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.

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