Getting rid of the gears in the Optima Mid
 

It's been a long time since I was on Oople. Just to let you all know, I am working on a twin belt optima mid at the moment.
It will be a system similar to the Schumacher Mi1, in which a short belt is driven from the layshaft which connects to the rear diff pulley, which is basically a double diff pulley.The layshaft pulley will be a 14T or 15T S3M same as the Lazer size. Right now my second revision is using 14T over the 13T of the first revision. One side will be using Lazer ZX diff pulley and the other side my custom designed Optima Mid Diff pulley, only available in gear diff at this time. The gearbox must be drilled to insert new 3D printed shaft inserts , the center gear shaft and bearings will be used back.
For the first prototype I had issue of the new short belt slipping. Once I upped the pulley size to 14T and tightened the belt tension a bit, there is no more slipping of the short belt, but now I have a problem with my XL mid belt pulley somehow not having correct tooth cutting dimension causing the original long belt to slip the pulleys on high loads. I had this same issue for a ball diff pulley I made for first revision.
I am working with my supplies to resolve this issue, I believe its just a CNC radius issue, as the original kyosho pulleys are sharped edged on the inside, but my machine pulleys have some radius ,causing the belt to want to come off the pulleys.
I will keep you all updated, but some of you already on facebook have seen my prototype pics.
Right now Standard Mid gearbox ratio is 2.6, with this new system it will be 2.21, if I decide to up the pulley to 15T it will be 2.06.
The advantage of this system is you do not need to grease your gears anymore and even if some sand get in it wont cause damage. This will greatly reduce maintenance time. The only wear and tear item are the new short belt, and top pulley, in order of higher wear.

That sounds cool.
Only raced my Mid once since I rebuilt it and it sounded like the gears were skipping under hard braking (even though it's got Thorp gears in it), but not been bothered to look in it yet.
So will be interested to see how this goes. Good luck with it.

Whilst you're here :thumbsup: Any good shops in KL worth visiting? I should be there later in the year and can't seem to leave my hobby behind...

Yes Tamiya in 1U damansara. Why not have a gathering here with the vintage guys ? Which is only about 2 guys right now lol !

http://i185.photobucket.com/albums/x...ps7qq6ut1x.jpg
Modified 3racing 14T pulley with 3D printed sleeve.
http://i185.photobucket.com/albums/x...ps47sfvg9h.jpg
Drilled gearbox using a 3d printed jig, with a 3D printed sleeve to move the center gear shaft position.
http://i185.photobucket.com/albums/x...pssgr6uqq9.jpg
Center gear shaft and 2 bearings re used coupled to a 3D printed belt flange. Also note the lazer ZX pulley combined with my new Mid half. Notice the scuff marks on the Mid Half diff pulley, this is caused by the incorrect inner radius on the machined pulley, pushing the belt of the pulley and causing it to slip.
http://i185.photobucket.com/albums/x...psqma5eez7.jpg
How it looks like assembled.

Hi Alcyon
This looks really interesting.
Maybe if you go this far may as well use a Lazer rear gearbox?
I imagine it could be adapted to the mid chassis or look into a open gearbox for the Mid similar to what James did for the ZX-R
How can I find you on Facebook

Hi Dan, been a long time. There are just too many things to change if I were to go for a lazer gearbox, the motor plate..chassis, it wouldn't be an Optima Mid anymore, the goal is to convert the Mid with minimal cost and max reusability of existing parts. And open type plate gearbox will again incur more costs. I basically have a machining problem and the accuracy of my 3D printer is deplorable to make the pulleys, I will be sending out STL files to a 3D print specialist and lets see if he can print the pulleys accurately.Look for my name RamaChandran on facebook, you will see a pic of me with glasses and a black T shirt lying down, with my wife with sunglasses taking the pic.
Just see the location to confirm, I am pretty sure you'll get me !

I see that does make sense, also the mid is different having the front belt driven off the rear diff rather than the layshaft. I was thinking a front Lazer diff housing would fit a mid but would that also make it not a mid.
I see you run a VTS slipper, is that still the same layshaft design?

Talk to Flatheadon here or Slavich Designes in Facebook he can make you pulleys, it may take a few years but you'll get them 😂😂😂😂

Cant wait anymore peakey. Besides i would rather have my machinist near me. Besides sweatshop pay here is lower ! Yes Dan its the same layshaft that works with vts and b4 slipper. It is the 3rd revision though because this batch has a shoulder on the inside so you can really crank down on the slipper without jamming the bearings.

Just to update everyone, after extensive testing, the twin belt system I have declare as a failure. the short belt just cannot take the load of driving the rear diff and the fronts at once. I had the short belt fail twice. I am now moving on to 48P gear set conversion.

is it possible to run the front belt to also been driven also from the layshaft similar to the lazer zx-r?? that way the only load on the rear belt is via the rear wheels.. then the rear wheels would be driven via both belts. just a matter of is it possible to run 2 belt pulleys on the rear diff? the kyosho triumph can run a dual belt on the rear diff.. might be a option
just a thought any way

The twin belt conversion already has two pulleys in the rear diff, however there is only space for one belt to drive the rear diff and the long belt to loop around to drive the front diff. Yes it is possible to have one pulley each side to drive the F-R diffs separately but this will require a change in the front as well as rear gearbox and to cut the upper deck to allow the front belt to go through. But in a way it completely changes the way the car looks and will not look like an optima mid anymore.

I remember seeing a similar conversion done with chains. I can't remember if it was on an Optima or a Mid, but chains on a Mid would be totally awesome. Could have the same stress/ breaking issue as the belts though.

not quite sure what you mean that it would change the front gearbox and the top plate..if you were to run a triumph rear diff case the front belt would take the same path as the standard mid gear box i would have thought the only change would be that the front belt would be driven straight from the lay shaft. the only change in the rear would be that the gears are replaced by a rear belt..just a thought.. i'm now more curious for myself if this would work

How about something like that cat setup?

It would change the front gearbox, by the outlet of the front belt. The front belt will no longer skim the chassis all the way to the back like on the Mid. it will gradually work its way up to the layshaft pulley. So the front gearbox opening is facing upwards at an angle, and lower belt cover can't be used. next you will need to cut some slots on the upper deck to allow the belt to pass through it like in the lazer zx.The rear gearbox will also need a bigger upper opening. Yes this could be done but like I said it wouldnt look like an optima mid anymore. if this is acceptable yeah I can do this.

You mean like 3 belts ? Problem is the optima diffs are offset . If a triple belt system like the cats is to be used, I need to have a centered front diff. Also a rear gearbox with more internal space, which I am afraid is not possible on the mid.

Dual chain drive optima mid
 

Found it: http://hybridmid.blogspot.com/2009/0...day-4.html?m=1
It's a mid rear gearbox, converted to dual chain drive, optima front end with a mono shock. It's glorious.

Back in the 80's when I took this lark seriously, those chains were a pain in the bum - stretched for fun - and then jumped teeth. Forever adjusting the original optima to keep the chain running, then removing links.

Finally modified it to fit original CAT pulley outers and belt and no more problems.

If you look at the pics of the upgrade diff for the re re xls that looks like it's a 2 belt system rather than a 3 so wait and see what it's like and if that might be an option to make fit