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Help needed: Loading mechanism (modeling+machining)

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Help needed: Loading mechanism (modeling+machining)

Unread postAuthor: PaperNinja » Tue Aug 21, 2012 7:07 am

I've drawn up what I need made :)

I'm sorry if you can't read it super well, just ask me to clarify! I did it by hand, but I'm pretty sure it's clear anyway.

I'm going to post links rather than pictures to not take up so much room. Please reply quickly with a price :)

http://i.imgur.com/yNPJx.jpg
http://i.imgur.com/Qvb3f.jpg
http://i.imgur.com/uK2EK.jpg
http://i.imgur.com/d2A6b.jpg
http://i.imgur.com/V1Dsm.jpg
http://i.imgur.com/Lw8IG.jpg
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Unread postAuthor: jackssmirkingrevenge » Tue Aug 21, 2012 7:21 am

Not something a machinist can really work from, you need clearer drawings, also you need to specify material, tolerances... try using a pen instead of a pencil ;)
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Unread postAuthor: dewey-1 » Tue Aug 21, 2012 9:59 am

PaperNinja wrote:I've drawn up what I need made :)

I'm sorry if you can't read it super well, just ask me to clarify! I did it by hand, but I'm pretty sure it's clear anyway.


This is what you have sketched.
I did not include 3/16 and 1/8 holes because there is no height dimensions or what they are to be used for.

Notice the problem of red to blue cylinder!
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Unread postAuthor: PaperNinja » Tue Aug 21, 2012 10:33 am

That is approximately what I have in mind dewey, though everything is hollow. I'm using a mag design like POLAND_SPUD's here. The 1/8" hole is for the rod that pushes up a rubber stop carrying a bb into the barrel (not shown in diagrams). The 3/16" hole is where I will connect this mag to the rest of my air chamber.

Here are better drawings:

Back view: http://i.imgur.com/6mmyT.jpg
Front view: http://i.imgur.com/QCJ3R.jpg
*note for front view, that .238 is the diameter of the circle... sorry for the ambiguity
Cross-section: http://i.imgur.com/MxlW6.jpg
Bottom view: http://i.imgur.com/wMF1e.jpg
Top view: http://i.imgur.com/yP7Bl.jpg


I don't really know what material I want :/
Whatever is easiest/best/cheapest... maybe aluminum or stainless steel.

I also am not sure what the thickness of the walls should be... this is going to be taking pressure (up to 160 psi) so maybe not to thin... like 1 - 1.5 mm?

I would like to tolerances to be fairly close, would .0005 or so be possible?
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Unread postAuthor: dewey-1 » Tue Aug 21, 2012 12:04 pm

You really have me confused now with ID's being shown.
What is the RED part ID and OD?
I see you also changed 1/8 to 1/4.
If you would draw dashed lines for the hidden lines for all the holes would help.
What secures the RED piece to the Blue piece?
What are the depths of the 1/8 and 3/16 holes?
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Unread postAuthor: PaperNinja » Tue Aug 21, 2012 12:15 pm

The red is .238 ID and approx .278 OD

I did change 1/8 to 1/4, sorry I didn't mention that.

I don't know what secures that red piece, maybe just do a short length of that red piece be machined with the blue as one part, then have the rest of that red tube start at .278 ID, (OD of short length of red) and continue on as .238 ID for the rest of the red tube. Then slip the fat end of the long segment over the short piece connected to the blue and epoxy.

I think a depth of .02 inches would work well, it doesn't need to take that much weight/pressure.
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Unread postAuthor: dewey-1 » Tue Aug 21, 2012 12:45 pm

What is your BB caliber/OD?
So the RED piece basically slides into your barrel correct?
Show a picture where you magazine goes, I assume the top of the BLUE piece.
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Unread postAuthor: PaperNinja » Tue Aug 21, 2012 12:58 pm

The red piece IS my mag. My air chamber attaches to the bottom of the green, pushing up a piston connected to a rod, which goes through the 1/8 inner hole. The rod connects to a rubber stop. When the trigger is pressed and the chamber is not charged, a spring in the green piece pushes down the piston, pulling the rubber stop to the .25 " below the red piece where a spring in the red piece pushes a bb onto the rubber stop. When the trigger is released the chamber is charged, pushing the piston in the green piece up, pushing the rubber stop up into the .25" above the red piece and seals against the barrel with the bb inside.

