Phil, I have a request. Could you please post a photo of your piston?

Phil, I have a request. Could you please post a photo of your piston?

Joined: November 28th, 2002, 6:26 pm

March 9th, 2012, 3:16 pm #1

I think you've said you're still using the stock rubber cup with its conical cavity. If that's true, something very interesting may be happening vis-a-vis the resilience of the rubber cup and the compressed charge. "Interesting" as in Webley Paradigm and pistons with spring stacks interesting.

By the way, have I ever mentioned that "serendipity" is just about my favorite word in the whole wide world?

ser·en·dip·i·ty/serndipitç/Noun: The occurrence and development of events by chance in a happy or beneficial way: "a fortunate stroke of serendipity".



Steve
Last edited by pneuguy on March 9th, 2012, 3:17 pm, edited 1 time in total.
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Joined: September 25th, 2006, 2:19 pm

March 9th, 2012, 4:23 pm #2

the meager pressure Phil is using will not compress the urethane upon itself. Even if it could, the amount it could compress would not effect the shot because such material is rated high hysteresis-wise. To that effect, the urethane family is extensivly used as shock absorbing material.
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Joined: November 28th, 2002, 6:26 pm

March 9th, 2012, 4:27 pm #3

...I think Phil said he's running with a ~3" tall stack of loose washers between piston rod and piston, in order to make up for the length he lost when he shortened the valve body.

How springy do you suppose that assembly might be?


Steve
Last edited by pneuguy on March 9th, 2012, 4:33 pm, edited 1 time in total.
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Joined: September 25th, 2006, 2:19 pm

March 9th, 2012, 5:27 pm #4

I am sure that a stack of steel washers of varying flatness is of spring value. But we now have to define what is is.

Lets face it, a bent flat washer is really a poor mans belleville, No?

Furthermore, if Phil would alternate a common lock washer with the flat washer mix, that would yeild much more springability.

I believe we have established that to achieve high pressure, the resultant depth of the compression chamber is only ~.050". So it wouldn't take much compression of the spring pack to accomplish that.
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Joined: November 28th, 2002, 6:26 pm

March 9th, 2012, 5:29 pm #5

But "fishy" only in a good way. I.e.: Definitely not "codfishy!"

More like: "Brilliant" (neon?) in a serendipitous way.



Steve
Last edited by pneuguy on March 9th, 2012, 10:31 pm, edited 1 time in total.
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Joined: June 25th, 2002, 1:34 pm

March 9th, 2012, 9:59 pm #6

the meager pressure Phil is using will not compress the urethane upon itself. Even if it could, the amount it could compress would not effect the shot because such material is rated high hysteresis-wise. To that effect, the urethane family is extensivly used as shock absorbing material.
a number of the stock piston cups at those pressures, the cups develop blisters from the air penetrating the material, don't know if that helps, but just an observation. james
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Joined: April 1st, 2009, 3:18 am

March 10th, 2012, 2:39 am #7

I think you've said you're still using the stock rubber cup with its conical cavity. If that's true, something very interesting may be happening vis-a-vis the resilience of the rubber cup and the compressed charge. "Interesting" as in Webley Paradigm and pistons with spring stacks interesting.

By the way, have I ever mentioned that "serendipity" is just about my favorite word in the whole wide world?

ser·en·dip·i·ty/serndipitç/Noun: The occurrence and development of events by chance in a happy or beneficial way: "a fortunate stroke of serendipity".



Steve
...just got home. Sure, I'll post a picture of the piston if you like. The piston itself is as stock as stock can be. However, how the seal meets the valve face is much different. The front half of the valve, if we should call it that, has a tapered edge to match that of the seal. Inside the seal is a pocket to allow the head of the exhaust stem to move outward (3/8" diameter). The stem will only move 2mm forward. The measurement to see how far travel is was taken by removing the trigger pack, marking the end point of the striker, then moving the striker forward via metal rod and remarking on the tube the striker end location. If the seal were to be the entire vessel for the swept volume, the created space is .008cu.in for this partiuclar seal. I do know there are some gains created within the base of the valve even though there is a nylon wsher press fitted in the 'void'. Instead of proclaiming a definate ".008cu.in volume", taking in to account the gains mentioned, the storage is more like .01 or so, putting the pressure around 5K psi. My estimate of, although a terminology error in the video (meant to say "60 pounds" not "60 foot pounds"), is seriously underestimated I feel. It is indeed diffcult to close and would not be for all. To be honest, I can't close it with one hand. The other hand is needed on the opposing side. Moving both hands together as low on the lever possible.




"The majority of things in our lives are created by folks no smarter than the rest. Afterall, the world is comprised, and operated by C average people intellctually, academically, and morally. These people are often the great pioneers that set the precedent for what excellence should be."
Last edited by Duane30 on March 10th, 2012, 3:29 am, edited 1 time in total.
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Joined: November 28th, 2002, 6:26 pm

March 10th, 2012, 4:37 am #8

...would clarify things -- and for more folks than just li'l fishy me.

Steve
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Joined: April 28th, 2010, 12:23 am

March 10th, 2012, 6:05 am #9

Last edited by robnewyork on March 10th, 2012, 3:15 pm, edited 1 time in total.
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Joined: November 28th, 2002, 6:26 pm

March 10th, 2012, 2:43 pm #10

Meanwhile, I took advantage of today's Saturday sunshine to round up a neighbor and a couple of family members and paid my penalty!

CODFISH! CODFISH! CODFISH! CODFISH! CODFISH!

Steve
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