This is part 2 of my effort to recreate the Torpedo Optima that Atsuhiro Ohno raced in the 1987 World Championships in Romsey, UK.
A lot has happened since I wrote part 1 of the Torpedo Optima article. I have been in a dialogue with Atsuhiro Ohno, the Japanese driver who ran this buggy back in 1987, and I have been in contact with Oga, the admin of the Pink RC blog mentioned in part 1. I also regularly communicate with Akira Kogawa, the designer of the Optima, and they have all helped me solving the mysteries of this legendary buggy.
I have received the G10 parts from Jeff and the decals from Nathaneal at MCI, they all looked great. I’m still waiting for the carbon parts from Fibre-Lyte and the painted body. Unfortunately Raul, who’s going to paint the body, has fallen ill, so I’m not sure when I will get it. But that doesn’t matter at all. The most important thing is that Raul gets better. Best wishes to you, buddy.
I started preparing for this build by rebuilding a set of Kyosho gold shocks and finding springs that somewhat resembles the ones on the original car. I have also cleaned up a set of wheels, and basically started collecting various bits and pieces for the build. Mostly from my own stash of parts. I will be using a few NIB parts on this build, but there will also be used parts, depending on the quality of those.
I have prepared a set of rear side plates, and the small plate that goes across the front of the top plate, by countersinking the holes that needs flat head screws, and I have cut a front under guard plate to match the one on the original car. Luckily I found a pretty beaten up front plate to cut. If I hadn’t found that trashed plate, I would have used a re-re plate, as I wouldn’t want to cut a good vintage one. The front under guard plate was simply cut with a Dremel and a cutting tool. The countersinking of the rear side plates was done by drilling with a 6 mm drill bit. The ideal process would have been to use special countersinking bits, but I found a drill bit that made the angle of the countersunk “sidewalls” very close to perfect. The top plate, the front side plates and the rear shock towers are coming pre-countersunk by Fibre-Lyte and Jeff.
Finding the special Option House W-0104 hardened chassis rails have proven difficult, so I have ordered a set of the OTW111 optional rails for the rereleased Optima 2016. They seem to be virtually identical to the W-0104 rails, but have a kind of champagne colour. I’ll probably try some tricks to get rid of the anodizing… I’ll start the build using standard rails.
The A-arms on the Torpedo Optima is the reinforced arms from the Optima Mid. These most probably have been added to the car at a later stage, as these were not commonly available at the World Champs in 1987. On the other hand, Ohno did get parts directly from Kyosho and Akira Kogawa, so it’s not entirely impossible that he got those back then. But then again I doubt the final design was decided at that time, and the Kyosho team most likely used prototype arms. Still I will be using a brand new set of these for now, but I’ll change them if I get any new info on the matter.
Something that don’t show in any of the many pictures of the Torpedo Optima is if it’s the standard OT-47 front hub set, or the OT-55 high angle set that is on the original car. I just had to make a choice and went with the OT-55 set, simply because those were the ones I had most of.
The shocks are the standard Kyosho Option House gold shocks that came with the Turbo Optima, and later were used on many of the Optima Mids. However they seem to be re anodized to a darker shade than original. The shocks I’ll use on this build are used, and of the standard gold colour. The black springs have, like on the original car, been changed for some silver coloured springs that are a little bit stiffer than standard.
Like on the original car, the wing will be mounted using this NIB OT-65 Wing stay set. This was an option part for the Optima and the Turbo Optima, and have tubes mounted on the top plate to hold the wing wire. The kit also comes with wing buttons to mount the wing to the wing wire.
There is also the Kyosho Option House W5005 special rod set, with adjustable rods on the original, and I’ll use this NIB kit.
I’ve also opened a new package of OT-11 suspension shafts, as I had a few of those among my NIB parts.
The bumper on the original car was home made, and very small. I tried to copy it as best I could by cutting it from a sheet of kydex. Kydex is a very easy material to work with by hand. It cuts easily, and most importantly; it’s very easy to bend. After I had cut a rough shape, I simply put it in a mug of boiling hot water for a minute or two. When I then took it out of the water it was very soft and flexible, flexible enough to bend around a sharpie marker, to get the right curve. It gets hard again very quickly, and it stays in shape when you have bent it. The first time around I wasn’t satisfied with the bend, so I simply repeated the process, and the next time the result was good, I think.
