The AirGun Guild

General Category => Contests, Give aways and more. => Topic started by: Alan on January 18, 2020, 11:32:18 AM

Title: Win an FX Radar Chronograph
Post by: Alan on January 18, 2020, 11:32:18 AM
We all know of Bob Sterne, and his contributions to the airgun hobby. His depth of knowledge of the science behind airguns, is in fact, legendary! Based on this, the staff of the AirGunGuild (Bob is a member of the staff), decided to challenge the membership about their depth of knowledge of that science. Therefore, in the next day or so, Bob will post his challenge questions. Since the answers aren’t simply yes/no, we’ll give the membership until February 1st., to post their answers. Bob alone will decide who the winner is, and rightly so. Whomever that winner is, will win an FX Radar Chronograph, as supplied by Utah Airguns.

Good Luck to all!
Title: Re: Win an FX Radar Chronograph
Post by: rsterne on January 18, 2020, 11:47:52 AM
Win an FX Radar Chronograph!

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 is 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 is the FPE at the muzzle for the intended goal?....

2.  To achieve 90% of Bob’s “lofty goal” FPE calculation, what setpoint pressure (in psi) do you need for the regulator?....

3.  What is the plenum size (in cc) that Bob would recommend?....

4.  If you achieve an efficiency of 1.00 FPE/CI, how many shots should you get before the pressure falls below the setpoint?....

The first person to post the correct answers (by time and date stamp) to ALL of the above questions in this thread will win the FX Radar Chronograph from the AirGunGuild!....  If nobody posts all the correct answers by Feb. 1st, I will decide an alternate method to determine the winner.... My decision is final....  ;) 

Bob
Title: Re: Win an FX Radar Chronograph
Post by: steveoh on January 18, 2020, 04:27:07 PM
Win an FX Radar Chronograph!

About the FX Radar Chronograph:

FX Radar Pocket Chronograph Features
* Uses Doppler Radar to obtain velocity, energy and other stats
* Controlled via Android/iOS smartphone app
* Bluetooth compatible
* Runs off three AAA batteries
* Allows user to input variables like pellet weight and radar return
* Measures velocity of Pellets / BB’s / Airsoft / Archery / Paintball

Using the first ever pocket radar ballistic chronograph from FX Airguns of Sweden, this
ballistic app enables the recording of data from 20 fps to 1100 fps.
Ever wanted to know the speed of your pellet, BB, Arrow or Paintballs, then this app will
allow you to create profiles and store data from all your testing and tuning.
Vocal shout outs for each shot can enable smooth target grouping at the range, just listen to
the result and don’t take your eye off the target.

Export the data strings for further evaluation, save and record your days testing using the
profile function.

It’s easy to check your power, take the FX Chronograph out of your pocket, start Bluetooth
and start the app on your phone.

Now you can check your power while zeroing and shooting groups.

Features Include:
- Realtime record of shots
- Clear display of shot strings
- Audio shout out’s, switchable OFF and ON **
- Profile Creation – Remember settings for easy recall
- Easy to select velocity ranges
- Scope Bore Height input (for future development)
- Input of Pellet data for profiles
- Multiple Unit Read Outs – FPS / MPS / FT Lbs / Joules / KMPH
- Radar Return adjustment for sensitivity
- Shot Count Data exportable to clipboard

Developments for future versions will be available and registration within the app is
suggested to enable update notifications.
Title: Re: Win an FX Radar Chronograph
Post by: sixshootertexan on January 18, 2020, 10:16:41 PM
140.31
3200
140
18
Title: Re: Win an FX Radar Chronograph
Post by: Nvreloader on January 19, 2020, 09:37:41 AM
140 fpe
2950 psi
120 cc
16 shots

Thanks,
Don
Title: Re: Win an FX Radar Chronograph
Post by: Capt45 on January 19, 2020, 11:47:48 AM
140 fpe
31psi
135 cc
9 shots
Title: Re: Win an FX Radar Chronograph
Post by: T3PRanchAGS on January 19, 2020, 02:19:55 PM
140 fpe
2428 psi
140 cc
4 shots
Title: Re: Win an FX Radar Chronograph
Post by: d_boom on January 20, 2020, 07:42:19 AM
1) 140 FPE
2) 3045 PSI
3) 140 cc
4) 20 shots
Title: Re: Win an FX Radar Chronograph
Post by: Alan on January 22, 2020, 04:27:04 AM
So far, no one has calculated (guessed?) the correct answers. Remember too, only the right answers get the prize. Keep trying folks!
Title: Re: Win an FX Radar Chronograph
Post by: d_boom on January 23, 2020, 05:31:33 PM
Assuming those of us who guess/figured incorrectly can still try again?  Here I go again;

1.  140 FPE
2.  2699 psi.
3.  140 cc.
4.  24 shots

I am interested in reading how Bob's figured these answers so I can better understand.
Thanks,
Danny
Title: Re: Win an FX Radar Chronograph
Post by: rsterne on January 23, 2020, 08:34:17 PM
I don't see a problem with entering again, but it will wipe out your previous answers, of course.... like changing your answers on a test....  ;)

I try and check it a few times a day.... I'm a bit surprised there aren't more entries, it's a pretty nice prize....  8)

Bob
Title: Re: Win an FX Radar Chronograph
Post by: Loren on January 24, 2020, 05:39:24 AM
Damn algebra!!

