Making the clam hinge stay

In what might just be the final procrastinatory sideshow in my quest to not be doing wiring, I spent the last couple days making a proper Porschesque clam stay, complete with wheel ratchet, double articulation, lightening holes and shiny aluminum and stainless steel.


This is another part not often seen on replicas, not least because it’s complex, expensive to reproduce and prone to getting gummed-up and not working. On the plus side: it’s wicked cool. You lift open the back half of the car as far as it will go, let it fall gently into the notch and the clam stays open. Then when you want to close it, just lift it up again that last two inches, and gently guide it closed. It’s like magic.

The secret is a three-pronged cog wheel that sets into one of two spots on the big pawl. Fully extended once, the rod sets the wheel to drop into the locked position; extend again, and it gently nudges the cog just past the lock notch, allowing it to spin 120 degrees or so and set up for the next lift. It’s a bit like a clockwork.

And I didn’t understand it either, even after looking at this:

356 Hood HingeThis is from the 356 Owner’s Manual. Turns out the same kind of mechanism suspends the hood and rear deck on Speedsters.

I didn’t want to make this part, but the original Spyder ones are NLA. The Spyder Factory makes their own version, but I’m not even gonna ask them. Carey Hines at Beck/Special Edition makes a similar thing that sells for $250. The mount points are a little different from the original Spyder (as there’s no inner clam piece on the Beck replicas), but it should do the job fine for most. I didn’t bite because 1.) it’s made out of steel, a bit heavy; and 2.) I wanted to make one.

I started by ripping a picture of the Spyder Factory’s item.clam stays by SFIt’s not very high resolution, but it does offer the basic proportions and shape. With that and the 356 drawings, I got to work on a model.IMG_0703I had hoped to get a working mock-up with this posterboard, but the foam core makes it impossible to do precise cuts. Still, it was good for sizing and scale.


To try to get the mechanism right I made a second model out of pressboard.IMG_0715I got it pretty close, but it still wasn’t working when I started cutting the quarter-inch aluminum plate.

Meanwhile I made a bracket to bolt it to on the frame side. With my usual precision draftsmanship, of course.IMG_0706.JPG


Welded that on and got back to the mechanism. Picked up these nifty brass Chicago screw-like things at Home Depot. Nice thick barrels will work as a bushing and they look right too.IMG_0722.JPG

IMG_0723.JPGBy day two I was feeling good about the overall shape of things. I cut the lower legs from some stainless steel and fitted all the hardware,  but I still didn’t have a thing that actually worked. IMG_0734.JPGThe star wheel basically jammed. It looked like the pawl side needed to be scooped out in a major way to let the cog pass. IMG_0735.JPGThing is, that’s not how the drawing looks.

I went back to the innerwebs looking for clues, and found356 closeupAH-HA!IMG_0750.JPG

IMG_0751.JPGA bit more filing on the cog star, and things worked perfect.

Then, back to the car to measure out the length of each leg and make sure it won’t interfere when closed.IMG_0755.JPGTransfer these to the real item…IMG_0757.JPGandIMG_0760.JPG

IMG_0762.JPGPukka, as they say.

Clears the spare tire as well.IMG_0765.JPGSo then it was just down to fettling and prettying it up. I welded a thick washer to my frame bracket to make the two lower pieces an even width all along their length.IMG_0767.JPG


Drilled the top piece because race car.

IMG_0770.JPGAnd so.IMG_0771.JPGTime on task: 13 hours, not counting the ridiculous time I spent making the clam-side bracket. As a practical matter, 13 hours (plus material) to make a $250 part doesn’t cut the Capitalist Test. But not much about this car does. And it is a prototype, so a lot of the time was spent chin-scratching and modeling. At this point I could probably make another in six hours in the shop. And if I has a laser or waterjet cutter, the four main parts could be made in minutes. Anyone else want one?


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