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Spring loaded ball valve design

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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Unread postAuthor: Technician1002 » Thu May 13, 2010 1:52 pm

Brian the brain wrote:Agreed.
In the same lie of thought I prefer small area differencial in a piston valve.
It waits longer to open but when it does more opposing force has left through the pilot.


This was a design goal of my new valves. Pilot is essentially fully vented to zero and the valve has a running start. This is how opening times under 1ms are done without a burst disk.
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Unread postAuthor: Gaderelguitarist » Thu May 13, 2010 1:55 pm

Marffy wrote:
Gaderelguitarist wrote:You could put the finished gun on a nice wooden stock and really have a home run.


Already made the stock before i posted :D


Sir, you have my respect. 8)
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so many muchness
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Unread postAuthor: boyntonstu » Thu May 13, 2010 3:10 pm

Technician1002 wrote:
Another tip: Close the ball valve to ~80 degrees where it still seals.

Spring does not have to pull that initial 10 degrees.


Believe it or not, this is a bad idea. Here is the argument.

2 cars are drag racing. One starts 20 feet behind the starting line and is permitted a rolling start. Neither car can cross the line early. Both cross the start line at the same time. One is traveling 40mph as it crosses. Which car will make the first 40 feet the quickest?

A running start before the valve cracks open is a good thing as the actual time taken to open is shortened once it actually cracks open.

All my valves are using a pre open travel distance for a running start when they do open.


I don't see it completely that way.

Both cars have the same acceleration and the head start car will beat the other car to the finish line. I agree.

The question is whether the time to reach 90 ft from 0 ft is shorter than the time starting from 10 ft to reach 90 ft.

Both valves will have the same acceleration.

Like a drag race, the shortest E.T. is the goal (assuming the same reaction time to green).

(Exchange degrees for feet)

Springs weaken as they retract.

Therefore the first 10* of rotation is acted upon by the strongest force.

I could be wrong.
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Unread postAuthor: Technician1002 » Thu May 13, 2010 4:32 pm

Who cares how long it takes to reach the starting line. i'm not in a western duel. A short delay from trying to trigger it until it goes bang is not a problem if it is relatively short. Here is a video where you can see the long delay from the time the trigger is pulled until the cannon goes bang. It is trivial.

Most here have already seen this video so I'm just providing a link. Remember, the knob pulls out about 2 inches before the valve starts to open.
http://www.youtube.com/watch?v=9Klxqav_6NM
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Unread postAuthor: boyntonstu » Thu May 13, 2010 5:45 pm

MRR wrote:
3. To loosen the screw is absolutely ok with me. If you feel uncomfortable with that then use a drop of Locktight.


What does loosening reduce?

If The ball valve needs 10 pounds to open, what will loosening do to that figure?
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Unread postAuthor: Marffy » Thu May 13, 2010 7:33 pm

boyntonstu wrote:
MRR wrote:
3. To loosen the screw is absolutely ok with me. If you feel uncomfortable with that then use a drop of Locktight.


What does loosening reduce?

If The ball valve needs 10 pounds to open, what will loosening do to that figure?


The nut holds the ball closer to the seal making it slightly tighter to open.
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Unread postAuthor: Labtecpower » Fri May 14, 2010 4:42 am

You may want to take a look at my gun, also with a spring loaded ball valve.
it opens pretty fast.
url; http://www.spudfiles.com/forums/my-thir ... 20335.html
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Unread postAuthor: boyntonstu » Fri May 14, 2010 7:25 am

Labtecpower wrote:You may want to take a look at my gun, also with a spring loaded ball valve.
it opens pretty fast.
url; http://www.spudfiles.com/forums/my-thir ... 20335.html


Nice job.

Do you cock the rubbers one at a time?

I notice 2 bands, have you tried more?

What is the weight of your projectile, the pressure, and the fps?


BTW Can anyone suggest a method the measure the opening time?
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Unread postAuthor: Labtecpower » Fri May 14, 2010 8:38 am

I used only one rubber band.
As I didn't trust the wood with more rubber bands, I didn't try more than one.

The pressure I used was about 100 PSI.
I used ammo of about 5 grams.
I can't guess the opening time, Altough it was pretty fast.
GGDT estimated a velocity of 100 M/s or about 300 FPS.
I can't give more information as I disassembled the gun, in order to use the parts for my piston valved copper gun.
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Unread postAuthor: boyntonstu » Fri May 14, 2010 11:19 am

Labtecpower wrote:I used only one rubber band.
As I didn't trust the wood with more rubber bands, I didn't try more than one.

The pressure I used was about 100 PSI.
I used ammo of about 5 grams.
I can't guess the opening time, Altough it was pretty fast.
GGDT estimated a velocity of 100 M/s or about 300 FPS.
I can't give more information as I disassembled the gun, in order to use the parts for my piston valved copper gun.


It would be interesting to compare damage between the piston and the BV guns.
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Unread postAuthor: Marffy » Fri May 14, 2010 8:27 pm

boyntonstu wrote:BTW Can anyone suggest a method the measure the opening time?


Measure how fast the ball valve spins with a high-speed camera. (like in mythbusters)
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Unread postAuthor: kydavies » Fri May 14, 2010 10:48 pm

im going to take a shot in the dark and say most people dont own a high-speed camera



Assume= Ass-u-me
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mikemurph wrote:yea, the ammo has been changed to a more aero dynamic projectile. it consists of the back half of a dart, and a hot glue ball
AHahahahah!!
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Unread postAuthor: Technician1002 » Sat May 15, 2010 12:06 am

One item that shows the performance of faster valves is launching lightweight projectiles. I was just out shooting glowsticks into the evening sky at the retreat. Woo Hoo, they have wireless.

Using the GPS we measured 310 feet at 100 PSI. Care to try it with a ball valve. In the daylight tomorrow, we will be launching marshmallows, regular and miniature.
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Unread postAuthor: Marffy » Sat May 15, 2010 1:03 am

kydavies wrote:im going to take a shot in the dark and say most people dont own a high-speed camera


I can't think of another way. Someone could get a really good camera (maybe 100fps) and estimate the opening time.
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Unread postAuthor: boyntonstu » Sat May 15, 2010 6:07 am

Technician1002 wrote:One item that shows the performance of faster valves is launching lightweight projectiles. I was just out shooting glowsticks into the evening sky at the retreat. Woo Hoo, they have wireless.

Using the GPS we measured 310 feet at 100 PSI. Care to try it with a ball valve. In the daylight tomorrow, we will be launching marshmallows, regular and miniature.


I have another idea to directly measure the BV linear handle speed.

Use the opening spring to directly launch a paper 'spitball' simultaneously with opening a BV and measure its speed with a chronograph.
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