Valve Body Material

[Slauma]

I'm looking to do something like velocity3x did with his 44mm Hungus and have the valve body custom machined out of something. It seems aluminum is a good material to use for something like I want (150-200 psi pressure range and ability to secure load bearing screws in it to connect the barrel and air tank). I was wondering if I could do this with HDPE or some other material that's less expensive than aluminum though. I know HDPE can be threaded with large threads, but I don't know if it'll hold small screws like aluminum will.

[USGF]

I'm looking to do something like velocity3x did with his 44mm Hungus and have the valve body custom machined out of something. It seems aluminum is a good material to use for something like I want (150-200 psi pressure range and ability to secure load bearing screws in it to connect the barrel and air tank). I was wondering if I could do this with HDPE or some other material that's less expensive than aluminum though. I know HDPE can be threaded with large threads, but I don't know if it'll hold small screws like aluminum will.

It might work if you make everything much thicker / larger. We find aluminum to be the best in terms of strength, cost, ease of machining etc. Really predictable results. Plastic parts for high pressure applications... I'd stand behind a blast shield when in use. Steel is much cheaper but of course it is harder to work.

USGF

[Slauma]

If I were to have a valve body machined out of aluminum (6061) what's the minimum thickness that any of the walls should have for operating up to like 700-800psi?

[inonickname]

If I were to have a valve body machined out of aluminum stock what's the minimum thickness that any of the walls should have for operating up to like 700-800psi?

Depends on the temper and alloy of the material, the measurements (eg. inside diametes), your safety factor and so on.

[Slauma]

Sorry, edited too late. Let's say we're talking about a 4" x 4" block with a 2.5" diameter hole. Is that any better or still not specific enough?

edit: I guess I could rephrase my question. Would 1/4" be safe for almost any aluminum? Or is this overestimating the strength of aluminum?

[USGF]

Sorry, edited too late. Let's say we're talking about a 4" x 4" block with a 2.5" diameter hole. Is that any better or still not specific enough?

edit: I guess I could rephrase my question. Would 1/4" be safe for almost any aluminum? Or is this overestimating the strength of aluminum?

Really, there is not enough detail in your question to give a safe answer. 1/4" plate covering the end of a 10 inch diameter tube might be unsafe. Capping a small tube, no problem. Switch to a welded application and it could be dangerous because you lose the heat treat. It is Very specific.

USGF

[Moonbogg]

It depends on how you make it. How are the end caps being held on? Very general questions like "would 1/4" be safe for almost any aluminum" are simply unanswerable. It sounds like you are in a hurry and are looking for a quick answer to ease your fears. This is guaranteed to get you hurt.

[Slauma]

I'm in no hurry, it's very unlikely anything with materialize out of this any time soon. I'm not looking for a quick answer to ease any fears, simply looking for answers, or at least some insight, to a question that I'm neither knowledgeable or experienced enough to answer myself. I understand that this is not a cut and dried sort of thing. I guess I'm asking the wrong questions. I don't have the knowledge of the subject area like many of the people on this board do, which can make it hard to formulate (and answer) questions. I hardly found my question "unanswerable" though. That is, it may not have a yes or no answer, but it can still be qualified. What factors come into play when trying to evaluate something like this? This is what I understand so far as far as what to consider

-material
-alloy
-temper
-shape (different surface areas mean different forces?)
-how pieces are connected
-other forces (force of piston)

From what I've found (please correct me if I'm wrong) 6061 (T6 or T651) aluminum alloy is fairly easy to find and widely used. It machines well, is lightweight, according to wikipedia it has elongation of 8% or more (T4 temper up to 16% elongation), and has a fairly high yield strength and tensile strength. I presume the cheapest way to actually get this machined would be from a a piece of 4"x4" square bar ~6" long. A 2.5" diameter opening would be put in the back side off-centered. Basically I'm trying to figure out how off-centered/close to the edge the hole could be. A picture would probably help me to describe this much better. Anyway, I don't plan on using any welding. I was thinking something like 10-32 or 1/4"-20 socket cap screws, not sure of their exact placement though.

I suppose I'm not really so much looking for yes or no answers as much as information that might be relevant or helpful to what I've described or anything about the accuracy of what I've said.

[USGF]

If you could post a drawing, we'd be in a better position to say yeah or nay or offer advise.

USGF

[Slauma]

Something like this. Anybody know how to thread things in SketchUp?



I've attached the SketchUp file also. The forum wouldn't allow the .skp extension so I just changed it. Change it back to .skp and it should work.

[velocity3x]

I'm looking to do something like velocity3x did with his 44mm Hungus and have the valve body custom machined out of something.

I trust that you own or at least have a large interest in a machine shop. If not.... a large budget will also work. Have you considered the satisfaction you might get from creating and building your own original design as opposed to knocking off mine?

[POLAND_SPUD]

@velocity
I think he meant only machining a valve just like you did not copying it...

though if you think he's imitating your design it suggest that it is similar to yours ?

[Slauma]

@velocity3x

I never would have expected this type of reaction from you. Firstly, I haven't used anything from you other than the idea of machining a valve (out of aluminum or HDPE). And even this part of my design I attributed to you in my very first sentence of my post.

Secondly, this is just a basic piston valve (this is the same valve design people use for PVC tee piston valves), the only difference is the material.

Thirdly, I have little to no idea of the processes or design involved in making your cannon, there are only (scratch that, it seems you've taken all of your pictures down...?!) a handful of pictures of your gun on the forum, none of which reveal anything proprietary about your gun.

If you were worried about anyone "stealing" or "knocking off" "your design" you should have been more weary to post it on an online forum. With how spectacular and amazing your gun is, it would of course have been a shame not to share it. I don't know if you actually did take down all of your pictures, but I can't find any of them now, and that's a shame because your gun really is a spectacular one that I'm sure many people could be inspired by on the forum (just as I have). But the purpose of this forum is to inform, educate, and share; so if you don't want people learning from or building on "your" ideas and designs then I don't know why you would post it in the first place. I don't know if you just wanted to flaunt the most badass spudgun ever (which in my opinion it is) or what, but I find it unfortunate that someone as resourceful and mechanically skilled as you is unwilling to help with a project like this (and even condemn it as a "knockoff").

[Slauma]

But hey man, seriously, I just want to let you know I'm not tryin to rip-off your cannon or anything. I didn't meant to make it sound like that. This cannon (if it ever even gets built) isn't anything like yours. I have to give you huge props on your cannon though, I could only wish to have a "knock-off" of it.

[velocity3x]

But hey man, seriously, I just want to let you know I'm not tryin to rip-off your cannon or anything. I didn't meant to make it sound like that.

In that case.....my apologies to you.