Back in May, Angie Anderson's brother Will posted a thread about his sister Angie. Angie has a medical condition that prevents her from being able to hip or chest load a conventional speargun. Since she grew up around the water and loved to spearfish, this was devastating for her. Tin Man first pointed out the thread to me, and he and I started discussing what kind of gun might work for her particular situation.
At first I thought a lever action rollergun similar to what I had built before might work, but after looking at it in more detail I realized that no matter what I did, she would be unable to load the top half of the band. After talking to Tin Man, we both came to the same conclusion: what would be required would be a miniature winch with an appropriate sized crank handle to stretch the band. The winch would be located under the gun, in front of the trigger guard. One end of the bands would hook to the sharkfin on the shaft just like a normal band, but the other ends would be hooked to lines that would run over the rollers, under the gun, and back to the drum on the winch.
With this as the concept, I began design of the winch. It took about 3 weeks to get a design I was fairly confident would work. Then, I build an aluminum working model of the winch. I used aluminum because it's much easier to work with than stainless, and I knew there would be a lot of changes that would be made along the way. Sure enough, I had to go back and redesign quite a few components of the winch. After several iterations, when I figured the aluminum model would actually work, I built a pine mock up of what I thought the gun would look like.
Then I mounted the aluminum model on the mock up gun so I could begin checking ergonomic issues. Back to the cad program again! I realized for the first time that, even though this was an aluminum version and couldn't take the stresses of the final version, I would have to design in some safety features. This would have to be done while keeping the design as simple as possible. I had discarded two previous versions of the winch because they were too complicated, and as I designed in the safety features the latest version was going down that same road. I finally came up with a design that incorporated the features I needed: It was small: 2" long x 1.25" high x 1.25" wide. It was powerful: Using a 6" crank I could make the 44" gun more powerful than a 55" gun with 2 - 5/8" bands. It was corrosion resistant: All stainless except for the sleeve bearings, which were bronze. It was light: It weighed in at about 2.25 x a typical trigger mech.
I made 2 guns. The first one I would shoot, the second would be Angie's. I made mine first so I could see how everything would come together before I made Angie's. After testing mine for 2 or 3 dive trips, I began hers. That's when she contacted me and said she was going to be taking a dive trip in August. Yikes! I finished everything on her gun except the winch, so I took the winch off my gun, mounted it on hers, and shipped the gun last Tues. When I get another winch finished, I'll either send it to her or just mount it on my gun.
More in the next post.