Friday 30 December 2011

My latest additions and worry

I got myself a new wing for my Optima Mid, made by durango. Have look at it.
I finally used up the rest of the stickers that came with the Marwan Repro body kit.
i changed the rear springs to assocateds green springs, the softest, and the front to silvers, the second hardest. I also reduced the droop a little bit on the shocks. Waiting for the durango shock boots which i will buy from 1 Utama tommorow, then the car is ready to run again !
Then the little debacle with dirt getting in the tranny got me worried. OT86 gear is still easy to get, and the center gear is made by pargu2000 out of aluminium, and its excellent. But no one makes the SG-25 plastic sprocket set, and its getting verh hard to get hold off these days, and also very expensive at $25. I saw a seller selling the ball diff casing for only $5.99 which is cheap, but i dont want to use ball diffs anymore. So who will make the SG-25s? My current sprocket gear is very new, and i only have one more new extra sprocket, then thats it. i think these could last me perhaps 3-5 years, if i dont let dirt get into the gears. But after that what then? I got an idea to make a single belt conversion for the Optima Mid, which you will be able to use any worn out sprocket gear, cause there will no contact with the gears anymore. Unfortunately my idea will require some cutting on the rear gearbox, a little drilling on the top deck, and total removal of the upper deck belt cover. The good news is i beleive the belt cover will not be needed there because there will no need to have any grease inside the tranny anmore becuase of the single belt drive. I will work on it once i run out of gears !

Saturday 24 December 2011

Optima Mid Slipper Clutch

Firstly you might ask me, why do you need a slipper clutch on An Optima Mid? Doesnt it already run well? Well, i dont think the Stock Mid runs that well. On very rough tracks, the lack of a slipper places great strain on the tranny, and also makes the car very hard to drive. If the surface is too rough or rutty, the sudden jolt from the rut to the wheels , coupled with the power and torque still coming from the motor while your finger is on the throttle, will cause your car to bounce badly, and could even flip the car in another direction.
I decided i needed to do something. I did some research on Losi and Associated's slipper clutches, and i found some designs requires thrust bearings and some dont. I opted for the cheaper option, and chose Associated's B4 slipper clutch. I got one complete set from ebay for $20, comes with the top shaft which i need for measurements, the 2 slipper plates, slipper pads, spring, and the spur gear 81T.
My plan was simple, design a shaft that on the inside, matched perfectly to the Optima Mids gearbox, able to place OT-86 gear on the shaft. On the outer part, it will match with the B4 slipper parts.
Here is what i came up with.

The second protoype i got from my machinist. The first one was a failure.
The gear cover on, with a hole made. I ran it this way for a pack. On the second pack, a bit of stone went in and chipped the spur gear. So i devised a round tube cover, see picture below.

This is a chinese medicine plastic tube, it was cheap, and the right size to contain the spring and the nut. I sawed the tube, then siliconed it on the gear cover. The removable cap allows me to adjust the slipper setting ! NEAT !

I tested the car at titiwangsa track in Kuala Lumpur, and the car was much much MORE EASIER to drive. It felt like i was watching a Pro CAT in action. Yes it was that good. I gotta take video , if only someone could help me. The track is extermely rough, but for the first time ever, i could drive it around the track, without the car losing a lot of control. In fact it was the first time i could drive the car lap by lap by lap, until the battery dumped! I even took the huge jump, that launched the car 4ft high, over and over again, and landed hard ! On the second pack, the tranny was making some noise. So i stopped the car. It felt like the bearings were contaminated and some sand got into the tranny. So i went home and took the car apart, sure enough some sand did get in. So i did a total stripdown, relubed the bearings, put molybdenum grease on the gears, and put heavy lithium grease in the gear diffs. You might ask me why i am not using  the ball diffs. Well, they require too much maintenance. The will foul up after 2 packs only. And with the slipper, the gear diff works well. I also sealed all the joining areas of the belt cover near the gearboxes, with flexible silicone.
I also found that the gear diff outdrive bearings are placed a little bit nearer to each other causing a 0.5mm gap between the outer bearing and the gearbox. This is what allowed the sand to inside the gearbox.
So i devised a simple way to keep sand out from this area. I cut thin sponge, and placed it at the diff outdrives, and tighthned the setscrew. Now my whole tranny is dirt proof.

Next i am planning to buy durango shock dirt boots to place in my shocks to cut down on maintenance. Now the only part requiring maintenance on my car is the wheel bearings, but that is normal even for modern cars.

Sunday 16 October 2011

latest upgrades

i have now gone back to Kyosho LA-26 arms, and i modified the A & L bellcranks after i found their shortcomings. the problems was the plastic 4-40 nuts were not strong enough to hold the screws. after a few hard knocks it worked loose. so i replaced the 4-40 screws and nuts with M3x25L bolts.
Notice the missing bearing on the left, lost it on a bad day, waiting for the replacement to come. notice i flipped the graphite bar upside down from the instructions, this allowed me to place the ballstuds facing up and higher, thus enabling the steering link to be parallel with the lower arm, eliminating bump steer.

notice the amount of wahser under the pivot post to raise up the ballstuds.

The steering link is parallel to the lower arm, so no bump steer here !

View without body with modern electronics.

With modern tyres

Fibrelyte James Instone Lazer ZX shock towers.

Fibrelyte James Instone Lazer ZX rear shock towers

Top view, notice the A&L sticker


Car now sits low with reduced droop , thanks to the New shock towers.
I tested the car now it finally it had a LOT of steering, becuase the bellcranks now work they way they should, and also because i grinded the back of the c hubs protrusion so that the knuckles can turn more. I just have to stab full throttle, when i want to turn let go then turn, the car will slow down by itslef becuase of the friction and grip of the front wheels. i can now point it to whiceever direction i want it to go to. but i havent tested it off road yet though.

Saturday 8 October 2011

More modifications...

Ok, the ZX-5 suspension was a dissapointment, not that it didnt work, becuase the width of the area going in the hingepins is short, it caused the hingepins to bend easily. So i decided to go back to the lazer ZX arms. Installed MPP ZX arms , which was a lucky find, i found 8 at hobby haven, each bag costs me RM5 only. Coupled to LA-59 front c hubs, and LA-28 rear hubs, i managed to laser-lise my Mid suspension. I like the lazer's arms better, becuase they place the outer hingepins inside the wheel, which makes rough track handling much better. I used the inner hole on the C hub to push out the front track, and used 3 racing 65.5 CVD. At the back, i am still waiting for LA245 CVD to arrive from japan. My A & L steering bellcrank arrived and cured the sloppy steering problem. I also managed to use back the Mids original battery holder system to hold my Lipo Saddle packs in. With Proline M3 soft tyres all around, my Mid will surely handle better.

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.