SpudFiles

more please

Not much to show from this week unfortunately. I spent most of my nights this past week building and then rebuilding the air chamber after it had leak after leak after leak before I eventually got it through to myself that epoxy resin alone makes a poor air seal, at least mine does (JB Weld). So now I'm currently remaking a new chamber with joints filled with a gasket maker sealant and a little epoxy to keep the joints from blowing apart. Soldering isn't really an option due to the custom cuts I made to the copper to get the copper as compact as possible.

Here's the unfinished flintlock hammer coming together

epoxy resin alone makes a poor air seal

How exactly are you making your joints?

I expect the Dutch members to jump in with their advice

My joints were just 1/2" copper pipes slathered in epoxy and inserted into copper fittings. My first chamber (the one in the first image) worked fine and held up to 400 psi without leaking). Now, with the ones I've been making, after about 300 psi the epoxy begins to crack and leak.

Due to its malleable nature, copper is not usually a good candidate for 15 minute type epoxy joints unless it's a really tight fit. You might want to consider a pouring of marine type epoxy.

jackssmirkingrevenge wrote:Due to its malleable nature, copper is not usually a good candidate for 15 minute type epoxy joints unless it's a really tight fit. You might want to consider a pouring of marine type epoxy.

This chamber is really beating me down, I've tried plumbing solder, epoxy, some stuff called 'Just for Copper which was a total let down. The solder worked but due to the close distance of the soldered joints I can't really heat one without the last one melting. Epoxy works most of the time but always seems to spring a leak somewhere. I'm just about ready to go get some mild steel pipe professionally welded before I pull my hair out.

On another note, progress on the lock is coming along nicely.

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Awesome!

Epoxy works most of the time but always seems to spring a leak somewhere.

Have you considered eschewing the 15 minute stuff for something different?

jackssmirkingrevenge wrote:[youtube][/youtube]

Awesome!

Epoxy works most of the time but always seems to spring a leak somewhere.

Have you considered eschewing the 15 minute stuff for something different?

Ah, thanks, guess the youtube address wasn't pasted correctly, it's a little different on this forum.

I've tried JB weld which has a 2 hour set time as well as some (loctite) marine epoxy, both failed. Thinking about wrapping the whole chamber in a few wraps of resin coated fiberglass I have laying around, another idea I had was to simply immerse the chamber in a block of polyester resin, then cut it out, fail proof.


Thanks for the link to your guide, I've read it and it's been a help in the past.

I have a question for you, Jack. Do you think 2 cu in at 400 PSI is just too much for epoxy to handle? My last chamber was 1 cu in and handled the PSI well, but I'm thinking perhaps the added volume is just overstressing the epoxy.

I have used epoxy endcaps in numerous 850 psi projects.

Here is an example using a copper tube as a chamber, no issues with leaks.





Of course it's important to roughen the epoxy contact surfaces, sometimes drilling holes and taping them over while pouring like daccel did here is a great idea to improve adhesion.

jackssmirkingrevenge wrote:I have used epoxy endcaps in numerous 850 psi projects.

Here is an example using a copper tube as a chamber, no issues with leaks.

Did you ever take that thing to 800 psi? If you did, might have to reconsider not going above 500 myself.

After another try it turns out that loctite marine epoxy actually held and is holding without leaks at 350 PSI which is as high as I've gone so far, so I can finally move onto other matters. That idea of drilling holes in the copper for the epoxy to adhere to is just great, will definitely try that next time.

Here's how it looks as of today.


Lock plate is finally secured into place, you can see the schrader stem sticking out of it, you can also see the pressure gauge below on the underside of the stock.
I can't wait to get this stock shaped up, it should be sleek!

Xamllew wrote:Did you ever take that thing to 800 psi? If you did, might have to reconsider not going above 500 myself.

Plenty, this shot is at 800 psi:

[youtube][/youtube]

Here's how it looks as of today.

Sweet!

Small Update:

The ball valve I was using was becoming fairly stubborn to turn, I think sawdust or other dirt might have caused this, I tried a bunch of different types of lubes, dish soap, silicon oil (actually made it harder to turn), valve grease, I tried cleaning the ball, I tried washing it, I even lubed the stem where the handle connected, but to no avail. This was a big problem since the entire operation relies on the valve turning when the hammer strikes it but that wasn't happening, even with a heavy mainspring the hammer could barely budge the valve handle.

My idea was to loosen the valve by spinning the ball valve handle in a drill at a fast speed, which I did, which did solve the issue and loosened the valve significantly...however I probably over did it because the ball valve was oven hot from the friction by the end of the spinning, however valve was turning almost effortlessly...but it was leaking from both the handle stem and the port so it had to be trashed.

My next plan is to try the drill idea again with a new valve but go a lot slower so as to not cause heat and damage the seal. I do not know why lube has no effect on these valves.

I have successfully lubed ball valves... ironically, sometimes the plastic used for the ball can absorb water and swell. That might cause some of the sticking. Maybe they can absorb some lubes too.

The ball valves in my water system stick sometimes. I don't lube them!

Could it be that you're not getting enough leverage at the point where the hammer strikes the ball valve?

Once again, excuse the long silence between updates. I had to move into a new home, I also had to start a new workshop which took a bit of time, but I simply can't get the idea of finishing the airgun out of my mind. So anyway here is another update: I got a new ball valve, covered it in plumbers grease and did the spinny drill thing again but slower, the trick seemed to work, the valve was smooth and light to turn and wasn't leaking, however despite this my hammer didn't have enough force to kick the valve handle all the way open. I thought a stronger mainspring was the answer but it still wasn't turning the valve handle more than 45 degrees. I finally realized that adding more weight to the hammer would allow it to impact the handle with more energy and so I finished up the hammer with a few pieces which increased the momentum it has to hit the valve with, now it pops the valve open crisply. Now with the sear in place and trigger installed i can finally fire the gun with the trigger, very satisfying.

The replica flintlock hammer/jaws with replica flint which is actually steel filed at random angles to give it the appearance of a jagged piece of flint, later I will dye the flint black to finish the look.