Rollergun Recoil and the Jerk (not the owner!)

[popgun pete]

Originally Posted by mclane234

Applying the same logic, why ask to delete these posts?

As a 15 poster, at the current count, why add these to your tally as anyone who reads from the start of this thread will see that you are barking up the wrong tree. You assumed something that was not true and in a childish display pumped out big font words to drive a point going nowhere. This thread is not about rollergun versus standard gun, it is about why they have less jerk, yet you come out with the absurd statement that I hate rollerguns when I have two of my own. It is patently obvious that you read nothing prior on here and just jumped in. I see that you are in Croatia, just ask Tomislav (Tromic) and he will set you on the right track as he knows me well with his work on the Tomba vacuum barrel system for pneumatic guns.

[popgun pete]

On another thread I mentioned Jack Prodanovich's rollergun, so I thought that I would add more info about it here. About twenty years ago there were some concerns that Mexico may seek to impose restrictions on the power of spearguns by limiting the number of bands to maybe one. They had already got rid of carbon dioxide guns by banning them and to some extent pneumatic guns that looked very similar as well as the guys policing the rules did not discriminate, if it looked like a gas gun then it was a gas gun.

Jack decided to build a single band gun that was very powerful by running the band all around the gun frame over rollers so that it was two stage loading. A unique feature of this gun was to use a transverse frame at the muzzle mounting horizontally disposed rollers. These photos were taken by John Warren and show Jack holding the gun. I can only assume that this very different layout was to make side to side tracking easier by reducing the lateral profile of the gun. The band used looks pretty thick in diameter, but I don't know its exact size.

Although the band is stretched out using the full length of the barrel when fully cocked, the ergonomics of cocking it have been well thought out with an intermediate band anchor location about mid-way up the barrel. The pulley system is fixed, however it would be possible to have a moving muzzle pulley system such as the one shown here: http://www.spearboard.com/showthread.php?p=2184811

[popgun pete]

Just found this communicationn written back in 2010 surveying the situation with rollerguns and their history.

There are a number of patents for rollerguns, the first being for the lever operated rollergun produced by "Hurricane", a French company. That was back in 1949! The lever under the barrel acts as a cocking aid to tension up the band after the usual drawback of the wishbone by hand. "Hurricane" made a wide range of diving gear including dry barrel spring guns using the "air bubble" principle. A later 1950's US patent is for a dual roller speargun designed to hunt catfish in lower visibility conditions, the rollers are in tandem on a single axle and offer more power in a relatively short gun, basically a modified muzzle dual band "Arbalete". In my view rollerguns should have been considered "prior art" when Marc-Antoine Berry took out his recent worldwide patent (2005, application was in July 2004) for single and dual axle rollerguns with two-stage loading, those ideas were known well before then, but no one bothered to patent them. The Jack Prodanovich two-stage loading rollergun had been on public view (see below) for years on this web-site http://rocknfish.com/Blue_Gun.html as was the multi-roller gun of Don Rollstead. I suspect that Marc-Antoine Berry's patent is now the stumbling block as it was used for the Beuchat "Revolution" speargun, plus previous patents were limited to the country they were taken out in. In 1984 the "Fer De Lance" rollergun was produced in the USA by Belcher Industries, it is a variation on the "In Depth Incorporated" band guns, the gun looks great, but is somewhat flawed as the large diameter rollers use a small diameter band and the muzzle band arrestor can crack when struck by the metal wishbone. There was also a tandem roller version, but I doubt that many of those were sold. The band runs the full length of the barrel, both top and bottom, anchoring just in front of the trigger finger guard.

Patent holders do not have to think up an idea first, they just have to get to the Patent Office first! And spend the necessary money to register and protect their patent, so they will want a return on this investment.

[popgun pete]

Some rollerguns which are of the band wrapping type in terms of the band going around a roller use a connecting link in some of the bands so that they can branch out into two bands. This means that at one end the band has the wishbone and at the other or rear end there are two anchor points, or four if you count the other two for the paired band on the other side of the gun that forms that particular band group. You can see these linked or composite bands on the Alemmani "Bluewater Express" which is a double rollergun. The composite bands are indicated by red markers and use the outer set of muzzle rollers on the gun. The central band group is of the top and bottom deck window pulley wrapping type where the bands pass through a window in the stock that contains pulleys or rollers. Thus these bands have their anchor on the top deck forward on the gun body and their run to the muzzle on the bottom deck via the windows in the stock. The Alemmani "Vela 135" also has such bands, but there they are part of a cable rollergun where the front end of the bands are connected to a moving shackle set of rollers which the long cable wishbone passes around and then runs forward to the muzzle rollers which are sized for cable, not rubber.

