Posts by popgun pete

Quote from Klabautermann

How about copyright protection?

The Chinese are not into copyright protection, they treat everything as "open source". Ditto for patents, until they have some of their own of course. Right now others do the R&D and the Chinese think it is OK to use it without making any royalty payments. Partly they are emboldened by many Western manufacturers relocating their factory production to China, thus effectively rewarding this behaviour, by tapping into the organized and disciplined cheap labour force there; well cheap for now that is! Once factories are closed down everywhere else their prices will go up as competition will have been destroyed and manufacturing capabilities lost in their target overseas markets.

Like "snap action" parts, the parts snap and then the gun, or that part of it, is out of action.

Much later I rejigged the patent's muzzle diagram to show how the three ball sear system works, so to complete that part of the story here it is.

If you want to see an actual "Drago" in pieces there is one opened up here with an analysis of the components: Technisub "Drago" pneumatic speargun | DeeperBlue.com Forums

Unfortunately no sign of a "Sagittario" yet to pull apart and explore its design in detail!

Most of the guns you listed are cocking stock guns in that they have a long extension behind the hand grip, except the Riffe Competitor, unless it is a CX. Most the railguns recommended are chest loaders in that you don't brace the gun against your leg to cock them but your sternum instead. All have the trigger mechanism located directly above the hand grip. Choose what suits you, plus you can always change guns at a later date, few divers only have one gun.

Sounds like he needs a longer shaft and a longer gun to go with it.

Maybe ask why the extension is needed, or is he asking for a longer shaft and just expressing it as needing an "extension". A length of 8 inches seems a lot given that the shaft must have some muzzle overhang as is.

Quote from Dangundy

Does anyone know if you can detach the entire plastic grip , trigger etc from the inner barrel?

Yes you can, just read right through that thread I indicated previously.

Read this: Pneumatic dismantling: how to get inside | DeeperBlue.com Forums

As the gun is already negative without the shaft (your comment, post #10) you can do what some old-timers did and stuff a long wooden dowel down into the barrel tube. This was done with lever-loaded rollergun conversions of standard "Arbalete" spearguns to brace the barrel tube from being bent at the pivot support location during the application of the lever. Water may get in by wicking along any small gap between the timber and the tube, but the timber gives you something to screw into. Not something that appeals to me, but evidently it worked until the timber deteriorated and the tubing corroded from the inside.

Omer had a roller in the tail of the sear lever on their "Excalibur" speargun's trigger mechanism. It was a conventional layout, may still be in production.

The direct ancestor of that gun can be seen here: http://spearfishing.world/spea…egends-collection-10.html at post #94. Note the earliest versions are not much more than a tube with a trigger (single-piece) and a purge valve at the rear to dump water from the gun when you push the spear in the barrel.

Diagram from the patent shows the inner works, you unscrew the tank a few turns to let pressure into the gun and then do it back up, the purge valve is at the rear and underneath.

You might be interested in reading this: Testing my new Asso 90 - DeeperBlue.com Forums

The poster has longer pneumatic guns too, so may be worth asking him.

The bands don't wrap any pulleys at all, what you see on those diagrams is cords or cable winding around back and forth on the gun. The reason these ideas have not been patented before is probably because no one thought that it was worth doing! There is not enough slack band length mounting space on the guns to work with, although the second set of muzzle pulleys idea could add preload to the side-pulley rollergun, but the lower cable draw could not be the length of the gun as shown (equal to the top draw) as it would stretch the bands out too much (unless the gun was very short). The full length cable draws top and bottom each translate to half lengths on the side-pulley (as the cable doubles up on itself), so that is a combined full length draw on the side-pulley with very little room left for the slack bands on the rear end of the gun. Hence the lower cable draw has to be shorter than full length or the bands will be overstretched. Line snagging potential would go up and you have taut bands covering the sides of the gun from end to end, so I don't see these "improvements" having much appeal. Added here for interest as someone else passed the info on to me, being surprised to see such a design at this late stage for rollerguns.

From the historical record it appears that rollerguns were originally designed as a means to achieve lever-loading of the rubber bands as you can then move the band anchor which is otherwise fixed by moving the lever and drawing the bands backwards underneath the barrel after they go around a set of pulleys or rollers mounted at the muzzle. The "United Service Agency" and "Hurricane" both made lever-loaded rollergun patent applications in France in 1949, the lever operation in a sense "supercharging" the gun with "easier loading" also being a key factor due to the mechanical advantage provided by using a cocking lever. There do not appear to be any rollerguns mentioned prior to these developments that go on to become production spearguns, but users began to realize that the cocking lever could be eliminated and more stretch could be used in the bands than was actually used for the shot by tapping only the "fat end" of the energy graph.