I am using normal 6mm airsoft pellets.
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Unread postAuthor: dewey-1 » Tue Aug 21, 2012 1:38 pm

PaperNinja;

Wish you would have explained that in your sketches that was the magazine. You are making this way to complicated than it really needs to be.

edit:
You will not get a machined part from anyone unless you have realistic plans that can be followed. Example; why do you need a magazine with .238 ID? That is the ID of a tightbore barrel (6.03mm) which is .2374 inches.

Also the tolerance of .0005 is totally unrealistic.
+/- .005 inches maybe a little easier.

Maybe you should learn Sketchup, it is a free CAD program.
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Unread postAuthor: PaperNinja » Tue Aug 21, 2012 2:05 pm

Hmm sorry I don't know what's realistic :oops:

I'll learn sketchup and just make a model.
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Unread postAuthor: PaperNinja » Wed Aug 22, 2012 7:32 am

So this is now it's own thread... better put some more info :)

I'm trying to make a mag design like this:

Image

The air hose at the bottom connects to my QEV air chamber.

The springs I have ordered:

For the mag:

1.75 " long, .218" OD, .6" compressed length, with .69 lbs at max. They are 12 to a package.

For the piston: .

813" long, .36" OD, .267" compressed length, 7.41 lbs at max. They are 5 to a package.

I planned my piston (that loads the bb) to be 1/4" thick, with a 'scoop' in it so it makes the bottom of the place where the bb is loaded round, to match the barrel that I will cut out.

The other piston is more flexible in thickness, but most likely will also be 1/4"

There is context to how I came up with my measurements. (I will have updated diagrams soon)

If anyone sees a design flaw, or an impossibility/improbability please mention it. (Use the 3d model and designs already here---scroll a little bit up) The point of how the red tube connects to the blue (ref, 3d model) has already been brought up.

Here's a picture of the mag charging with the QEV. The trigger has not been pulled yet.
Image

Also please note that I didn't really make this thread, it's a side conversation that got moved from the machinists thread.
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 22, 2012 8:54 am

How does air go past the loading piston?

Why such a tiny magazine?

What keeps the BBs from shooting out?
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Unread postAuthor: PaperNinja » Wed Aug 22, 2012 9:04 am

JSR wrote:How does air go past the loading piston?


It doesn't. The right end of the barrel attaches to the QEV, it's only closed because I was lazy.. The loading piston is attached to the QEV air chamber/exhast port.

JSR wrote:Why such a tiny magazine?


In my drawings it's 7". It will hold a lot more bb's xD (mebbe approx 24).

JSR wrote:What keeps the BBs from shooting out?


?
The air from the loading piston should not escape past the loading piston.
When the trigger is pulled, air goes from the QEV air chamber out the barrel, letting the spring push the piston down and loading another bb.
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 22, 2012 9:55 am

PaperNinja wrote:It doesn't. The right end of the barrel attaches to the QEV, it's only closed because I was lazy.. The loading piston is attached to the QEV air chamber/exhast port.


Ah, right. Like the attached.

In my drawings it's 7". It will hold a lot more bb's xD (mebbe approx 24).


If your spring is only 1.75" long though...

The air from the loading piston should not escape past the loading piston.
When the trigger is pulled, air goes from the QEV air chamber out the barrel, letting the spring push the piston down and loading another bb.


There is a possibility that the mag spring will push the BBs out on its own...
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Unread postAuthor: sharpshooter11000 » Wed Aug 22, 2012 10:01 am

You need to make the loading piston longer, if it pushes the bb all the way up to the barrel the bbs in the magazine will be pushed under the loading piston.
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