Author Topic: 2031 fps on Air ! - Now 2162 fps !  (Read 1989 times)

rsterne

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2031 fps on Air ! - Now 2162 fps !
« on: March 22, 2016, 06:55:08 AM »
Lloyd Sikes at the AirGunLab has broken 2000 fps in his first attempt.... The barrel is a .278 cal smoothbore (piece of DOM tubing), 47.5" long, powered by a 55 cc reservoir with a unique pellet release mechanism that allows full pressure against the pellet before firing.... The 9.1 gr. pellet was made from aluminum, sealed into the bore with an O-ring, and this test was done at 4000 psi....

https://www.youtube.com/watch?v=JWt5DnfYH3I&feature=player_embedded

This permanently puts to rest the idea that 1650 fps (the molecular velocity of air) is the limit for a PCP.... Congratulation, Lloyd, on a job well done....

Bob
« Last Edit: March 31, 2016, 08:39:45 AM by rsterne »


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match

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Re: 2031 fps on Air !
« Reply #1 on: March 22, 2016, 07:10:48 AM »
Wow - just shy of mach 2 at STP.
Did he record the air density (temp, pressure/altitude, humidity) so we can calculate the mach number?
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Alan

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Re: 2031 fps on Air !
« Reply #2 on: March 22, 2016, 10:22:37 AM »
Ah! But the big question is, how practical is it?
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rsterne

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Re: 2031 fps on Air !
« Reply #3 on: March 22, 2016, 11:54:03 AM »
You only need temperature for Mach number.... it was inside his garage, so I would guess 15-20*C.... 1116-1127 fps at those temperatures....

Bob
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ztirffritz

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Re: 2031 fps on Air !
« Reply #4 on: March 22, 2016, 04:56:14 PM »
On Mythbusters they were trying to accelerate a pingpong ball and found that evacuating the air in front of the ball had a HUGE impact on the speed.  Has anyone ever contemplated changing the airpressure in front of the pellet just before the pressure is released behind the pellet?

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« Last Edit: March 22, 2016, 05:00:25 PM by ztirffritz »
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rsterne

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Re: 2031 fps on Air !
« Reply #5 on: March 22, 2016, 05:43:09 PM »
When using relatively low pressure air behind the pingpong ball, and with the light weight and large surface area, a vacuum can make a huge difference.... When you have 4000 psi driving it, removing 15 psi of air in front of a bullet will only have a small effect.... some, but small....

Bob
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oldpro

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Re: 2031 fps on Air !
« Reply #6 on: March 24, 2016, 08:42:28 AM »
2031 FPS thats crazy and makes me think "What is the ceiling" or is there one?
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Re: 2031 fps on Air !
« Reply #7 on: March 24, 2016, 09:17:57 AM »
299 792 458 m / s (apx) is the practical maximum speed limit.

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rsterne

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Re: 2031 fps on Air !
« Reply #8 on: March 24, 2016, 10:03:49 AM »
I "c" what you're getting at.... *grin*....

Practical, not really, but it sure is interesting.... To achieve these velocities, we end up with the mass of the air used to propel the bullet an order of magnitude, or more, greater than the bullet.... For Lloyd's 2031 fps shot, the bullet weighed 9.1 grains, but the air itself weighed 256 grains.... of which 118 grains was being accelerated along behind the bullet.... Obviously most of the energy is not being used effectively with such a light projectile.... A typical bullet in that caliber (0.278") would be 10 times as heavy, about 91 grains, which would bring the amount of air used back into proportion (somewhat)....

Pushing velocities further can be done, but with (severely) diminishing returns.... To gain just another 2% in velocity would require one of the following.... 12% more pressure.... a 14% longer barrel.... or an 11% lighter bullet.... Changing from the 55 cc reservoir to an infinite one at the same 4000 psi would not get you there.... I don't see an easy path to get to Mach 2 (2250 fps) on air, or even Nitrogen, unless we can make a much lighter projectile that will survive the launch.... Of course using Helium could see us push to (or beyond) Mach 3.... because the mass of it is so much less (1/7th that of air)....

Bob
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Bob La Londe

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Re: 2031 fps on Air !
« Reply #9 on: March 24, 2016, 11:09:59 AM »
Well, I chose the word practical over the word theoretical because I wanted to avoid discussions of quantum pellets arriving before they left. 

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rsterne

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Re: 2031 fps on Air !
« Reply #10 on: March 24, 2016, 11:58:48 AM »
Actually, my response about what is practical was in answer to Alan's post....

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Alan

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Re: 2031 fps on Air !
« Reply #11 on: March 24, 2016, 01:16:33 PM »
It is a shear case of the Pareto Principal. It applies equally with powder guns too. I'm sure we all remember the Weatherby magnum series for guns and cartridges. The truth be known, the venerable 30-06 was just as good for 80% of the game on this planet. But those who choose to have a Weatherby, for whatever reason, paid big bucks to get there. I sort of feel the same way; Is a $2,400 airgun that much better than a $600 one? No for me it isn't.
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rsterne

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Re: 2031 fps on Air !
« Reply #12 on: March 24, 2016, 01:26:39 PM »
I agree 100%, in terms of the practicality.... These experiments are only designed to increase our knowledge and understanding of PCPs, period.... However, unless we understand where the limits are, and why they exist, we don't know if there is any point in persuing them further, IMO....

It is no different than building a Supersonic airliner.... Just because we could, when we made the Concorde, doesn't mean we should have.... so that the few who could afford to fly in one could just say they did it.... A century from now, through better knowledge of all the aspects of aviation (and space travel), we may look back and wonder what took us so long.... Just over a century ago, travelling any distance by horse and buggy was the reliable, and sensible choice....

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rsterne

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Re: 2031 fps on Air !
« Reply #13 on: March 31, 2016, 08:39:03 AM »
Lloyd has upped the bar again.... 2162 fps with a 7.7 gr. 0.278" cal. projectile at 4600 psi in a 46" barrel....

Bob
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