The Dyna Scorpion – part 1

Please Take Notice

This is not a webshop, and beside what’s listed under the “FOR SALE” tab in the menu, nothing presented here is for sale, so please don’t ask. If I have anything I would like to sell, I’ll post it in the “FOR SALE” section.

The original Dyna Scorpion was made by the model shop “Dyna Models” in Yokohama City, Japan, around 1983. The base was a Kyosho Scorpion with a custom chassis and lots of hop-up parts. I decided to try to recreate this “beast”, using all the correct parts I could find, substitute the ones I couldn’t find with suitable era correct replacements or just manufacture my own parts (with a little help from my friends) when there were no other options.

The original Dyna Scorpion.

Looking at the few existing images of the Dyna Scorpion, here is a list of the parts I (again with a little help from my friends) could identify:

  • Thorp wheels with mounts and foam tires.
  • Dirt Burners! aluminum wing.
  • Dirt Burners! monoshock unit.
  • Dirt Burners! (RCH) bumper.
  • Dirt Burners! (RCH) front shock tower extenders.
  • Dirt Burners! rear cage.
  • Parma shocks.
  • Parma motor heat sink
  • Parma Unser Buggy body
  • Kyosho Land Jump ball connectors.
  • KO radio gear.
  • Custom made chassis, top plate and front bulk heads.
  • …..and probably stuff I forgot.
The Dyna Models shop in Yokohama, taken from a Japanese “RC Encyclopedia” book.

Remember that this was in Japan, where the Dirt Burners! brand sold hop-ups from various sources, like CRP, RCH, Thorp, Parma, MIP, Proline, and a number of less known Japanese brands like Paranoia and Rainbow. My “research” into Dyna Models shows that they sold both Dirt Burners! branded parts, US branded parts, as well as several parts with their own logo. The wheels were known as “Thorp” in the US, but they were sold in “Dyna Models” bags by Dyna Models, even if the Japanese Dirt Burners! obviously had close ties to Thorp. I guess there were much parallel-import going on.

 

Dyna Models branded Thorp wheels.

Well, back to the project. I managed to find the shocks, the front tower extenders, a similar bumper (not exactly the same), the motor heat sink, the wing and some similar KO radio gear. I decided to drop the MSC, and rather use a period correct KO ESC. The standard Scorpion parts were also no problem, as I have Scorpion parts galore. Team Bluegroove in Canada luckily had the body in their product range, so that was no problem either. But as you probably understand, that was not enough to build a Dyna Scorpion….

Some years ago I had a few sets of the Dirt Burners! monoshock units made at a local school, and I still had a set left. The fiberglass chassis, top plate and aluminum front bulkheads and rear cage were something I knew I had to either make myself, or have some of my friends around the world make for me. Jeff Malar in the US, who btw. is a brilliant guy, cut the fiberglass parts, after I had created CAD drawings of them from the pictures. Derrick Durbin said yes to make the aluminum bulkheads (I’m still waiting for them….), and I made a simple jig to bend a cage from some aluminum rods. The wheels I have basically given up on finding, but I found a way to mount wheels and tires from a AYK 566B Super Trail instead. I think the AYK wheels look good on this build, but I will of course swap them for Thorp wheels if I can find some.

The second set of chassis plates.

The first set of chassis plates were too thick for my liking, so I had Jeff cut another set. That also made it possible for me to make some updates to the design, to make them more like the originals. It was mostly small adjustments, like moving some of the cut outs and holes. I actually nailed the important parts the first time, including fitting them to the bulkheads.

The bulkheads also had to be drawn in CAD, so Derrick could cut them. I know he has much to do, so I ordered a 3D printed set from Shapeways, just to use as placeholders so I could continue with the build, until Derrick could cut the real ones. I’m very pleased to say I didn’t need to do any adjustments to make the bulkheads and the chassis plates mount together. Yes, I know I have said that twice now….. But I’m quite proud of that, having just a couple of grainy pictures to work with.

The placeholder bulkheads from Shapeways.

The front axle of the original is cut and spliced with a “barrel” connector, that makes it possible to easily adjust the width of the front end. Derrick will be making the barrel as well, but I found a Graupner “Kupplungsbuchse für 5mm Wellen” that I could use as a placeholder. The difference between the Graupner part and the original is that the original has some convenient holes to easily adjust the angle of the front end, as well. The Graupner part will of course be changed when I get the real parts from Derrick.

The jig for the cage.

The rear cage was from Dirt Burners! and had a nice bend at the end, that distinguished it from the other cages on the market. I soon understood that this cage would be impossible to find, so I decided to make my own. I made a wooden jig, and drilled holes to easily make all the bends needed, both for the top part and the two connecting parts. It still has to be welded together, but I have arranged for that to be done. I just haven’t had the time. I think I managed to capture the shape of the original nicely. It probably should have a little more of a upwards bend at the rear, but I could always make another if needed.

