Posts by popgun pete

Well I have never seen a Hawaiian sling type shooter with line wrap rigging like that, but I take it you want more line just in case. Rather than a reel have you thought of a line pack which is a closed plastic cylinder (such as a tube plastic pencil case) with lengths of line wrapped back and forth inside (held in the wraps by a disposable rubber band) and only deploys when line pull from the standard line opens it up by pulling off the end cap. Otherwise it just drags along behind your weapon being relatively streamlined. A reel is good for the retrieve, but hard to wind mounted on a device such as you are using. Other line solutions have been line stuffed back and forth through a hole cut in a solid rubber ball and line wrapped on a conical spool where the line pulls off the narrow end. In the old days everything was tried, so a look into the past may provide you with some other solutions.

I am attaching a photo of a gun with a line pack. Ignore the scale, but the principle used for extra line will be the same

Thanks for the compliment Don Paul, hopefully users will adopt these measurements so that in any technical discussions we will all be talking about the same thing!

Pneumatic speargun manufacturers often have slightly different ways of measuring their guns and the quoted sizes are often rounded up to give a more “marketable” number, such as 55 (for a 54) or 100 (for a 97) centimetre length model.

Here I am proposing a set of dimensional parameters that operators can measure up for themselves and use for discussions when comparing guns based on their physical characteristics rather than their performance characteristics. Particularly when trying to estimate their capability in have the necessary reach for muzzle loading the gun and whether they may need to select a shorter weapon or make use of an extension loader if their physical reach falls short of the “SLL Max” (please refer to the diagram).

Note I have used an "Aquatech" hydropneumatic gun for the diagram (it was the "right size" image), but for this purpose we will think of it as a pneumatic gun with a sliding inner barrel piston that the spear tail inserts into at the muzzle.

Don Paul will remember a similar discussion here a few years back, but I decided to formalize the nomenclature.

Here is the answer, the muzzle relief ports are in the wrong place to allow water in the inner barrel an alternate series of pathways to escape, so the Copino "Divider" model will be hydro-braked when it shoots. Nemrod did exactly the same thing with their near identical muzzles until they moved the ports rearward in the "Clipper" guns and they may have made retrospective changes to later production of their previous models.

This Copino rear handle pneumatic gun from 1973 is of interest, particularly as it is a gun that Nemrod should have made as they had the basis for the required parts in their inventory. A partitioned air reservoir, two power gun, like the Mares "Sten" from about 7 years prior, there is a problem with it as Copino too closely followed Nemrod with this feature. A clue is you can easily see it on the muzzle detail if you know what you are looking at. I have written about this before, so it should not be too hard to figure out.

Photos are extracted from the Jimdo museum web-site mentioned here earlier.

Here is the second diagram from the French patent showing more internal detail. A bit of a chore swimming around with this thing would be my assessment of it, however it is cocked by muzzle loading, same method as the compression spring gun it is derived from.

Quote from Ramon

The interesting rifle is the catapult model an innovation for that time, a number of units were made due to its complexity in handling, too futuristic for that time, its scope was 2 meters accurate. Marc-Antoine Berry made a model based on catapult, is not the same but is based on an idea that did not work because of its complicated operation, the arrow was introduced into the lower tube and shot out the thick tube was only for the cañon not bend .

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El fusil interesante es el modelo catapulta una innovacion para aquellas fechas, se hicieron una serie de unidades debido a su complejidad en el manejo, demasiado futurista para aquellas fechas, su alcance era 2 metros certeros. Marc-Antoine Berry hizo un modelo en basado en catapulta, no es igual pero se basa en una idea que no funciono debido a su complicado manejo, la flecha se introducia dentro del tubo inferior y salia disparada, el tubo grueso solo era para que el cañon no se doblara..

