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Another Semi-Auto Idea (updated)

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Another Semi-Auto Idea (updated)

Unread postAuthor: Hubb » Wed Sep 26, 2007 12:04 pm

While tinkering with my Tippmann 98 the other day I got to thinking. Since Tippmann uses a hammer to open their valve, why couldn't I.

Anyway, the way it works is this: Once the trigger is pulled, the sear disengages the hammer, causing the hammer spring to move forward, striking a pin. This pin releases air and the power tube (valve housing) directs air around the valve and to the front of the marker. Access air is then directed to reset the hammer.

In my design, it will essentially work the same way: The trigger operates the sear, which operates the hammer. The hammer moves forward, striking a pin on the check valve. The opening of the check valve causes the primary valve (probably a sprinkler or diaphragm valve) to open, thus firing the cannon. The pilot air coming through the check valve will reset the hammer.

The hammer will only open the valve for a very brief period. The hammer spring tension will be adjustable to strike the valve harder (releasing more air) if necessary. This may lead to multiple shots for a chamber, if not, I don't see why it wouldn't make a semi-auto out of a regulated air system. Also, I'm pretty sure this system might not work for a large cannon, as the check valve may not open long enough to exhaust the pilot area, but it could probably be upsized with customized parts.

Some of you may be thinking that you can't get stock Tippmann parts. Here's a link to that stuff.

Let me know what you guy's think.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 26, 2007 12:18 pm

You can take the firing mechanism out of a cheap cap-firing revolver to hit the hammer valve, that way you don't have to waste any air resetting the valve. You can easily adapt a blowgun or even a shrader as your pilot valve that's struck by the hammer.

One problem from what I gather is the amount of time it would take a sprinkler valve to reseal, your tank would probably be empty by then.
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Unread postAuthor: williamfeldmann » Wed Sep 26, 2007 12:20 pm

It's a good idea but you would need one heck of a check valve to pilot much in a bigger system.

My major concern is that the check valve couldn't keep a sprinkler valve open long enough for very big of a gun with only that momentary opening, and a sprinkler vavle is going to have a much higher chance of repeat shots than either of the others (unless you hve a plan for that as well).

Why not just run the trigger straight to the check valve? You would hold the trigger for however long you wanted and when you let go the pressure would shut the check valve (check valve has to go behind the trigger, basically mirror image) and push the trigger back forward. It would be just as fast acting and with less complicated parts. Simpler = more reliable.

EDIT: in response to Jack, I have had sprinklers close fast enough to have less powerful second shots off the same tank charge, hooked up to a constant air source, it is not inconceivable that you could have several momentary shots off 1 tank of air, but it would need to be a BIG tank, or hooked to continuous feed.

And damn it Jack beat me again.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 26, 2007 12:21 pm

With that reasoning, might as well use a normal modded sprinkler valve and just open the blowgun briefly :)
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Unread postAuthor: williamfeldmann » Wed Sep 26, 2007 12:29 pm

Hubb mentioned using a diaphram or piston, as well, in the diagram, but I still think the best odds are with a sprinkler. So why not shorten the open time of the sprinkler? Other than messing with the spring (adding blocks to stiffen it) which would make the valve open harder too, what could we do to ensure early close?

The trigger and check valve would work faster than the blowgun due to flow wouldn't they (assume blowgun on hose to get to trigger placement)?

EDIT: And pulling a trigger and releasing it would be a naturally faster movement for the human hand than doing the same for a blowgun if I remember my college physiology classes correctly (doubtful considering the quatities of adult beverages that were consumed in and around the same time) :D
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 26, 2007 12:41 pm

You could just use a pop-off valve as a pilot and have the "trigger" as the blowgun that feeds the system.
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Unread postAuthor: Hubb » Wed Sep 26, 2007 1:00 pm

I was going to try to utilize this (or something similar) in my upcoming project, which is a small pneumatic. I was wanting something that functioned quickly and naturally and look good at the same time.

