Update: Adjustable cam pulley

OKay gents, here she is the much needed and anticepated adjustable cam pulley.

I spent the last two days going over fastners for proper torque and stress along with the vibrational issues they would indure. that was the biggest pain, the other pain was engineering around the small "real-estate". the neatest feature of all is that you no longer need to pull pins or jump teeth or even loosen the tension to adjust the cams.
these were designed based upon the cam adjustment pullies you'll find on hondas. however the similarity stops there. the honda based ones rely on tangs from the toothed wheel to transmitt torque to the cam. given the loads and speed of the 308 this wouldn't work. both parts of the pulley ride past each other at .001" across a .5" face on two sides. close for no axial movement but allows for degree adjustment.
the specs:
7075 aluminum, this is FAA certified aluminum; 95k tensile strength vs 45k for 6061-t6. Hard anodized
Custom spec'd ARP fastners M6x1.0 12point head, Helicoil inserts to negate shear.
Stainless Belleville washers double serrated DIN 6796

the pulley still retains the one pin that aligns the teeth and cam to 0*, the outer edge of both pieces are engraved with 1* increments from 0* to 10* for advance/retard to make adjustments easy to read. those marks don't show on the rendering, but would be found on the pad above the pin hole.
I'll have a physical part in 2-3wks.

now for the pic of the model....
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for those wondering the mass of the aluminum removed for the pin hole access is equal to the mass of the pad for the degree engraving. net result keeps it balanced to eliminate vibration. that was some fun calculating...thank god for computer engineering softeware...

 

the pocket needed to get the pin into the cam removed a specific amount of material which would have the effect of an out of balance wheel, by adding the pad where the engraving is done that pad offsets the loss of material. it's hard to describe with out better pictures, i'll try with the model.

 

ohh.. i'am planning on that also but that would drive up cost to the end user. sourcing the belt won't be hard but re-engineering the pullies will require some time. the current radius's between the parts has to be taken into account and the cam cover plate would also be changed. not to mention i would personlly feel better test bedding something like that first before droping in the publics hands. something like that would most likely be 6-9mnths out. but i do think we may see this from some other sources before i even get up to batt.

for now this would allow the replacement of the stock pulley while retaining the rest of the system. cost effective for those not wanting to spend $2k-2.5k on a complete swap. 'ballpark figure'

the current cost of this part would be somewhere between $200-$250 per pulley ready to install. the price of 7075 aluminum keeps going up.

 

it's the radius the belt undegoes when traveling past lower pulley. sourcing a new longer belt i.e. another manufacture would be needed only to satisfy the larger pulley. the larger pulley would reduce the stress on the belt and allow for a larger berring.

but like dominos tip one over and more fall, a larger bottom pulley won't fit under the stock cover. new cover? or cut up the old one?

 

7075 is much harder than 6061-t6 and anodizing. McMaster Carr does carry alot of fastners and is where i'll be sourcing the belleville washer. thier bolts however are std. ACME ASA where as ARP manufactures thier own bolts to a higher degree than the ACME ASA.
vibrational harmonics are a concern, the only ASA bolt to handle that would be a nylon patch/pellet bolt. but frequent use would remove the benefit of the nylon.

i tend to over engineer things, the last thing i want is for it to get loose at 7k rpm. better safe than sorry

 

here is a better rendering i just did adding the hardware and degrees for more clarity.
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as i sit here doing this i know why these parts in general are not done for these cars. i'm 40+hrs onto this already for just R&D still have the manufacturing process to handle. if i was to bill someone for this, it would be a quite a few sets of these before they turned a profit. if it wasn't for the few of us industrial types who find this fun, we'd be screwed...

 

belt info,
the Dayco belt we use is an 'S' profile, top of the page on the link.
http://62.110.184.188/dayco/en/products-belts-profiles.htm
interesting read, now to find out if another profile is better. a cross reference on size would be nice. more digging...

 

more info on the digging...
to redesign the belt system using larger pullies and a longer belt would take some good engineering. just increasing the pulley dia. and slapping on a longer belt isn't a good idea like i thought it would be.

the life of the belt has a few factors to consider, enviroment, tension (critical), construction.

the enviroment of a the timing belt on the 308 isn't that bad, no acids or steam. so a low factor here. the tension is a critcal piece, heres why. under the proper tension the belt will provide positive engagement with no slip or deformation. loosen the tension just a bit and the 'slap' will cause slipping, jumping and blisters. to tight and deformation with shearing will occur. construction is the pitch and depth of the teeth and design of engagement.

the Isoran belt is the 'bees knees' of belts, so we can factor out the belt material. the big issue we have figured out is the lower pulley bieng so small, we can get around the jumping a tooth with current setup by using a deeper profile however the current pullies are to shallow for that. so if one is to re-engineer the pullies you might as well go larger. next can-o-worms, going larger means we need to decide on a pitch profile and dia size of pully, then the tension needs to be factored to achieve the correct belt tension given the leangth etc. of the new belt.

so as we can see it is do-able, but it needs to be done right or we can make the situation worse. the time needed to re-design the set-up is huge! sure i could spend the time doing it, i figure it might take me a few months to get the number right and settle on a pitch design, each have thier comprimises. and lets say i can get an off the shelf belt that fits the design criteria. bringing it to market would cost me the materials and manufacture time. i'd have to negate the R&D becouse calculating that in would drive the cost up. and how many would i even sell to make the venture worth the time?

fear not i'll still be fidiling with the project, i don't see the light just yet. maybe i need new batteries

the majority of this information comes from Dayco and my old trusty machinery/engineering books. even a simple crown would keep the belt self centered and avoid wearing the edges, but that crown has to be exact or you'll 'break the back' of the belt.

for now i'm happy with my adjustable replacement pullies...

 

the squishy pink stuff between my ears, har har i use Acad to draw up and model the parts. the rest is old school paper and pencil calculations.

 

this is a strange answer but here goes, Isoran is a proprietory weave of 'fiberglass' and rubber boding agents. i'm using that word loosly becouse no-one will tell me what it is exactly, here is another wierd part to it. it is not made in the U.S. or used here other than bieng imported for our cars. Dayco uses Kevlar in the U.S.. it would seem that reading between the lines Kevlar and Isoran are near identical. I talked to the U.S. branch of Dayco and they have no information on the Isoran belts, not made nor marketed here. I ended up having to discuss this with the import manager for the European Market.
A call to MegaDyne even netted me some very paraniod people, who am I, why do I need to re-search the composition of belts?... etc. just trying to find the right belt for the application is going to take some convincing to get the info i need.