Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

BLACK BETTY - HPA Select-Fire Foam Blaster

by DaXLR Nov 23, 2018
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Ironically, I've been kicking around a concept not too dissimilar to yours for years. I've never gotten past the systems test stage myself however.
For standardization and reducing internal component size, you might want to give Clippard ( http://www.clippard.com ) a look. I've had good luck with them and their pneumatic components can get downright tiny! Also they have pressure vessels that are pressure rated, so you dont have to roll the dice with making your own. You can get a lot of their inventory through McMaster Carr if you need it in a hurry as well.
Using a single action piston to cycle the bolt would also eliminate the need to wind your own spring. (I realize it's a little late for this now, but I'm thinking of improvements for V2)
Introducing some sort of flow limiter (like a needle valve) between the solenoid valve and the bolt piston could help delay the action of the bolt long enough for the dart to clear the barrel, thus allowing more consistent velocities. Or so goes my thinking.

I'm definitely going to keep an eye on your progress with this!

I'll definitively check out Clippard if only to have a consistent source for the build parts. Also McMaster Carr would be super convenient but they're a pain to deal with for shipping to Canada (even though I have a registered buisness, since it's under my name they often just cancel my orders stating they don't ship to individuals).

I'll definitively consider the single-acting piston for the next iteration. Making my own spring was neat, but ultimately it was a bit of a waste and added complexity.

I tested the blowback with a needle valve and it doesn't add any significant delay. I'll need to come up with an actual, mechanical delay to the action, but I already have several ideas that don't add much complexity.

Thanks a lot for the input and stay tuned I'm going to get back on the project soon and try doing a full devlog on youtube to get people's input as I go.

ok can u make a full parts list and an estimated cost i would liketo build one but i need to know the cost thx

man this is gorgeous can u make it so i can make it on my 5x5x5 printer bed thx

I don't plan on doing any kind of major redesign to account for smaller print beds. It's easy enough to slice down the .STLs yourself if needed.

That thing is awesome! But it looks sooo difficult to make ^^