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by D_Hall
Sat Jan 25, 2020 2:00 pm
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Re: Describe the ultimate potato cannon

I confess that I've not really thought about the details of the valving since I doubt I'd get the funding to build such, burst disks work well, and burst disks are a negligible cost in the Big Picture. The point being that whimsy aside, the gun would almost certainly use burst disks. With the valve ...
by D_Hall
Sun Jan 26, 2020 1:06 am
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Re: Describe the ultimate potato cannon

I swear to all things holy and not, if I had the money lying around, I'd build it. I would actually be crazy enough to go through with building this thing. It would be absolutely hilarious. Let's just say that I didn't come up with the performance specs on a whim. I was asked by some folks if it wa...
by D_Hall
Thu Feb 13, 2020 11:59 pm
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Re: Low-friction/Specialty Ball Valves?

You're not going to get much lower friction than teflon seals, but they can still be a bear to turn. Ball valves simply aren't designed for quick/easy motion.
by D_Hall
Sat May 30, 2020 1:25 am
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Re: My current hobby: Cowboy Action Shooting

Turns out that the same guys who run the Cowboy Shoots also do what they refer to as BAM shoots.... Bolt Action Military. Basically the idea is to use a bolt action military rifle in as-issued condition that dates to 1945 or earlier. It also turns out that my Mom once bought an 1895 Mauser on a whim...
by D_Hall
Fri Jun 12, 2020 2:36 pm
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Re: Port size vs performance

The purist in me loves the idea of a port that is actually larger than the bore, with the breech tapering down such that flow into the bore is smoooooth and maximized. But yeah, the realist in me realizes that for the vast majority of cases this is beyond overkill. Hmmm... Let's see if I can come up...
by D_Hall
Mon Jun 15, 2020 5:17 pm
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Re: Port size vs performance

Some more thoughts on the thought experiment.... It assumes constant density, but this is obviously incorrect. But what DOES density do? In the first moments after the valve opens, not much. Constant density probably isn't a bad approximation. But as the projectile accelerates we know that pressure ...
by D_Hall
Wed Jul 01, 2020 5:50 pm
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Brass as the foundation of a projectile?

I'm sitting here looking at a piece of 38 special brass. It just happens to be on my desk (yes, really). And I'm thinking to myself, "Self, this might make a good projectile." More to the point, I could see epoxying a nail in the primer pocket to make a dart. But a dart that is reasonably cheap/easy...