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blow forward design

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blow forward design

Unread postAuthor: bobgengeskahn » Wed Mar 17, 2010 3:40 am

Hello all,

I've been brainstorming for the last few days and came up with an idea for a "bolt action", but tonight I decided to try and adapt it for a semi auto/self loading set up and wanted to know what ya'll think. The plan is to use regulated CO2 and 6mm airsoft BBs. My concerns are mainly about the return mechanism (the smaller piston that pushes the cylinder back), I have only seen a few that work off of a bleed, what considerations should be taken when designing a bleed system like this? or is there all together a better way to do this?
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Attachments
Slide valve 2.jpg
Epoxy is dark green, the blue is the hop-up bucking (for those familiar with airsoft), the purple is the actual rifle body, the gold is the barrel and is longer than shown :-p, the regulator on the back is a palmers direct stabilizer that is threaded straight to a 1/8 NPT brass fitting, there is a spring that is not drawn that is behind the chamber that pushes it forward when the trigger is pulled. The proportions are all off, but you can get the idea.

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Unread postAuthor: iknowmy3tables » Mon Mar 22, 2010 8:18 pm

the idea of a sliding chamber seams pretty ludicris, that requires more force to move, the 2 o-rings also tend to create a lot of friction that must be overcome, and blowback/gas piston designs tend not to give a lot of cycling force unless the pressures are really high

and the valve is opened by spring force that also closes the bolt right? but the maximum spring tension force

due to lack of reply I believe not many people are understanding your design including myself, I would highly advise posting more diagrams of the system at different stages of operation, possibly with colored in areas of pressure. and ammo in the magazine would help cause it took me a bit to realize the hop up was not the loading port

edit: actually cut out the regulator and hop-up because they add a lot of confusion

I actually recall a very similar design that we deemed unpractical long ago because the friction in the seals was too much for blow back force cycle
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an old design deamed unpracticle.PNG
an old design deamed unpracticle.PNG (15.14 KiB) Viewed 741 times

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Unread postAuthor: bobgengeskahn » Mon Mar 22, 2010 8:45 pm

lol, thanks for the reply, I had totally forgotten about this post and have basically taken it back to the drawing board.

as far as the concept with the moving chamber, I had thought about that or a moving spool on the inside of the chamber after I saw the video on technicians' QDV. He was operating his smaller cannon at 100 psi (if i remember correctly) and he said it required only about 6 pounds of force to pull the valve back.

This idea was hopeful that there would be a similar result if the stem was pressurizing the chamber, and the chamber was moving to cut off the supply.

once i get something else worked out I'll try to get an animation working (never done one before but i know there are threads on it) and ill remember to cut out the hop-up and reg :tongue1:


Edit:
I did not notice the .png that you posted. that design, in concept, looks a lot like technicians QDV... is the reason that his requires so little force to actuate because a. his design is high volume, b. low pressure and c. large surface area on the piston???? if so, is this style of a QDV simply impractical with a high pressure, low volume system??? (since thats what im going for)
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