Optima Mid Runner Budget Build to LWB conversion

[XLR8]

Just wrapped up this Optima Mid runner and thought I’d share some pics before getting it dirty at the track. I’ve spent the last few months collecting some OM parts cars and spares from ebay and I’ve nearly enough parts to build two SE’s (future shelfers) and this Mid runner (the runner used the most well-worn and ragged of all parts on hand). One of the SE’s are nearly completed, and I may post some pics of that car in the gallery when the body and decals arrive and the body is finished. Meanwhile, this one is ready to roll. The drive train includes an aftermarket steel idler gear (from ?) and an original diff gear, top drive gear and belt that were still in good shape (did belts ever actually wear, stretch or otherwise fail with these cars?). I replaced the original dog bones and axles with the Kyosho re-released versions (the new axles use pinned hexes rather than the tapered drive hexes) and the wheels and tires are also from Kyosho. The only Mid body I have was pretty badly scratched, beat-up was painted blue and the paint was heavily scratched as well. Initially, I’d planned to run it as-is but then decided to investigate the possibility of stripping the old paint to re-apply a little nicer vintage style paint job. Apparently, from what I've read, removing paint from lexan doesn’t always work well so I ultimately decided to just clean up the body, paint the outside and apply a box-art decal set from MCI. So, after thoroughly cleaning the lexan and trimming the ragged edges, a light coat of Pactra polycarbonate white paint was applied as a primer for the three coats of white gloss Krylon epoxy enamel. I’ve had good results in the past applying enamel over poly paint (enamel paint seems to adhere well to poly paint but not directly to lexan).

The rear suspension assembly is reversed, locating the shocks behind the arms, to ease access to the motor and spur gear. The wing mounts on this car had been broken-off the trans cases but I was able to mount the wing to the shock and camber plates using some good ole Yankee ingenuity; a piece of Kydex, some wing wire and scratch-made wing buttons. The Kydex plate seemed like a good place to mount the ESC’s switch.

The Belt and Gear covers and undertray are from Team Blue Groove. Most of the old Philips head screws were replaced with 3mm stainless hex machine screws that remained from some other projects. The chassis plate screw holes were countersunk to accept flat head screws so they wouldn’t interfere with the undertray.
The electronics are just some odds and ends scavenged from vehicles that I don’t run anymore. The motor is a Reedy 550-SL 3500kv, ESC is an Associated XP SC450-BL, servo is Hitec HS-645MG, and receiver is from Futaba. I’m a little worried about running that 550 motor with a light 45amp ESC but I will attach a fan to the ESC’s heat sink and hope for the best. I will run only 2s, the car is pretty light and gearing is very conservative so maybe it will be okay.

Anyway, I’m really looking forward to getting this car on the track. Should be good fun.

[matt1ptkn]

... and this Mid runner (the runner used the most well-worn and ragged of all parts on hand). ... The only Mid body I have was pretty badly scratched, beat-up was painted blue and the paint was heavily scratched as well.

Still looks better than 95% of my builds. Nice looking buggy!

Anyway, I’m really looking forward to getting this car on the track. Should be good fun.

I'm sure it will be! Enjoy!

[NomadRacer]

Exceptional build, my friend! Really dig those wheels.

[XLR8]

Thanks Matt and Nomad. The body turned out better than expected. In fact, I'm starting to consider the same exterior paint process for some other old beat up bodies I have but no longer run because they're just too ugly.
I discovered the wheels from this youtube video.
https://www.youtube.com/watch?v=VQuzpfuWWDE
They came with tires mounted and ready to go. I think I got them from one of the ebay members who part-out new RTR's and they were something like 33 bucks shipped. Anyway, I've another set for a Javelin runner that I'm working on at the moment. I'm thinking about building an old school aluminum wing for that car. I'll post pics when it's finished.

[Coelacanth]

Very nice build, I also like your choice of wheels.

[NomadRacer]

Old school aluminum wing, like the ones from Thorp! Ditch the rivets on the end plates and go with some cool 2-56 or even 0-80 hardware.

[XLR8]

Thanks Coelacanth. I recall that you gave me a number of wheel options a while back which would have have worked out well. While I was looking at those, I stumbled upon the video I linked above. That sealed the deal for me.

