Delta Super-J electric 1/8 project

[V12]

Some people may know my love for Delta cars.
I always dreamed about driving a Delta Super-J at a race track but it had to be electric, because I gave up on gas engines long ago.
Around one year ago I started to brainstorm about the project and it was no easy task at all.
Delta actually released a Super-J electric version around 1979 or 1980 but I couldn´t go from there.
They used a fix gear ratio which didn´t work for me and I didn´t wanted to use the old Astro motor.
Also the saddlepack batteries and the mechanical speed control were mounted to the same original radio tray for the gas cars. This also didn´t work for my project.

One of the main problems was, the rear bulkhead was not any intended for use of an electric motor. This means the electric motor had to be mounted different.
I went with an add-on plate to the bulkhead. But the shape of the original bulkhead was reduced to the minimum for saving weight, so it was quite difficult to find a solution and needed a lot of brainstorming, testing, redesigning ...

The design of the add-on motorplate also was dependend of the motor. So I had to choose the 'right' motor and calculate what gear ratio or rollout would be needed.
I was used to 4268 motors and 4S setup at 1/8 scale 4WD cars but I thought that would be power overkill and maybe damage the balldiff. Also the size of those motors are too large. So I went with a HW3660 and 2S setup which also reduced overall weight by around 400g.

The next problem was, I couldn´t mount a pinion to the motor because the spur gear is located very close to the bulkhead. There is no room for the hex driver to fix the pinion to the motor shaft. So I had to design an adapter to move the spur gear around 3mm, at the ball diff.

The original Super-J was made to withstand the strong barriers of the Midwest race tracks. And the quite stiff chassis was intended for high grip levels.
My friends and me think such stiff car won´t really work on low to medium grip tracks, especially not with the high power and torque of modern brushless electric motors. So I designed a new chassis. I wanted to use a shape what looks close to the original chassis from a distance. So the change had to made different. Well if someone remembers the old RC12i ...

The radio tray also had to be redesigned. The cutouts for tank, throttle servo and receiver battery were not needed anymore. But had to be replaced for the 2S Lipo and ESC. The servo position was slightly changed and optimized also.
The overall shape is very close to the original first generation radio tray but looks a bit different of course.
And there is one major difference which could be noticed only by people who really know the original Super-J car.
I would like to know who may find that detail.

Another problem was the lack of front wheels. And I wanted to try different front end setups which couldn´t use the original wheels.
So the idea was to use modern 1/8 scale wheels. But how to convert the 3/16" wheel axles to take 12mm wheels?
This was one of the most complicated parts to design. In the end I went with a design which came with my old Schumacher C-Car 1/12.
Live axles which carry internal very small bearings. And a quickchange system for the front wheels at the same time.
But those aluminium parts were very difficult to make. Big thank you have go to my friend W. who did an excellent job in making these adapters and some other aluminium parts for this car.

Unfortunately I had no Kydex plates, and not in the Delta style blue color. So I decided to go for grey PVC plates for the radio tray and bumper.

Overall there are a lot of details which had to be noted and thought of when making this car. And the journey is not over. This is an experimental car for the moment and might be modified later.
Rollout had been held lately and it was great fun.

[1300GT]

Really nice work.

You cut a hole in the front of the chassis with a hole saw?

[V12]

Thanks
The hole at the chassis was done with a jigsaw and sanded. As most of the chassis work.
Actually I went with a square sheet of glasfibre pan and went from there.
For sanding the hole I used sandpaper 180 which was glued to a 2" round wood. Works pretty good and fast.
But it´s a lot of dust and mess.
I wish I would be able to do CAD.

Also the radio tray, the bumper and motor add-on plate was done by a jigsaw.
Designing the chassis and radio tray was done right at the plastic sheets after raw drawings at the paper.

[Phin]

Very nice.

I've had a few ideas for a electrifying a 1/8 Associated car, but either using a 10th/12th scale pan car style t-bar rear pod, or a more ambitious modified WOIN design like a Montica P8C or Serpent 988e Taipan.

[V12]

Thanks.

Well the photo shows the car from the top. But hides some secrets
The original Super-J used a quite stiff chassis design. Especially at the rear what isn´t perfect at all. But most 1/8 cars were like that.

I wanted to keep the overall look close to the original car but that doesn´t mean it is made or may work like that.
Right from the beginning I wanted to get more traction out of the whole car, because the brushless motors provide way more torque than the old and even the current gas motors. My chassis works similar to a t-bar, have a look at the RC12i and Serpent Taipan and you know what I mean.
For this reason the radio tray had to be changed also. The original tray is bolted to the rear bulkheads what make the rear end even stiffer.
I mounted the radio tray to the chassis so the chassis tweak could work. This is also one of the major differences I meant before.

The front end also was redesigned and uses kingpin springs and quick-change adapters for current 12mm front wheels.
The parts for making these changes were quite a task to design and make.

[V12]

... or a more ambitious modified WOIN design like a Montica P8C or Serpent 988e Taipan.

The Motonica and all the other 1/8 cars designed that way don´t handle very well. At least if they use the typical stiff rear end and the connection rod which replaces a center shock.

The Taipan is an advanced design but not perfect. I have such car.
The front end is lacking damping and real springs.
If you do the Julius Kolff conversion the car works 100% better. The mod could be seen at the Serpent 988E/Taipan group at FB.
Julius did a great job on designing a shocktower and mount.

But overall I prefere a 2Wd car with rear diff. For me this is more fun than the 4WD cars with solid rear axle.
This project car works quite good but I plan to do a more advanced 1/8 electric car similar to a Pro10 car. Something for winter time.
And the next car should be less weight because this one is more than 2100 g. With the larger 4268 motor and 4S battery it would be more heavy than a Taipan or Buri.

[Phin]

I'm not too worried about how they'd handle since 1/8 on-road racing isn't a thing around me. It'd just be for the fun of the build, and to see how creative I can get using nothing but old parts to replicate the design of modern cars.

I agree that a rear diff is preferable, and I'm hoping to keep the rear diff if I go 4wd. Solid/spooled rear axles seem to be the thing with pan cars these days though (12th, 10th & 8th scales).

[V12]

A spool or solid rear axle needs less maintenance than a balldiff but it doesn´t do any good to the handling of a car.
I never liked the front spool at touring cars and always preferred the oneway.
For current 1/8 cars they need to be driven completely different and it´s absolutely not to my liking or my driving style.
That´s why I went with this project.
I don´t care about laptimes anymore because I retired from racing a couple of years ago. I just want fun at the track and the 2WD diff car is way more fun to me.
But if someone just wants point and shoot at the track, such car or any other 2WD is not suited.

This project needed a lot of creativity as well. I used original parts when possible.But there were also some really tough problems to convert from gas to electric motor which required special parts. Also I had to find a way to use different front wheels because original wheels are very hard to find. And I wanted solutions which work perfectly, not any cheap China made parts which look awful at the car.

[Phin]

Spotted this 1981 attempt at a Super-J electric in a magazine:

Talk about bad handling characteristics...I can only imagine what dangling 6 cells that far out over each side of the car, then reducing the weight at the rear axle would do to driveability. Also, even with 12 cells, at 1980s-era battery tech I'd still guess at less than 10 minute run time between charging.

No surprise 1/8 electric didn't catch on 30 years ago.