I rigged a Heinrich line release system with this gun. I wanted to target practice with it in the pool. The pool is short and one way to stop the spear from hitting the wall when missing the target is to use one wrap of line. I've also been curious about using one wrap of line in general.
With the Heinrich system wrapping the line around a pin or a tab puts pressure on the shaft to turn. When using two wraps of line each loop puts equal pressure on the shaft to turn in opposite directions, so the shaft stays straight. In the case of one wrap of line the shaft turned to the right.
The solution to this problem occurred to me pretty fast. The reason it did is because up until an hour ago the shaft was rigged with the shooting line connected at the back hole behind the notch. I'll take this opportunity to say that I really dislike that system. I find that the shooting line going into the mech housing with the back of the shaft can create a situation where the shaft falsely engages the mech. I'm not sure what goes on inside but I don't want to deal with it. So today I got around to drilling a hole in the shaft ahead of the notches as an alternate connection point for the shooting line. Another good reason to have the shooting line attach in front of the notches is to eliminate the hassle of getting the shooting line out of the way when loading the wishbones on the notches.
Once all done and the shaft was turning to the right whereas it didn't before, it was easy to realize that it was the shooting line on both sides of the shaft at the back that eliminated the space and stopped it from turning. I therefore thought how can I eliminate this space. A pin on one side of the track seemed like a good idea. I have various stainless steel pieces that I keep for just such occasions. This particular one was the safety from a Riffe speargun, I always remove them. A quick test showed that it provided the right thickness.
Followed drilling a hole of the same diameter.
Pushing in the pin and cutting it flush with the side of the track. As you can see the shaft is now straight. The shaft slides into the mech housing smoothly, doesn't catch on the pin at all.
It's possible to install another pin on the other side but it's not necessary at this time. I thought I'd share this very simple and easy to do mod. It may also help in situations where there's a little too much space above the back of the shaft and a turning shaft may skip over the sear. Although I would be weary to rely on solely this fix to remedy that situation.
Cutting the line release slot and drilling the pivot screw hole in the right place is probably the biggest PITA of the whole process, and where it's easiest to make a mistake. Additionally the problem with most pipe and wood guns is that the line release doesn't reset automatically, which is a hassle when loading the shaft. Please post a pic of the line release on your gun so I can make a comparison and point out advantages and disadvantages.