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Discussion Starter · #1 ·
Hey everyone, I've been wanting to try this for a while and decided to make a how to on it once I got it working. This is a really simple technique that is used in the home brew pneumatics world for making a sealing face or a low pressure piston, so I thought Id give it a shot here after seeing Vindi do the same thing with a mouse pad in his DMR thread.

I will skip the measuring process since anyone doing this should have read Vindis DMR thread already, and get to the meat of it. What Im doing here is using hot glue to make a spacer that is fixed to the piston head instead of having to find a pad and glue it to the head. The advantage to this is that its cheap, super simple, it provides a good seal (if done properl) and you can do it easily without having to find that "perfect" thickness item to space your piston.

1. remove your O-ring and do the measurements.




2. grease the inside of your cylinder and insert the piston, however make sure the piston head is clean so the glue will stick. (silicone spray works great for this)


3. space the piston in the cylinder appropriately and tape it in place. for my application the spacing was 1/4" and i happened to have some 1/8" gasket material laying around so I was able to use that. (I was originally planning on just using that, but this looks cleaner in the end and I wanted to give it a shot.)



placing the whole thing face down on the table is probably the best way to do this part.

4. fill the space with hot glue. the glue will look bubbled out when you fill it in, but it will flatten out when it cools, you want it to be level if possible. after this you should put it into the freezer immediately! this will help it to set faster and cool harder than just letting it sit out, leave it in there for about 15min just to be safe.


5. when it cools it should be dark and firm, then you can remove the tape and push it out from the back end and it should look like this.


6. if you need to you can clean it up with an exacto knife and if you really need to you can cleanly take it off and start over.
 

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woogie said:
Quick question....... What will this accomplish?

I don't use AEG's so I have no idea what this will do or does. So please enlighten me..
It does a few different things. First, it times your piston with the sector gear (the gear that engages to piston) to be a perfect mesh. If not, it's fairly easy to strip out a piston in a high velocity set-up.

Second, it "softens" the impact of the piston flying into the front of the gearbox. This is especially important in a version 2 set-up because they have notoriously weak front ends, and anything to dampen the impact is beneficial and will save you move in the long run.

Third, depending on the material used, it'll dampen or change the pitch of the AEG cycling, which can help with the generally loud audible noise an AEG makes. This can give you a little extra time to get a few more shots of or give you some extra time to bug out because it's harder to locate where the shots are coming from because of the change in sound.
 

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+1 from me too

Splendid idea, just a few of things I'd add to it though....

1/ I'd abrade the face of the piston with some coarse sand paper to aid in the hot glue sticking, and remaining stuck, to the piston head.

2/ I'd put a single thickness of thin tape around the inside of the cylinder, and then grease it, so that the new piston head wasn't murder tight in the cylinder, as it would help keep the existing piston head central in the cylinder as they are generaly smaller in diameter than the cylinder. It also shouldn't be forgot that the piston lifts up very slightly when its engaged by the sector gear (due to the slack in the piston runners) and this will place undue friction on the new square sided piston head, which if will in time (and if you havn't keyed the piston face properly) cause it to peal off

3/ I'd then try and reinstate the vent holes in the face, but adding them with a nice smooth port in to each one to make them nice and efficient.

Other than that, an outstanding idea that I wish I'd thought of, and 1 I will probably rob when I fit my new piston and head into my EMR
 

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Ok I got ya. Hell this may work great if you have a problem with your piston in your bolt rifle as well.

May have to see what this will do, now all I need is a gun to mess around with.... hmm. ... anyone wanna donate a rifle
 

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Discussion Starter · #9 ·
vindicareassassin said:
+1 from me too

Splendid idea, just a few of things I'd add to it though....

1/ I'd abrade the face of the piston with some coarse sand paper to aid in the hot glue sticking, and remaining stuck, to the piston head.

2/ I'd put a single thickness of thin tape around the inside of the cylinder, and then grease it, so that the new piston head wasn't murder tight in the cylinder, as it would help keep the existing piston head central in the cylinder as they are generaly smaller in diameter than the cylinder. It also shouldn't be forgot that the piston lifts up very slightly when its engaged by the sector gear (due to the slack in the piston runners) and this will place undue friction on the new square sided piston head, which if will in time (and if you havn't keyed the piston face properly) cause it to peal off

3/ I'd then try and reinstate the vent holes in the face, but adding them with a nice smooth port in to each one to make them nice and efficient.

Other than that, an outstanding idea that I wish I'd thought of, and 1 I will probably rob when I fit my new piston and head into my EMR
Thanks vindi, that means a lot coming from you. a little feedback about your additions though...

1. I used a similar technique to this for a high pressure low volume gas cannon I built. The piston was a solid piece of poly carb bar and I used this exact technique to put an end on it. I messed up the first time so I had to cut it off, the hot glue stuck so well to the face that I couldnt get all of it off with the razor. So although abrading the face would make it stick a LOT better, I'm not sure its necessary, and I wasnt sure if this would work so I didnt want to take the chance of messing up my face


2. Part of the advantage to this (as I see it) is the seal that it creates. The piston still moves very freely inside the cylinder due to the silicone residue on the cylinder. And I can see what you are saying about the square face, and I had actually thought about that, I have been thinking that I would take a hot piece of metal and melt the new face to round the edges off a bit... not sure if this would work over time, but its worth a shot. (Ill know better once I get the right gears installed and can start using it again)

3. right before I started with the glue I was thinking that I should try to preserve the holes, but I was kind of at the point of no return
. A way that I was thinking of doing this would be to put spacers in before gluing, but I'm not sure what. Or what I did in another project was to heat up a pin and push it though the glue, this just requires cleaning the face with an exacto knife after since you are pushing glue out to make the holes.
 
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