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05-09-2021, 08:07 PM | #1 |
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Seawolf "Velair": Another pneumo-powered Arbalete
Seawolf-Sub who manufacture a range of band powered inverted rollerguns have now created an air powered version somewhat similar to the Infinitengines "Dreamair" except that the operation of the compressed air drive system is very different. Unlike the Dreamair" which is an air powered high speed winch driving through an axle with inner and outer co-axial winding drums the new "Velair" uses a sliding rod gas strut system that operates in reverse. Compressed air pressure tries to pull the thin rod connected to a piston into the cylinder bore rather than pushing it out. That means when you pull on the gun's cable wishbone to cock the gun the rod is drawn out, but is being resisted by the air pressure trying to move the rod back in again. Through the use of the sub-pulley inverted rollergun cable layout the stroke of that moving rod can be half of the wishbone draw on the top deck. By using a smooth metal rod the gun’s pressure boundary can be traversed by the rod moving through a pressure seal, making the seal more reliable than if it was traversed by a cable.
The schematic below shows the operating principle, but not the actual layout which will depend on how the system is realized to obtain the necessary piston, piston stroke and air tank dimensions. To have a useful gun these pneumatic Arbaletes need a big piston diameter, the “Velair” is reported as having a piston of 32 mm diameter. The larger the piston cross-section for a given start pressure in the gun then the more force you have available, hence you can afford to throw some of it away in inefficiencies. |
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