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Mini-Rollergun

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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defofthecrown

Morone saxatilis
Mar 8, 2003
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I've been busy w/ guns this winter. On april first I can get busy w/ diving. Here's one of the last winter projects.

LOA: 23.5" or 60cm comparible to 32.5" or 83cm euro LOA
"Euro Barrel Length": 12",30cm comparabile to 23.5",60cm euro gun
Band stretch; 24",61cm
6mm Spear Length 26", 66cm
Roller Dimensions: 1 1/4" x 1/2" rated to 300lbs set on 1/4" bolt.
one x 16", 41cm 5/8ths powerband
~8' range from handle to 2/3 shaft length.
4" pushrod
Weight ~2.2lbs Ballasted

I have no idea how this will shoot. The combination of the roller and the short pushrod allowed me to effectively cut the barrel length in half from a 60cm euro gun to 30cm rollergun barrel. So this THEORETICALLY will have more power (based on band stretch) than a 55cm gun which is the smallest common comercially available gun. This might be nice for holes and Charleston-esque visibility 0'-4'.

I have concerns that the shaft will be too light to have a strong impact at 8' the maximum range. If this proves to be the case I will have to cut a new shaft from 9/32 or 5/16 and see if that works. I also don't know if it will be accurate w/ such a short barrel. I'm looking forward to getting it wet. Of course this gun will only be used in 0-6' vis so it's speed and manuverability might do the trick.

The construction is similar to my first homebuilt w/ fiberglass over wood construction. The trigger is lexan. The line release is a home made fiberglass 'aligator' clip which is nice w/ one wrap but a real pain in the @ss w/ two which I prefer. It is now rigged w/ 2 wraps of ~250lb vectran w/ a polyester core. I might re-rig w/ one wrap and lose ~2' or 25% of my range if need be. The line must be wrapped like a Spearfishing specialites 'speedload'. In other words a small rubberband/bungie is rigged on the shooting line so both wraps can be set at the same time. The under of this gun, and the entire thing for that matter, is very cramped. It was hard to find space for all the things that need to be on the gun shooting line, lanyard hole, line release, etc. The shooting line wraps must travel back and forth w/in a 1/2" width for it entire length to avoid the bands on the underside of the gun and the rollers. B/c of this I made the muzzle closed w/ a 'u' shaped piece of stainless.

The ballast is a little light so the butt floats up w/ the shaft in but it is overall negative. The lead was added to the handle so the gun stays in a natural sshooting position when released. The rollers offer sufficient weight to keep the gun muzzle heavy.

There are groves routed into the underside of the gun on either side for the band to sit in when the gun is loaded and lower drag (Of course you could swing a mailbox underwater if it was this short). The muzzle is enclosed on either side of the rollers to keep the band in place. I build the gun w/out this but had to add it to keep the bands from, painfully, jumping off the rollers. It was tricky to load at first, but I've got a technique that works pretty well and now can pull it back no problem, not sure I could handle one twice this length though.
 

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Reactions: Mr. X

Fish Tale

New Member
Sep 12, 2004
64
6
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That's very cool! It looks great!

Did you grind a cutting point on your spear?

I was just thinking about your mini rollergun a bit more. What a cool project!

I was thinking about your power to spear weight ratio. I've read some articles that talk about spears loosing accuracy when they have too much power behind them. At distances of less than 5 feet accuracy probably won't be much of an issue but I bet your could easily move up to a 5/16 inch shaft and maybe get a little more stability and still have plenty of penetrating power and speed to get it done. I also wonder if a heavier spear might break spines and sever spinal cords more often. Always best to keep the speared fish from going spastic and ringing the dinner bell for Mr Gray suit when vis is really bad.

I would think a 1/2 inch band would also work for the 6mm spear.

Very cool little gun! When's dinner?
:)
 
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defofthecrown

Morone saxatilis
Mar 8, 2003
298
30
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It works! I tell you what, there isn't a lot of pop but I sent the shaft through a rockfish on the maiden dive. The surge was so strong that I couldn't do too much target practice. It like to compare it to a 50cm euro and see if it shoots harder. Shoots fast and it's nice and accurate

It's also sooo smooth underwater. I always carry my guns at their midpoint while diving b/c I really lik to feel balanced. With this gun I can swim w/ my hand on the handle and not feel like I have too much drag.
 

Shellback

New Member
Jul 22, 2003
7
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71
Very Sweet! Have you built a larger version?
Do you have some plans or drawing you will share with us, or a link to direct us to some designs?
Mark
 

defofthecrown

Morone saxatilis
Mar 8, 2003
298
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Hey Shell,

I don't have plans for the gun, nor designs to build a larger one. I think I'd like to go multiple bands over longer rollerguns. I do think the really short design justifies it enough to build one for the hell of it though! The designing is pretty straight forward was there a particiular design concern you wanted me to cover b/c I'd be happy to expound on anything you need? Also there are one or two good webpages just search google.
 

Shellback

New Member
Jul 22, 2003
7
0
0
71
Thanks for the response. I guess my main interest other than any design "concerns", would be the benefit of the roller. Does the longer length of the band vs teh shorter spear just produce greater speed out of the muzzle. I do like the aspect of the shorter overall length for hole hunting, or using something around an 80 that has the power of saw a 120.
I would appreciate the links that you used for your reserch before building.

Shellback in Portland
 

defofthecrown

Morone saxatilis
Mar 8, 2003
298
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http://rocknfish.com/Rollergun.html
http://www.roamingsolutions.net/niko/index.htm

Here you go. The second one has a few links on it as well. As far as the benefit goes it's pretty straightforward. Slack rubbers exert no power. A traditional design leaves almost one third of the speargun barrel unuseable b/c the rubbers are 'spent'. Therefore to maximize the power on a single band speargun while limiting length and rollergun would be best. This is a little oversimplified b/c it makes the lost mass of the shorter spear negligble where it clearly is not. I think it can be offset by using a thicker spear, but that hinders penetration to a degree.

As far as I know this is the smallest rollergun out their. Something like an 80cm would be more common (and a bitch to load). Also check out Scott Merlo's website for the only comercially made rollergun i'm aware of and ... www.arbalegno.com for a pretty little 60cm gun.

-Chris
 

ajwaverider

New Member
Jan 3, 2004
422
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I was just looking at Jack Ps' website and I noticed something Rig brought up in the other rollergun thread.Jacks desighn cocks two times,once on the shaft and the second on a second catch under the gun.Do you think you will build another version like that Chris?
 
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