Top Mounted Band design for roller speargun

[QBlackreefco]

I have been playing around with the idea of a sort of hybrid roller speargun that has top mounted bands. The premise to the design is to allow for the kicker band to be top mounted and function as both a traditional band to quickly accelerate the shaft out of the mechanism (and build more momentum for the roller band) but also add pre tension to the roller band. I have the diagram below for reference.

The design should be extremely powerful, and be far easier to load since it breaks the load into two steps

 

[popgun pete]

Here is one way of doing it. Gladiator rollergun.

 

[QBlackreefco]

Here is one way of doing it. Gladiator rollergun.
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Thats a clean design! The main objective of the top mounted band design I am playing with is that it would release the shaft similar to a crossbow so the wishbone on the bands would not need to touch any sort of riser like the gladiator pictured. Im also trying to combat the need for so much pre tension to make power like most single rollers. Im making up for this with the two stage load system. I guess the only speargun on the market with such a method is the seawolf

 

[popgun pete]

Rollers are usually mounted so they take advantage of a single horizontal axle, rollers set in the horizontal plane as you are showing are going to need strong mountings or they will cantilever if only fixed at the bottom end. Bands can only be attached to bands by "Y" connections, you see these on most band battery inverted rollerguns where they allow loading effort to be split.

 

[QBlackreefco]

Rollers are usually mounted so they take advantage of a single horizontal axle, rollers set in the horizontal plane as you are showing are going to need strong mountings or they will cantilever if only fixed at the bottom end. Bands can only be attached to bands by "Y" connections, you see these on most band battery inverted rollerguns where they allow loading effort to be split.

For sure! I typically utilize threaded inserts on my bamboo guns to spread the forces out for structural support. Going to definitely test this one thoroughly to prevent levering out.

Contrary to the Y connection I trend towards just tying the kickers directly in line onto the rubber. Even with degradation and wear this method tends to last just as long as the Y connection surprisingly. And a heck of a lot easier to tie

 

[popgun pete]

Jack Prodanovich made a rollergun with horizontal rollers. The idea was to create an alternative to multi-band guns as they were looking like being banned in Mexico, but this never eventuated and so the gun remained a one-off as far as I know. Photos taken by John Warren and were part of an instructional website which unfortunately no longer exists. Note the bracing frame for the roller axle mounts. Much of spearfishing's heavy duty gear evolved from the work of Jack and his colleague Wally Potts. They were only interested in spearing larger specimens which the European arbaletes at the time were not so suitable for doing.

 

[QBlackreefco]

That's a wild looking contraption. Almost crossbow'ish. Ive been playing around a similar design for a sling