage race. But it was worth the effort. Now I have this car from another universe in my hands and I am a little, very excited boy for this moment.