Test of PEEK as a high pressure valve material

[Big Bore Bart]

   Tom:  In the case of an ICE, the valve is under control of the cam/rocker until the valve stops moving.    The last .015" is still very much under control as the clearance cannot occur while the valve is open.    An airgun valve is in fact working on an uncontrolled crash basis.

[lloyd-ss]

Doing some quick math (not checked ), if a PCP valve has a dwell time of 2.8msec, and a lift of  .10", I calculate an acceleration of 16,900 ft/sec^2 ? I need to check my math, LOL.  That is pretty abusive acceleration.
Lloyd

[QVTom]

   Tom:  In the case of an ICE, the valve is under control of the cam/rocker until the valve stops moving.    The last .015" is still very much under control as the clearance cannot occur while the valve is open.    An airgun valve is in fact working on an uncontrolled crash basis.

Thanks B^3, I guess I didn't think that one through.

Tom

[PakProtector]

Doing some quick math (not checked ), if a PCP valve has a dwell time of 2.8msec, and a lift of  .10", I calculate an acceleration of 16,900 ft/sec^2 ? I need to check my math, LOL.  That is pretty abusive acceleration.
Lloyd

2x/t^2=a...so t= dwell over two, x equal .1 and as long as we keep units consistent we'll get the right answer... I recorded 4,000 m/s^2 on my RX2, which could be rounded to say 12,000 ft/s^2...so the 16k acceleration you mention Lloyd seems not unreasonable at all.

roughly is 10^-1/10^-6, so roughly 10^5 ft/s^2...not unreasonable numbers at all...

cheers,
Douglas

[lloyd-ss]

Doing some quick math (not checked ), if a PCP valve has a dwell time of 2.8msec, and a lift of  .10", I calculate an acceleration of 16,900 ft/sec^2 ? I need to check my math, LOL.  That is pretty abusive acceleration.
Lloyd

I gave this some more thought and figured it a couple of different ways.  I was ready to post and see that Doug added some more info.  Thanks for keeping me honest Doug!
So if the math is reasonable, can we look at the closing half of the cycle because that seems easiest  to analyze. The main component of closing force on the valve, as has been pretty thoroughly discussed and agreed upon, is the pressure times the valve stem area.  So with a .156 stem dia, and 2000 psi, the closing force is 38 pounds.  If the valve weighs .08 ounce, or .00017 slugs mass, and accelerates from zero at the full open position for 0.10" to the seat, the velocity of the valve when it hits the seat is only 43 ft/sec, which is 29mph.  So even though the closing acceleration was over 6,000g's, the velocity at impact was relatively slow.....I guess.  Those plastic valve heads hold up forever, so the impact on the seat can't be too bad.
I think, like Doug said, the hammer hit makes some funny things happen in the valve stem.  Pretty much instantaneous acceleration.
Lloyd