here is my latest thought in trying to drive the alternator, power steering as well as drysump pump and a supercharger. ive had the stock crank pulley machined to remove the first vee which allows the steel toothed pulley for the drysump to slip over the outside. this part seems more straightforward, the next bit im not sure about.

the idea was then to stack this assembly on top of the supercharger pulley, the problem i can forsee is that this new stack gives a distance of 1.5" from the inner shoulder of the supercharger pulley to the outside shouder of the stock crank pulley - illustrated in last pic.

im not sufficiently familiar with either the crank nose or engineering to know if this will work or if it will impose too much strain on the bolt holding it to the crank. any thoughts?

as a point of interest the stock crank pulley is hollow, it has an inner and outer diameter/skin.

 

What about the Air Con and Smog Pump?

 

Way too complicated. You need to have one single pulley made from billet. Competent machinist is able to do that as long as you can give exact measurements.

 

erkka, that might be the final solution - to machine one solid piece. again to do this i still need some advice on how thick to make the initial shoulder if it is made in alloy, to support the whole pulley assembly. in terms of exact measurements, these pieces i am making now might become the 'mock up' fabrication - we shall see, i would still like to use these parts if it is possible to save time and cost. does anyone have ideas on how thick the shoulder for the pulley can be?

 

Pulleys which are delivered in SC kits are usually made from billed aluminum. All I have seen have had much thicker shoulder than stock pressed steel pulley. As long as strong and longer bolt is used there shouldn't be any problems.

If pulley is done from single billet or from two separate billet pieces like in many kits it seems to have been made its possible to take thickness down to ½" level. At least then you know you are in same territory as all the rest. Just to be extra safe in case you are not comfortable using thicker setup.

 

Balance is going to be a bitch on that one

 

well, im open to suggestions on this one including a complete rethink. but as far as i can tell i need something similar to the first pic ie supercharger pulley followed by drysump pulley followed by powersterering and alternator...

 

I'm not so sure the whole billit thing isn't overkill. I mean they are nice, but If you look at what, say, the mustangs guys use it looks like it might be less precise. If you do want to machine something like this and don't know a machinist you can rely on the not soak you more than necessary, you might try emachineshop.com

 

does anyone have a picture of the crank bolt and the nose of the crank with just the harmonic damper fitted? as i said i havent even looked at these, seeing what im dealing with here may help!

 

If that monstrosity is the only alternative, I'd be looking REALLY hard at direct electric drive for some items.
You'll never get that sucker properly balanced, and that load on the nose of the crank will have some serious leverage to bend things out of shape.

Steve
'89 944 S2 - Alpine White
'88 928 S4 - Grand Prix White

 

electric drive for the alternator? i think DR uses the same belt to drive both the supercharger and the alternator - so i guess thats possible. the power steering could be driven using an electric pump. doing that would remove the stock pulley from this equation entirely, just leaving the supercharger and drysump pulleys.

 

Electric drive for the alternator? Hey, what a great idea

Guys, drnick just invented perpetual motion. How cool is that?

steve

 

Thicker the wall the less felxing it will do. So If I was you, I would make it as thick as possible. Takes less machining too so it will cost less. Also, I'm all for the one piece pulley too, balancing a multi part pulley is a real PITA.

 

Hello Drnick have you had any luck with this project I am going down the same road and will be glad to share info with you as I go along, since the people here that have actually been successful modifying cranks have not responded with there experience.

Although Imo000 has been very helpful with his write up on how he went about doing his. Thank you

Is one piece the only way to go?

Can you stack pulleys and still balance?

How would you go about balancing the crank pulley ?

Thanks Happy New Year
Matt

 

Why not shorten the stack by driving both the power steering and alternator with the same belt? Electric PS also seems like a good idea.