The front shock tower I designed, and Jeff cut, was a perfect fit, and fits straight on to the inner upper arm-link mount. On the rear tower I must have miscalculated a little, as the slots where the small knobs from the rear plates should go, are off by a millimeter and a half. I will have to use the Dremel to do some adjustments before I can put it on. I have done a little redesign of it and sent the new files to Derrick, so the actual aluminum tower that I will eventually use are correct.
The spur and the counter gears were prototypes for the Option House W0110 special spur gear and the W0111 special counter gear. One thing that differs the prototypes from the final products is that the small center gear on the spur was metal on the prototype, but plastic on the production part. I really wanted that metal gear, so what I decided to do was to use a Robinson Racing 48 pitch set, that has a metal center gear. OK, the spur is blue (but actually round and not oblong like a lot of those Robinson gears) and the counter gear is white, but those are behind the gear cover anyway.
Among the newly obtained info I got from talking to Atsuhiro san was the fact that the prototype belt drive kit is very different from the commercially available Kyosho Option House W-0105 kit. According to Ohno, the prototype kit had no tension spool for the belt, and the diffs are actually ball diffs, made by, and given to him, by Akira Kogawa himself. Unfortunately (but understandably) there is no option to take the original car apart to document these parts, as there is a fear that something might break, ruining this fine specimen of a classic buggy.
So what I will do is use a set of Option House ball diffs for the Optima Mid as those drop straight in to the Optima gearbox, and I would believe they are based on the same design as Kogawas prototype ball diffs. The front diff I have rebuilt with new balls, but plates and out-drives from a Lazer ball diff I had. The rear one is built with all new parts. I have heard about people successfully running belts in their Optimas without the tension spool of the special belt drive kit, but I have also heard people saying that under certain circumstances the belt will touch the gearbox at the place where the belt leaves the box. This could mean excessive wear on the belt over time. But then again, belt drive kits like the Wasp kit and the TBS kits all use the standard gearboxes, and most importantly, that’s the way Ohno ran the original. Being unsure what to go for, I let the good people of the Kyosho Optima Series Facebook group decide by a poll. From the beginning it was clear that I should go for the standard gear box, without the spool, so that’s what I will do. Then I encountered a bit of a luxury problem, some might say… I couldn’t find any standard rear gearboxes among my Optima parts, but I actually found three Option House boxes…. Luckily I found a nearly complete Optima chassis that I got a while back and had forgotten about, and it had a standard box that I could use.
The universal drive shafts on the original was made by MRE/Tech Racing. I have never seen any of those for sale anywhere, so I simply went for the Option House W-5061 uj’s. Those are very close to the MRE uj’s, so that will have to do.
In part 1 I wrote a little about the Sanwa Speed Controller 1000 used on the original Torpedo Optima, and that it was a special limited made-to-order ESC. From what I can find it’s the Sanwa Champ that’s the commercially available ESC that looks the most like Ohno’s. Of, course, Atsuhiro san had a custom made second row of FET’s on his ESC, so finding something that will be impossible, but at least it looks like the Champ has the same form factor as the Speed Controller 1000, and I believe it’s the same case that is used, making it as close to the original as I’ll possible get. Daniel Rowlands was kind enough to give me his Sanwa Champ. Thank you so much Dan!
Then there is the Ni-Cads… the thing that gave this car it’s name, “Torpedo Optima”. The torpedo configuration was commonly used by the Kyosho team during the last year of supporting the Optima, and it’s just two rows of 3 cells mounted lengthwise at the sides of the chassis. The “torpedos” used on Atsuhiro san’s Optima had red shrink wrap, and on one side you could read the word “Sanyo” through the wrap.
Those batteries back then were 1200 or 1400 mAh, but if I should consider to run this car, I really want a little more running time than those old batteries would provide. Luckily I got a newer Team Orion 2700 mAh Ni-MH racing pack with a Scorpion I bought a while back, and that pack became the donor for my torpedo sticks.
I first unsoldered the plug and wires, then wrapped it in white shrink wrap. After I had shrunk the white wrap I applied a decal with the logo for “Sanyo” in black to one of the sticks, and then used red shrink wrap on top of that again. I had hoped that the black should show well through the red wrap, as I had used white underneath for the best contrast. It did show through, but not as much as I had hoped, but it will have to do. The other stick did not have this lettering on the original car, so I left that one plain red. Now I need to solder them together and add the plug, but that will have to wait until I have them mounted on the car, so I can get the correct length for the wires.
Well, that’s it for part 2. As before, please comment or ask questions, and I’ll answer as best as I can. You can expect to see a rolling chassis in part 3!