Is this a feasible valve design?

[Splathappy]

you could dump a imput reg to set the operatation pressure and
put somthing like a rock to regulate the volumne of air .

[Drake]

One thing i've noticed in your design.

the way that the input hole from the power source is between two o-rings, which you have higlighted in red. The dynamics of the air, would push it forward and possibly shoot the bolt out of your marker as soon as you turned on your air source. You need to anchor it to something at the back, so it doesn't take a trip.

You could actually hook up a trigger mechanically to move the bolt/spool back and fourth manually, with a rod and pivot, similar to the three-way articluation of a Palmer Blazer. Then have a spring or something to reset the spool, like a spring that resets the mag bolt.

[athomas]

Originally posted by Drake
One thing i've noticed in your design.

the way that the input hole from the power source is between two o-rings, which you have higlighted in red. The dynamics of the air, would push it forward and possibly shoot the bolt out of your marker as soon as you turned on your air source. You need to anchor it to something at the back, so it doesn't take a trip.

The air pressure would push the bolt to the back using the rear o-ring with the same force as the push to the front on the forward o-ring. The result would be that forces on the bolt would cancel out letting it sit motionless.



All that is needed is a ram to push and hold the bolt forward for a certain amount of time while the air is allowed to flow out the front and then pull the bolt back when it is done.

[Drake]

Well, the problem is that when he gasses up the marker, the air will flow up and out, and push one side more than the other.

Plus, that's ideal physical conditions. I really wouldn't rely on the pressure exerting the equal amount of force on both sides of the bolt.

[athomas]

The only area that pressure will be exerted will be on the o-rings themselves. Any other pressure will be exerted inward on the bolt equally on all sides.

Up and out would mean out the back and out the front at the same time cancelling each other out. Therefore, no movement. Any differences would be so small that it probablty wouldn't allow for any movement.

The bolt will be attached to some sort of ram and/or sear which will move it or hold it in place as well.

[hunter100]

before you guys get too excited discussing the problems with the design, you should know the original post was only for the valve design. I left off the rest of the stuff because I was lazy and didn't draw them out. Here is what I was thinking for the actual gun design

[hunter100]

oh, just to clarify, the thing on the bottom is the solenoid spool valve, the same used on an impulse or intimidator. The broken air passage going to the solenoid goes all the way to the front, I didn't want to draw it crossing the high pressure passage, I thought it would be confusing as it is a seperate air chamber.

[Crimson_Turkey]

Is the area between the front o-ring and the 2nd o-ring needed? Just move the feed neck back a bit and chop that off.

[QUINCYMASSGUY]

thought

OK, looking good but you might have hit two design snags. On timmys, viking, bushmasters, etc, etc, the reason a LP reg is there is to be used to cycle the gun, not shoot it. There is no way a gun will fire on 100psi and most lp regs go as low as 30-50 to cycle the gun. It would be the 200-400psi straight from the VA that would need to go up in the bolt to fire. The second snag is the airline that you said will go to the front. If the bolt goes forward and gets a brief blast of air from an airline on the other side of the breech, it would have trouble cycling back. Look into how a ram works, you see it is different. I like your originality, and if you want to try something other than a ram thats cool, but I don't think this way of resetting the bolt will work well. Keep trying though, trial and error produces results.

[hunter100]

Crimson_Turkey: Yes, this area is necessary. You need it to maintain an airtight seal around the bolt. Otherwise, when the tip of the bolt passed the feed neck, all the pressure would vent up the feed neck. By adding the space, it keeps the pressure sealed in the tube until the tip of the bolt is in the barrel.

QuincyMassGuy: I think you might have misunderstood my design a bit. The low pressure reg is used to supply air to the back of the bolt only via the solenoid. The lpr would be screwed into the front of the high pressure side of the gun in order to get air, but a hose would go from the reg to the low pressure side. The lpr is only used to push the bolt forward, the spring returns it. I don't see why the bolt would have trouble cycling though, once the seal was breached and the paintball fired, the blowback action on the bolt as well as the spring tension should be more than enough to reset the bolt to its resting position.

[athomas]

Hunter100: Its a good design so far. It actually resembles a rough drawing I have sketched in my office. Hopefully you get it figured out. I see an area for improvement. You may want to decrease the size(diameter) of the piston part of the bolt at the back. Keeping it a large size will mean you will have a harder time finding a regulator to operate at the low pressure you will need to comfortably push the bolt forward without too much force. Remember, too much force will cause chops. A stiffer spring to reduce forward force will allow a higher pressure to be used, but a higher pressure at the large volume will be a big waste of air that has to be vented to allow the spring to return the bolt.

I too am wondering why you are using two o-rings on the front section of the bolt. The front one really isn't needed. The only operation it performs is to seal the bolt in the barrel. The amount of air that would potentially escape around the bolt when the gun is fired is so small, that it really isn't needed. I would go as far as to say that it could even impede the cocking action of the bolt if it got cut as it passed by the feed tube.

[hunter100]

Those are both good points. I figured the first o-ring would be needed to reduce blowback when it fired. I know of bolts that have o-rings on the front, and I also know there are many that do not. It would be something worth investigating. In fact, is there a thread around here somewhere about sealing the barrel and blowback?

As for the bolt size in the back, here is what I was thinking: Instead of lowering the operating pressure below what a lpr can effectively deliver, just lower the dwell time from the solenoid. I guess you could also just replace everything with a standard ram shaft, but that would require redesign of the entire bolt. Do you think the efficiency would drop too much because of the size of the bolt? Keep in mind the air only has to move the bolt one way. So, what would the difference in consumption from moving a ram 2x size one way as compared to 1x size both ways?

[SlartyBartFast]

Major Design Problem

Hate to say it, but I see a major problem.

I bolt movement controls the burst of air that propels the paintball, barrel length would have to be perfect.

Otherwise, once adjusted for velocity, the bolt is either opening while the ball is still in the barrel or it's still closed while (and venting) after the ball has left the barrel.

Or, it's going to be a nasty balancing act of pressure and bolt cycle dwell to adjust velocity.

[athomas]

The in-lb of air wastage at the back of the valve would be equal to the volume of the cavity when the bolt is forward multiplied by the resulting pressure contained when the bolt is forward. Your volume would be somewhere in the vicinity of .5 cubic inch. The pressure would be determined by the amount of air allowed to enter during the dwell time.

One problem I see with using the dwell to limit the pressure of the air behind the bolt is the rate at which the air flows. You would have to make the dwell time in the micro seconds as opposed to the milliseconds. Remember, enough air can flow behind a ball to allow it to exit the barrel in under 5ms. The amount of air required to to that is considerably larger than the amount of air you are requiring to move the bolt. Therefore I am guessing that the amount of air that would flow into the area behind the bolt would be greater than you need, resulting in a higher than needed bolt pressure. A way to limit the air flow would be to put a flow restrictor of some sort in, The amount of restriction would have to be experimented with.

The easiest way I can see to alleviate your problem is to make the back end of the bolt smaller. Use an insert in the back of the gun to take up any slack in the cavity and provide a smaller diameter hole for the smaller bolt piston. The smaller end would be easier to control with a normal regulator and valve.

[athomas]

Re: Major Design Problem

Originally posted by SlartyBartFast

Or, it's going to be a nasty balancing act of pressure and bolt cycle dwell to adjust velocity.

Sort of like all the major electronic guns on the market now that have a regulator for adjusting input pressure and a dwell setting for adjusting the amount of time the bolt is forward.:)

Actually, the dwell that is being talked about right now is the amount of time the valve is open to control the air to the bolt movement, not controlling the time that the bolt is actually allowed to be forward.