B-17 ball turret, Mark I

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The good news is that I finished the yoke/flange support for the ball turret. The bad news is that it doesn’t fit. So I guess I’ll call it the Mark I and use it as a template for the Mark II.

So why did this happen? Well, mostly because I didn’t take enough measurements and partly because the ball turret yoke changed over time, and I went with the design that took up the most room. But mostly I didn’t take enough measurements before I started bending paperclips.

Here’s the deal, I found the kit supplied yoke laughable. It should extend all the way to the top of the fuselage and it turns with the ball turret. In the real thing, the two struts upon which the ball pivots are attached to a metal ring that is inside a flange that sits on the floor of the fuselage. The metal ring is geared and electric motors turn the metal ring within the flange. The kit parts in no way reflect that.

So using a circle cutter, I made the two bulkheads and the brace that hold the yoke in place, and then I cut the outer flange and the inner ring. Then I bent paperclips into the proper shape, made my own pivot arms and glued the whole thing together. And yes, it’s pretty trick to sandwich a disk of styrene between other disks of styrene and not have it become a fixed lump. A layer of Vaseline protected the inner ring from affixing to the outer flanges and also provided some lubrication.

Unfortunately the large triangular part of the yoke is too tall. It should be about half that height. That square box should contact the lower bar. But I learned the concept is sound. The ball pivots on the supports and the inner ring swivels within the outer flange.

Believe it or not, I have not succumbed to rivet counting. I’m not trying to faithfully duplicate the Sperry ball turret, just suggest it.

By the way, I did dry brush the edges using acrylic paint. I found that a drop of airbrush medium keeps acrylic from drying too fast, and I used my trusty draftsmen pen to drop a smoke gray wash to simulate grime. I also am getting more comfortable using my Neo for Iwata airbrush.

One technique I’ll abandon is using Mr. Surfacer to build up the thickness of the paperclips. Instead I’ll just spray primer to get the thickness I desire. And I did use the trick of masking tape to build up the thickness of the joints, but I should have scored the ends of the tape before removing the get a cleaner separation.