Recently acquired an Optima - seeking some opinions

[doublfelix]

Hi all,
I've been lurking on the forum for a little while after acquiring this car at a swap meet trying to learn about it, but posting a topic seems like the most direct way for me to actually make a plan and get working on it. I've been out of RC for 20 years or so, but my almost 5 year old son got a re-release Midnight Pumpkin out of the blue for Christmas this year, and driving it around with him reminded me just how insanely fun these vehicles can be. I started looking locally for something cheap I could tinker with and at some point be able to drive alongside the Pumpkin, and stumbled on this at a swap meet.

From what the seller told me and some comparison to instruction manuals, it looks to be an Optima Mid (haven't measured wheelbase yet) that has been set up to run dirt oval, though it came with the original buggy chassis and possibly the original wheels and tires as well. It has no body, is set up for the battery to be mounted on the left side, and has some DIY looking body mounting solutions.

My main questions are:
1. I've always kinda wanted an RC rally car, and I've seen some Optima rally projects on various message boards (though in many of them the pictures are no longer hosted). Are there any suggestions for finding a reasonably available / not outrageously priced rally body that fits this chassis, or do I need to start a scavenger hunt?

2. Any thoughts on whether I should switch back to the original chassis vs. keeping what's on there now? I'm guessing with a rally body clearance won't be an issue, but maybe there are other considerations I'm not thinking of.

Thanks in advance.

Edit for some photos

[klavy69]

pictures would help

Todd

[Coelacanth]

That indeed looks like a regular Optima Mid. The Turbo Optima Mid SE would have counter-sunk holes in the original chassis plate; at least from the side shown in the pics, that plate looks like the holes are straight-drilled. There's a lot more DIY going on there than the body mounts...obviously the whole chassis and nerf bars are also home-made, but done pretty well. If it was me, I'd put the car back to some semblance of originality, then modernize it somewhat...but that's just an opinion.

Looks like a fun project, no matter what direction you decide to go!

[Wahrsuul]

That's a custom chassis, never seen one like that for the Mid before. From what I can see, that looks to be an Optima Mid or Turbo mid chassis, there were no differences between those 2 chassis plates. Also, those rims are the originals with an Optima Mid, just painted silver.

I'm with Coelacanth on this, I'd put the original chassis back under it and go from there. I have 3 Mids, and a lot of old parts, so feel free to ask if you need anything, I might have it laying around.

[DennisM]

Your buggy is a Turbo Optima Mid SE

The wheels are original chrome wheels that came with the buggy, tires are a different matter

I would put the original chassis back on it.

If You´re in Europe, there´s a guy on German ebay selling wide touring/rally bodies - I saw a Lancia Delta HF integrale not too long ago.
Otherwise, I´d recommend TBG.

On a sidenote - the Optima mid and the Turbo Optima does not have the same chassis. Optima mid is OT 91 and Turbo Optima Mid is OTW 3

Turbo Optima Mid and Turbo Optima Mid SE shares the same chassis.

[Coelacanth]

Your buggy is a Turbo Optima Mid SE

Turbo Optima Mid and Turbo Optima Mid SE shares the same chassis.

We're kinda speculating unless we see the bottom surface of that chassis plate. Straight-drilled = Optima Mid; countersunk holes = Turbo/SE.

The Platinum shocks instead of Golds and triangular bracket above the motor area would seem to suggest that it's a Turbo Optima Mid SE, though.

[RichieRich]

Doesn't the SE chassis have a bit of a bronze anodize on it? I thought the plain Jane Mid chassis is just plain stamped aluminum. I think it's an SE.

[mugenbulldog]

Definitely a turbo optima mid se. In addition to what others have noted; also the shock towers and smoked lexan covers.

[doublfelix]

Here is the bottom side of the stock chassis, it has some scuffing but seems to be in decent shape. Oh and countersunk holes as several guessed there might be


The stock wheels and tires I referred to in my original post which were not pictured. Tires are Kyosho logoed Bridgestone Sand Supers, and I'm not sure if they've ever been driven on.


Also some spare diffs that came along with the car as freebies


Now that we're pretty sure it's SE, I'm going to download that manual, clear some workspace, and figure out what I've got and what I'm missing.

[Coelacanth]

A one-way front diff...nice option. Those are pretty pricey on eBay these days!

[HKS_TRD]

That front diff looks like a ball diff to me

[Phin]

My main questions are:
1. I've always kinda wanted an RC rally car, and I've seen some Optima rally projects on various message boards (though in many of them the pictures are no longer hosted). Are there any suggestions for finding a reasonably available / not outrageously priced rally body that fits this chassis, or do I need to start a scavenger hunt?]

Sellers antiquesandmore100, and bubs_trains_and_hobbies on eBay have some Parma bodies that may be wide enough to fit. Definitely send an email to check dimensions first though.

Dennis mentioned TBG's replica's and I can confirm they've got a Porsche 959 body that fits an Ayk Radiant and an RC10. The 911 should fit too.

[doublfelix]

Thanks Phin and everyone else for the input and advice. After a spring that included sick kids, sick adults, sick dogs, a yellowjacket infestation in the basement, and a backlog of toys in need of repair that cluttered up my workbench, I finally found a couple hours to work on the Optima. I removed everything from the custom chassis, disassembled, inspected, etc. and then transferred things back to the original chassis.

Photos are how it is sitting right now - from looking at the manual I appear to be missing the 1. lower belt cover, 2.front bumper, and 3. battery holders. I also need to track down a pinion gear for the 24° stock motor (27T) that was thrown in as part of the deal, is there a gearing chart somewhere (or in other words, what size pinion am I looking for?). There are also a few screws here and there that have either started to strip, have the wrong type of head, or are (will be) missing.

Any suggestions on where the best places to look for these couple of parts, assorted screws, and pinion gear would be? Are there any troublesome parts from this model that I should think about replacing simply because I have it apart right now?

Pics:

[Coelacanth]

I also need to track down a pinion gear for the 24° stock motor (27T) that was thrown in as part of the deal, is there a gearing chart somewhere (or in other words, what size pinion am I looking for?). There are also a few screws here and there that have either started to strip, have the wrong type of head, or are (will be) missing.

Your optimal final gear ratio is less dependent on your motor as it is on other factors, like your spur:pinion ratio and tire diameter, because all else being equal, every 540-size motor rotates the same distance in one revolution (and therefore has no difference in rollout ratio). The stock Optima Mid has an IGR (internal gear ratio) of 2.64; the EGR (external gear ratio) is your spur-to-pinion gear ratio. You haven't mentioned the number of teeth of the spur gear you're using. (Stock Optima Mid had a 74T spur and 20T pinion, I believe, for an EGR of 3.70.) Multiply your IGR x EGR gives you your FDR, or final drive ratio.

If you can provide your tire diameter, you can calculate your tire circumference; divide that by your FDR and you'll have your rollout ratio...I aim for that number to optimally be 1.00, plus or minus 10%; i.e. 0.90 - 1.10. Anything in that range is probably close to ideal. If you're aiming for a bit more torque, go with the choice that's 1 tooth less; if you want more top speed, go with the choice that's 1 tooth more.

Let me know your tire diameter and spur gear tooth count and I can provide a couple pinion numbers that would be close to theoretical best. I made my own spreadsheet to calculate this.

[Coelacanth]

Did my comment above break the Kyosho forum or something?