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All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here! |
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02-15-2017, 06:06 PM | #46 |
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Re: Rob Allen Tuna Rollergun
If I can meet up with my buddies out at Catalina, one of them has a RA 110 that was set up with a RA roller by the Freedive Shop. It's a 110, just like the two traditionally rigged RA's I'll have with me. I'll get to do a side by side comparison. Should be fun!
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02-15-2017, 06:34 PM | #47 |
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Re: Rob Allen Tuna Rollergun
Good, get the same person to shoot both guns and then you will get a valid comparison. When I gave my dive buddy my gun, with which I am a crack shot, he could not hit the side of a barn with it, so the shooter can play a significant part in gun performance. I was equally hopeless with his gun.
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02-15-2017, 07:02 PM | #48 |
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Re: Rob Allen Tuna Rollergun
Thanks for Joining the Discussion Rob Allen!!
I have a question, A common issue with roller guns is they can shoot low, this is due to the bands lifting around the rollers just before the spear exits the muzzle and hence lifting the back of the spear. Have you found a way to counter this issue in your new gun? I am pretty sure my picasso roller has this issue on full power, i will share my proposed solution tonight when i get home tonight. |
02-15-2017, 08:51 PM | #49 |
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Re: Rob Allen Tuna Rollergun
The solution is to stop the bands rather than the wishbone, but you give up some powered travel distance on the gun. Like enclosed tracks, which would also counter the problem, you have to give something away to gain more in the process, as long as it is a gain and not a loss overall. Back in 1950, Pierre Martineau, the guy who invented the rollergun, also had this idea, but for a different problem. The idea of a rollergun actually predates him, but was not patented as such. The next image is what early spearguns looked like, including rollerguns, before the "Arbalete" wiped the floor with them.
Last edited by popgun pete; 02-15-2017 at 09:06 PM. |
02-15-2017, 11:18 PM | #50 |
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Re: Rob Allen Tuna Rollergun
So, I'm going to ask what's probably a foolish question, (not my first, or my last). Is all this quest for more power out of a given gun length based on the assumption that you want to increase the gun's effective range beyond one line wrap? The guns I've shot, from 70 to 130 cm's, were all very accurate, and certainly seemed very powerful, out to one line wrap with their standard band setups. That is to say, two 5/8" or two 9/16" bands.
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02-16-2017, 02:27 AM | #51 |
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Re: Rob Allen Tuna Rollergun
Some fish require a faster intercept speed, some more penetration, hence a bit more power is useful in a given length of gun, however rollerguns were originally designed for short guns not to have ridiculously short bands. The rollergun as a long gun is a relatively recent development, although the United Service Agency "Fusil Americain" was a long gun based on the spring gun era's idea of a speargun. Such guns sunk without much trace, a product looking for a market, rather than the other way around. A flatter shooting trajectory is possible if the shaft has less time to fall, thus a higher shaft velocity which requires more power. That said plenty of fish are taken with standard band guns shooting two line wraps.
The "Fusil Americain" rollergun can be seen here: http://www.skindivinghistory.com/gea...ican-guns.html Not many divers would countenance dragging this metal monster through the water during a hunt! Last edited by popgun pete; 02-16-2017 at 03:13 PM. |
02-16-2017, 02:28 AM | #52 |
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Re: Rob Allen Tuna Rollergun
Ok, I will try answer some of the questions but first a little history.
We started tinkering with roller guns a long time back and have made around 30 proto types to date. This excludes all the different setups tried on each gun. During this time we spent long days in my pool with high speed cameras to see just what is going on. We feel we have solved many of the issues rollers have. The main problem is trying to prevent the shooting line being momentarily caught under the bands on the way down the barrel. This is what we think is causing roller guns to shoot low. A side effect is also poor penetration. If the shooting line does not get caught, it shoots straight and has good penetration. (On a side note, we also found penitration is up to 30% less if the gun is not held firm.) The only way to see if the line gets under the band is with a high speed camera. This is not a muzzle wrap as the line is pulled out during the shot by the shaft. In theory the roller gun should give way more power than conventional guns due to the stroke being longer. This is true with shorter guns but as the gun gets longer, the advantage decreases. We found that a 1,3m standard double band gun with double wrap, same shaft diameter and diameter bands, shoots no different to a 1,3m roller. Same accuracy, same penetration, no advantage. It is our opinion that a 1,1m roller is the longest viable length in a single roller set up. This gives you a slight reach/range advantage over a 1,3m single wrap and, will be easier to manoeuvre. We have not tested double rollers yet.