The composite bands are there to aid loading as the bands can be cocked by drawing the wishbone back with one of the rear anchors engaged and the other one free. The gun can then be flipped over and the second anchor engaged by pulling the second band pair back. In the "Bluewater Express" the rear band pairs are a wraparound band and a tied end band which is essentially a short wishbone to hook over the rear anchor point, this being a pulley mounted in a horizontal drum fashion just in front of the trigger finger guard. In the above diagram we can see the rear anchor B for the composite bands and the forward anchor A for the window wrapping band set. Note that window wrapping band sets are always under prestretch as they are used to operate further up the band stretch gradient of that band set in order to harvest more force from the bands while still having enough real estate on the gun body to occupy, otherwise they would never fit on the gun.

Make up of Composite Bands: Here we will just consider one side of the gun. If the bands were just rubber with no limiting cords inside them then at a node where two bands join onto one band the force each side has to be the same as the node does not move when the gun is cocked. If the two bands on the bifurcated side are at 200% elongation then the force is doubled (as there are two bands) and if the band they are joined onto is of the same diameter then it bears the force that it will produce at 400% elongation which would be too much for it. The limiting cord inside the single band can be sized to stop the band at 200% elongation after which it in effect becomes simply a connecting cable. Taking that cable length you calculate the lengths from the node at the front cable stretched back to the rear anchors. Those lengths will be the stretched lengths, hence if the rear bands are at 200% elongation then those lengths need to be one third of that when you cut the bands to size, allowing for the node length and the wishbone length.

When the gun shoots the bands give up their energy in the sections, so you add up the work energy triangles, not the forces as the contributions from each band are not constant over the wishbone draw length. This is demonstrated by the use of those green triangles on the rollergun Work Energy diagrams. Here I used 200% elongation and the same rubber diameter, but the logic is the same whatever you scale it up to.

[popgun pete]

Here is another Alemanni rollergun, the "Carbon Stilo Express 115" that uses composite bands on what is a double rollergun. Note that this is a rollergun and not a cable rollergun as the muzzle rollers are sized for stretched rubber. This gun basically uses up all available space on the bottom deck of the gun to stow the bands before they are cocked for shooting. Cocking requires two wishbone draws followed by the setting of the second set of bands of the outer composite bands on the mid anchor point on the gun. For some reason there is a connecting link on the central or inner band group that may be there to attach an optional set of bands in a piggy back fashion to create another rear band set for anchoring on the mid anchor provided by the larger of the two drums.

[kon]

I know I mentioned it in the Alemanni thread, but the Stilo Express 115 Carbon was a complete game changer for me. I tried several brands of guns prior to it, and there's simply no comparison for me. I used to miss often, maybe half the time, but with the Stilo I'm at a solid 90% plus hit rate. I've had it for maybe 1.5 years, and I can't say enough about how much of a difference the right gun can make, in terms of confidence, effectiveness and enjoyment.

I just wrapped up another week in La Paz and used the Stilo exclusively to land many fish with consistent head shots on several pargo. I think aside from the gun's design and muzzle (which make aiming easy), the complete lack of recoil is a big part of what makes the gun so accurate.

[popgun pete]

Originally Posted by kon

I know I mentioned it in the Alemanni thread, but the Stilo Express 115 Carbon was a complete game changer for me. I tried several brands of guns prior to it, and there's simply no comparison for me. I used to miss often, maybe half the time, but with the Stilo I'm at a solid 90% plus hit rate. I've had it for maybe 1.5 years, and I can't say enough about how much of a difference the right gun can make, in terms of confidence, effectiveness and enjoyment.

I just wrapped up another week in La Paz and used the Stilo exclusively to land many fish with consistent head shots on several pargo. I think aside from the gun's design and muzzle (which make aiming easy), the complete lack of recoil is a big part of what makes the gun so accurate.

Great, someone who has actually used one. Do the instructions for the "Stilo Express" say anything about the link in the inner band group? I ask as there are only single bands each side of the link, i.e. no extra band at the rear end.

[2fishin2]

yes there is a shorter inner band attached to the longer outside band for a total of 3 loading bands

[popgun pete]

Originally Posted by 2fishin2

yes there is a shorter inner band attached to the longer outside band for a total of 3 loading bands

Where is it compared to some reference point, say the reel, as I cannot see it on the inner band group?

[kon]

Originally Posted by popgun pete

Great, someone who has actually used one. Do the instructions for the "Stilo Express" say anything about the link in the inner band group? I ask as there are only single bands each side of the link, i.e. no extra band at the rear end.

I'm not sure I understand the question. The inner roller band is broken down into 4 sub-bands, and attaches to the first wheel from the muzzle as shown in the photo. The outer roller band breaks down into 6 sub-bands, where one set attached to the second wheel and the second set attaches to the third wheel that sits between the reel and gun body.

Loading works like this: 1) you attach the inner sub-bands to the first wheel, and the longer outer sub-bands to the third wheel (and you leave both there for the day). The sub-bands for the second wheel you leave unattached. You then 2) use a load assist to pull the inner band band back to the right sharkfin, then do the same for the outer band, and finally turn the gun over and attach the sub-bands to the second wheel. After you shoot, you disconnect the second wheel sub-bands, and then repeat part 2. It sounds more complicated than it is, I reload very quickly, not much longer than a standard 2 band gun.

