roller wishbone retainer

Quote from mosaad

I have seen a design of roller speargun using a tube as a retainer ,they just cut it half as a section and fix it to the end of the muzzle they leave a gap to keep allowance for the shark fin ,I like the idea and thinking to do same with 1/4 in pipe 1/16 thick but here my question is their a possibility the spear shark fin will rotate left or right and hit the retainer after pushing the trigger ? it can rip it off with spear high speed or it won't?

It might roll and hit, but I doubt that the shark fin would come off. In the old days such a slot was opened out to create a ramp like entrance that would push the shaft upright as it hit. Not very quiet and would slow the spear with the impact. Slotted wishbone notch shafts would have no problem. If an enclosed track was used then the shaft would not roll, also flat topped eurogun spear tails are tightly held up against the sear box roof, so are unlikely to roll much as they zoom along the shaft guide track.

The "Addict" band guns used to have a belled out muzzle just in case the ears on the shaft for the line slide stop gave the muzzle guide tube a whack on the way out of the gun. The shape is shown on this "make your own gun" diagram.

I wouldnt make the wishbone elevator enclose the shaft unless you are using a notched shaft. Also 1/4 inch pipe (id) im assuming is too small to do that (with shooting line).

If there is any shaft rotation caused by a number of things (bands not loaded or made exactly the same length or thickness or one weaker than the other, water motion pushing against the shaft, etc.) your shot will be off and you may damage your muzzle if it is constantly being hit by the shark fins.

Quote from mosaad

but using notch spear with roller not giving accurate shot !band will bush notch little up when spear near the retainer and shot will be low ,is that correct?

If im not mistaken, I think the dilemma with rollers is the low shot. This is I believe caused by pre-loading the band(s). At the muzzle, when bands come to an abrupt stop the momentum of the band puts downward force upon the muzzle. This causes the muzzle to lift slightly resulting in the shaft end being tipped up resulting in a slight downward trajectory.

rollers that are not pre-loaded dont generally have this problem

Ive noticed this on my single roller, but strangely not on a double roller. The only conclusion i can come up with is that pipe gun rollers just dont have the mass (stability) to hold a shot, but if you shoot a roller long enough the adjustment is easy.

A way to remedy this would be to make the muzzle rail (track supporting the shaft) a bit lower than the track on the barrel.

To answer your question, I dont think it is the notched shaft that causes the muzzle flip.

Hope this helps,

Josh

Yes the wishbone will still hit the retainer (elevator) but if the bands are preloaded, 100% lets say the downward force will be much greater than if the band has 0% pretension. Less downward force, less muzzle flip.

If the wishbone retainer were at a 90 degree angle with the shaft, stopping the wishbone before the change in direction, this would prevent muzzle flip and keep directional forces parallel to the shaft flight.... however developing a wishbone retainer like this while allowing for snag free line release will be a challenging task.

Show us some pictures.