Jack: As far as your first post, the pilot air is air wasted anyway so I figured I could use that air to reset the hammer. As far as the tank emptying, my cannon was going to be hooked up to a regulated CO2 system. If the main firing tank emptied, it would be okay because it would simply refill (thus, the reasoning behind "semi-auto").

As far as opening and closing of the check valve, it states above that the valve will be open for a very brief time. Probably less than .25 sec. My main concern about this was it not being open long enough to exhaust the pilot, which is why the spring would be able to be adjusted, probably with a nut / bolt like on a rear velocity adjuster from a paintball marker.

In the case of just having the trigger connected to the check valve, I could just go with a ball valve. The handle to the valve would be the actual trigger. The problem with this would be the reseting time, as it would let more air out than I wanted, even if I added a spring to the back of it.

Basically, I was looking for a way to quickly exhaust the pilot air, while eliminating the human element of manually opening a valve.
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Unread postAuthor: grumpy » Wed Sep 26, 2007 1:14 pm

hi, i am new to this forum but have built several launchers over the years, i don't think they understand how a blowback valve works. i also play paintball and have used tippmans since they were first made in the late 80's. i am also atempting to do the same thing but on a larger scale as i want to shoot the 2 inch nerf rockets. i think the hardest part will be finding the right size springs with the proper tension in order to get the correct velocity, i do think it can be done.
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Unread postAuthor: Hubb » Wed Sep 26, 2007 1:22 pm

Welcome

I was going to use the internals from a 98 and be able to adjust the tension for the hammer spring like on a rear velocity adjuster. This tension adjustment may have something to do with the velocity but I doubt it, due to the check valve being a secondary valve. I do think, however, that it will affect the hammer travel speed.

I'm thinking the hardest part will be lining things up correctly. I may have to use some of Jack's epoxy techniques.

btw: I do believe Jack knows what this system is. He has used successfully on more than one occasion. I feel, however, I may have missed some information in the original post that might have confused someone.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 26, 2007 1:27 pm

Oh I get how it works, my worry is that for the strength of hammer you'll need, the check valve isn't going to provide enough air to re-cock the hammer, particularly as it closes the minute the check valve starts moving back.
I'm thinking the hardest part will be lining things up correctly. I may have to use some of Jack's epoxy techniques


lining things up correctly is lathe and drill press territory, down the epoxy-lined path of alignment only coarse anglo-saxon blasphemy lies.
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Unread postAuthor: Acdcmonkey1991 » Wed Sep 26, 2007 1:37 pm

I'm actually currently working on a hammer valve exactly like this. The main tube is 3.4 in. copper, and the hammer is made of o-rings, and 1/2 in. copper pipe fittings that slide easily in the tube. The only difference is that mine will actually function like a paintball gun.
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Unread postAuthor: grumpy » Wed Sep 26, 2007 1:39 pm

tension on the hammer spring has everything to do with the velocity as it controls how hard and how long the hammer keeps the valve open, also you might want to look at the x-7 since it's been modified for better airflow and will also work in the 98. i don't think a check valve will work as it may hamper the blowback and not let it recock.
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Unread postAuthor: Hubb » Wed Sep 26, 2007 1:44 pm

jackssmirkingrevenge wrote:Oh I get how it works, my worry is that for the strength of hammer you'll need, the check valve isn't going to provide enough air to re-cock the hammer, particularly as it closes the minute the check valve starts moving back.


That was the main concern I have (lining thing up will probably be easier than I thought because I may end up using the Tippmann receiver I have three).

Is there any ideas of how I can make this concern go away? Maybe a different valve I can use?
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Unread postAuthor: Acdcmonkey1991 » Wed Sep 26, 2007 1:54 pm

It looks like you could line everything up fairly well without machining anything.
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Unread postAuthor: Hubb » Wed Sep 26, 2007 2:14 pm

grumpy wrote:tension on the hammer spring has everything to do with the velocity as it controls how hard and how long the hammer keeps the valve open...


Very true...for a paintball marker that utilizes this design to operate the main valve. However, the hammer is going to strike a valve to pilot a larger, main valve. With this setup, the best (and probably only) way to adjust the velocity would be to adjust the pressure of the chamber.
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