Reply To: A theoretical exploration of physical possibilities, AKA Let's Make A Monster

Forums General Discussion A theoretical exploration of physical possibilities, AKA Let's Make A Monster Reply To: A theoretical exploration of physical possibilities, AKA Let's Make A Monster

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I_Like_Irons
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“jps2486”I have a better idea.  Let’s start with a spring from a car’s front end, a piston from a Pratt & Whitney R2800,  a flag pole to cock the thing, and a 5 inch barrel from a Navy destroyer.  We can shoot Isis ragheads from 5 miles.


Well, let’s see how your numbers work out.  A single P&W R2800 cylinder has a displacement of 175 cubic inches.  A five inch 38 caliber naval gun has a volume of 3730 cubic inches, and a single car strut spring will not have nearly enough energy to get an approximately 40 pound pellet to travel 5 miles.

(Note: Naval guns and artillery pieces are often defined by the bore diameter (caliber) and the barrel length in how many calibers long it is.  That makes the 5″ 38 caliber gun barrel 190 inches long.  This proportion is quite useful in predicting how a particular gun design will perform with respect to velocity for a given pressure and projectile geometry.)

Now what might be practical to make.  Let’s start with a 7000 grain (1lb) pellet with a diameter of 1.875″ ( 1–7/8″). Put this out at a velocity of 850 ft/s. An RWS 48 in .177 has a barrel length of about 90 calibers long, and it achieves the desired velocity with a similarly proportioned pellet.   This gives the 1.875″ diameter bore a length of  about 168 inches or 14 feet. 

Now we need a piston that has a proportional volume to that of the RWS 48.  This I do not know, nor can find quickly. If anyone knows then please add this information. We also will need a spring or series of springs to achieve the same pressure behind the pellet.  The pressure is something else I do not know.

Dual pistons connected together would be beneficial.  One thought I have (since this thing would be pretty long) is to have one larger piston  that surrounds the barrel, while the other smaller one is behind the breach.  Both would have the same effective piston area, travel distance, and springs.  The difference in piston area is  only due to the outside diameter of the barrel.   The larger piston would have both an outer and inner seal. 

Since the thing would be an artillery piece, the recoil should be absorbed by a spring system on rails.  For that is what we strive to do with our artillery hold on spring powered air guns.