Open and closed bolt spool valves I sketched up in MS Paint ~2004.

[Siress]

I just stumbled across these gifs while doing some much needed data cleanup. Obviously I never followed through with them, and I know the DP G3 series are the appropriately engineered version of the open bolt variant. Did anyone make anything like the closed bolt variant? Just by looking at it you know it's going to be tricky to time the exhaust such that it doesn't effect the next ball to drop in, and that the bolt-opening pressure has to be higher than the bolt-closing pressure.

[Rusty Brass]

I love stumbling across old stuff I geeked out on. That closed bolt design is a trip. A slightly longer nose on the bolt with some extra travel might help with possible timing issues?

[Siress]

Absolutely. I think it'd even have a return spring built into it to smooth out the bolt-open cycle under HPA. Now days someone could just specify LP tanks only, though.

[moving_target]

I think on the old site... yoda9000 maybe? somebody, did a whole closed bolt spool development thread that reminds me of this gif

[DocsMachine]

[...] and that the bolt-opening pressure has to be higher than the bolt-closing pressure.

--Not necessarily. There's more area on the back of the bolt, so the same pressure could easily push it open. In any case, you'd want to be venting the air holding it open anyway.

I'm not aware of anyone who successfully made a closed-bolt spooler. Smart Parts tried like hell to make the 'second generation' Shocker (the '03-up ones) a closed bolt, since they'd spent the better part of a decade by that point bragging about how much better the Shocker was over everything else, thanks to it's closed-boltedness.

Supposedly they could never gt it to work right, and/or was too slow, comparatively, than an equivalent open-bolt, so they designed it as the open bolt and came up with that "Seal Forward Technology" crap to convince everyone it was just as good as a closed bolt.

Doc.

[Macdave06]

Supposedly they could never gt it to work right, and/or was too slow, comparatively, than an equivalent open-bolt, so they designed it as the open bolt and came up with that "Seal Forward Technology" crap to convince everyone it was just as good as a closed bolt.

Doc.

Smart Parts always was better at hyping up products than engineering them.

Sent from my SM-G960U1 using Tapatalk

[Trbo323]

--Not necessarily. There's more area on the back of the bolt, so the same pressure could easily push it open. In any case, you'd want to be venting the air holding it open anyway.

I was just thinking of this, you would have to play with the dimensions of the bolt but it would be entirely possible to run that on one pressure. The opening side just needs more surface area than the closing side

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[Siress]

--Not necessarily. There's more area on the back of the bolt, so the same pressure could easily push it open. In any case, you'd want to be venting the air holding it open anyway.

I'm not aware of anyone who successfully made a closed-bolt spooler.

Great point about venting. I think I was never motivated to do anything with the closed bolt variant because I never bought into the closed bolt theory. The only reason I even sketched it up was because my field owner was obsessed with closed bolt, and i was hoping hed finance development of a gun. I certainly do not want to open that Pandora's box again though. Care to sketch up how you'd balance out the surface areas? Not sure I'm envisioning the same thing you mean.

[DocsMachine]

Care to sketch up how you'd balance out the surface areas? Not sure I'm envisioning the same thing you mean.

-There's no real need to 'balance', though that's how a lot of markers do it. Basically, if you're venting one side and pressurizing the other, the 'area' acted on by said pressure can be anything you want.

Ideally, though, you want both volumes minimal, both for reduced air consumption (assuming the pressure is not also part of the firing burst) and the quickest cycle time. (Which used to be of paramount importance, of course, back in the ROF Wars days. )

As far as 'balance' goes, you could theoretically use a pressurized section as a spring. In the lefthand image, technically you wouldn't have to 'vent' the breech end of the bolt. If you just pressurized behind the bolt to the same pressure, the greater surface area would still force the bolt closed. Then when that pressure is released, the now-much-higher pressure at the front would push the bolt open again.

I say "theoretically", because in reality, it likely wouldn't work as well as actual alternating pressure, or even just a spring. But it illustrates the point.

Doc.

[JCC]

Look at the old Novas. The whole barrel moves, but they fire from what can commonly be described as closed bolt position though they technically do not have a bolt. With them a spring opens the breach, ball drops, air pressure builds up against the spring, and closes the breach. When its fire all pressure is dumped thus nothing holding spring back, it moves, ball drops, closes again. In theory this can be done easily with eyes to help the timing. Without eye high rof would be hard to achieve. Since it dumps entire air chamber on each shot, dwell is not a factor in velocity (assuming minimum setting is enough to empty dump chamber). You use eyes to tell it when the next ball is fully loaded, and then close breach and dump chamber fills. Have to use closed bolt eye logic like an eblade. You have 2 sets of moving parts. A spool valve that seals the dump chamber that is moved by changing airflow by a solenoid. Then a air passages from the dump chamber to the "bolt" that when dump chamber is full/filling would push forward and shut breach with ball chambered. When fired, the noid flips the pressure, opens the valve, dumps the air chamber firing the ball, no longer under pressure bolt moves back (via spring), next ball drops, upon being detected by eyes the noid is flipped off, dump chamber fills, and pressure from the dump chamber that is routed to the bolt pushes it forward closing the breach. Closed bolt and spool valve. Takes the idea of the Nova where it routes the pressure from the dump valve to move the barrel, and instead of moving the barrel you move a bolt instead. Eyes to get timing down and your good.

