Author Topic: Win an FX Radar Chronograph  (Read 3680 times)

Mrshosted

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Re: Win an FX Radar Chronograph
« Reply #15 on: January 31, 2020, 05:58:40 AM »
1. 98 fpe
2. 2175psi
3. 98 cc
4. 20 shots
« Last Edit: January 31, 2020, 08:29:11 PM by Mrshosted »
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rsterne

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Re: Win an FX Radar Chronograph
« Reply #16 on: January 31, 2020, 12:08:23 PM »
Just 12 hours left to put in your entry.... The contest is closing at midnight tonight, PST....

Bob
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Nvreloader

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Re: Win an FX Radar Chronograph
« Reply #17 on: January 31, 2020, 02:21:49 PM »
Bob
Here is my SWAG,

140 fpe
2500 psi
75 cc
9 shots

Don
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Insanity

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Re: Win an FX Radar Chronograph
« Reply #18 on: January 31, 2020, 03:17:12 PM »
140fpe
2800psi
140cc
11 shots

nervoustrigger

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Re: Win an FX Radar Chronograph
« Reply #19 on: January 31, 2020, 08:49:30 PM »
1. 140.3fpe
2. 2705psi
3. 140cc
4. 24 shots
« Last Edit: January 31, 2020, 08:51:42 PM by nervoustrigger »
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FL Rat Hunter

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Re: Win an FX Radar Chronograph
« Reply #20 on: February 01, 2020, 04:52:41 AM »
140 FPE
3000 PSI
140 cc
21 shots
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Alan

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Re: Win an FX Radar Chronograph
« Reply #21 on: February 01, 2020, 06:17:06 AM »
It is over guys, and Bob will declare the winner very soon.
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Alan

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Earl

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Re: Win an FX Radar Chronograph
« Reply #22 on: February 01, 2020, 06:42:55 AM »
140
2777
127
17
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rsterne

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Re: Win an FX Radar Chronograph
« Reply #23 on: February 01, 2020, 09:01:15 AM »
Good morning, gentlemen.... Here is what you have been waiting for.... Here are the contest questions and the answers (in red):

You have been reading Bob Sterne’s articles, particularly those at Hard Air Magazine, and now you want to put that information to use.  You want to build your own custom PCP, and need to figure out some important details.  Your goal is to end up with a regulated PCP, fed by an onboard 500 cc bottle that can be filled to 300 bar.  You want a .257 cal that shoots 70 gr. slugs at 950 fps, from a 24” barrel.  You need the answers to the following questions (all answers to be in whole numbers, no decimals):

1.  What will be the FPE at the muzzle?

FPE = 950 x 950 x 70 / 450240 = 140 FPE.

2.  To achieve 90% of Bob’s “lofty goal” FPE calculation, what setpoint pressure (in psi) do you need for the regulator?
 
Maximum theoretical FPE is Force (lbs.) x Distance (ft.)… My “lofty goal” is half of that, so:
FPE goal = 0.257 x 0.257 x PI/4 x Pressure x 24 / 12 / 2 = 0.05185 x Pressure…. Therefore:
Pressure = FPE / 0.05185 = 140 / 0.05185 = 2700 psi
To reach 90% of that, you need to start with Pressure = 2700 / 0.90 = 3000 psi.

 
3.  What is the recommended plenum size (in cc) that Bob would recommend?
 
I recommend a plenum of 1 cc per FPE, so that would be 140 cc.

4.  If you achieve an efficiency of 1.00 FPE/CI, how many shots should you get before the pressure falls below the setpoint?
 
Fill pressure = 300 bar, and Setpoint pressure = 3000 psi / 14.5 = 207 bar
Pressure drop = 300 - 207 = 93 bar.  Reservoir volume = 500 cc / 16.4 = 30.5 CI
Total air available in “standard CI” = 93 x 30.5 = 2837 CI
Efficiency is 1.00 FPE/CI, so 140 FPE requires 140 CI of air per shot
Number of shots = 2837 / 140 = 20 shots.

 
Several of you got the correct answers for questions 1 and 3.... One of you additionally got the correct answer for question #4, and his answer on question # 2 was within less than a third of a percent of the correct value.... Therefore, the FX Radar Chronograph is awarded to (drum roll please)…. Loren....

Bob

PS … Honourable mention goes to FL Rat Hunter, who also got 3 correct answers, but entered after the midnight deadline....  8)
« Last Edit: February 01, 2020, 09:04:14 AM by rsterne »
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Alan

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Re: Win an FX Radar Chronograph
« Reply #24 on: February 01, 2020, 09:24:39 AM »
Loren, send me a PM with your full name and mailing address. I'll have Utah Airguns drop ship it to you, rather than let it go through my hands.
  • Roswell, New Mexico
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steveoh

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Re: Win an FX Radar Chronograph
« Reply #25 on: February 01, 2020, 09:37:37 AM »
Cool beans! Congrats Loren!

And thank you Bob for coming up with the challenging question for this contest, and thank you Alan for providing the reward!

This was fun.  :D
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Loren

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Re: Win an FX Radar Chronograph
« Reply #26 on: February 01, 2020, 10:14:50 AM »
Thanks to all !!!!



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FL Rat Hunter

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Re: Win an FX Radar Chronograph
« Reply #27 on: February 01, 2020, 11:14:10 AM »
Woo Hoo!  Better late than never I guess!  Congrats Loren! 
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Alan

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Re: Win an FX Radar Chronograph
« Reply #28 on: February 01, 2020, 03:54:37 PM »
Stay tuned, as we're going to have another one very soon.
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Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

Insanity

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Re: Win an FX Radar Chronograph
« Reply #29 on: February 01, 2020, 06:07:10 PM »
Gratz Loren.