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All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

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Old 02-11-2014, 04:32 AM   #16
eightythree
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Re: Quad Roller Tuna Cannon

Thanks for the feedback guys. I definitely hear everyone on the safety issue - I assure you the last person that wants a 10mm spear flying back and impaling them is me!

Spearq8 - thankyou for the constructive tips. I will definitely go with the slide ring option when testing this gun, as well as going one band at a time. I have trawled these forums (and I think) I have read every roller thread going. I have put a lot of thought into this build, and I have read your previous posts regarding the diminishing returns of increasing the initial velocity of a spear. That's why I went with the heaviest spear I could get my hands on, so thank you.

Also I love that you mention alternatives such as Tungsten! has anyone tried this, how would tungsten go in terms of stiffness etc. A quick google search revealed it wouldn't be to hard to get some tungsten rod its just $$$$$$$$$$


I see this as a great way to test the theory as with this gun I can easily see the results of one rubber vs 2,3,4. I can use 14mm vs 16mm, and I can switch the ET track to a smaller diameter spear.

I froth on the technical side of this, I love the physics, I think I am going to try and find a tungsten supplier now haha!
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Old 02-11-2014, 04:57 AM   #17
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Re: Quad Roller Tuna Cannon

Cant wait to see this finished.
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Old 02-11-2014, 07:25 AM   #18
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Re: Quad Roller Tuna Cannon

You matete,this is not a cannon,its nuclear weapon!
Can I give you some tips for the muzzzle? First of all its a pain to load so many rolls.I understand the way you position them-middle against middle,it makes the nose thinner,but that also makes the bands under verry close to each other.They stick together and its difficult to load becouse of the mutual rubber friction.Also the edge of each roll will cut the midlle if the next band.To prevent that all rolls must be different diameter.I have the same concept in my small gun. Its only two bands and I load it on stages,first two up then two down.You cant load it with hook only from upper side,must make 8 loading mooves in your case.Its much easyer with two rolls,or three.
You can use the benefit of enclose track-you dont need the bridge at the muzzzle-the wishbones stop on the track itself.But you must load all bands on one sharkfin-the last one.Its easy with two but Im not sure for 4 wishbones.The bridge is useless unless you make it higher than the fins to alow them go under,but thats bad,wishbones must stop ecsacly before the spear's body,not higher,becouse it will make in your case super friction at the muzzle and also will damage your wishbones.
And for the roller you dont nead great mass-just to float with the spear is enough and then balance it.
Good luck with the project!
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Old 02-11-2014, 07:29 AM   #19
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Re: Quad Roller Tuna Cannon

Yes Tungsten would be a dream metal to use for spearfsihing, but it would have to be alloyed with something or be the inner core of say a SS shaft. I did the calculations some time back and if I remember correctly you could pass the 1kg mark with a 160cm shaft at 6.5mm !!! Now when you put into consideration that your cross section is much smaller, then just imagine what type of penetration you will get! My guess is that for your gun an 8.5mm and 160cm tungsten alloyed shaft would give you about 1.8kg ... that would be within my theoretical calculation of what 4 roller bands could absorb. But man oh man ... that would be some serious power that could be very lethal and if I would build something like that I would have a string attached to the trigger and have the gun mounted and shoot it off via string while I hid behind a wall .
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Old 02-11-2014, 05:23 PM   #20
Snapper Mangler
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Re: Quad Roller Tuna Cannon

Quote:
Originally Posted by spearq8 View Post
But man oh man ... that would be some serious power that could be very lethal and if I would build something like that I would have a string attached to the trigger and have the gun mounted and shoot it off via string while I hid behind a wall .
That's what I said!!!
Haha
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Old 02-12-2014, 12:33 AM   #21
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Re: Quad Roller Tuna Cannon

Brah!
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Old 02-12-2014, 10:40 AM   #22
The Plumber
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Re: Quad Roller Tuna Cannon

I really like the shape and offset roller design you came up with.
As I've joined the roller craze as well, I'm looking forward to seeing the finished product, and results.
"Anything worth doing, is worth overdoing" (Steven Tyler.)
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Old 02-15-2014, 07:31 AM   #23
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Re: Quad Roller Tuna Cannon

Had some time today to do a bit more. Seal I love your guns, your designs are fantastic. Unfortunately I don't have access to rollers of different diameters, so I will just have to make do. I am sure there are going to be many areas of this build that I will learn from and be able to improve on.
I routed in the roller recess today and gave the muzzle some basic shape. Next weekend I will work on the shooting line recess . Unfortunately I don't have time to play with the tools during the week.


Last edited by eightythree; 02-15-2014 at 07:33 AM. Reason: .
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Old 02-15-2014, 07:37 AM   #24
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Re: Quad Roller Tuna Cannon

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Old 02-18-2014, 12:13 AM   #25
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Re: Quad Roller Tuna Cannon

Sorry, I read up, if I missed it. Whats the total overall length?
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Old 02-18-2014, 12:35 AM   #26
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Re: Quad Roller Tuna Cannon

Pretty insane!

Wear Kevlar and a full face mask.

I'd wear a jock too. If the muzzle gives way, those 4-bands and the wood shrapnel are coming back towards you!
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Old 02-18-2014, 12:43 AM   #27
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Re: Quad Roller Tuna Cannon

If there is no extra pressure on a trigger mech with a roller set up, I don't see the structural integrity being an issue, but I'm not build expert. I wouldn't be afraid to load and fire it. Probably go 2, then 3 then 4 bands.
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Old 02-18-2014, 03:49 AM   #28
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Re: Quad Roller Tuna Cannon

The muzzle "sees" an eight band gun as the rollers are being pulled from top and bottom, unlike the trigger mechanism which only "sees" four bands on the top deck. The band anchors on the lower deck experience the balance of the pull from the "lower" bands. All rollerguns have to be strong in the muzzle due to the pull running on both decks of the gun.
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Old 02-18-2014, 05:26 AM   #29
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Re: Quad Roller Tuna Cannon

Yea there is no-problem with roller structural strenght.Its even better becouse the pulling forces are equal up and down and the body will never "bend" like a bow.This and the low recoil alows the roller body to be much thinner from the side and lighter.My new carbon project has only 3 sm profile at the muzle and mooves verry easy in the water.Also the balance is perfect even with 10 mm spear
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Old 03-09-2014, 06:37 PM   #30
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Re: Quad Roller Tuna Cannon

Any progress buddy?
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