[Siress]

I think I get what you're saying JCC. Adding a spring (e.g. wave spring) here would help reduce the bolt-open pressure. Might even get it to match the bolt-close pressure. Nice one. And the eye logic - definitely on point there.

[JCC]

You add a spring there instead of any air pressure. Air pressure pushes forward collapsing spring and closing breach (as long as operating pressure is stronger then spring no issue). When you fire the gun air dumps down the bolt launching ball and spring no longer having any air pressure pushes bolt back allowing next ball to drop. Next ball triggers the eye that says were ready to fill dump chamber for next shot. The dump chamber air is same air that pushes bolt forward against the spring closing the breach.

Seems simple in my mind. You just eliminated the air where that arrow is point all together for proper spring. The valve that controls the filling of dump chamber has two jobs. When solenoid is de-energized and guns as rest it allows dump chamber to fill. When noid switches on air flows to other side of spool valve; it opens dumping the air down the bolt, but at same time that movement that allows that air to dump has to also cut off the air feed to the dump chamber. So lets say no ball is detected. The bolt would stay back and the air supply to dump chamber would remain blocked. As soon as ball drops solenoid flips, spool moves as the pressure changes to other side, it opens air to dump chamber, as dump chamber fills that pressure also closes bolt. Probably need around 7-10ms of dwell to empty the dump chamber completely, then you need an "open" time which will be determined by eye and how fast paint feeds (+ time to fill dump chamber once balls is chambered), so at 10bps and 10ms of "dwell" open time could be as high as 90ms (way more then needed with modern loaders).

Closed bolt was basically killed during ROF wars. It is inherently slower to feed, but now at 10.5bps and very capable loaders no reason it can't be done. The biggest issue you will find now is same issue I have playing with autocockers now. Modern paint sucks. One ball will roll out while the next takes a lot of force to move down barrel. Why going with a barrel a bore size are two larger is common practice as it provides more consistent results with crap paint, but with closed bolt that just means roll outs. A closed bolt gun would have to come with an actual preventative way to stop rollouts beyond sizing of the barrel bore. Adding detents to the barrel itself seems most logical to me. Automags had the barrels with the wire detents forever ago.

[Siress]

Nice write up, JCC. I agree on all points. It'd be cool if someone of means prototyped this for funsies... Might be possible by just replacing a bolt assembly... *cough* DocsMachine *cough* Maybe this is how the your airsmithing youtube channel starts, eh?

[JCC]

I bet this could be pulled of with a custom bolt assembly in some markers. Some markers already have a spring to help return bolt. The big thing is usually the bolt is part of the spool. Meaning its the bolt moving forward that also opens the air to then go through the bolt. The tail of the bolt would have to be separated from the front. Tail moving forward and back would still open the valve chamber dumping air down the barrel. The trick is getting air from that rear dump chamber to the back of the bolt where it would hold the bolt forward in closed position. I am going to try to explain this, but its going to be hard without picture.

The valve would be a round can as usual with holes through it leading to either side of the actual moving spool (bolt tail usually) hole in front of the can when air is directed their pushes tail back, hole in back of can lets air behind the tail pushing it forward. There is also a chamber of air behind the tail. When tail moves far enough forward bolt closes, and that chamber of air dumps. That is normal variety. We need the bolt to have already been pushed forward while the dump chamber is closed thus the need to make the bolt and spool different parts. You have to get air from dump chamber to the bolt to push it forward to closed position. This is the trick as its air from the rear of the gun has to get to the front. In a custom built gun you just make the passages into the body, but if retrofitting you would have to make a valve that along with having the holes that let air in through the walls of the valve keg to whatever part of the bolt it seals against you would also need holes length wise through the valve so the valve would have to be much thicker then normal. Those holes would route air from the dump chamber to rear of bolt holding it closed against the spring.

Then on firing the spool moves forward in the valve as directed by the change of air flow from the solenoid, when it moves far enough forward the air flow to the dump chamber is cut off, and just a hair farther forward the air dumps down the bolt firing the ball. There is no longer any pressure built up holding the bolt closed, the spring pushes it back, ball feeds, upon eyes detection of the ball the noid switches air flow back, spool moves the opposite direction, closing the opening that allowed the air out the bolt, and then opening the dump chamber to receive more air. That air fills the dump chamber, but is also routed through are special valve to rear of the bolt where it pushes it to closed position. Guns ready for next shot.

The big thing is the bolt is no longer part of the actual spool. The bolt works more like a pneumatic ram with a spring return. Ram airs up it moves forward, airs down it moves back. The movement of the bolt is not directing airflow, airflow is directing the movement of the bolt. Compared to the normal aspect of a little bit of air from noid moves the bolt, but the bolts movement releases the large amount of air that actually propels the ball. That still happens, but its not the bolt, but a spool that moves independently of the actual bolt.