48 Inch lever Action Rollergun

Quite awhile back my teak supplier told me he had a handrail from a yacht, and that it would make a great speargun. Since the deal sounded "too good to be true" I ended up the proud owner of a yacht...handrail. He was right about the wood. It was really a beautiful piece, and it was when I looked at the shape of the handrail that I decided I would need to break some of the conventional rules of building spearguns. So I decided I would start with what would be almost the final shape, and go from there. Good thing I got a deal on the wood. The piece looked like an inverted "U", and the legs were kind of beat up, so I planed them off and ended up with a piece like this.

Then, I cut a piece out of the middle to give me the 2 halves I wanted. I ripped 2 lams from the piece I cut out and glued them to the bottom, giving me my blank, which now looked like this.

I installed one of my delrin enclosed tracks without any problem since I'm using a milling machine and the bottom and sides of the blank are flat. This would have been a real challenge with a router. I decided to use a Tin Man handle and trigger/ pushrod, and that went in the same way you would install it with a conventional gun. But, since I was going to be using brushed aluminum for some other stuff on the gun, I didn't want the black handle frame. Tin man to the rescue- turns out he had a couple of prototypes from when he was developing the handle, so they were bare aluminum- just what I wanted. More in the next post.

I used a Neptonics reef mech, and went with the side slot for the release lever since it was at the height on the gun that would match the muzzle. I had to make a longer lever since the gun was too wide for the lever supplied with the mech. I wanted it to auto reset so I made and installed the Tin Man auto resetting torque spring "thingy".

Then it was on to the muzzle. I drilled the hole for the "axle", which was a 1/4" diam. threaded insert, then milled the slots for the delrin rollers that I had made earlier. I made a combination shooting line anchor and muzzle reinforcer from 3/16" thick aluminum. It fits in a slot milled into the underside of the gun and extends 6" back from the end of the gun. Two pins hold it into the gun, and since the axle passes through it, it transfers load from the axle back into the gun and takes load off the end pieces of wood, which really just hold the axle in place.

Next post I'll get into the lever installation.

OK, now you can start to see why I made the blank so wide. Rollerguns tend to be high because they have bands on both top and bottom, so my goal was to make the gun as streamlined as possible by grooving the top and insetting the cocking lever up into the gun as much as possible. Problem is that when you do that, a lot of the wood is removed. In this case, the track goes in 1/2" from the top and the cocking lever goes up about 5/8" in from the bottom, so most of the strength of the blank comes from the wood on the sides- everything's a compromise. I'll have to hunt with it to see if the width is a problem, but it shoots a 1" group at 14' in the test tank, so I like it so far.

The lever is set up to give a 2:1 mechanical advantage when cocking from the bottom. When the band is cocked on top, it's about a 190% elongation. On the bottom, it finishes the load at anywhere from 300 to 400% elongation, depending on band length. That's where the lever comes in. There's no way I could handle 350% elongation, but with the lever it's half of that. 175% I can handle.

It's late- more pics tomorrow.

As I looked at the larger pics, I realized I had already made some modifications to the gun after some of the pics shown were taken. The safety latch, for example, is a little different. Originally, it was like this with a solid end cap.

I had the lever come off the safety latch when I was testing the latch, resulting in the lever moving forward with enough force to actually bend the 3/4" (Actually .830" outside diam.) aluminum pipe. While a testimonial to the strength of the pinning and installation of the aluminum side pieces that hold the lever pin, it was a little scary. So, I modified the end of the lever to incorporate a secondary catch, similar to what the latch on my original "Dirty Water Rollergun" had. Now, if the latch is bumped and releases the lever, it gets caught by the second catch filed into the end of the lever, and has to be manually released with my finger before the lever can be released. After the gun is fired it's a simple matter to do both releases and after you shoot the gun a few times it's second nature. If you want to unload the loaded gun you just reverse the loading procedure, uncocking the lever first, then unloading the band on top. The force unloading the lever is very managable if you're expecting it since you're working with the 2:1 mechanical advantage because of where the band is attached to the lever.

Here's what I ended up with.

I also realized that the length of the wishbone loop where it connects to the lever was important. Too small and it won't roll over the button easily, too large and it comes off when the band is relaxed. A small "o" ring over the loop solved that problem.

I added a couple more items. I installed 2 pins to help keep the shooting line in place. (Note the gun is inverted in the photo)

Then I made a delrin light holder and installed an LED dive light on the lever, which was really the only place it could go. If it works for shooting in holes it will be great. If not, Im just out some delrin and some time making the bracket.

And, finally, I also added one of Josh's safeties. I use it mostly when I"m making changes to the gun and need to test it in my shop. In the water when I'm hunting with the gun, I'll use until the gun is cocked, then hunt with it in the "fire" position.

Here's how it turned out. I'm pretty pleased with it so far (After just shooting it in the test tank). Just like the other rollergun postings, it has a nice soft recoil, and is very accurate. With Tin Man and Jim Cuda's spreadsheet, it is really easy to do "what if" cases without doing all the calculations to design. Thanks guys, but I wish you had come up with it a couple of months ago! It's easy enough to have a light band for dirty water hunting around small wrecks in the bay, and a more powerful band for the gulf wrecks. The spreadsheet also is handy for comparing guns. If you have a gun that has just the right power, it's now easy to configure a different size gun with the same power. I'll shoot the gun for q while, and if I'm happy with it the next one will probably be a 38" mid handled version of the "Dirty Water Rollergun" that got me started with rollerguns in the first place.