140 FPE Muzzle Energy
2991 PSI reg pressure
140 cc Plenum size
20 shots

Cool contest!!
Title: Re: Win an FX Radar Chronograph
Post by: Alan on January 24, 2020, 05:53:58 AM
Loren brings up an issue. The rules indicated that you must have a certain number off posts first, but I'll officially negate the rule for this contest. I hope this will increase the participation.
Title: Re: Win an FX Radar Chronograph
Post by: jackpine on January 31, 2020, 01:58:35 AM
I'm a bit surprised there aren't more entries, it's a pretty nice prize....  8)

Bob
cool contest
great prize
completely over my head- I just want to go out and punch paper and shoot squirrels :)
Title: Re: Win an FX Radar Chronograph
Post by: Alan on January 31, 2020, 04:52:23 AM
Just one more day to take a stab at it. If no winners, we'll come up with another set of questions.
Title: Re: Win an FX Radar Chronograph
Post by: Mrshosted on January 31, 2020, 05:58:40 AM
1. 98 fpe
2. 2175psi
3. 98 cc
4. 20 shots
Title: Re: Win an FX Radar Chronograph
Post by: rsterne 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
Title: Re: Win an FX Radar Chronograph
Post by: Nvreloader on January 31, 2020, 02:21:49 PM
Bob
Here is my SWAG,

140 fpe
2500 psi
75 cc
9 shots

Don
Title: Re: Win an FX Radar Chronograph
Post by: Insanity on January 31, 2020, 03:17:12 PM
140fpe
2800psi
140cc
11 shots
Title: Re: Win an FX Radar Chronograph
Post by: nervoustrigger on January 31, 2020, 08:49:30 PM
1. 140.3fpe
2. 2705psi
3. 140cc
4. 24 shots
Title: Re: Win an FX Radar Chronograph
Post by: FL Rat Hunter on February 01, 2020, 04:52:41 AM
140 FPE
3000 PSI
140 cc
21 shots
Title: Re: Win an FX Radar Chronograph
Post by: Alan on February 01, 2020, 06:17:06 AM
It is over guys, and Bob will declare the winner very soon.
Title: Re: Win an FX Radar Chronograph
Post by: Earl on February 01, 2020, 06:42:55 AM
140
2777
127
17
Title: Re: Win an FX Radar Chronograph
Post by: rsterne 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)
Title: Re: Win an FX Radar Chronograph
Post by: Alan 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.
Title: Re: Win an FX Radar Chronograph
Post by: steveoh 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
Title: Re: Win an FX Radar Chronograph
Post by: Loren on February 01, 2020, 10:14:50 AM
Thanks to all !!!!



Title: Re: Win an FX Radar Chronograph
Post by: FL Rat Hunter on February 01, 2020, 11:14:10 AM
Woo Hoo!  Better late than never I guess!  Congrats Loren! 
Title: Re: Win an FX Radar Chronograph
Post by: Alan on February 01, 2020, 03:54:37 PM
Stay tuned, as we're going to have another one very soon.
Title: Re: Win an FX Radar Chronograph
Post by: Insanity on February 01, 2020, 06:07:10 PM
Gratz Loren.
Title: Re: Win an FX Radar Chronograph
Post by: Earl on February 01, 2020, 09:10:02 PM
If you want more people to enter a contest, make it quick and simple to enter.
Picking a number between 1 and 999 will probably get a lot of entries.
Title: Re: Win an FX Radar Chronograph
Post by: Steelhead on February 02, 2020, 06:41:45 AM
Earl,

The guild does have contests like that, but a lot require a bet of effort. This one is for the advanced airguuner and it encourages a shooter to learn about the important basic formulas of airguns. So not only does one learn about the physics of airguns  but they can get a really cool prize for doing so. A win win.

Hang around a while. You'll get as much or more than you give.

Title: Re: Win an FX Radar Chronograph
Post by: Alan on February 02, 2020, 07:59:13 AM
Kevin is correct. I would like to think we're all a family here on the Guild. As a family, we share what we know, or at least what we think we know. Corrections in that regard, have always been welcome, and that's as it should be. Bob Sterne, whom I believe is one of the most knowledgable folks in the hobby, graces our pages with his presents, in more ways than one! This last contest, if we can call it that, was in the vain Kevin expressed—learning. I fully admit I've learned a lot, and in fact is one of the reasons I took over this site when Travis left. We value your input too, Earl, and I do plan on making changes to the contest rules, to make entering an easier task.
Title: Re: Win an FX Radar Chronograph
Post by: Earl on February 02, 2020, 08:39:58 PM
My mistake.
I assumed the purpose was to get more members to join.
I can calculate the foot pounds of energy.
The other 3 questions were much to difficult for me to answer so my answers were a WAG.

Title: Re: Win an FX Radar Chronograph
Post by: Mrshosted on February 03, 2020, 07:58:29 AM
Thank you for the opportunity to learn