Balance Spool Valve

[josephlys]

I've looked at balance spool valves and they seem to be more reliable than close ratio T-piston valves that rely on a pilot valve to fire. If I'm using 3/4'' PVC setup, then should I look for 3/4'' o-rings or rubber washers that fit snugly, cause now what I should look for is a tight fit right. Is it difficult to get a perfect seal? Here's a rough sketch of what I'm hoping to build.

[POLAND_SPUD]

that's basically a QDV

[josephlys]

How bad would the recoil be if I'm using light ammo like 80gr-100gr projectiles. Piston would be 500gr (30g+) the most. I'll use stacked rubber washers as the bumper. Does this look safe?

[far_cry]

500 gram its a lot , it can break the pvc easily

make the piston lite as possible

[jackssmirkingrevenge]

I think you will find this helpful: http://www.spudfiles.com/forums/tutoria ... 21740.html

Note that the tee has to be significantly larger than the barrel in order to allow enough flow.

500 grams for the piston sounds like a gross overestimation, but look to make it as light as possible. Alternatively, try andrepent for your sins

[Brian the brain]

500 gram is ridiculously heavy.
You could use a bolt and washer type piston and get a fraction of that weight.

If you have an electric drill you can easily file down the washers to the required sizes to make it fit perfect.
The idea is to use a thick rubber washer, that fits inside the O-ring ( nice fit) and then keep the O-rings locked in between two larger metal washers on either side of that.
Lock them in place with locknuts.

The rubber washer keeps the washer-to-bolt gap airtight and
makes the O-ring seal adjustable.
Squash the rubber washer and it will expand, in turn pushing the O-ring onto the pipewalls.
Ideally the O-rings should fit perfect though and don't need the adjustment to seal.

I personally prefer to use just one O-ringed seal and keep the barrel side seal flat.
Just like in a piston valve basically.
This would be better than an O-ring IMHO because it causes NO drag and it is not submitted to wear like an O-ring that needs to pop in and out of a pipe, of slide over a hole, wichever form you choose.

The trick is to get the flat sealing surface OUTER diameter ( or rather the pipe it seals onto) identical ( or slightly smaller, but only just!!) to the other sealing "surface".
Wich , in this case, would be the INNER diameter of the pistonhousing

[Gippeto]

Piston would be 500gr (30g+) the most.

Where's Stuey when ya need him...what part of 500 GRAINS did you guys NOT understand?

Busted for NOT reading the post.

I know....I do it too.

[jackssmirkingrevenge]

Ohhhhhhh.... right

carry on

[Technician1002]

I have not built one in a T with a split spool, but the one piece spools with lots of bumper performs well. Using a bumper on a bent rod will bend it lots more. Plan on a substantial bumper the spool will strike. A directly connected trigger is a bad idea. Look into ways to prevent the trigger from slamming back when triggered. it packs a punch.

[josephlys]

Piston would be 500gr (30g+) the most.

Where's Stuey when ya need him...what part of 500 GRAINS did you guys NOT understand?

Busted for NOT reading the post.

I know....I do it too.

Lol

Technician1002, I was weary about the trigger as well, it looked like it would have crushed my fingers. But it was a simple design with less moving parts. Oh well

Is there really any difference between a '2 piece spool' and a '1 piece spool' in a T, cause both look like they work the same in a T?

[Technician1002]

A 1 piece spool is used in a small gap to increase strength. It is easy to make a 1 piece spool slide on the trigger bar. A 2 piece spool is made to reach a further distance. The extra rod in the middle adds mass and prevents use on a sliding rod. Allowing the spool to pop without smashing fingers is a good thing. The design as shown above may glance off the bumper, bending the rod in the process. A gap width in the middle of the T about 1/2 the diameter of the ID of the barrel should work well and permit the use of a short spool.

The shorter the spool travel the less speed the bumper has to endure. A balance between the distance the valve opens and how far the piston launches before bumper impact is an art to fine tune for both performance and reliability.

A spool in a T may peel the O ring off the spool as it pulls into the T. I recommend using a through pipe instead with ports to keep the rings on the spool.

One of my early designs did launch the o ring when shot with more than about 50 PSI. I've used ports instead of a gap for this reason ever since.

[al-xg]

http://www.spudfiles.com/forums/paca-mk ... 21703.html

This is basically the same system as described in your first post.

[Hubb]

Look over Tech's spool valve. It is one of the best I've seen and should be able to be configured into what you are looking for.

[Brian the brain]

Busted for NOT reading the post

Busted for using the metric system exclusively on a daily basis and for assuming he meant gram.
Although it is technically incorrect to use gr. to indicate grams it is widely used, in my counrty at least.


I would have never guessed it should be grain...
Simply never occured to me.


Ask a Dutchman or Frenchman for that matter what this means:
The more you drink, the more W.C.

I bet you he won't think of double vision...rather of a toilet.

[josephlys]

I think I'll use more bumper, extend it, add more padding. Or maybe change the trigger from L shape to a T shape. The extension will help prevent the trigger that I'm pulling from coming down on me fingers, maybe even shorten the trigger. I'll also try to cut down any unnecessary weight. Also use a T-fitting as the handle instead of a L-fitting. A 25gram spool @ 8bar shooting 5-6gram ammo doesn't sound too violent. I really like the 1 piece trigger, I'll see what can be done to make it safe to use. Hehe wish me luck, and thanks for the all the constructive feedback.