Proper Optima Mid Slipper Clutch
 

For all you fans of the Optima Mid who still race this car today, i want to inform you guys that i finally decided to do something about the slipper clutch non existence on this car, thus making it not easy to drive. I plan to use associated B4 slipper parts including the spur gears, becuase the parts are cheap and easily available, and also simple in design, without the need to for thrust bearings. I beleive by designing a new top shaft for the Mid, whereas the inner part of the shaft will mate perfectly into the Mids gearbox, but the external part of the shaft will mate perfectly with the B4 slipper parts. the only problem i forsee is the gearcover will have to be cut on the outside and a plug made. I will be designing and making a protoype and will test it extensively. My question is : how many of you guys would be interested to mount the B4 slipper on your Optima Mids? i would only have to make the top shaft, but in volume i can make them cheaper. i estimate they will cost U$30 shipped worldwide if in singular quantities, if 10 pcs i can bring down the price to $20 shipped. By the way if you think you cant trust me, look me up, on ebay and youtube and bmxmusuem i am alcyon2sp.

Sounds good, I'd be interested in one :D

me too

small question: did you verify the B4 spurs are available in suitable sizes for the optima mid?
I'm just asking 'cause I looked at alternatives for the Triumph and lazer spurs and did not find B4 (style) spurs that were large enough for those cars.

Optima Mid's use an 87 tooth spur iirc.

wooow, careful adam: the B4 teethsize is different form the optima-mids teethsize. What you need to compare is the spur diameters

yes i have checked, you an get a 74 or 75T B4 spur, close or the same with the optima mid. byt the way the Mids Spur is 74T not 87T. i have to get off my lazy ass and start designing !

ah, I think I see what Adam meant: you need a 87T 48dp B4 spur to match the original 74T 0.6M spur diameter
If you'd use a 74T 48pitch spur it would be way smaller and difficult to reach with an average sized pinion.

I would deffo have one of these:thumbsup:

i will do a comparison and check.
here is the screen capture of the shaft i designed last night. i managed to cut it down by 2mm ant the slipper side to make it as short as possible. i think the end of the gear cover will have to be cut to fit in the longer end shaft, am still trying to think of a way to cap the cut end of the gear cover. Nevermind, let me solve one problem at a time. i just send the cad drawing to my machinist and lets wait for the prototype to come !

If you can come up with a solution for the optima/ultima aswell, and a simpler slipper system for the lazer too... let us know.

I love driving my oldies but the lack of slippers makes them wear and break too easily

sorry my friend, i don not have the Ultima and the optima with me, i only have the optima mid and the Lazer ZX-r. The optima mid was my first pro car back in 1990.

some simple and easy to source solution for the ZX-r , preferable in 48pitch or 0.6mod would be fine. No need for one-ways or third diff etc: a solid pulley for the fornt and rear. (I have a one-way unit for the front diff anyway)

protoype
 

supplier just called me, my proto is ready, will test fit tommorow night !

Nice, any chance you can sell it as a bundle: with the spur and B4 parts needed?

sorry my friend, i cant do that, i do not have any special deal with associated to get them at cheaper price. Also i tried fitting my shaft last night and found the tolerances are all out for the bearing fit, it was way too tight. so i took some sandpaper and slowly polished it. now the end sections can fit the bearing in, but the middle section needs some more polishing. also the inner circlip groove is too narrow, i must send it back to get it widened. Another problem is the slot side for the B4 parts also is too tight and wont go in. i will use my workplace drill to clamp it and do some polishing today. as a consequence of spining the shaft manually to polish, i now have a blister on one finger on each hand (ouch). since this is a prototype i guess i expected it. i will have to fine tune the tolerances more on the minus side to get it to fit immediately. i hope i can fix it in my MID by sunday and do testing.

Ive already been down this route. The hyperclutch layshaft needs lengthening by a fraction so we can fit my design spur within the two plates and leaving the thrust race with enough room for the spring so it does its slipping or none correctly.

well, i tried polishing the shaft, but end up ruining it when i got impatient. i redesigned the shaft with tolerances more on the minus side, and i told the machinist i will pass the optima mid top gear and the B4 slipper plates to him to do a matching test before giving the parts to me. hopefully by tommorow morning i can pass all these parts to the machinist to start work, and in another 2 weeks get my working prototype. the good news is the length i designed was almost spot on, so i shortened the shaft a bit by 0.5mm. i tried putting the gear cover on, and definitely a hole must be made on the side and a extension cap made to accomodate the new longer shaft end.

I wasn't fishing for a cheaper price , just hoping to buy all the right stuff together.
Which spur are you gonna use now? Could you measure the outer-diameter for me please?

hi there, i just sent all the stuff to the machinist. i got a 81T Associated spur now. it is just a wee bit smaller than the original optima mid spur, hardly noticable, that means a matching 48P pinion should go right in to maintain the same final ratio as the original. i should get the second protoype in 2 weeks tops. i wont give up on this design and will see it through. on another note, i will be driving my optima mid in a few minutes at the track today, it has been months since i last ran it cause it was always raining every single day. about the b4 parts, if i were to get them for you it will probably cost more. i will give you the breakdown of the parts for it though. i will also give the gear cover extension, but you probably have to make the hole on the gear cover yourself.