The parts of the cage, bent to fit.

At first I didn’t have any of the blue Parma shock absorbers, and I planned to use red Kyosho CB-88s instead. But Mike in Ohio helped me finding a set, so I could make it as faithful to the original as possible. I also got a set from Sami in Finland. If you study the original, you’ll see that the long shocks up front leaves very little suspension travel, so I decided to go with the shorter version instead, even if that was breaking away from the original.

Parma shock absorbers.

Mike also helped me finding the Parma motor heatsink needed for the build. Strangely the heat sink I got seems narrower than the original, but it will have to do. You will have to study it carefully to notice.

Parma “wrap around” heat sink for the motor.
Tamiya Frog version of the RCH bumper.

The RCH bumper used on the original was the Tamiya SRB version. This bumper is rather rare, but I managed to find a couple for the Tamiya Frog and one for the Kyosho Progress/Gallop in the same style. The main difference between the SRB and the Frog versions are how they are mounted. By drilling a couple of new holes, I made the Frog version fit, and you’ll have to look underneath to see the difference. I also have some Kydex sheets, and a very accurate drawing of the SRB version, so it ‘s always a possibility to cut one myself. It shouldn’t be too hard. But I think I’ll keep the Frog version for now.

One of the aluminum Dirt Burners! wings I may use for this build.

I found four Dirt Burners! aluminum wings with different mounting hole patterns. I haven’t studied them yet, but I’m sure one of them will be close enough to the one on the original Dyna Scorpion. The mounts for the wing puzzles me, as they look very weak, and would probably break easily. But as this car will, at best, get some very gentle runs, I decided to go with the same style for autenticity. For mounts I used the optional wing mount for the Kyosho Optima, as they look quite much like those on the Dyna Scorpion.

The Optima wing mounts fitted to the cage.

The Gear box and wheel hubs are fitted with ball bearings, but the differential is the standard Tomahawk/Turbo Scorpion gear diff. I do have a Thorp ball diff, but I’ll save that for another build. The gear box it self is a bit worn and dirty, and I’ll change that to a better one when the rest of the build is finished.

Old KO radio gear, but unfortunately with the newer plug style.

The Dyna Scorpion in the pictures used KO radio gear, and a variable resistor manual speed controller (MSC). I’m not sure about the motor, but it looks to have a Yokomo or Kyosho type 540 can/end bell. I have some old Yokomos that could fit. The only Kyoshos I have with silver cans and black plastic end bells are some LeMans 360 motors, but as those are 550 style, I’ll have to go with a Yokomo. The original KO radio gear are of the old style with the larger connectors, but the receiver and servos I have are of the newer connector style. The electronic speed controller (ESC) that I will use, a Super Racing Max RM-7 Limited, has the old style connector, so I’m currently not able to connect the ESC to the receiver. I’m still looking for the older style receiver, though. I chose to use the ESC instead of the MSC for two reasons. Reason one was for simplicity. Those old MSCs are a mess to work with, and reason two is that I have “always” used ESC’s. The only car I have ever used with a MSC was my first Tamiya Sand Scorcher, but even that was upgraded with a ESC after a short while. The RM-7 Limited was perfect for this project, and fits very nicely between the chassis and the top plate. The only problem is that large connector plug.

KO Super Racing Max RM-7 Limited ESC from the first half of the 80’s.

Here is my Dyna Scorpion Replica as it is at the moment. It still has the red shocks, and I haven’t mounted the right motor and motor heat sink yet. The electronics are in place, but I can’t connect the ESC as it has the wrong plug. The steering servo is (like on the original) only mounted with servo tape. I don’t feel that is a proper solution on a race buggy, so I’ll add some mounting brackets that bolts on to the top plate. The front bulkheads are still the 3D printed placeholders, so the front geometry is a bit messed up, because it’s impossible to lock the axle to the 3D printed part.

Partly done build, with electronics and a few placeholder parts.

To be continued…..

Please Take Notice

This is not a webshop, and beside what’s listed under the “FOR SALE” tab in the menu, nothing presented here is for sale, so please don’t ask. If I have anything I would like to sell, I’ll post it in the “FOR SALE” section.

About TomEG 71 Articles
I have been into RC cars since the beginning of the 80's, but have really never been much of a racer. I competed in some local races and some "Tamiya Cups", and actually came 6th in the Tamiya Cup Norwegian Nationals in 1987. My main interest has always been building and modifying, and that's where I still am today. Through the years I have been able to build a solid network of contacts around the world, consisting of both former and current members of the industry, as well as quite a few of the former top drivers. I have a genuine interest for the history of the 1/10 scale off-road buggies from the 80's.

2 Comments

  1. I like your website a lot, I am very interesting on all of your articles and also I am interest of the history of 1/10 off road scale, where all is started for me, back in the mid of 80’s.

    Thanks for your work, thanks for sharing with us your passion.

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