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.

break a leg :thumbsup:

just came back from the track, it was hot all day but it rained all night last night, so i thought the track would dry out, i was horrified to find it submerged with water about an inch high.. 80% of the track ! so i tested the car in an open grass and sand field. the car was really fast but a lack of slipper made it diffcult to stab the throttle from low speed, so i have to the feather the throttle in the corner and when the car straigthens out gas it all the way.. did find my optima mid reliable though, it was traction rolling crazy too, so much grip. here is a pic of my turbo optima mid SP.

Nice hop-ups you got onthere. How about some body-off shots?
I'm building a one-off with long wheelbase and lazer suspension too.
At the moment it sits on a lazer 'sport?' chassis: the kelron one. I like that one 'cause it's much wider to accomodate saddle pack lipo's and has no holes in the bottom. But ofcourse it needs stiffening... a lot. Right now it kind of feels like I have a tad too much tension on the belt when all is flat out.

here they are my friend.
Lazer ZX suspension, James Instone Lazer ZX Fibrelyte shock towers, self modified original battery holdowns for lipo saddles. Original kyosho Graphite chassis from LWB conversion. Ball diffs front and rear. i am thinking of changing to gar diffs cause they need much much less maintenance, and i beleive they will work well with the slipper clutch.

Cool but you need to clean up the cabling a bit ;)
Which moterplate is that?
I have the kyosho optional one for the TF1 which fits and has the same style cooling ribs, but doesn't work with the gearcover.
Do you feel the belt covers are really needed? I only have the short ones to install and was hoping to go with a bellypan but no belt covers

its difficult to tidy up with brushless cause theres just so many cables. anyway, you must have all belt covers on this car. Just a small amount entering the gearbox is enough to destroy the gears. the undertray helps a lot but still some pebbles will get in. the motor plate is A & L one i think from the 80's. so is the bellcrank. i bought the car used from my friend and it had those hop ups on it. i suggest you chuck the flexy kelron and get at least the aluminium LWB chassis. I used to have a kelron self made chassis and the damn thing flexed even by just the servo pulling on the bellcranks ! hmm, by the TF1, you mean the EP spider, optima mid based touring car from 1995 ? by the way, where are you from and how old are you. i am 35 and been into rc since 1990.

Yes, the A&L steering was easy enough to recognize. I had forgotten they also made a moterplate for the optima mid and not only for their lethal weapon transmissions.
I'm 38 and live in Belgium. I got my first car: a boomerang in the year it was released. I think it was for saint-nicolas so I guess I'm celebrating my (24th?) RC anniversary on tuesday.
Yep the original spider. I was given this one after a friend got his TF-2. I'm surised you know it: somehow very few people seem aware of the existence of Kyosho's first narrow tourer.
Don't worry about the Kelron: I'm not counting on that for rigidity, it'll just serve as mounting space for the electronics and saddle pack.

the reason i knew about it was a kit came to my local hobby shop in 1995, and when i saw it i iimediatley recognised it was an optima mid with short arms! it came with a 94 celica body, on the box art it was painted silver. also 1995 rc car action made a shooutout between all the tourers of that time and this was included. frank masi commented how much he loved the optima mid, and kyosho brought it back as a bitching tourer...

got my shaft back from the machinist, i am still not happy with the tolerances both inside the gearbox and outside. The spur gear now can move up and down a bit, and i had to install a spacer to hold the b4 plate properly, and i need to extend the screwing side by 1mm. otherwise everything looks great and seems to work fine. a push test confirms the smoothness of the spur and pinion, it was noticably wayy quieter than the original mids spur and pinion mesh. will be testing the car this saturday.
Merry christmas everyone !

Thanks for posting pics of your mid, sure brings back some memories. I used to use that shell on my Lazer too :Dx

i am glad to report that the slipper seems to work well, a test in my house shows the slipper is silent and slips consistently. i am charging 3 saddles now and will be taking a 3 pack spin later this evening if it doesnt rain.

Having run an Optima mid briefly in the late 80's (nice selection of extras btw), it sounds like your problems are due mostly to the huge increase in power that LiPo/brushless is giving you over what the car was designed for. An insanely hot motor back then was a 10-turn, and would probably be a triple or quad-wind to tone the torque down to something manageable. Additionally, in order to make the batteries last 5+ minutes, it was necessary to let the car roll through the corners power off, then pick the throttle up gently on the exit so as not to take too much out of the cells. Ah, the joys of racing with 1700mAh cells... :)

i guess so, but the rc10 at the time did have a working and better slipper clutch didnt it? even back then, compared to the zx-r, the mid wasnt as easy to drive, simply becuase the lazer had a better and more consistent slipper. i just tested the car an hour ago and i am very glad to inform that the slipper works VERY well. The setting is consistent until the battery is out, and never once did the pad or spur burn out like it did when i tried to let the original OT-88 slip a lot. The car was VERY much easier to drive. setting a slipper is a compromise between the high traction and low traction conditions, so i set the slipper for the high traction area of the track, otherwise the car will not have enough speed to clear the jumps. but at the low traction loose sand area, i had to feather the trottle to prevent wheelspin. The car is so much more easier to drive. In the high traction section i stab the throttle in the corners and yet there is no wheelspin at all! i also took huge jumps many many times and the slipper "slipped" and protected the internal gears. I did install pargu2000s aluminium center gear with new OT-86 counter gear and new SG-25 sprocket, and the car is super smooth. Hard landings were quiet too, testament of the protection it provided the internal gears. i am glad to say i am ready to mass produce this shaft, with minor tweaks to make it better. Video is coming soon. Merry christmas and Happy New Year to everyone!

The RC10 - being 2wd - needed a slipper even in the late 1980s just to stop it back-flipping. And blowing the gearbox.

Also, the tracks of the day tended not to feature jumps sized for motocross. :)

The ZX-R came out some time after the Optima Mid, so I should hope it was an improvement...

by the way how did you choose your nick? does it have anyhting to do with the optima mid stretch ?

@alcyon: nice work there! Once you're happy with the tolerances, would you consider getting another couple of these made? If so, I'd be interested in 2 of them anyways, maybe 4. Pm me when you have a chance, thanks!

yes adam, it would be great if all who want these let me know in this forum so that i can make all the necesary quantities, that way it will bring down the cost. i will make a video showing my car in action with the slipper and then you be the judge !

I did run a long wheelbase chassis for a couple of meetings, but the nick had already been applied...

hi i just noticed your board while looking for an lrp x12,nosram or similar i have been building buggies for about a year now in all my collecting i came across a brand new optima mid(se or turbo not sure,gold shocks)hardly any wear on original tyres in a friends loft,it still has the original spur,pinion&slipper i like the way the drive system is fully encased.i ran it for a few days then took it apart but its all still there just mixed in with other parts,i'll sort some pictures if your interested we could do a swap for parts or come to some arrangement would be nice to see it get a good home.offroad170/B44.1,catsx2,xray 808.

http://www.youtube.com/watch?v=YdBUdcm15Xg
my latest video