The vintage Hurricane rollergun was a resource which stimulated me to experiment with the concept of cocking bands with a lever. Ron Mullins had obtained a vintage 1960 Skindiver Magazine which illustrated the design of a cocking lever. He also allowed me to photograph an example of this gun which is in his personal collection. Please see the images of my attempts to actually cock this mock-up device. The value of an experiment like this is that I did not have to build a complete speargun to explore how the mechanism works.
Please be aware that this model mechanism is set up to have a total elongation of 275% of the rubber band. The first step (not shown), I pulled the band back upon the tab on the simulated gunbody. In this image the tab is seen upside down on the left side of your screen. The rusty brown tube is the simulated gunbody and the black tube is the lever. I am using a descriptive convention of zero degrees to describe the lever facing forward. At 90 degrees it faced straight down and at 180 degrees (not shown here) it folds back against the other tube. The band would be totally cocked at this point. The inititial manual cocking produces about 100% elongation in this test. The band is doubled in length. It is under about 50 lb. tension prior to using the lever. The pivot between the lever and the gunbody is at my knee. You can see two tandem rollers which are at the front of the simulated gunbody. This single band uses the first roller. In this frame I am attempting to get the band to start to be cocked.
You can see the band on the right side is starting to stretch and be pulled around the roller at the front. The force on the device is very significant. I cannot say that this was easy to do. Perhaps in the water, but not standing on one foot on the driveway. I still have a bruise on my knee. Note that in the next frame, I have gotten the lever to be at a point past 90 degrees. The pressure on the lever is now starting to become much easier to close the angle.
As the ancle goes from 90 degrees to 180 degrees the effort that I have to expend is considerably less. Still, if the lever is released it with close back with considerable uncontrolled force. I would hate to get a body part stuck between these closing steel bars.
WARNING, KIDS DON'T TRY THIS AT HOME! There is considerable force from the band which tries to snap the angle shut. During this phase the percentage elongation on the band goes from 100% to 275%. The tension goes from about 50 pounds to 120 lb. at 180 degrees (closure of the angle). Upon allowing the angle of the lever to go back to zero degrees the lever snaps shut with uncontrollable force. This fact indicates some bodily risk involved in using a lever system like to cock your band.