Seawolfsub "Velair": Pneumatic Powered Inverted Rollergun

  • Seawolfsub, who make rollerguns and inverted rollerguns, have been developing a pneumatic powered Arbalete. This gun is the "Velair" and instead of a rubber band battery it uses a pneumatic system whereby the cables are pulled by a rod connected to a piston which slides in an airtight barrel connected to a compressed air reservoir. The inverted rollergun cable and sub-pulley system allows the power stroke of the pneumatic drive to be half the length of the wishbone draw on the top deck. This pneumatic system is the reverse of a gas strut as pulling the piston and connecting rod out cocks the gun and the increased pressure with the system then cocked serves to drive the piston and withdraw the rod back into the barrel. Details are unknown, but the following diagram illustrates the operating principle.

  • Here is a Velair 65 being tested in swimming pool.

    When the gun shoots the pulleys under the barrel drive rearwards and haul on the cable which acts as a wishbone to propel the spear. The advantages of a compressed air energy storage system is that it is more efficient than using rubber bands and when used in an Arbalete you can use both hands to cock it, something that you can rarely do with a conventional pneumatic speargun. The overall efficiency of the gun is lowered, but a large diameter piston can be used which is not possible in standard pneumatic guns and thus allows more force to be produced by the available pressure stored in the gun.

    The video can be viewed here on the Seawolfsub Facebook page.

  • This gun has also been discussed on another forum, although there seems to be much confusion in the earlier pages as to how it works, but on this page we can see a comment on the gun's cost by a user, Luigi Purreti.

    Seawolf velair (novità) - page 7

    Il 95 in demoltiplica viene 760€ allestito di tutto, il v3 ( doppia demoltiplica) 840€. The (Velair) 95 in gear ratio is € 760 set up for everything, the v3 (double gear ratio) € 840.

    What the v3 version is I don't know. The double gear ratio may mean extra pulleys or a second "pneumatic engine", but the Seawolf-Sub website is not very forthcoming on many details, which is understandable if they are still working on it.

  • This appears to be the Velair V3 version as the run of cables involves three strands on the moving pulley block. That means if the pulley block is pulled back one centimetre by the orange cable it will move the blue cable on the diagram by 3 centimetres, so you get a 3 to 1 on the cable drive instead of 2 to 1. However the energy of the gun is dictated by the power stroke on the orange cable and in the V3 version it is reduced in length compared to the previous model, so while a 3 times multiplier seems an improvement the gun's pneumatic engine now has less energy to work with. The speed of the pneumatic drive is not a constant as it is affected by the load it has to overcome, the same with rubber bands retraction velocity as the load slows them down if you substitute heavier shafts.

    Velair V3.jpg

    velair muzzle.jpg

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