a matter of curiosity- why do we have to machine the new heads? I am aware of all the advantages of billet constructed items- but virtually nothing else on the motors is milled.
Why not vacuum cast the heads? this would lower the "per item" cost to nearly nothing, and make starburst patterns a piece of cake. Of course, there is always a failure rate when casting aluminum but a skilled eye can almost always catch a flaw once the leftover slag has been blasted off the parts.
Final cleanup would be done on a mill, of course but both material and labor cost would be reduced dramatically.
You're absolutely right! And I may look into it again, but the following is typical with castings. The economy is bad: so some of what I have experienced in the past may be old news.
The casting process is driven by volume. The initial cash outlay for tooling and a run of say 500 pieces, (which is a small order), would take forever to amortize. I don't have that many orders, and I'm not willing to put out that kind of money on a hope that they would sell. If you have an inside track to this I will gladly buy your castings in 50 lot, and machine them myself to suit my engines.
I would have to find a foundry up north as the foundries here only do ornamental items like lamp posts. Shipping would become an issue.
The cylinder heads would be all but useless unless they were dowel pinned to the jug and the deck height was carefully set. Ideally you want .030-.040" clearance between the piston and head at the squish surface. These would not be a simple bolt-on, "done", upgrade. The customer would have to send thier jug to a machine shop that would then dowel it to the drawing I provided. While this would of course be possible, it would drastically limit sales...so then we go back full circle and I have to ask myself if I really need a lifetime supply of small cylinder heads.
It's more practical to make them from billet on the CNC.
Here's an analogy based on a capability that I have in my shop; a Brown & Sharpe No.2 Automatic Screw Machine. These machines create turned parts at a rapid rate. For example a brass Carb jet every 12 seconds, bronze bushings in 4 seconds, the cam for my clutch actuator kit in 35 seconds, etc. etc. It's an automated machine for making turned parts up to 1 1/2" in diameter. This automation comes with a price.
For each job a set of plate cams have to be made, as well as the actual form tooling for the part. The cams are purchased from an industrial supplier that specializes in this type of thing. The cost is typically $350.00 for a set of cams. The form tooling, part-off blades etc. are made in-house. This can take anywhere from 4 hours to several days.
Once the machine is set-up to rock and roll, it is best to run at least 5,000 parts in order to amortize the cost of the cams, tooling, and time spent setting the machine up. If 5,000 parts represents a 10 year supply why bother...even though the per piece cost was very low it means nothing if you can't sell them.
I used the Brown & Sharpe to make the clutch actuator cams because every quote I got from shops with CNC lathes, (I don't have one yet), was in the $4.00 range. I made 500 cams @ 1.80ea. It took about 3 hours to produce them. It would have been better to have made 5,000. The per piece price would have been material cost plus 35 cents, or 80 cents each. But how long would it take to sell 5,000 clutch kits. I've sold about 100 since last September.
Jim
Edit: O ya and 2 NOS three speed Archer hubs.
