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DSTV - Save the birds, ban the (blow)guns

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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DSTV - Save the birds, ban the (blow)guns

Unread postAuthor: dongfang » Sat Jul 28, 2007 3:47 pm

I got tired of triggering my piston valves with expensive sprinkler valves and blowguns with too little flow, so I thought up the DSTV (Darn Simple Trigger Valve). It introduces pull-cord triggering to spudding.

The pistons should be aligned so that they open at the same rod position (so use a threaded rod for easy adjustment).

I'm about to build one now. I found some endcaps that slide beautifully in some reducers, which again fit inside a 32 mm tee.

OK will tell you later if it also works :lol: Need to get some o-rings and some 20 mm pipe or rod first.

Regards
Soren
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Attachments
dstv.PNG
The DSTV. The curly blue thing is a spring (any should be ok). The yellow cross section stuff (hmm, almost invisible) is o-rings.
Pilot chamber of piston valve attaches on the left.
dstv.PNG (8.99 KiB) Viewed 1535 times
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Unread postAuthor: Gepard » Sat Jul 28, 2007 3:51 pm

Quick thoughts on it suggest you add another disc to the threaded rod in the middle so when you fire the air won't escape through the pilot....

EDIT: You don't need the spring do you?

Michael
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Unread postAuthor: noname » Sat Jul 28, 2007 3:56 pm

I made a manual piston valve before I knew how pneumatic ones worked. It was similar to this concept, and worked better than the ball valves I had previously been using. Should work.

If you want to pilot valves with a blowgun, make a diaphragm valve. I have a co-axial with a 2 1/2" (~63 mm) chamber that can pilot with a blowgun.
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Unread postAuthor: dongfang » Sat Jul 28, 2007 4:33 pm

Hi,

It's a trigger valve; it's supposed to just dump air into the open.

noname: Ahh, yes that's another way to use it; enlarge it, add Gepards's stop-the-down-flow disk and put a barrel on it. Anyway I did write it's for triggering a piston valve.

What do you make the diaphragms of then? And (noname), what is the seat diam. of your valve? I suppose you make them out of a tee, with a reducer glued into one end, with a pipe through it that continues into an elbow? The diaphragm seals on that elbow? It there a something supporting the elbow, apart from the pipe it is glued to?

Regards
Soren
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Unread postAuthor: noname » Sat Jul 28, 2007 5:01 pm

I use 1/16" or 1/8" sheet rubber. They work in inline valves or in a regular co-axial setup instead of a piston. They also work great in Ts.
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Unread postAuthor: dongfang » Sat Jul 28, 2007 5:24 pm

Hi noname,

OK, thanks.

How do you fasten the diaphragm around its edges? Of course a union could do it, but inside a tee?

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Soren
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Unread postAuthor: Alabaster » Sat Jul 28, 2007 9:43 pm

Whats to stop the little wire from snapping and the bolt from shooting out towards the user?
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Unread postAuthor: noname » Sat Jul 28, 2007 10:25 pm

I cut the diaphragm so that it's about 1 1/8 the size of the pipe, then push it in. The edges get bent towards you, and that holds it fine.
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Unread postAuthor: Alabaster » Sat Jul 28, 2007 10:43 pm

Nice cause if this works it would be a good innovation.
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Unread postAuthor: dongfang » Sun Jul 29, 2007 6:20 am

Hi,

EDIT: You don't need the spring do you?


No. It's for luxury only. Auto reset. And for safety: I forgot to add a stop on the drawing to prevent the bolt from going UP. Assume there is one. The spring also helps prevent accidental firing because of - well, whatever could make the bolt creep down.
A second stop to keep the bolt from going too far down - so one can just fire by pulling it a little violently maybe - would also be nice.

Whats to stop the little wire from snapping and the bolt from shooting out towards the user?

What would make it do that? Ah, OK, maybe I see something: Move the red piston seats a little farther out towards the ends of the tee, and move the pistons accordingly.

Thanks noname; so you jam the diaphragm between the tee body and a pipe? Maybe I'm asking silly questions but I have never seen pictures of a home made 'phragm valve, and never tried to make one myself.

This silly little trigger valve was really to have been a miniature DFTV. But I discovered an error in my design, on the train back from my parts supply store*, so I thought up this as an emergency solution instead. But it might end up better than the original plan.

Damn, that has happened many times: I have coffee and do some work or whatever on the way back from where I buy parts - and immediately I think up a much cooler idea for the gun design. Then I am left there with a pile of non refundable o-rings and other stuff for an outdated design revision :(

*"Koi-Breeder", where I (to their great amusement when I demonstrate the guns,and to their great annoyance when I call them and ask them about the exact inner diameter of a blah blah..). They are not amazed at people who happily pay ~$2000 for one koi, however. A koi is a fish.

Regards
Soren
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Last edited by dongfang on Sun Jul 29, 2007 6:27 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 29, 2007 6:26 am

I got tired of triggering my piston valves with expensive sprinkler valves and blowguns with too little flow


I like your idea, but why not simply improve your piston specs (tight fitting piston, minimal pilot volume etc, as discussed in the other thread) and continue using the same actuation blowguns?
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Unread postAuthor: dongfang » Sun Jul 29, 2007 6:37 am

Hi jack

You mean, firing a piston valve directly with a blowgun?

OK, it's because I would have trouble getting an o-ring on the piston. It would require me to move the piston (and valve seat) further out towards the pilot end of the tee. That's OK but there would be very little clearance left for piston travel (or I'd have to take chances with endcap strength).

Also, I understand that (some) people who had perfectly sealing piston valves still experienced drastic performance improvements when triggering with something with a better flow. I think Joe from Spudtech mentions a factor 4 improvement in opening speed when he got the idea of using a sprinkler valve.

For my first piston valve I will continue using the sprinkler. The point is, I don't want to buy another sprinkler for the second. Too expensive here.

But I will make the DSTV with a threaded bushing, same as the spriklers, so I can move them between the valves and compare.

EDIT: I'll also try to get the bugs out of my miniature DFTV design. I believe it could make a great blowgun controlled trigger valve.

Regards
Soren
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Unread postAuthor: spud yeti » Sun Jul 29, 2007 8:02 am

I like your idea, and think that you should continue to build it, because even if something else might give better performance, at least its original and cheap. Only 1 question, why dont you just put it inline like this:
Image

Just an idea though, but I like your concept.
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really good quote/phrase here
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 29, 2007 10:17 am

I guess i'm spoilt with the epoxy style construction I use, it lets me keep pilot volume to an absolute minimum and so far I haven't had to actuate with anything with larger flow than a schrader valve.
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Unread postAuthor: spud yeti » Sun Jul 29, 2007 11:54 am

Wow, thats a real luxury. I also try to keep my pilot volumes to a minimum, giving the 1/4 diameter of piston travel.
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really good quote/phrase here
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