Sunday 18 September 2011

Dont Do this at home ! a Mistake !

I just finished painting my new Marwan repro body. here is how it looks like.

Notice the rear track width is less than the front !

Looks like i made a big blunder, now only i noticed that the rear track width is less than the front ! Before i throw in the towel on this suspension, i got one final trick up my sleeve, the TF-5 touring car rear hubs. I tried it before and it actually placed the rear wheels more outwards, but the bearing spacing was more than the ZX-5, hence, the pin couldnt go through. But i beleive the bearing spacing is the same as tamiya buggies, namely the Dark Impact buggy 64mm CVD. So i will get the hubs tommorow and keep you guys posted. If all else fails, its back to the original suspension, of which i have plenty of arms. Right now i just need 2 things to really complete the car, the Alec & Lane (A & L) bellcrank, and the AE B44 battery hold downs. i have just placed on order on the A & L #2182 ball bearing steering system.

Latest newsflash, the optima mid and lazer has wider track width at the front than the rear ! this is normal !

Saturday 17 September 2011

1st outing, a disaster

I went to SS19 subang track for my first optima mid run in 11 years with high hopes. To sum it up, there was more bad than good. the good first. The car was really silent and smooth ! Making only as much noice as any other modern car on the track ! The Car was also very fast on the straights with the 10.5T motor. i heard other people were using 5.5T to 7.5T. Also the car tracked well and braked straight. Now the bad news. The optima mid understeered horribly, it was so bad that even the 2WD cars were over taking me in the corners ! I had to slow down so much just to corner tightly. I beleive its becuase of the UM-14 original bellcrank, which had too much slop in it, it was practically allowing the front wheels to flop left and right about 10 degrees without even engaging the servo! Also on the ground, the servo cant turn the wheels to full lock. So thats probably why the car understeered so badly. The more i pull the throtle, the more it pushed, if i pressed to much gas out of the corner, i lose rear traction.
Next i had trouble going over the small jumps. The car kept flipping front wards and slamming the wing bad.
But i finally got the hang of it, and gassed partial throthlle until i hit the jump and pressed full gas, and the car cleared the small jump. The big jump was another story, i crashed the optima mid in every possible way. Landing nose first on the front side of the landing, landing sidewards and somersaulting countless times.
But i did manage to clear the jump nicely about 3 times. the trcik is to climb the inclination as high as possible, the go down with partial throttle, then as you are reaching the top of the jump gas it all the way, and keep on the throttle until the car clears the jump. The problem is right after the big jump is a sharp 100 degree corner to the left, so i tend to let the gas go in mid air to slow down the car to not overshoot it, but that is causing the problem with the big jump. I must overcome this mental handicap.

Friday 16 September 2011

Building the Ultimate Optima Mid

The Kyosho Optima Mid will always have a special place in my heart. It was my first real pro car i bought in 1990 used from a creep named zain. He was a creep becuase he cheated me and my buddy who shared to buy the car by not giving us the graphite chassis that was supposed to come with it. Yes he sold me the LWB version, and substituted the chassis with a flexible kelron type material that was cut rather nicely but flexed too much. At that time i didnt know much and thought i got the real deal. I also acquired the SWB aluminium chassis Optima Mid the following year, i thrashed both cars from that time to about 1997 when the car was no longer servicable anymore and moved to toruing cars.
I recently acquired a used Turbo Optima Mid Special from my longtime friend Jason Yeo at a bargain price, and it came with the orginal kyosho graphite chassis, finally ! Looking at the original suspension and comparing it against the Lazer ZX, its easy to see that it is very dated. The hingepins are before the wheel and upper camber links rather short. So i decided to rebuild this car with a view to keep its original looks, which i love so much compared to todays buggies, but update its suspension. After some studying, i found that the new lazer ZX-5 arms uses 3mm hingpins also, but the arms are more narrow than the Mids. So that means its possible to place it in the suspension mounts, with the use of spacers to space the arms.
Together with Lazer ZX shock towers and ZX-5 shocks from 3 racing, front CVDs for the ZX-5 and rear the original sliding dogbones, with TG10 rear axle, the car now has the ZX-5 arms and hubs on it.

The built up car with Jason Yeo's original Mid Custom body, i bought Marwan repro Mid Special body but havent had the time to piant it yet.



Lazer ZX front shock tower, next upgrade fibrelyte Lazer ZX shock tower

Lazer ZX-5 suspension pieces and CVD from 3racing

Chassis view of all modern electronics

Spur gear view, nice !

Look how i spaced the arms. the rear of the front arm is touching the gearbox mount, and the front CVD is angled forward about 2 degrees. if you want the CVD to be completely in line, you have to grind the garbox mount about 3mm.

The original Graphite chassis- my big deal !


Rear ZX-5 arms hubs and TG10 axle mathced to original optima mid dogbone, and yeah racing hexes

How i spaced the rear arm

Look at the ZX-5 shocks from3racing and the ZX shock towers, next upgrade fibrelytes
I have encountered a few problems with the rebuild. The biggest is the original UM-14 steering bellcrank servo saver. it saves the servo all right, but also is a slouch in steering, it will turn if the car is moving. Next upgrade, change to the lazer zx bellcrank or A&L which will cost me 53 dollars.
Another problem is the saddle pack battery holder. I find that the associated B44 battery post and bar will line up perfectly at 75mm spacing, but i have problem trying to order it from amainhobbies at this time, and definitely will order it when i can, for now i use double sided tape to stick the battery in. Also the body cant really come down completely with the new bulky brushless escs.
Last night i also found a problem with the drivetrain, it was very smooth without the pinion in, but as soon as i put the pinion in, it was extremely nosiy. i swapped a few pinions, name from atlas, then finally when i put in a 20T tamiya pinion, it became silent. Phew, i thought this car was a goner ! Cant wait to test it today. For now its running with Lazer ZX-5 RTR tyres which i got cheap, they are not as good as prolines cause they dont have inserts in them, but they should be better than  my old tyres.