There has been a recent patent to provide an extension of this principle by utilizing another set of pulleys at the muzzle, I have attached modified diagrams from the patent to show how some of the various concepts work. It will be interesting to see if anyone produces any guns, but with more crowding of available space on the gun body the utility of these designs is suspect as there are more things to go wrong. Slack band length and where it fits on the gun is a key factor as bands can only be stretched so far before they yield, so the bands cannot be too short or they will soon be unusable.

The international patent number is WO2012150387A1 published on 8 November 2012 and the inventor is Gueye Lamine; priority date is 2 May 2011 in France. International application was a year later, 2 May 2012.

The "Scope-Arrow" speargun is a surface to water interface fishing device, it is not for use by divers. The viewing "telescope" looks through the barrel tube to sight the quarry and the rubber eye-piece is in a sense the rear butt pad, so the user does not wear a dive mask. There is an optional fitting to brace the gun on the side of the boat or you can oppose the recoil with both hands firmly on the double handgrips, otherwise you will take that impact on your eye-socket. Shoots lightweight fibreglass spear with two rubber bands. The spear gets up to speed, as do the bands, with much of their power stroke taking place in the air, so that requires less powerful bands than if the gun was completely submerged. Eggbeater-type (threadline) fishing reel retrieves the catch and you shoot straight off the reel, hence the choice of that type of reel with a flipping bail arm and the line pulling away from a drum pointing in the direction of the shot. Very nicely made and more of a curiosity than anything else unless you plan to use it in the way that it was intended (if local regulations allow that type of fishing, not all do). Many of these "Scope-Arrow" guns show little signs of any use, probably as once owners realize just what it is for the gun ends up in the storeroom. The US patent for the gun can be found on-line, company is "Suwa Tekko Sho", with detail drawings of every aspect of the gun. Not really an antique, mid-seventies from memory, and a number of them have been sold on eBay over the years.

The Omer "Cayman ET rollergun" is a speargun that has a variable position rear band anchor provided on the lower deck of the barrel so that you can adjust the total band stretch, the length of band fitted on the gun being fixed (unless you change it separately). This rear anchor adjustment allows the operator to change the energy stored in the gun for different shooting requirements. Any rear anchor location positional change alters both the preload (or residual band tension after the shot) as well as the amount of energy which will be stored to propel the shaft. In the "Rollergun Figure 13" diagram shown here there are three alternative rear anchor positions illustrated, i.e. Max, Medium and Low. The idea is to use the higher force derived from extra band elongation by harvesting only the energy in the upper portion of the energy graph (green area) and not utilizing the rest of the energy (blue area) which is lost when the bands are unhitched for reloading. The first band draw on the top deck, where you reach further forwards on the gun, requires less pull than the second band draw on the lower deck, but when the gun shoots the energy is used in the reverse order to that in which it was applied to the gun.

Note that the diagrams shown previously were about the energy stored in the guns, not what comes out with each shot. Bands reversing their travel direction and being bent in a half loop around rollers or pulleys require some energy to be removed from the system in order to do so. During cocking of the bands the energy used to turn the rollers and, if applicable, bend the bands around the rollers is not stored in the bands but immediately dissipated as heat. During the shot that energy has to be resupplied from somewhere and that will be from the remaining energy reserve that is actually stored in the bands. That lowers the efficiency of a rollergun, but not its effectiveness.

This diagram shows the missing loading steps that had not been shown before, plus it shows how the band stretch comparisons were generated. The rollergun is now longer compared to the ones shown in earlier diagrams.

Dual axle, twin band rollergun allows the three band standard gun to "overtake" it with respect to energy storage unless the rollergun uses more preload in its two bands. This is because the rollergun stock is made longer with the dual axle spacing, but there are no changes to its band lengths or elongation which are now simply offset due to the axle spacing, while the standard gun receives longer bands proportional to its added stock length (to match the length of the rollergun).

However if the axle spacing is small, compared to the wishbone travel length on the gun body, then the rollergun stores more energy than the three band standard gun of the same length as both guns are now much longer in the barrel and the standard gun's band length does not change appreciably with the addition of a slightly longer section to its barrel.

A speargun needs to be balanced for the best performance, and that is "balanced" in an all round sense. Longer range usually requires a longer gun, powering up short guns does not compensate for the lack of increased sighting radius on the short gun, but of course it depends on how much extra range you need. A harder to load gun means you will invest more energy in the shot, which means more to you when you miss! Buy a longer gun and keep the shorter one for the conditions where that is all you need.