Yeah, Nomad, I think the wing I was thinking of were made by Thorp. It's made from just say 0.030" aluminum sheet stock. Anyway, they were banned at the tracks because the didn't want to issue leather gloves to turn marshals. I don't have turn marshals at my track so no worries there. I do have some 0-80 sst socket head cap screws but no nuts to go with them. I could undersize the hole and let the screw make its own threads. Aluminum is pretty soft so that may work. Anyway, thanks for the tip; no rivets in the wing.

[XLR8]

This is the sort of lacerater I had in mind for the Javelin. Although, taking a fresh look at this again, there are lots of interesting designs out there. Maybe I'll change my mind and go with something else.

[XLR8]

The weather here this week has been simply outstanding and I’ve finally been able to set aside some time to run the car. I’ve never actually driven a Kyosho Mid before, so this was a completely new experience for me.

My first impression was just how insanely quiet this car is; by far the quietest RC I’ve ever run. Squeeze the throttle and there’s a small whistle from the spur then, apart from slight tire noise, it’s dead quiet. I mention this because usually (not always) quiet equals efficient since, at least in theory, the system isn’t wasting energy to overcome some mechanical interference that's creating sound waves so more of the available energy can be used to propel the car. Also, since this car uses a metal idler gear, I’d expected it to be noisy, but it isn’t.

Second, as you’d expect from any car with a relatively high front weight bias, this car has a ton of steering response. I really needed to re-learn how to drive a 4WD RC after driving 2WD for so long now. I dialed back the steering Dual Rate to about 70%, disabled the drag break (I typically run 5% DB on 2WD because it seems to aid corner entry), and tried to re-trained my mind not to lift entirely off the throttle while entering the corner. So, took it slow initially and after a little fiddling with steering and throttle settings and about 10 minutes run time, I was able to hustle the car around the track pretty well. After 10 minutes, motor and ESC temps were good. The 550 motor seems to make a lot of torque and is a good fit for this car – acceleration is instant -- I like it.

Another thing I noticed was that the rear spring rate and damping still needs a little attention. The rear of the car tended to rebound far too much mostly over the smaller ripples in the track while the front remained planted.

It’ll require more suspension tuning to improve the handling but, so far, the car is a lot of fun to drive. Big smiles from me. I’m really looking forward to running the wheels off this summer.

[XLR8]

Oh, I forgot to mention that this car could definitely benefit from a little extra wheel base. It reminded me of the first generation Schumacher CAT (short wheel base). At times when I misjudged available rear traction in a corner, the car tended to hook instantly; too quickly to react and catch it.

[Wahrsuul]

That's why they built the longer chassis Optima Mids. I've got one of the original mids, and 2 of the extended versions. Still have a full extended chassis and parts to extend a standard mid as well.

[XLR8]

So, the longer WB car uses a longer upper and lower chassis plate, belt, and belt covers? Oh, and a longer body I guess. Is that it or are there other differences?

[Lonestar]

Awesome build! Looks beautiful for a parts car

So, the longer WB car uses a longer upper and lower chassis plate, belt, and belt covers? Oh, and a longer body I guess. Is that it or are there other differences?

The first longer chassis was the mid custom indeed exactly for the reasons mentioned above - that's also when 4wd's transitioned to saddle packs, although the MC could use lifted up sticks, still.

Other than these mods, and the usual availability of different shock/chassis material combinations, no mods iirc. Then they went to the Lazer (Legend in between but was it ever commercialized?). Then Kyosho fell off the face of the RC earth for like 10 years or so as the later lazer versions were desirable for sure but so exotic and expensive than even the most seasoned yokomo racers couldn't understand the product line Then the Lazer ZX-5 brought kyosho back to the top of the 4wd game.

[RCveteran]

So the rere Optima Universals fit these without any mods as well? Both front and rear? Part OTW125?

[GoMachV]

So, the longer WB car uses a longer upper and lower chassis plate, belt, and belt covers? Oh, and a longer body I guess. Is that it or are there other differences?

Mid you decide you want to make it a longer wheelbase, I still have some chassis sets that are longer than stock and just under the kyosho version long wheelbase chassis. They are our original chassis from our trailing arm kit but cut down for stock suspension. The only thing we don’t have is the belt cover, which TBG sells.