This is the collar for my DIY Mk V Dive Helmet, and it’s been a real pain to get right. I definitely should have worked harder on the underlying structure, because it would’ve made the final steps so much easier. Now, I’m in a construction cycle that doesn’t seem to have an end. But the collar is finally starting to look like what I think a Mk V Dive Helmet collar should look like. It’s a lot of work. Apply body-filler, file it down, shape it, look at it, file it, look at it, file it, sand it, look at it……
Gas can be manually exhausted through the exhaust port, via a hand knob, or with a chin button inside the helmet. The chin button is just a spring-loaded valve that you operate by moving your head inside the helmet, and pressing on the button with your chin. I think this is probably because it’s easier than taking your hands off your work, or trying to operate the external valve with heavy gloves. Although, you can certainly turn the knob externally.
Exhaust gas travels from the inside of the helmet, through the valve and along the exhaust port, a cylindrical fixture mounted to the side of the helmet that directs the flow around the helmet and exhausts it out many small holes drilled in the end of the port.
I’ll start with the exhaust valve handle. It’s basically a star-shaped square, with a ball at the end of one of the points. I’m making it out of polymer clay. It takes several attempts to get a close enough replica. There is the handle, a boss to keep the handle separated from the exhaust manifold, the chin button, a spring to allow the chin button to spring back to it’s original position, and the shaft to connect everything together.
Now that the exhaust manifold is is attached to the dive helmet, there is work to be done on both ends of the manifold — the vent holes at the back, and a hole for the exhaust valve shaft at the front.
Exhaust Valve Shaft Hole
The exhaust valve need something to revolve around, so I’m putting a shaft through the manifold. This shaft (just a dowel) will connect the handle to the chin button inside the helmet. I’m using a compression spring to provide the action.
But a hole that accommodates this dowel and spring won’t provide any “spring-back”. So I need to fill in half of the hole, in order to give the spring something to compress against. I’m going to drill out the exhaust manifold, into the helmet. Then I’ll plug half of the drilled hole with a piece of polymer clay rolled in a cylinder shape. I’ll get a rough shape, then cook it, then sand it until in can be pressed into the manifold hole. After gluing the plug in place, I’ll drill a smaller, dowel-sized hole though the plug. The shaft will have to be sized just right, so that the spring is compressed slightly against the plug when glued to the handle. That way, the spring is always keeping pressure against the handle and the chin button. And when the chin button is pressed, it compresses the spring even more, allowing it to spring back when the button is released.
Manifold Vent Holes
After more sanding, to refine the manifold shape, I marked holes over the round end of the manifold. I tried to start marking in a uniform pattern, but it gets tiring, so the dots just get sprayed all over. After marking the dots, I drilled them out; just deep enough not to penetrate the helmet.
After throwing on a coat of grey paint, it starts to look like it belongs.