SWB Optima Mid Modern Racer

[alcyon]

I got a lot of Optima Mid parts I have amassed since 1990 to 1992, which I still have until today. Seeing so many people building SWBs, I have gotten an itch too.

This was a small sample of my parts bin, putting together my brother's Turbo Optima Mid.

I just couldn't wait to build the drive train, so here it is with the ball diff I removed from my LWB runner, I rebuilt the ball diff and its going in this car. Notice the custom center gear I made out of hard PEEK. I actually sold a black delrin gear to a Taiwanese guy called Po Chen, and he broke that gear, so I made this PEEK gear and sold it to him, and he said it caused his center shaft to overheat and melt his gearbox. The funny thing is , I am using the delrin gears in my runner so far with 15 packs, and its holding up well, heck even jopp3 said my delrin gears are good. So anyway I will be trying this PEEK gear and I wanna see if indeed it does over heat the center shaft.


This is my own designed Optima Mid B4 layshaft.

After 5 hours of hard work, this is the result.


Notice the custom long front towers. All the towers used on this project will be custom cut FRP, because I don't want to ruin the original Kyosho OTW-2, and I am planning to use modern Sworkz big bores on this car, as they are cheap and looks good, besides adding the much needed front arm travel. If you look at the pic of the car with the front wheels on, notice that the left arm is up higher and the right simply cannot travel upwards. This is because the knuckles I used were from a touring car, and it places the bearing closer towards the center of the car, thus causing the dog bone to bind. I will be replacing those knuckles with my ground down ZX-5 knuckles from my LWB runner, and will be making my own ball bearing c hub for Lazer suspension to be placed on my LWB. I am planning to run this car with original mid arms.
At this time, these are items that I don't have yet to complete this build.
1. 5x8 bearings for the belt idler
2. Another pair of modern kyosho 62.5mm universals for the rear.
3. A body set.
4. SWB upper belt cover.
5. Modern Sworkz shocks
6. Ground down ZX-5 knuckles to fit into those A & L c hubs, the c hubs are super strong ! Never bent or broke them, but have broke quite a number of front arms.
7. Associated SC10/B4 slipper pads.
8. A working steering system, I have the originals but they have too much slop, I think I want to go the route of my LWB steering.

I plan to run the same electronics as in my LWB mid which is a hobbyking 100A ESC with 8.5T sensored brushless motor. As I have bought a LPF SAVOX servo for my touring car, I will then use my old SANWA ERG on this Mid. Of course I would need another 2.4GHz Sanwa receiver. Not forgetting a soft case lipo pack. As this is not my all out racer, I will keep custom parts to a minimum, unless I see that this car has further potential, perhaps I would upgrade to Lazer ZX suspension all around.

[HKS_TRD]

Will be watching this project with great interest
The front shock tower looked like a MK1 ZX-R tower to me
I am also going to be doing some upgrades to my SWB Turbo Mid SE-X and I am slowly amassing bits for another modified SWB Mid, I have those C hubs didn't realise they were Andy's, I'm planning on getting them anodised
I also have have alloy wishbones not sure if they are Andy's but I also have Andy's wishbones and Knuckles for that project

[rccars4sal]

It seems like we build 1 mid,, and it takes a parts lot to make it complete,, so after doing an inventory,, theres another mid just short of completion! I got tired of them,, but yes,, theres another just waiting in bags and boxes.... I like mids.

[alcyon]

HKS TRD, those towers are custom cut before the ZX-R was released. It was made for the ZX to be used with long shocks in the front, remember that trend in 1990 ? rccarsforall, these parts actually came from a working car that I dismantled to get my LWB running some time in the mid 90s. You know how it goes, you run the SWB, then you wonder if the LWB will give you an advantage, then you build up a LWB, then after that you long for the SWB again .
To me the SWB looks better, but the LWB has better battery options besides being cleaner because it has an undertray. Last night I removed my ground down ZX-5 knuckles and placed them in my SWB A & L c hubs and there is no more suspension binding, wheel travel is now equal. I asked my plastic supplier to make my own designed white POM Lazer ZX, ball bearing equipped C hub that allows the use of standard ZX-5 knuckles which are tougher and cheaper than plastic OT-16s. Hopefully he can get them ready by this Friday so that I can test them on my Lazer suspension LWB mid.

[alcyon]

Spent some time last night sorting out the wheel hexes. Need to buy new Yeah racing standard touring hexes cause I have 7mm offsets which are too wide now. Pic is shown with ZXR rims and tyres.

Steering system installed, adjusted to minimum bumpsteer.

rear FRP towers installed. Notice I place the upper tower on the rear, I did this on purpose because I want to place the shocks rearwards.
Planning to use TB03 rear stub axles with the kyosho sliding dog bones temporarily till I buy LA245 modern universals for the rear.

[HKS_TRD]

Looking good, I noticed you have set the steering parts up differently to your LWB build, is that to do with the castor on the front hubs?

