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Valve mod - pcp pistol |
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J-S 
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Joined: 19 Oct 2014 Location: Auckland Status: Offline Posts: 388 |
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 Topic: Valve mod - pcp pistolPosted: Yesterday at 11:39am |
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very cool
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J S Airguns
Air Arms TX200('s) Theoben Sirocco HW77 FWB 300s Webley Patriot One or two others... Current projects: Too many.. |
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Pauly5
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Joined: 10 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1323 |
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Posted: 19 Sep 2024 at 11:19pm |
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Barrel is around 300 mm, so not a small pistol.
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RangerPete
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Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 719 |
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Posted: 19 Sep 2024 at 10:19pm |
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So how long are you planning on making the barrel?
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Walk quietly, but carry a big stick.
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Pauly5
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Posted: 18 Sep 2024 at 9:50pm |
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Slowly doing stuff.
NZ Post has botched up Nunga's foundry delivery, so valve on hold. I bought a piece of 3.9 mm piano wire today. Pretty hard, and hopefully harden up, but I might try that for the valve stem. I also decided to use the .25 cal FX barrel I had. It was off a Bobcat. I cut it down and reduced the breech end to fit into what will be the breech block for this build. Fits nice and snug with no movement. FX only rifled the last 2 or 3 inches of these barrels and you can see that they make the muzzle smaller diameter to do this, then thread on a piece to match. You can see the marks on the outside where they "squeeze" the rifling in giving it a "smooth" twist.   |
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RangerPete
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Joined: 18 Apr 2023 Location: Cambridge. Status: Offline Posts: 719 |
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Posted: 09 Sep 2024 at 11:08pm |
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Good luck with that 😂
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Walk quietly, but carry a big stick.
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Pauly5
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Joined: 10 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1323 |
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Posted: 09 Sep 2024 at 10:06pm |
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Well I tried cutting one of my donor screw drivers and it was hard. The hacksaw had trouble biting into it. It made a small nick, so I just put it in the vice and it snapped on the nick.
Doing pest control I was always up in ceilings and sparkies often forget stuff and they do like to have expensive screwdrivers which are decenyly hardened. So I have a couple I can wreck. So this will be my valve stem.  |
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Pauly5
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Posted: 07 Sep 2024 at 8:26pm |
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So should I remake that valve seat in brass and the harder material for the moving part of the valve. Poppet valve?
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BC_Clark
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Joined: 15 Feb 2024 Location: Auckland Status: Offline Posts: 6 |
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Posted: 07 Sep 2024 at 7:50pm |
Some of my most powerful and highly stressed valves have been with 385 brass seats so I can say that normal HPA usage is no challenge. |
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nunga
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Joined: 08 Mar 2013 Location: Pukekohe Status: Offline Posts: 946 |
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Posted: 06 Sep 2024 at 5:49pm |
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Thats because 385 brass as a lot of lead (around 3%) compared with other types of brass which makes it very good for machining it is also know as free machining brass. But it is a lot softer as well so i dont know how it would handle been used on HPA valve seat. If you have had good results using it BC_Clark then i would be happy to mix up a batch for you paul, like i said i have everything here and i will be smelting other stuff this weekend anyway.
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2nd place HP springer - WFTF World Championships 2014
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BC_Clark
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Posted: 06 Sep 2024 at 5:20pm |
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A thing about dissimilar metal corrosion is it depends on the ratio of surface areas of each metal. A stainless seat in an aluminium airgun could have no issues but an aluminium seat in a stainless airgun would be at high risk. Look up the galvanic series and make sure that the most reactive metal makes up the vast majority. I find 385 brass to be very good for seats. It machines and polishes well. Bronzes can be more tricky. |
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nunga wrote: