I am trying to mount an alternater to my already crowded engine . Right now i have a crank trigger, then a spacer and drive manderal, which is keyed and 5/8 diameter. On the manderal is a cogged pulley to drive the injection pump, then a. 3 1/2 inch V belt pulley to drive the vacuum pump. I need a double V belt pulley, 5/8 keyed shaft, 3 1/2inch inside for the vacuum pump, 5 inch outside to drive the alternater. There is no room for the extra width area for the set screw to butt up against the cogged pulley .
If i want to mount the alternater as the drive belt being the farthest out on the drive manderal, i need a weird pulley with a 3 1/2 diameter, then a 5 inch diameter, then the step for the set screw, with a 5/8 shaft and keyway.
I have tried to come up with other ways to mount this alternater, but there is only one spot left to put it. I have thought of ways to create the pulley i need, like having one custom machined, but am asking if there are other possible solutions to this mess?

EDIT. DOH! HOMER moment! I can space the vacuum pump forward enough that i can use a regular configuration stepped pulley, if any body makes what i need. V belt, stepped two grove, 3 1/2 inch and 5 inch, 5/8 shaft, keyed. Any one know of a source for a light aluminum one that can handle the load of an alternater, and a vacuum pump? Max rpm, 7600.

You need a double (5.5" & 3" grooves) crank pulley? You may have to bolt/weld 2 of em together.

RR, i may have to resort to that. Most of what i have found are too eak to handle a big load. As it is, i had to fill the 3 1/2 cast unit i use for the vacuum pump with epoxy to keep them from cracking and failing.

If you can send me an accurate drawing, i can give you a quote on a pulley. Being a 5/8 keyed drive, I would suggest 7075 as material. Alternator mass being driven by a 5/8” shaft on a 5” pulley would be extremely hard on the key way. 6061 would most likely oogle out the key in a short time.
Material can get expensive. 7075 material cost about 44.00 per inch of length on a 5” round. By comparison, 6061 is about 18.00 per inch.

I am struggling to get an accurate mental picture of your setup.

As an FYI - this is my setup. I made the pulleys and they are bolted together.

A couple of pics of my stuff. I am going to check and see if i can get a larger diameter shaft and pulley for the injection. That should help the situation some.

Use a longer cogged belt and have the crank drive the fuel pump and air pump. That's how I got mine setup and so far it seems to be doing OK. However I haven't had it to the track so I haven't had it to any significant rpm. BTW I'm also using a cog belt to drive my alternator. I'm a little concerned about it because my crank pulley doesn't have any type of guide on it.

I found a 6 inch vacuum pump pulley by STEFF online. That would allow the use of a double 5 inch pulley, with a max speed of 6100 rpm for the vac pump, 15,000 for the alternater. That helps, with a lot more options. I am checking tomorrow on a larger diameter drive manderal to help with the load on the pulleys' keyway.
EDIT; I have been forced to build a new drive manderal with a 1 inch shaft to gaurantee this piece will be strong enough. I plan on using the spacer shown, but will make a new manderal .

Update; A 6 inch long 1 inch diameter keyed shaft is on the way from Grainger. 24 hour delivery is pretty good! Also have a 14 tooth by 1 inch bore drive sprocket for the fuel pump on the way. I have a friend that is cutting me plates to weld onto the shaft to make it a mandrel, using a laser cut machine. The last piece of the puzzle is the two grove pully I need. Best option is for a 4 inch plus 5 inch, with the set screw part on the 5 inch side of the pulley. I see I have a message on that ,maybe a quote?

Greg, if you need pulleys or mandrels made. I can ask Paul (PBM) if he has time. Let me know.

Thanks HB, will PM if I need help.

Posting a picture of what i am up to