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Machinist in America?

A place to ask general spud cannon related questions.
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Unread postAuthor: Willdebeers » Sun Jul 31, 2011 2:05 pm

Lockednloaded wrote:I doubt I'll ever go over ~ 10x, but all the parts on my gun can handle 20x so I'd likethe piston to handle that as well. I don't know if you've seen my valve, but there will always be an air cushion and a thick rubber washer to cushion the piston force


Would you want a hole/threads in the piston? I also have a whole tap/dye set so I can do that too.
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Unread postAuthor: saefroch » Sun Jul 31, 2011 2:06 pm

I advise against aluminium. I think there was an aluminium piston in the past, but it didn't survive long. Steel is really the best option, I'd just get around the density by using a design like SB15 and MrCrowley used. Or you can try modelling your build in GGDT to try out different piston masses.
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Unread postAuthor: Willdebeers » Sun Jul 31, 2011 2:22 pm

saefroch wrote:I advise against aluminium. I think there was an aluminium piston in the past, but it didn't survive long. Steel is really the best option, I'd just get around the density by using a design like SB15 and MrCrowley used. Or you can try modelling your build in GGDT to try out different piston masses.



Steel is awfully heavy though.

It is also a $%^& to machine with.
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Unread postAuthor: ramses » Sun Jul 31, 2011 2:38 pm

Realistically, a toolie piston made of steel would probably weigh as much as a solid aluminum one.
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Unread postAuthor: Technician1002 » Sun Jul 31, 2011 2:47 pm

There are high strength low weight alternatives to steel. Magnesium is a relatively inexpensive alternative. Often the materials can be found at a junkyard for cheap. They won't come in your desired shape so there will be some labor to cut a part to shape.
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Unread postAuthor: Lockednloaded » Sun Jul 31, 2011 3:24 pm

Willdebeers wrote:
Lockednloaded wrote:I doubt I'll ever go over ~ 10x, but all the parts on my gun can handle 20x so I'd likethe piston to handle that as well. I don't know if you've seen my valve, but there will always be an air cushion and a thick rubber washer to cushion the piston force


Would you want a hole/threads in the piston? I also have a whole tap/dye set so I can do that too.


Do you have imperial taps? If not I suppose I could buy some metric bolts here, so it's not much of an issue.

@sae,
I guess weight really isn't an issue, but a destroyed piston would. I've never seen an alu piston fail though, and I don't want to complicate things for the machinist.
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Unread postAuthor: Willdebeers » Sun Jul 31, 2011 3:56 pm

Lockednloaded wrote:
Willdebeers wrote:
Lockednloaded wrote:I doubt I'll ever go over ~ 10x, but all the parts on my gun can handle 20x so I'd likethe piston to handle that as well. I don't know if you've seen my valve, but there will always be an air cushion and a thick rubber washer to cushion the piston force


Would you want a hole/threads in the piston? I also have a whole tap/dye set so I can do that too.


Do you have imperial taps? If not I suppose I could buy some metric bolts here, so it's not much of an issue.

@sae,
I guess weight really isn't an issue, but a destroyed piston would. I've never seen an alu piston fail though, and I don't want to complicate things for the machinist.


I have every size from 4 - 13mm.

I have a bar of aluminium that is just over 3/4", which would be much easier, and it is a dream to turn anyway.

If worse comes to the worse I could always machine a steel one if the aluminium one vapourises itself.
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Unread postAuthor: Lockednloaded » Sun Jul 31, 2011 4:18 pm

I doubt an aluminum piston would break especially since it my PVC/epoxy one survived 7x but only suffered sealing problems at 8x because my o-ring groove was distorted by heat
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Unread postAuthor: Gun Freak » Sun Jul 31, 2011 4:19 pm

Yeah, I think a 3/4" aluminum piston, at low mixes, with an adequate bumper will be fine.
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Unread postAuthor: ramses » Sun Jul 31, 2011 4:24 pm

I have imperial taps.
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Unread postAuthor: Lockednloaded » Sun Jul 31, 2011 4:33 pm

I think what I'll do is ship the machinist a padded flat rate envelope inside a small box with the o-rings so that they could ship it back no cost to them
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Unread postAuthor: SpudBlaster15 » Sun Jul 31, 2011 4:50 pm

If you want a high strength, lightweight piston material, look into 7075-T6 aluminum. It has roughly equivalent strength properties to mild steel, while being only 1/3 as dense.

It's quite expensive, but that shouldn't be a significant concern for a component this small.
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Unread postAuthor: jrrdw » Sun Jul 31, 2011 4:59 pm

Send the cylinder your going to use so the piston can be custom fit. Not every ones indexing are going to be just like yours. You also have to account for bearing play, dial lash and all the other variables from one tool to another.
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Unread postAuthor: Lockednloaded » Sun Jul 31, 2011 5:18 pm

Jrrdw, I was planning on sending the 3/4" nipple to him as well. Also do you think you could start a machinist wanted thread? Threads like these could eb condensed and the machinists among us could just check there every once in a while
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Unread postAuthor: jrrdw » Sun Jul 31, 2011 6:00 pm

Lockednloaded wrote:Jrrdw, I was planning on sending the 3/4" nipple to him as well. Also do you think you could start a machinist wanted thread? Threads like these could eb condensed and the machinists among us could just check there every once in a while


I'll talk about it with the other mods/PCGUY and see what they think about that...
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