[alcyon]

Looking good, I noticed you have set the steering parts up differently to your LWB build, is that to do with the castor on the front hubs?

Its not because of castor, but because the hubs are taller than stock LA27 hubs. Also I am using the ZX steering plate here, and if I used the same setting as my LWB which is using A & L graphite plate, the ZX steering link plate rubs against the front gearbox. So I moved the two 5x8x2.5 bushings to the bottom to lower the main steering rotating parts. Then I basically used a short ballstud to mount on the ZX link plate, without washers. On the ZX-5 knuckle, I used long ballstuds and placed two M3 nuts to raise the ballstud to limit bumpsteer. Then of course now the steering tie rod must be placed above the uni crank so that it wont rub the link plate at full right lock.

[HKS_TRD]

My LWB Mid has the same setup as yours and I use the ZX link plate with no rubbing on the gearbox, I just had to file a notch in it which you appear to have done to yours too

[alcyon]

My LWB Mid has the same setup as yours and I use the ZX link plate with no rubbing on the gearbox, I just had to file a notch in it which you appear to have done to yours too

But anyway, I may have to reconfigure my LWB steering cranks because of the new white ball bearing hubs that should be ready by this friday . Again the knuckle heights will be different, and I will only know what to do once I install them. I think the height of your crank might be a little different than mine, depends on the spacers you put at the bottom. The A & L graphite plate is a lot slimmer than the ZX one. On my LWB the crank is raised higher but the link plate mounted under.

[alcyon]

Updates !
After flipping the rear arms so that I can mount the shocks lazer style, I noticed that the rear CVD exit the diff swept forward. This could cause handling problems. If the arms are swept rearwards, the rear will lift on acceleration, if its swept forward, it will be pulled down, besides from the force of inertias of course. In order to get the car to handle the way its supposed to, I decided to grind off 4mm from the arm.


After grinding and shimming, this is how it looks like.

The arms are 45mm wide, I ground them down at one side only to 41mm. This will force the CVDs to be aligned with the diff.
I also bought 3racing 4mm touring car hexes and now I have the correct wheel spacing, I also bought off a first generation Durango DEX410 shockset from my LHS who sold it to me for the price of 3racings ZX-5 shocks. These shocks are really quality stuff, I could tell when I put them together. With kyosho bottom rod ends, the fronts are about 89mm, just right for this long shock tower. I used 2 hole pistons and kinwald 27.5wt oil, but the damping feels too hard to me, so I will be changing to 3 hole pistons. The spring rate seems right, it feels soft, unlike the 3racing ones which are too hard. I also built one rear shock and found that its length is 97mm with short kyosho rod end, seems to be just right for the mid, to be placed in the inner most hole of the rear arm, which will give just the right ride height.
Tonight I will assemble the rest of the shocks and mount them on the car.

[alcyon]

Finally installed the shocks but for the life of me, I cant figure out why is the shocks so hard. I used the original Kyosho gold springs and its softer but, still too hard for my liking. I even changed to 20wt oil, and its 3 hole piston all around, yet it still seems too hard, unlike my Kyosho big bores on my LWB which are super soft. If I cant solve this I wasted $35 on these shocks and several hours building them.
Anyway since I had nothing else to do, I decided to make a hole in the middle of the gear cover. Seeing that I botched up 2 covers before, I got an idea to ensure I make the hole gob smack in the middle.

Once you place the cover on the motor plate like this, its a lot easier to get the center point.
This is the finished product super glued.

I will try some more ways to make the shocks softer.

[Coelacanth]

Finally installed the shocks but for the life of me, I cant figure out why is the shocks so hard. I used the original Kyosho gold springs and its softer but, still too hard for my liking. I even changed to 20wt oil, and its 3 hole piston all around, yet it still seems too hard, unlike my Kyosho big bores on my LWB which are super soft. If I cant solve this I wasted $35 on these shocks and several hours building them.
I will try some more ways to make the shocks softer.

For my CYANide Optima, I bought 3Racing Lazer ZX-5 shocks...I found those to be particularly firm, too. In addition to going with lighter oil, one thing I did to make them softer is to open up a piston hole completely. I used an X-Acto knife to cut the edge of the ring through to the hole, making the hole into a tiny slot. You could repeat that for the other holes if necessary. Give that a try.

[alcyon]

Thanks man. Thats a good idea . I will take the easy route and just drill out the pistons.

[alcyon]

latest update. got a stick pack, now sourcing for a brushless esc and motor, servo mounts and servo saver.
Got to test if my PEEK center gear does indeed melt the gearbox or not.


just got a orca qspark esc. Gonna test the car in a few hours.
http://www.youtube.com/watch?v=QrZf_AYY0og&feature=youtu.be

ran it onroad in front of a RC shop. it rained earlier so playing touring car or buggy is out of the question

[alcyon]

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went for a vacation on the beach, took some pics and Video. The OT66 was amazing on the beach sand and grass. The SWB Mid is surprisingly stable and not as twitchy as everyone says.
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