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Discussion Starter · #1 ·
I went a head a started the side project for this summer. Thanks to a link posted on the Polarstar HPA Gas Box thread I downloaded the plans from http://kuba-t1000.com/minigun/index.php?akcja=tutorials_airsoft_aeg_to_hpa_conversion_mod and bought two feet of 1" diameter T6 extruded aluminum round rod from here http://www.onlinemetals.com/merchant.cfm?pid=1090&step=4&showunits=inches&id=195&top_cat=60 .

So far I have built the external spring guide. Its a little out of spec but I think it will still work. We'll see.



 

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Discussion Starter · #3 ·
Thanks for the bill of confidence. Turing these on a wood lathe with hand tools is not exactly ideal but so far it looks like this will work since most of the sealing surfaces have o-rings. I'm not a machinist by any stretch of the imagination. I actually feel more confident building the mosfet and flashing the hardware with the program.

I'm not getting much done this weekend but I should have some time this coming week.
 

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Discussion Starter · #7 ·
Looking into the system's design I think I can increase the volume 1.5 times by extending it. I'll revisit my idea once I finish this one first. I'll probably use a CA SR-25 MB for this but this could work in a V2 as well. Basically, I can't run over 125PSI in my gun since its homemade and local rules say so. I can't complain, I help create them. But there is nothing said about volume which will allow me to dump even more expanding gas into my inner barrel resulting in a huge velocity gain. This change in the design will require permanent changes to the MB and would never be able to use it as an AEG but I don't care about that anyway. I also found brass tube that has the same dimensions of AEG cylinders and probably bolt action rifles too. Using this as cylinder stock I can create what ever length I want and basically increase and volume to what ever. This would be a cool add-on for the A&K SVD or anyone looking to make a semi or bolt action rifle external air. Anyway, this is all speculation. More later.
 

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mateba said:
Looking into the system's design I think I can increase the volume 1.5 times by extending it. I'll revisit my idea once I finish this one first. I'll probably use a CA SR-25 MB for this but this could work in a V2 as well. Basically, I can't run over 125PSI in my gun since its homemade and local rules say so. I can't complain, I help create them. But there is nothing said about volume which will allow me to dump even more expanding gas into my inner barrel resulting in a huge velocity gain. This change in the design will require permanent changes to the MB and would never be able to use it as an AEG but I don't care about that anyway. I also found brass tube that has the same dimensions of AEG cylinders and probably bolt action rifles too. Using this as cylinder stock I can create what ever length I want and basically increase and volume to what ever. This would be a cool add-on for the A&K SVD or anyone looking to make a semi or bolt action rifle external air. Anyway, this is all speculation. More later.
Ah, loopholes. How I love them.

Hope it work, if it does, it will be amazing!
 

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mateba said:
Looking into the system's design I think I can increase the volume 1.5 times by extending it. I'll revisit my idea once I finish this one first. I'll probably use a CA SR-25 MB for this but this could work in a V2 as well. Basically, I can't run over 125PSI in my gun since its homemade and local rules say so. I can't complain, I help create them. But there is nothing said about volume which will allow me to dump even more expanding gas into my inner barrel resulting in a huge velocity gain. This change in the design will require permanent changes to the MB and would never be able to use it as an AEG but I don't care about that anyway. I also found brass tube that has the same dimensions of AEG cylinders and probably bolt action rifles too. Using this as cylinder stock I can create what ever length I want and basically increase and volume to what ever. This would be a cool add-on for the A&K SVD or anyone looking to make a semi or bolt action rifle external air. Anyway, this is all speculation. More later.
As soon as I posted that link I started thinking of ways to make it more efficient too. But yes, the number one thing that I saw off the bat was tha tyou can create a lot more cylinder volume... if you wanted to. There are a lot of ways that this design can be improved, but its is a really simple way to modify your existing AEG with a minimal amount of work.
 

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Discussion Starter · #10 ·
Here are some of my other parts. The piston (center right) is screwed up. The rear plug (far left) needs a little work or complete replacement if I decide to use a CA-25 MB. The cylinder head (far right) probably looks familiar, which means that V3 will work since the piston length is the only determining factor. The spring guide was posted above. I also included a piece of stock 1" T6 so you guys can see what it looks like before I even work on it. I might get some pictures of my work station later. The new piston is about an hour or two away from being done. I have thought about get some of this 1" brass tubing. http://www.smallparts.com/dp/B000FN43GY/ref=sp_dp_g2c_asin . Its not cheap but its within spec for standard airsoft cylinders. I could make an extended cylinder for my SR-25 and have plenty left over for what ever later. Might be useful to you AEG guys out there. It's OD, ID and wall thickness is guaranteed to ~.0015" tolerance.