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02-16-2017, 02:53 AM | #53 |
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Re: Rob Allen Tuna Rollergun
Shooting lines being gobbled up by the rollergun's bands are a problem if the gun does not use a line side system. The line running along the shaft with an attachment at a shark fin tab or transverse hole in the shaft forwards of the wishbone drop in points doubles up on itself as the gun shoots unless a bungee pulls it out straight, which it is not likely to do. Rollerguns historically ran their line wraps directly under the barrel tube or off to one side outboard of the pulley drive, you can see the front line wrap hook on the muzzle roller side guards or shields in the "Fusil Americain". (fig. 10, item P)
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02-16-2017, 03:45 AM | #54 |
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Re: Rob Allen Tuna Rollergun
We also though the shooting line would just double up on itself. It doesn’t. There is so much water that sticks to the bands and the shaft that the majority of the line gets sucked along remaining straight, with the shaft. The fluid dynamics are amazing, not at all what most think. The one way to prevent it is to have a slide. This means shorter range or, another wrap.
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02-16-2017, 05:06 AM | #55 |
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Re: Rob Allen Tuna Rollergun
Both mono and cord, or just mono for the shooting line? Pin muzzle or closed? The old French rollerguns used closed muzzles, nylon cord shooting line and line slides, the majority being the "Hurricane" brand with lever charging (the reason for using rollers to reverse the bands) and the simple rollergun like that which we have today.
Note that the "Comet" is a rollergun using the "Corsair" handle without the metal frame shoulder stock and is very much like the Sampson Gun, in fact you can draw your own conclusions about what inspired the latter. The Sampson Gun had twin line releases, the "Comet/Corsair" only had one. An example of the "Comet" can be seen here: http://www.skindivinghistory.com/gea...ing-rol02.html and its more conventional pistol grip version here: http://www.skindivinghistory.com/gea...mpounding.html The basic gun, sans rear shoulder stock, but with a rubber butt pad can be seen here: http://www.skindivinghistory.com/gea...r-powered.html All the known rollergun types are analyzed for their energy storage capability here: https://forums.deeperblue.com/thread...agrams.107171/ Last edited by popgun pete; 02-16-2017 at 03:39 PM. Reason: changed the image size |
02-16-2017, 05:18 AM | #56 |
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Re: Rob Allen Tuna Rollergun
We found dyneema cord better than mono. It made no difference between pinned or notched shafts.
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02-16-2017, 07:47 AM | #57 |
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Re: Rob Allen Tuna Rollergun
Hi Pete, you are 100% right about the stopper before the muzzle (I did think of that this morning after examining my gun).
This pic should show how the spear is sitting before it passes the muzzle. And here is where the proposed problem lies, the rubber passes around and under the muzzle rollers and lifts the spear (Note the bridle ends up infront of the hooks) The proposed solution = A new double Bride, a short one to stop the rubber passing under the rollers and a long one that will pull the spear (and not be lifted) Here is the new Bridle installed |
02-16-2017, 07:52 AM | #58 |
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Re: Rob Allen Tuna Rollergun
Sorry if the images are big and not rotated properly, i will fix that tomorrow.
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02-16-2017, 09:04 AM | #59 | |
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Re: Rob Allen Tuna Rollergun
Quote:
I'm still not understanding why are attaching the bridal to the sharks fin and not the wish bone Sent from my iPhone using Tapatalk
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02-16-2017, 09:53 AM | #60 |
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Re: Rob Allen Tuna Rollergun
Whoa finally some Real info on Rollerguns. There's no way to figure this out without Side view Video.
Pete, are those essentially the predecessors to the RoiSub concept? Stopping the Bands inline before the Muzzle so there is no capturing of the Shooting line? Rob, did you try any different configurations of how the shooting line is attached to the shaft, ie middle connection like the Europeans use? Did you try a Slider? for old times sake? Part of me thinks that you could have better shooting with a line attached forward on the shaft clearing the muzzle before the wishbones get close. When my friend did endless hours of High Speed Side View analysis on how shooting lines deploy and why they might grab it was amazing to see the same loops and sine in the shooting lines over and over.. you can adjust the Sine by changing the different lengths of the equation, but you are essentially dancing around the problem here. Big loop of line needs to go through tiny hole.. Add to this any other instability like Bands slamming into muzzle.. and it's prone to disturb the shot. Maybe not even every single time.. but many. I look at the Roisub style and wonder hmmm..seems like you could add some springs up there to buffer and draw out the compression of the band stop, and by the time the reaction starts to influence the stock, the shaft is already gone. Did you see any other influences like the Bands thickening up at the roller and causing a downward force on the muzzle? Rob, does it must make you rethink all of those Closed Muzzles? It's physics.. even a little bump or grab has a big effect on a shaft 10' out.. Ofcourse the line is captured.. How many times have you looked at that little space and thought hmmmmm... think anything will touch? Because it only needs to just bump or grab for just a millisecond to make everything go south 15' out.. Many many many times there is some kind of interference in shooting line deployment on all guns which resolves itself without the shooter knowing.. but it throws off the shot. This is not limited to Rollerguns, but
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