Many people are familiar with the term “spec house.” When a home builder has extra time or capacity they may, without an order on the books, speculatively construct a residence with the hope it will sell once it’s built. There is often a financial risk which subcontractors may share…all hope for a big win but it can be a bitter experience.
Sometimes metal parts get made the same way. Ideally, a shop has orders to fill, customer designs to build, and when completed they will get billed for and 30-60 days down the road a check will come. However, if we happen to have a little time on our hands we may find ourselves looking around thinking “Hey, what if we could make a few of some particular item and people would buy ‘em?” Now this sounds great, but believe me, 98 percent of the things people have ideas about will never make a return the investment required. Sometimes it’s better to just make your own stuff for fun and not count the costs when you start entertaining such ideas; call it “research and development” and then get back to business.
However, once-in-a-while a plan will come along that seems like it has a chance. I have a friend who works with older Corvettes and who tends to have some solid ideas. When he handed me a rusted disc brake backing plate for a particular model and asked if I could make some new ones just like it, I was interested and we sat down to discuss the questions.
Why would anyone buy it? How many might do so? How will it compare to anything now available, and will people be willing to pay enough? It would be costly to tool for, and there was the chance that we would do all that work and still simply not be able to make the part. It was a tough piece with some seriously weird stretching and stamping involved. The answers were, it’s kind-of an odd-year part and good reproductions of were not available, so demand would be low but sure. If the piece was good enough, we’d sell a few. I thought about it for a few days, and bit.
Typically, to stamp a component out of sheetmetal you start by machining out a set of dies, one of which is an impression of one side of the part and one of the other. This alone can take days or weeks of precise cutting, filing, and polishing on heavy blocks of steel. When finished you can place a piece of material in between, press the two halves together, and likely produce a torn, wrinkled mess which is worth nothing. The next steps go backward from there and involve the design and development of additional dies and processes that prepare or “preform” the metal for the shape it needs to take, and more work will be required for all the trimming and punching done before and after the forming. For this part, the flat blank to start with needed some strange cutouts which I wasn’t going to do, rather I drew a sketch to hand off to a waterjet-cutting shop that had the patience required to handle the many revisions which would come as development progressed. We’d form a part, measure the results, then adjust the specifications to compensate and try again.
All of this occurred in between building regular orders, and time went by. Eventually my Corvette man began telling people he was going to have these available…requests came in…and the pressure was on. Only problem was, we couldn’t make the d@*# parts. There was one specific area where all we got was cracking, no matter what we did. I tried this preform and that, with each experiment plan taking hours of careful work and ending in failure as well as costing another water-jetted flat blank (or ten) at $5 a pop. The OEM suppliers had it a little easier here as for large quantities they could order whatever grade of draw-quality steel was appropriate, but we were stuck with off-the-shelf “cold-roll” which is plenty strong but less ductile. As the pile of split parts grew I was finally forced to just weld-up a bad one for a trade-show sample. Argh.
After numerous experiments and “thinking-outside-the-box” sessions we finally hit on the right combination of starting shape, pre-forming, and die lubrication. With some additional fine-tuning of processes we were rewarded with a part that is nearly indistinguishable from the original even on direct comparison.
It was a happy day to finally send a box of good parts off to the plating company for finish and it’s gratifying now to see a set of on a freshly-restored chassis. We’ve made a couple small runs, not enough to pay for the trouble involved, but maybe in a couple years it will pay off. So it goes with speculation. In the meanwhile, I’m making car parts, which, after all, is something I’m always happy to be doing.