New oleopneumatic invention traction roller Dyneema

  • Inner cable sweeps the interior as the inner drum winds in the piston, as shown in the sketch. The bore size of the barrel determines whether it has a free path without touching anything as it traverses the surface of the drum. The gun will be longer than the sketch image shows, but gives a general idea of how it needs to work.

  • Apparently the inner drum is more of a cylinder in the third version, so its contribution to gearing is fixed in the single alloy barrel model. You would still have some gearing in the beehive shaped outer drums, but the advantage is less than with spiral track drums on both. One needs to remember that the shot is the loading effort replayed in reverse, hence provided you can cock the gun it does not really matter. On a standard pneumatic the compression ratio is about 1.10, so the force at latch is 10% greater. Might not sound much, but with pneumatic guns that are pumped right up that extra 10% can be an eye-popping effort with your arm in a position where you cannot apply much more grunt. If the gun had a constant pressure then loading would be easier, but that would require a massive air reservoir allowing the gun to have a compression ratio of 1.0. Now with the Dreamair you can offset that 10%, or part of it, by the gearing system offered by the spiral drums. That means you have a chance of loading it at higher pressures, so any gearing helps. In fact you really need it as the compression ratio is about 1.50, which is 50% more effort at latch.

    The downside, if say you are comparing it to a multiple band gun, is that in effect you are loading all the bands at once, there is no splitting of the loading effort. That is why for higher pressure you need the Dreamloader, which stages your effort rather than splits it. Compressed air is a lot more efficient at energy storage than rubber bands, but losses in the drum and sliding piston system are unknown, although they should be low with some energy being required to spin the drums and axle.

    The “Dreamair” is a big piston gun which would not be practical in a standard pneumatic gun layout with a wet barrel, but provides higher force levels thanks to that larger cross-sectional area facing the gun’s internal air pressure.

    Edited once, last by popgun pete: added a photo ().

  • There is now a version of the "Dreamloader" which gives a 3:1 mechanical advantage by adding another set of pulleys on each side of the loader cables. The original "Dreamloader" with the pulleys in the wishbone hooks gives a 2:1 advantage. The loading handles need to pull three times the wishbone draw distance instead of twice the distance if you use the extra pulley sets.

    Dreamloader 3 to1 advantage 1.jpg

    Dreamloader 3 to1 advantage 2.jpg

  • The basic advantage of this speargun design is that it combines the much more efficient energy storage of a pneumatic system with the ability to load the gun with both hands. On a normal pneumatic gun you need one hand to stabilize the muzzle while you pull on the loading handle and if needed can only employ the other hand once the spear is nearly fully inserted and the gun is no longer in danger of pivoting off your foot where the rear handle is pressing.

    The big diameter piston of 500 mm squared cross-section means that internal start pressure can be relatively low while providing a high level of force for spear propulsion. As water never gets inside the gun the piston has pressure on one side and a near vacuum on the other in what is a sealed system, so it is completely unaffected by ambient pressure at depth.

    Rather than the piston pushing the spear it pulls it via a cable drive using an axle in the muzzle. The only other pneumatic guns with rearward travelling pistons as they shoot are the hydropneumatic guns, but facing water braking inside the gun they require very high start pressures or multiple loading strokes to drive shooting pressure up. This makes for a lowered operating efficiency compared with standard pneumatic guns, while the Dreamair's high efficiency will only be offset by friction of the piston seals and the need to wrap and
    unwrap the cables and spin the pulley/drum axle. A big loading effort can be used as the spear is no longer transmitting the force to the piston during loading as like band guns loading and gun cocking are two separate tasks.

    Pneumatic guns combine loading and cocking which is very efficient while the gun body and spear are short, but drops away if cocking requires several pushes to complete the charging of the gun for shooting when the gun is much longer.

    To obtain a piston cross-sectional area of 500 square mm the diameter of the piston has to be slightly over 25 mm, therefore it is about double the size used in most pneumatic guns of a conventional layout. An even larger piston of double the area (1000 square mm) was used in the oval bore alloy guns which were essentially monotubes.

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