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by hectmarr
Tue Jun 09, 2020 4:11 pm
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Browning Airstar 200

I am struck by this spring compressed air weapon, which compresses the spring with an electric motor and reduction gears, using a chain similar to those used by motorcycles. Interesting! ;)
by hectmarr
Wed Jun 10, 2020 1:24 pm
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HA-VI

I am trying some ideas to simplify my weapons as much as possible. This new sistem has the following advantages: 1- It has no piston 2- It has no spring 3- It does not have a rupture disc 4- It has no solenoid valve 5- It has no dead spaces between the combustion chamber and the firing barrel The 1/...
by jackssmirkingrevenge
Fri Jun 12, 2020 3:35 am
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Re: Port size vs performance

I think your reasoning is spot on.

Port size and opening time are what determine the rate at which pressure rises behind the projectile.

That rate of pressure increase is not linear vis a vis the port size so it reaches a point where the advantage of making it any bigger is minimal.
by mrfoo
Fri Jun 12, 2020 6:10 am
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Re: Port size vs performance

Quite. There's going to be a point of diminishing returns where, for a given design and geometry, going bigger will eventually slow the piston down. There's a lot of benefit to be had, for a port that's smaller than the barrel, from profiling the edges of the port, both chamber side *and* barrel side.
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 hectmarr
Fri Jun 12, 2020 4:21 pm
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Re: Port size vs performance

Important thought experiment and clarifies in theory the same doubts that Moonbogg has. It must be taken into account that larger diameters generally use larger dead spaces, but it depends on the geometry of the transfer, as mrfoo says. The final gun, in my view, does not exist. The interesting thin...
by mrfoo
Sun Jun 14, 2020 4:12 am
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Re: Ideas for biodegradable cannon-balls

I'd guess a simple flour / water paste would work. Plain flour, though, not self-raising.
by hectmarr
Mon Jun 15, 2020 10:28 am
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Re: Ideas for biodegradable cannon-balls

I recommend the meatballs my mother-in-law makes. :shock: I never consume them and they can be useful for what you are looking for. I always told myself that the woman had the soul of an ammunition manufacturer and not much of a cook :lol: :lol:
 
by Doc j
Mon Jun 15, 2020 4:19 am
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Re: Ideas for biodegradable cannon-balls

Make molds with gap sealer silicon mixed with cornflour makes a putty B4 it sets.

Maybe this, wat put into Mold.
But it shrinks a bit I think.

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 KannonKing
Mon Jun 15, 2020 3:36 pm
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Re: New member... my baby, Big Red

Pickle me grand mother. "big belly laugh". Dunno about ya tech thing variables golf balls. Yeah 750 mtr range... I av golfer, smak em 240 mtrs. When I get onto em , Its "Anzac" on the tee. One minute of silence, that is.... Gahahaha. I'd Rekon I give big red, prob 5 mins of silence after seeing it ...
by KannonKing
Mon Apr 27, 2020 1:14 pm
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Re: New member... my baby, Big Red

My apologies, I was being a little facetious, I would never consider detonating such a fuel/oxidizer mix. I thought the "miniature vacuum pump" was my obvious tell... I'll be sticking to a high nitrogen content with this device thank you very much. ;) And I'll cancel the snark until you get to know ...
by ToasT
Fri Jun 19, 2020 3:36 am
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Re: Ideas for biodegradable cannon-balls

I have used clay, it needs to be dried for several days, the larger, the longer it will require. If not dry, it tends to splatter and leave the barrel as a cloud. Clay will tend to shrink quite a bit, and depending on the clay, shrinkage is not consistent, so it can be a pain getting the size right....
by ToasT
Fri Jun 19, 2020 3:13 am
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Re: Port size vs performance

Not that I have much to add to this, but It's threads like this that make me a fan of spudfiles.