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will this hurt my piston ?

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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will this hurt my piston ?

Unread postAuthor: jsefcik » Sun Aug 28, 2011 2:23 am

I have recently built a piston cannon, shoots golf balls very well, but wanted to upgrade to a tennis ball barrel but not shooting tennis balls but hole soda cans, maybe even filled with cement!!!

will it hurt my piston in any way?

and how will the recoil be?

i know its prob a dumb question but id rather learn then break anything!!!

my barrel port is 1 1/2 for golf balls
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Unread postAuthor: Crna Legija » Sun Aug 28, 2011 2:51 am

dont know what the piston is made of so can't answer.

just start with low pressure 30ish psi to get a feel of the recoil probs wont be that bad.
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Unread postAuthor: Gun Freak » Sun Aug 28, 2011 7:01 am

When I said make a thread about it I was kidding :D
Stop saying you built a piston valve... I built it :D
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Unread postAuthor: velocity3x » Sun Aug 28, 2011 8:22 am

will this hurt my piston ?


Pistons lack a central nervous system, therefore they are not capable of experiencing physical of emotional pain.
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Unread postAuthor: jackssmirkingrevenge » Sun Aug 28, 2011 8:45 am

velocity3x wrote:Pistons lack a central nervous system, therefore they are not capable of experiencing physical of emotional pain.


:D ten points!
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Unread postAuthor: Technician1002 » Sun Aug 28, 2011 9:51 am

It is true that when a barrel has a heavier projectile, the force on the piston when it opens is greater. As long as the bumper is up to the task, the piston should be fine.

As far as high recoil, that is highly variable depending on factors such as valve flow rate, pressure used, and projectile weight.

I'm assuming you are changing from a golf ball barrel to a tennis ball barrel. This implies the same size valve is used. A small valve will limit the flow rate and thus the recoil force. Even with a larger valve, shooting full cans of soft drinks is a hand-held operation at 100PSI even though the recoil is respectable.

I have a video online of launching a full can on my youtube channel.
It is in my Uploads.

http://www.youtube.com/user/Technician1002
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Unread postAuthor: jsefcik » Sun Aug 28, 2011 10:16 am

velocity3x wrote:
will this hurt my piston ?


Pistons lack a central nervous system, therefore they are not capable of experiencing physical of emotional pain.



I didnt ask for a smarta** answer



the piston is made from threaded bolt washers o rings and nuts

p.s. gunfreak please post a pic
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Unread postAuthor: velocity3x » Sun Aug 28, 2011 10:36 am

jsefcik wrote:
velocity3x wrote:
will this hurt my piston ?


Pistons lack a central nervous system, therefore they are not capable of experiencing physical of emotional pain.



I didnt ask for a smarta** answer


Sorry......but I couldn't resist :D It's a long life, hard and requires a sense to humor to cope.
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Unread postAuthor: jsefcik » Sun Aug 28, 2011 10:38 am

velocity3x wrote:
jsefcik wrote:
velocity3x wrote:
will this hurt my piston ?


Pistons lack a central nervous system, therefore they are not capable of experiencing physical of emotional pain.



I didnt ask for a smarta** answer


Sorry......but I couldn't resist :D It's a long life, hard and requires a sense to humor to cope.


just answer what my question asks
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Unread postAuthor: mattyzip77 » Sun Aug 28, 2011 10:58 am

Gun Freak wrote:When I said make a thread about it I was kidding :D
Stop saying you built a piston valve... I built it :D

It depends on the length of your barrel and if its rifled or not??? :)
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Unread postAuthor: Mr.Tallahassee » Sun Aug 28, 2011 11:05 am

jsefcik, don't be such a hard**. It isn't something you want to do to people who are trying to help you. Humor keeps life interesting so learn to take a few. I am generally one of the most smart mouthed people you will ever meet. That's the reason I'm a happy, upbeat person most of the time.
The answer to your question is no. It will not hurt your piston or damage it as long as you have a good bumper.
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Unread postAuthor: jsefcik » Sun Aug 28, 2011 11:13 am

Mr.Tallahassee wrote:jsefcik, don't be such a hard**. It isn't something you want to do to people who are trying to help you. Humor keeps life interesting so learn to take a few. I am generally one of the most smart mouthed people you will ever meet. That's the reason I'm a happy, upbeat person most of the time.
The answer to your question is no. It will not hurt your piston or damage it as long as you have a good bumper.
]


I have a half tennis ball bumper in right now, but want something that will be strong as hell, was thinking of a solid piece of rubber that covers the back of the bolt

or just drill a hole for the bolt to go into ,

any ideas for a good bumper?
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Unread postAuthor: mattyzip77 » Sun Aug 28, 2011 11:28 am

There was just a thread on this like a week ago I think?? Cut up a piece of a old flip flop aka shower shoes, or add the other half of the tennis ball??
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Unread postAuthor: jhalek90 » Sun Aug 28, 2011 6:57 pm

jsefcik wrote:I didnt ask for a smarta** answer
just answer what my question asks


well, when you ask a dumba** question, your lucky to get ANY answer around here.

There is more than enough info on this forum, do some research.

You seem to have a reputation for asking questions that could be answered with a little research and some common sense.

:now for the helpfull bit:
Your piston should be fine.... its the piston housing i would worry about.
Like everyone has said, get a good bumper. I would recommend a VERY strong spring, just keep enough of a gap between the spring and the piston, to allow it to open fully before it hits the spring.

I found that solid rubber bumpers transfer most of the piston energy to the piston housing.... and do very little to help in a PVC housing.

You want a bumper that will compress more, and compress slowly... like a strong spring.

Some simple math for you...
If you piston has a 2'' sealing face:

The surface area of your exposed sealing face is: 3.14xr^2 or (3.14x1) 3.14 square inches.
PSI=pounds per square inch.
So you have 3.14 pounds of force, per PSI acting on your piston.

At 100 psi, you have about 314lbs of force to try and stop. Get a good bumper.

(of course my math is simplified a bit, but its good enough for what your doing.)
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Unread postAuthor: Moonbogg » Sun Aug 28, 2011 7:21 pm

jhalek90 wrote:
jsefcik wrote:I didnt ask for a smarta** answer
just answer what my question asks


well, when you ask a dumba** question, your lucky to get ANY answer around here.

There is more than enough info on this forum, do some research.

You seem to have a reputation for asking questions that could be answered with a little research and some common sense.

:now for the helpfull bit:
Your piston should be fine.... its the piston housing i would worry about.
Like everyone has said, get a good bumper. I would recommend a VERY strong spring, just keep enough of a gap between the spring and the piston, to allow it to open fully before it hits the spring.

I found that solid rubber bumpers transfer most of the piston energy to the piston housing.... and do very little to help in a PVC housing.

You want a bumper that will compress more, and compress slowly... like a strong spring.

Some simple math for you...
If you piston has a 2'' sealing face:

The surface area of your exposed sealing face is: 3.14xr^2 or (3.14x1) 3.14 square inches.
PSI=pounds per square inch.
So you have 3.14 pounds of force, per PSI acting on your piston.

At 100 psi, you have about 314lbs of force to try and stop. Get a good bumper.

(of course my math is simplified a bit, but its good enough for what your doing.)


Its more complicated than that. You have to find the kinetic energy from the speed and mass of the piston and then calculate the deceleration introduced by the bumper to arrive at the impact force. Its too hard for me to do accurately so I made a crude attempt to get into the ball park to see if my housing would hold up. Want to know what my answer to the problem was? "I'm not too sure so I better just use a damn good bumper" :lol:
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