I would say that "Catapult" gun is the Spanish response to the "Fusil Americain Sous Marin" with the two pistol grips shown here:
Spearguns, Fusil American guns, www.skindivinghistory.com

The gun is band powered using an upper slotted barrel for an impeller unit to travel in which is hauled forwards by a roller system that wraps the bands back under the barrel where the band anchor can be moved rearwards to change the shooting power if you operate a hinged lever. The spear tail can be locked into either pistol grip's sear mechanism to effectively provide four shooting powers with the gun acting either as a rear handle or mid-handle gun. A lock-out function in the safety mechanism prevents the forward sear interfering with the shot being taken from the rear handle.

French patent is dated 28th April 1949 and this diagram shows how the gun operates.

I wonder if the "Dragon" pneumatic is a re-issue of the "Galeon" as it has a similar construction with the handgrip being a separate moulding to the mid-body section. The "Dragon" grip is black and inserts into a yellow upper body, whereas the "Galeon" has grey and black respectively. I have seen many "Galeon" guns in the seventies, but never seen a "Dragon" until this Jimbo page displayed them. Nemrod often re-used some parts in their next series of guns and some grips even crossed over to be used in a band gun, e.g. the "Gaucho" grip which made an earlier appearance on the "Silver" series full length concentric tank guns. Very interesting to see all the Spanish guns shown on the one web-page which facilitates visual comparisons between the various models.

Quote from Dude george

Wow Pete! Way over my head, time to Google and try to figure this out...

Sent from my SM-G800H using Tapatalk

Read about it here where I have gone into it "chapter and verse" as the saying goes.

https://forums.deeperblue.com/…/pneumatic-spearguns.110/

I would like to see the gun succeed, but it faces a number of problems, including potential inefficiency. Rather than the power angle I think the greatest benefit is that risky muzzle loading is eliminated, but I say that as a spearo who has fired and loaded all manner of pneumatic spearguns for many decades. However on occasion there have been some near misses (personally) and a few unlucky individuals have received a spear in the head when carrying out this task, often being complicit with their own stupidity, e.g. using a tin can as a hand loader.

A "Dreamair" speargun must be close to being put through its paces in the marine environment as here we see a couple of them at the seashore. They certainly look the part in these detail shots taken from the "Infinitengines" Facebook page. There is a lot of time and money sitting there on the rocky shore, so hopefully they will perform as intended. Technically they are pneumatic powered cable rollerguns with a variable ratio pulley drive or "CVT".

Apparently the "3" stamped in the clamshell handle halves identifies them as a matched pair when all the current batch of handles was being anodized. That way the drilled holes and cylindrical bosses front and rear match up when the components are retrieved from the vats and re-assembled in their pairs. The Sampson gun handles have similar numbers inscribed on them, but with more digits as larger numbers were being processed for each batch. The Prodanovich is virtually a hand-made gun, not a production model as the Sampson gun was, but both use sand cast alloy handles.

This is the single-piece trigger version with the rotating safety lever that was omitted on the later two-piece trigger version. Often owners put their initials inside, but who it is I have no idea. Interesting to also see the number 3 in the handle halves. My gun has no markings inside the handle at all and I am its second owner, so not everyone marked their guns. Over the years these guns have been made by different helpers in Jack's shop, so there should be someone who can comment from that aspect if they chance upon this thread. I have referenced this to someone who knows a lot more than I do and knew Jack personally, so there may be an avenue there to learn more.

I guess where there is a market there will be a product. I assume this rollergun muzzle has been tested by the developers, but the line wrap guide prongs made of plastic on the upper nose seem a bit vulnerable. In the normal course of action they will probably work OK, but if the unloaded gun takes a hit on some hard object then they may break off. Many years ago when plastics were not as good as they are today thin section parts that provided a long lever arm to their base often snapped off, so mould makers made them thicker and more faired in to the base that they projected from or replaced them with metal prongs screwed into or embedded in the moulding. Damage was incurred by mishaps both in and out of the water when the gun was not under the diver’s directional control and the collisions had not been anticipated.

