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Old 02-10-2014, 02:51 AM   #1
eightythree
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Quad Roller Tuna Cannon

Long time lurker, first time poster. I love the creativity, craftsmanship and progression displayed on this forum. Below is a project I have started, which is perhaps a bit extreme but hey that's the whole point isn't it!

I have made a couple of multi band roller guns now, they have been very powerful and accurate so I thought I would take it to the next level. I am building a quad roller cannon. 10mm shaft. Below are some photos of the build so far, I hope you like.

Track in


Component recess and pin holes


How rollers will sit (I think for now at least)


Wing lamination


Laminates sanded and prototype bridle holder (bridle holder needs some adjustment)





Not really sure how this is going to turn out, but I'm going to build it and find out.

Last edited by eightythree; 02-10-2014 at 05:00 AM. Reason: photos not working
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Old 02-10-2014, 05:25 AM   #2
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Re: Quad Roller Tuna Cannon

Welcome 83.

I am looking forward to seeing this in the flesh next time I am up your way.
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Old 02-10-2014, 05:33 AM   #3
eightythree
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Re: Quad Roller Tuna Cannon

Haha fancy seeing you here Pank! How cool is this forum!
I'm in curl curl and around most weekends so let me know next time your heading up.
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Old 02-10-2014, 06:27 AM   #4
lordyaussie
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Re: Quad Roller Tuna Cannon

Yeww 83 is on spearboard now too
Welcome

Does indeed look to be a terrific gun, I hope it is a winner in performance!
Are you using neptonics rollers?
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Old 02-10-2014, 06:52 AM   #5
johndoelman
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Re: Quad Roller Tuna Cannon

nice!!!
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Old 02-10-2014, 09:23 AM   #6
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Re: Quad Roller Tuna Cannon

Best first post ever.

That's serious gun building. Thanks to share this build.

Why are the widest set Rollers furthest forward and not the other way around?

My concern about this gun is safety. Essentially you are building an 8 band gun. 10mm shaft. Will the Mech hold? Will the Shaft Tang Hold? Will 4 bands on each fin tab hold? If there is a band tangle, what happens when 8 bands of force on a long 100 mm shaft stops suddenly? Did you consider running any reinforcement in the Muzzle? Ie CF Strips or Metal?

Outstanding building. Those Dogtooth stand no chance.
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Old 02-10-2014, 09:35 AM   #7
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Re: Quad Roller Tuna Cannon

Wow. Can't wait to see the finished project
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Old 02-10-2014, 11:37 AM   #8
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Re: Quad Roller Tuna Cannon

Wow cannon is an understatement.
Ulusub is right, I would honestly be scared to fire it the first time.
Maybe find a olympic sized pool and build a jig to hold the gun and fire it remotely the first 10 times
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Old 02-10-2014, 12:02 PM   #9
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Re: Quad Roller Tuna Cannon

I agree, best 1st post ever.
I like the look of it so far and you're right, the just doing it to see what happens is the reason. Very clean looking build. That Neptonics Tuna mech ought to be fine. I mean even an Alexander can only go so far and I've never nor have heard of one failing from overloading.
Where are you getting your roller hardware?
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Old 02-10-2014, 12:15 PM   #10
phil herranen
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Re: Quad Roller Tuna Cannon

Quote:
Originally Posted by Behslayer View Post
Best first post ever.

That's serious gun building. Thanks to share this build.

Why are the widest set Rollers furthest forward and not the other way around?

My concern about this gun is safety. Essentially you are building an 8 band gun. 10mm shaft. Will the Mech hold? Will the Shaft Tang Hold? Will 4 bands on each fin tab hold? If there is a band tangle, what happens when 8 bands of force on a long 100 mm shaft stops suddenly? Did you consider running any reinforcement in the Muzzle? Ie CF Strips or Metal?

Outstanding building. Those Dogtooth stand no chance.
A roller band dose not increase stress on the trigger it only has a longer power stroke , as far as stress on the trigger is concerned this is a 4 band gun .

The bands are staggered correctly , how he did it will limit the shooting line being trapped by the bands at the muzzle .

