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Pneumatic Cylinder For Bolt Action

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Wed Jan 25, 2017 3:37 am

Gippeto wrote:
That 22kg with a 4:1 lever would only be a little over 5kg.

Have the P17 back together and will bring it in to test on the scale.


I realised that my earlier calculation is wrong, 1" bore makes 0.785in2 bore area and to get 150 psi it needs 117.75lb which makes 53kg.. That would need 10:1 lever to pump. :(
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Gippeto » Wed Jan 25, 2017 12:38 pm

Took 25 lbs of force to close the lever measuring with the bathroom scale. This works out to ~132psi (910kpa)....much lower than I thought it would be. :? Will run it over the chrony to check velocity.

On the face of things, seems 130ish psi might be enough to be viable....
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Wed Jan 25, 2017 1:25 pm

btw i checked again the calculation for a 3/4" bore diameter and 130psi pressure it needs 57lbs
and 3:1 lever would be fairly easy to cock the system.

Theres one more thing here, to achieve a 130psi compressed air with 3/4" bore and 4" stroke length a 8,96552 mechanical compression ratio is required and it will need 0,197in3 head space in chamber.

From what i understand there will be 0,197in3 of compressed air and this needs to be at least 2 - 2,5 times the barrel volume to launch something from it doesn't it..?
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: farcticox1 » Wed Jan 25, 2017 4:17 pm

Are you planning on 1 pump to build the pressure or multiple pumps ?
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: farcticox1 » Wed Jan 25, 2017 5:50 pm

I'm actually getting interested in this now, if I didn't already have 4 diiferent guns on the drawing board already :shock: this could be No. 5

This may help, I like the way the pump linkage changes as the piston reaches it's end of stroke.

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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Thu Jan 26, 2017 4:42 am

Thanks for your interest, hope I can get this project to an end, the idea was simply a pellet or bb gun like pcp but without the "pre" charged side. So it needs a pump within. Like the one you posted, the 1377 or p17 or the one with Zoraki hp01. (BTW I really like the design and working principle of crosman 1377 i think it's simple and brilliant.)

Here the multipump action seems a bit hard to replicate because of the air compression chamber with 2 valves on 2 ends. (The orange part above the trigger on your posts image) The one in p17, which I'll try to replicate, may work with a simple extra space in the pump as a compression chamber. (Will be way easier I guess)

Another great fantasy about this project is multipumping the air to another chamber and using the compressed air for a minimum of 5-6 shots. Like I said earlier I am new to pneumatics so guess I first have to start with easy things.

(Ordered some steel pipes, fittings, valves and a qev already)
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Anatine Duo » Fri Jan 27, 2017 3:27 pm

Rather than an air cylinder have you considered using an inexpensive pump? That will have a handle and check valve in it. You might still want a linkage for leverage.
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Re: Pneumatic Cylinder For Bolt Action

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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Fri Jan 27, 2017 4:53 pm

Hello there, after Gippeto's opinion i am thinking of making the pump myself :)
Guess it'll be the first finished part.
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: farcticox1 » Sat Jan 28, 2017 12:33 pm

I tried a small cylinder as a pump, I think it was 1" bore, 2" stroke, managed to get 130psi on the full bore side, so now I am wondering if this would work, the reduced bore rod side would act as a precharge pump

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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Sat Jan 28, 2017 4:07 pm

my idea is a little bit different do you have a software to draw these or are you drawing in paint..?
btw sorry but i have to ask, do you have any equipment to try this..?, i need someone to tell it works.. :)
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: farcticox1 » Sat Jan 28, 2017 4:21 pm

I like to use MS Visio for the basic line drawings, all the parts are already loaded, you just drag and drop then connect them.

Image

I do dabble with Solid Works sometimes

Image

There is simulator software as well if you want to try pneumatic layouts

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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Sat Jan 28, 2017 4:27 pm

thats nice thanks for the info, btw the more i looked at your design the more i liked it.
Do you think a cylinder can fill a 100-150cc air chamber to 130psi by pumping..?
İ don't know how to do it but this may lead to a semi auto.
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Ragnarok » Sun Jan 29, 2017 9:14 am

farcticox1 wrote:now I am wondering if this would work, the reduced bore rod side would act as a precharge pump

It won't. In a double-acting configuration like this, the first stage would need to have a higher volume than the second, else you're not increasing the pre-charge pressure in the second stage.

Here, the first stage actually has a *lower* volume, so it's doing nothing useful. It just means the pump is drawing in most* of its air on the compression stroke rather than the return stroke, but I don't see any benefit to doing so.

*As the internal volume of the cylinder actually increases as the rod slides out, it would actually still need to draw in some air on the return stroke.
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Does that thing kinda look like a big cat to you?
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Jude » Sun Jan 29, 2017 10:31 am

Mates i was searching for homemaid airguns on youtube and ound something interesting here;
https://www.youtube.com/watch?v=is4tJXlDxqM
but couldnt understand where this one stores the compressed air, does it store it in the hose..? is it even safe..? :)

btw if anyone can understand how it works can you please explain it please..?
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Re: Pneumatic Cylinder For Bolt Action

Unread postAuthor: Ragnarok » Sun Jan 29, 2017 10:48 am

I'm not entirely sure. It's possible it's a coaxial configuration.
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