Other than that the design looks nice from a stylistic viewpoint and the alternate position band anchor rail for fitment under the barrel is a good idea provided the barrel tube is sealed at the fixing screw locations for non-foam filled barrels.

I rearranged the drawing to show how the bands are pressed onto the prongs on the muzzle, being trussed together to form small loops at the front. The ring sight on the muzzle serves as a band catcher if the tail driver unit flies forward and out of the track. The spear shaft is round, but has a square tail notched on either side for the twin sear teeth to grab onto. A tubular line slide holds the spear centralized in the front of the track which is of a square cross-section. Virtually everything is there that we would expect to see in a speargun today, but this is in 1943.

After the war has ended the bands are changed to anchor in holes in a more conventional (for the time) vertical muzzle plate. Most of the gun production seems to have remained in France, but the Cavalero Champion Arbalete and the similar Beuchat Peche Sport models would have been the dominant band guns of that era and through into the late fifties/early sixties.

Band rot is when the rubber breaks down through oxidation processes which cause the rubber to revert to a sticky substance. It is not transmitted to other bands as say an infecting agent which promotes degradation, the real culprit is oxygen, or ozone if rubber is stored next to electric motors or equipment which produce contact sparking. Rubber compounds usually contain anti-oxidation additives, but these get used up over time. Lower temperatures slow down the oxidation reactions in the rubber, but they don't stop them.

Quote from virgili

I'v been using for several years pneumatic guns on the Med Sea coast...
usually we load the gun by holding the shaft in the right hand, gun barrel in the left hand, then we do pushing at the same time the shatf and the gun with the fin by kneeling...
and you?
does it work better with this innovation?

The problem with this gun is the start loads are too high on subsequent draws of the wishbones, just look at the figures, even if the gun works. It is trying to operate like a band gun, but there each wishbone draw is the same, with the "Dreamair" they are not. Only the increments are the same, but the base for each draw increases. Basically you would not have the strength to load it unless the pressure in the gun was significantly reduced. That drops the power of the gun, so why use this complex design for no advantage?

Doubling the pressure doubles the load on the sliding piston with the gun cocked and the inner cable attachment to the piston has to bear all that load. At 11 atm (12 atm absolute) that final load was 240 kg, at 23 atm (24 atm absolute) the final load will be 480 kg. I don't think that is very realistic. A dual axle gun has the inner cable doubled up around the pulley located on the face of the piston, hence two cable strands then run back to the piston to share the load rather than one strand with the single axle version (refer to the earlier "inner cable system" diagram), but now the pulley axle which the inner cable runs around and its mounting position on the piston have to withstand that load.

The increased pressure 11 to 23 atm (12 to 24 atm absolute) doubles the stored energy, the use of dual axles separates the loading effort into two parts, but they are not equal parts. To understand this we only need consider the piston being moved. The first wishbone draw will move the piston to the halfway point of the fully cocked gun. Hence with 24 atm absolute in the gun the pressure will provide 240 kg at the start and 360 kg (multiply start figure x 1.5) at the end acting on the inner cable attachment to the piston. The second wishbone draw will then move the piston from that halfway point to the fully cocked position, that will be 360 kg at the start and 480 kg at the end acting on the inner cable attachment to the piston. These calculations are simply made as the compression ratio dictates the pressure changes in the gun.

Thus subsequent wishbone draws commence at higher pressures and higher loads as the piston progressively moves, they cannot all start at the same load because the pressure in the gun increases with each loading step of the piston movement. I cannot see a CVT system bringing about a change in this situation as each outer drum on multi-axle versions of the gun should have the same spiral track form so that the wishbone cables unwind and wind in a synchronized movement, they cannot have variable "gearing" as they all shoot together even though they load separately.

