Brainstorm on a mechanical SLG

[Trbo323]

Ok, wanted to post my idea here and see if anyone can poke holes in it to see if I'm missing anything



So, first thing I'm planning is to extend the threading in the air transfer tube and put in a plug, that's the red dot at the front. Next run a nipple into the existing threading in the front of the transfer tube to now take air out from there. That air goes through the green line into the trigger switch.

At rest the air goes through yellow tube, back up into the air transfer tube and into the dump chamber.

Once trigger is pulled the trigger switch changes air direction, cutting off flow into the dump chamber and directing air to the ram to pop the sear. Since there will be no incoming air into the dump chamber the bolt should remain forward until the trigger is released and air then flows back into the dump chamber

2 things I'm trying to sort out though,

1) how does the air get back out of the ram

2) exactly which switch and ram to use from mccaster carr. I'm thinking the correct choices will also get air out of the ram, just trying to sort out all the jargin

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[MrBarraclough]

Wow, that's an interesting, if elaborate solution.

To my mind, a mech conversion of the SLG requires accomplishing only one thing: tripping the sear in a way that allows it to reset even with the trigger held down. Blowbacks do this by using a sear that engages a friction plate only when under compression from the striker/main spring. There might be a way to do something like that with the SLG, but of course that would mean fabricating custom metal moving parts instead of using off the shelf pneumatics.

(Thinking out loud here) I like the idea of using a pneumatically operated ram to trip the sear, but worry about the difficulties of trying to redirect and cut off the main air supply when the trigger is depressed. I wonder if you could avoid the need to do that if you could rig a ram to pop up, but then reset without any change in the trigger input. A ram that vents when it reaches the end of its travel would be a start; if it was pushing against a spring then it would try to reset after venting. Venting could be accomplished by drilling a vent port lower than the position of the piston at the end of its upward travel. That still leaves a problem, since if you're continuing to supply air to the ram, it's either just going to bounce back and forth between both states as air rushes in to replace the lost air, or it's going to stick in the up/extended position if the incoming supply is able to overcome the spring bias even with the loss from the new exhaust port. I suppose the former could be a feature and not a bug if you wanted a mech full auto, assuming you could get the bounce rate to coincide with the cycling of the bolt.

It seems that what you need is a valve that when activated, cuts off incoming supply while also allowing air from some other reservoir to vent into the ram.

[markdem]

Its dirty but: quick exhaust valve + adjustable bleed screw installed into the purple line.

down side is it will piss air when trigger is pulled. Kind of annoying. But hey, maybe youll get lucky and the pressure differential (during switching) may be great enough to activate the QEV without having to bleed externally

[Jsc5150]

I would be reworking the sear mechanism to accept a traditional sear tripper blowback.

Physically operating a pneumatic ram to trip a sear kinda feels like building a car just to charge a phone.

That being said, the most efficient design is for people who hate fun

[Trbo323]

I would be reworking the sear mechanism to accept a traditional sear tripper blowback.

The biggest problem with doing the sear that way... Is that I absolutely hate how those feel

But also I thought about this. The way it moves in a blowback the sear actually catches the hammer and then moves forward about a quarter inch. There's just not that travel space in the slg bolt. It can't go 1/4 inch back from where it already catches the sear and going forward 1/4 inch means I just have to shorten the bolt tip by an equal amount so paint can still get into the breach. This then in turn means no bolt tip o ring and possibly an open bolt face up the feedneck while firing

The slg sear also catches the bolt from the front of the sear rather than the back like blowback so I would have to figure out some way of making the whole contraption work in reverse from what it's typically set up as

Physically operating a pneumatic ram to trip a sear kinda feels like building a car just to charge a phone.

That being said, the most efficient design is for people who hate fun

More or less this is more along the lines of a pnumag which is basically what I'm aiming for anyway

I would love to make one without the sear but that's a whole different level of work. Not to mention, assuming it worked right (big assumption) it might be just on par with the modern mechanical spools so, no real benefit at that point.

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