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.