If we go back to the 11 atm (12 atm absolute) example and have four axles and four wishbone cables on that gun then the gun will still only store 900 joules, but loading will then move the piston in quarter steps. The pressure will start at 12 atm (120 kg load) and move to 15 atm (150 kg) on the first wishbone draw, on the second draw it will start at 15 atm and move to 18 atm, the third draw will move that value up to 21 atm and the fourth and final draw will result in a pressure of 24 atm. Thus wishbone loadings start from 120 kg, 150 kg, 180 kg and 210 kg respectively for wishbones 1, 2, 3 and 4 in terms of the force on the inner cable. For the 23 atm (24 atm absolute) example you double all the above numbers. On a two axle version you omit the second and third draw figures, therefore the numbers are first draw 240 kg to 360 kg, second draw 360 kg to 480 kg on the inner cable system.

Even with a CVT system the piston loads dictate what can be done with the gun in a practical sense and there is a limit to physical drum sizes and spiral track profiles as ultimately the spiral track length has to accommodate the length of cable being wound on an off. A longer gun would need wider drums to provide more track length in the grooves for the longer cables. Spiral track drums would need to be synchronized from side to side on the axles so that they are at the same rotation, they cannot be out of phase, ditto for drums on multi-axle versions. Thus the design becomes a lot more complicated to make than it may appear on initial inspection and I doubt that CVT system would be able to deliver the performance expected. However cylindrical drums may work with a constant transmission, the outer drums being double the inner drums in terms of diameter so that for the same number of turns of the axle the outer drums let out double the length of cable that the inner drum winds in and vice versa.

Looking at the numbers on the diagram makes me wonder how achievable they are. The stated loading effort starts at 120 kg (264.6 pounds) and ends at 60 kg (132.3 pounds), that is a pretty big loading effort, yet is the complete reverse of the usual loading force distribution where the start effort is less than that at the end of loading, not greater. If the air pressure in the gun is 11 atm (gauge) and it has a piston of 10 sq. cm. cross-section then the force on the piston at the start of loading is 110 kg and at the end of loading is 220 kg, assuming that the "Dreamair" gun has a compression ratio of around 2. The piston looks like it moves half way up the barrel to the fully cocked position, thereby halving the volume which results in a doubling of air pressure inside the gun. As the pressure vessel is closed off from the environment and there is a vacuum with the gun cocked I suppose we should consider the absolute pressure rather than gauge pressure, in which case the gun pressure will be 12 atm absolute and start and end forces will be 120 kg and 240 kg respectively. That 120 kg figure lines up with the start figure on the diagram, but the end figure of 240 kg is four times the stated end value of 60 kg which requires a 4:1 ratio of the outer drum to inner drum diameters to reduce the force in the wishbone cable. Based on the forces acting on the piston and a travel distance of 0.5 metre the gun should store 900 joules which is also the figure quoted for the CVT system on the diagram. Hence no losses are calculated for the CVT system or any friction losses associated with the moving piston, although these calculations are based on a compression ratio (CR) of 2 and that is only an assumption on my part. The proportions on the gun schematic indicate that the CR may be less, but a figure of 2 provides the 900 joules result based on the piston's energy storage. The areas of the green and red bordered shapes on the diagram represent the energy stored; a joule is a Newton-metre and a Newton is a kilogram force multiplied by 10 (actually 9.8, but 10 is close enough for our purposes here).

Quote from Dan

Thank you Pete.

The real question is even if everything works as intended does it result in a more powerful/accurate/easy to handle/affordable speargun.

On face value I don't see this as being a very efficient or reliable weapon, but the proof will be when one is actually tested. The short piston stroke uses about half the length of the gun compared to a standard pneumatic, but it has a much bigger piston. I think the gun would be expensive to make and assemble compared to other spearguns. However the imagination displayed and styling is certainly worth looking at, but the protracted development time indicates some problems. The KISS principle works best when designing spearguns as there are less parts to go wrong.

How the sub-pulley system on the inner cable operates for extra axles.