[popgun pete]

Originally Posted by kon

I'm not sure I understand the question. The inner roller band is broken down into 4 sub-bands, and attaches to the first wheel from the muzzle as shown in the photo. The outer roller band breaks down into 6 sub-bands, where one set attached to the second wheel and the second set attaches to the third wheel that sits between the reel and gun body.

Loading works like this: 1) you attach the inner sub-bands to the first wheel, and the longer outer sub-bands to the third wheel (and you leave both there for the day). The sub-bands for the second wheel you leave unattached. You then 2) use a load assist to pull the inner band band back to the right sharkfin, then do the same for the outer band, and finally turn the gun over and attach the sub-bands to the second wheel. After you shoot, you disconnect the second wheel sub-bands, and then repeat part 2. It sounds more complicated than it is, I reload very quickly, not much longer than a standard 2 band gun.

I already understand all that. When I refer to a band group that means a pair of bands, so the “Stilo Express” has two band groups going from one side of the gun to the other, an inner group closest to the spear and flanking it, and an outer group that occupy the sides of the gun body and in turn flank the inner band group. The inner band group, like the outer band group, has a link in it, but there are only four strands of rubber used there, so why have a link in it? The outer band group are composite bands as the front sections that run to the muzzle rollers are stretch limited and joined at the rear end by links to a pair of bands, one is a wraparound band and the other is a tied band set ending in a cord wishbone, hence there the band links serve a purpose.

[popgun pete]

Although somewhat forgotten these days, the Beuchat "Revolution" rollergun had a composite band drive, the main band joined at its rear end by two separate loop bands that were pulled back onto rear band anchors after completing the cocking of the top band. Expensive in their day, the “Revolution” guns probably do not look as costly now given what the price is on these later rollerguns.

[kon]

Ok, this is beyond my knowledge, but here's the answer Behslayer posted to your question in the other forum:

Hello Pete,

The forward Sections of the bands (the ones which go around the rollers and then are on top of the gun when loaded are different from the Rear Sections (which remain on the bottom of the gun)

The Forward Sections are smaller diameter (to allow them to go around the rollers easier), Regular ID which allows a thin Holowcore Dyneema line to run through the bands so the Forward section can be set at low stretch i.e. 300%., and the regular ID and Hollowcore makes the band less stiff than a Small ID band as it goes around the roller so it's less likely to cause Muzzle climb.

The Rear Sections of Rubber are Thicker Diameter and Small ID creating an Inversion of power. i.e. More mass/power pulling backwards than forwards. They are Pretentsioned when using the gun. The gun will require being loaded with a Load assist. The second Band Section on the Outer Band applies more power to help get over the initial hump and get the shaft moving. Otherwise a Kicker band on top could be used.

I may be wrong about all of this but that is my understanding.

[popgun pete]

Originally Posted by kon

Ok, this is beyond my knowledge, but here's the answer Behslayer posted to your question in the other forum:

Hello Pete,

The forward Sections of the bands (the ones which go around the rollers and then are on top of the gun when loaded are different from the Rear Sections (which remain on the bottom of the gun)

The Forward Sections are smaller diameter (to allow them to go around the rollers easier), Regular ID which allows a thin Holowcore Dyneema line to run through the bands so the Forward section can be set at low stretch i.e. 300%., and the regular ID and Hollowcore makes the band less stiff than a Small ID band as it goes around the roller so it's less likely to cause Muzzle climb.

The Rear Sections of Rubber are Thicker Diameter and Small ID creating an Inversion of power. i.e. More mass/power pulling backwards than forwards. They are Pretentsioned when using the gun. The gun will require being loaded with a Load assist. The second Band Section on the Outer Band applies more power to help get over the initial hump and get the shaft moving. Otherwise a Kicker band on top could be used.

I may be wrong about all of this but that is my understanding.

It is possible they linked the inner band group as it was easier to pull it through the muzzle rollers while changing bands and tying knots with the band linking sections making the bands ends not so springy when they were being fitted or removed. If the bands had all been the same length then it may have been a reduction of parts inventory strategy by using the same band in a number of places, but looking at the photos they are slightly different. Running through the rollers may be the reason, but when stretched out the bands narrow down. In the photos where the bands are being removed they look the same size front to rear, but when prestretched on the gun the front ones look slightly narrower.

Here is another model of the Stilo Express where the bands run straight through without a link on the inner band group.

[popgun pete]

Maybe this is the answer, they want the rubber at the front end to thin out and blend into the muzzle in the front section of the gun.

A rubber band is basically a long cylinder with a certain volume of rubber. The amount of material stays the same when we stretch it out, therefore an increase in length by say a factor of 4, which is a 300% elongation, means that the cross-sectional area is reduced by a quarter. Area equals pi times radius squared which means the radius of the band is halved when stretched to four times its original length. Area A/4 = (pi x R^2)/4 = pi x (R/2)^2. Thus a 16 mm band will thin down to 8 mm at 300% elongation. This calculation neglects the hole through the center of the band, but we could do the same calculation for a tube.