I finally figured out how to make the cutwaters (the bulgy parts of the piers) for my Kankakee River bridge. They're basically a quarter-spherical cap on a short half-cylindrical shaft, but actually
making things in that shape proved harder than I thought.
Since I was working with MDF, I decided to wait until I had a chance to do the majority of the "machining" work outside, which happened to be at the MARRS workshop today. MDF, you see, doesn't make sawdust when you work with it--it makes an ultra-fine, clingy, suffocated cloud of powder. You'll want to minimize how much you work with it in an unventilated basement.
Other than that, though, the lack of grain and easy machinability made it perfect for this job.
Here's what a quickie jig, a half-inch roundover bit, and a router managed to make out of a long strip of half-inch MDF:
Then I separated the "product" (at the bottom) from the "waste" (at the top):
And here they are, sitting in place on the module (although not yet painted or secured). Note that I really only
need eight cutwaters; the number that I made "just in case" should give you an idea of just how confident I was that I wouldn't screw a bunch of 'em up during fabrication.
:
I'd say they're not perfect compared to the prototype, but they're close enough to make me happy:
