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Old 05-09-2021, 08:07 PM   #1
popgun pete
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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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Old 05-09-2021, 08:09 PM   #2
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Re: Seawolf "Velair": Another pneumo-powered Arbalete

You can see the "Velair" in action here.
https://youtu.be/DVZeI8ll-I4
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Old 05-09-2021, 08:19 PM   #3
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Re: Seawolf "Velair": Another pneumo-powered Arbalete

A few photos of the "Velair", you can see the outer cable drive system.
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Old 06-05-2021, 05:29 PM   #4
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Re: Seawolf "Velair": Another pneumo-powered Arbalete

Target shooting in swimming pool with Velair 65. A 4 metre shooting distance, 7 mm shaft.
On the Seawolfsub Facebook page /seawolfsub/videos/477098620063791


Note that with the gun cocked to shoot the twin pulleys on the wishbone cable have been dragged forwards to midway under the gun barrel. On pulling the trigger these pulleys zoom back to the rear of the gun and they draw back the wishbone cable which in turn drives the spear from the gun.
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