Anybody got the exact measurement of a CA-25 air nozzle? I am guessing 23.25mm but I have plenty of room for now.
 

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Discussion Starter · #12 ·
Thanks! No worries on the lathe. I got a couple of longer drill bits today. Hopefully this piston will do better. I will still need to redo the rear plug for the extended cA-25 cylinder. Need to order my solenoid, fittings and tubing if this part turns out alright. I am still looking to a Solenoid that will fit inside the MB. I'll explain turning the parts in detail after this is complete. Even if this goes all to plan I will still need to build a MOSFET and flash it with the right coding.
 

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Discussion Starter · #13 ·
Well I got into the shop tonight and got about an hours work in. Its not much but I did some more pictures.

This is my work station


These tools do most of the work


Piston before I got started tonight


Piston after I finished tonight


Well maybe tomorrow...
 

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I'm surprised you've had so much success with the wood lathe. I did some work on one trying to turn some poly carb bar stock for a simple piston on a spud gun build a while ago and was having a hell of a time getting a good smooth surface on it. My hat is off to you sir.
 

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Discussion Starter · #15 ·
Thanks
I call it "chattering" when it seems that the chisel has apparently been bouncing of the surface and makes small gouges. I get a lot of that unless I have just sharpened my tool. I think heat has something to do with it. I try not to take a small final cut and I use 600 and 1500 grit (dry and wet) sand paper afterward. I have learned a new level of patience, I am still not at the point on this part if I can even use it yet.

I ordered a 3V110-1/8 (12v grommet) solenoid valve and some fitting from STC Valve this morning. http://www.stcvalve.com/3_Way_Directional_Solenoid_Valve_Specifications-3V110.htm Should be here early next week. I know a little premature but I think I am going to get this one right and I want to have the valve here when its done. This solenoid valve barely fits inside my donor gearbox (Echo1). I will most likely force it inside even if I have to cut the sides out. But, it should all fit. I might even be able to keep the Mosfet and battery inside the lower receiver and pistol grip. I am thinking about an 11.1v 1500mah Lipo but only because it would be fine for other uses. This system will not need a lot of capacity and a 800mah would be more than enough. Either way its a ~$7 battery. http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6307

I have an idea about a front gearbox spacer for a V2 to use in a SR-25 body. I think I can use the first piston if I can get the drill bit out. This part will help guide the piston's nozzle into the hopup unit and also allow the hopup unit to seal off to the gearbox. I think I will still need a spacer for the rear but cutting a piece of stock to length and drilling a hole in it will work if I just want to use a longer screw.
 

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Discussion Starter · #17 ·
I might be able to salvage piston #2. I got it drilled fine this time but I drilled too far and lost my enter for making the whole that matches the rear plugs nub. I'm gonna try a little JB Weld and see. I agree that the ER-25 is not the best base not is using a standard V2 in a replica that an accept an extended V2. I like the idea of a V2 since its more compatible with other guns. Besides I think I'll need to cut the sides out of the MB to get he solenoid to fit inside. I would be a waste to tear up a CA MB not to mention there is way more material that would need to be removed.

Received the solenoid valve and fittings today. Will pick up a center drill on Monday and try to correct my error. Once I have that done I will get a small 11.1v Lipo for it.
 

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Discussion Starter · #18 ·
Good news, I was able to salvage piston #2 with JB WELD. Not my first choice but better than scrapping 6-8 hours of work and material. I worked on tolerances today, cut a ACM spring down and made the front spacer for a V2 to fit a SR-25. It's ugly, but it should work. I used piston #1 to make it so it has some unnecessary character.

I don't have any pictures today but I may have a video tomorrow. I have the parts done and its a matter of getting two filed down to my replica's specific lengths and buying a lipo. This will be operating on just mechanics since I have yet to build the MOSFET to control this digitally. But, it should feed BBs and shoot in semi-auto.
 

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Discussion Starter · #19 ·
I works from what I can see. I don't know where my 1/8NPT tap has gotten off to so I can't put a fitting inside my rear plug. I just put my 1/4 tube in the rear plug which is a very loose fit. I don't have any o-rings on any of my parts but the solenoid valve works and the piston nozzle is moving with 100PSI and up. I'm happy! The design works, now all I have to do is actually hook it up and seal it off. I'm using my solenoid off the manual switch but I have my battery ready. I got a Thunder Power 11.1v 1350mah 20c LiPo. I know, I'm over my budget now but I can make it fit inside my pistol grip. I'll have to route my air hose out the buffer tube but thats no big deal and has been done before.
 
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