Line snags on a gun with a heavy shaft are not a issue if it snags it will simply snap the line or cable .
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Old 02-10-2014, 02:58 PM   #11
eightythree
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Re: Quad Roller Tuna Cannon

Wow thanks for the feedback guys! phil has pretty much answered the questions for me r.e. The mech holding and why I have staggered the rollers that way. It means all the rubbers will sit flat and not overlap each other ( my first double roller had the widest at the back, it shot fine but just looked untidy the way the rubbers sit.)

And I am scared of this gun haha! When testing firing it will be shot with one band first, working up to the four, one at a time as long as I am happy with each test shot. Also the way it is made if I want it can just become a triple roller, and change the ET to accommodate a 8mm spear. But as I have already eluded, I want to start extreme see what happens. It may not work but only one way to find out

The rollers I have produced myself, they are black delrin with bearings (nylon bushings and glass bearings)

Last edited by eightythree; 02-10-2014 at 03:57 PM. Reason: Add info
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Old 02-11-2014, 12:02 AM   #12
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Re: Quad Roller Tuna Cannon

Wow! This is an incredible project.

Has anyone seen or heard of a builder making a quad-band roller-gun before?

Good luck. It will be nice to see how it progresses.
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Old 02-11-2014, 12:08 AM   #13
manoa matt
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Re: Quad Roller Tuna Cannon

I wouldn't mind seeing that gun on the rack in the 2nd picture that is just out of the frame. That wouldn't happen to be a 3 band inverted roller would it?
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Old 02-11-2014, 01:36 AM   #14
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Re: Quad Roller Tuna Cannon

Posting to subscribe. This should be really cool!
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Old 02-11-2014, 02:07 AM   #15
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Re: Quad Roller Tuna Cannon

Why not !!! Seriously though this could be dangerous and it is good that you are scared of it. I would certainly start the gun off with a slide ring on the shaft first and make sure there are no tangling problems before going without a slide ring. On a technical note, assuming this gun will be using a 160cm shaft @ 10mm ... that is 1kg of mass. My guess is that you will easily saturate the band load required of that shaft with 2 rollers using 5/8" bands on a 120 band stretch top with doubled band stretch bottom. More power than that will not get you any added velocity at longer range and will be just wasted effort, although for short range the extra velocity will be there. You reach a point where no matter how much velocity you add to the shaft initially, this velocity gets quickly sapped by drag forces of the shooting line + shaft + shark fins + hydrodynamic forces. A good way to think about that is this ... assume you want to shoot at something that is 1 meter underwater and you start off with a .223 high velocity rifle bullet, it will have tremendous initial velocity but then drag forces will quickly slow it down no matter how fast its velocity entering the water is. If you doubled the load on the .223 bullet, I can assure you that although you might make a bigger splash, the damage on the target at 1m underwater would be the same if not less. Now move that caliber to .50 and that bullet although slower will do much more damage as it will have much more inertia from the added mass to overcome the drag forces. So you would need more mass to the shaft and at 10mm I think that is simply not enough to absorb the power load of 4 long and hot 5/8" roller bands. If you look at the longest Omer 115 ET roller, it is shooting a 7mm shaft that weighs about .5kg and they discovered that to saturate the maximum band load out of that shaft, they actually had to drop down to a 14mm single band ... any more power was wasted and not gained downrange. So if you take a rough estimate and say you want doubling that on a 1kg shaft, that would be two long 14mm bands. Maybe there are other factors that are there, but I still would be very surprised if you gain anything from a 1kg shaft by going more than 2 rollers and 16mm bands. That would still be 2 divisions of band diameters higher. Most likely for a 4x band long roller gun to get its maximum performance, you would need a shaft that weighs something around 1.8 to 2 kg !!! To do that you need to go to a thicker shaft, or longer shaft (much longer), or to go to an exotic alloy metal shaft that has much higher density (eg. tungsten alloy).

Will be interesting to see results and maybe all this theory can be thrown out the window. Only way to find out is to actually try it and that is how progress is usually made. Good luck on your build and keep us posted on progress!
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