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Ft/lbs V Fpe? What?

Discussion in 'Technical' started by pjgtech, Apr 12, 2018.

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  1. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Got myself a new Chrony (Air Crony mk3). I will do a separate review, but I like it...

    After putting a couple of my guns thr the new chrono, it gives the fps, great, so using chair gun and the pellet weight, etc, I can work out the Ft/lbs output, but it also has an "energy" column that shows very high fpe figures.

    So my basic question is what is fpe and how does it compare / convert to ft/Lbs?

    For example my .22 HW97 (using H&N FTT 14.66gr) is giving consistent fps of around 589 which, using chair gun gives an average of 11.3 ft/lbs, but the air chrony is giving an "energy" readings of around 170fpe?

    Confused by this FPE reading, what does it mean? Any advice, info appreciated thanx.... :cool:u
     
  2. mikeyhall1

    mikeyhall1 Pepe Le Pew

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    FPE = foot pound energy :thumb:
     
  3. mikeyhall1

    mikeyhall1 Pepe Le Pew

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    I’ve no idea though why it would give you a reading of that though ....
     
  4. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Yeah, I figured thats what it is, but my rifle is not giving 170ft/lbs its giving 11.3, so why is it 170?

    Whats the difference between FT/lbs and FPE? and I assume you can convert one to the other, but a quick google search didn't show me how? or what the relationship is..... I'm sure someone will be along in a minute with a simple explanation that I have completely missed somehow... :cool:
     
  5. hughlle

    hughlle Very Active

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    So far as I'm aware there is no difference between FPE and ft/lb. Just different abreviations for the same thing.

    Sounds like something is being done/read wrong with the air chrony software.
     
  6. Sky

    Sky Super Moderator Staff Member Mod/Admin

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  7. mikeyhall1

    mikeyhall1 Pepe Le Pew

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    That’s what I thought..
     
  8. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Yeah, weird that its reading the fps correct though, I've emailed Air Chrony, (just) and I was also gonna email BAR (where I bought the Air Chrony from) but they don't have an email contact due to, "the shop being very busy", great customer service guys, way to go.... 8-( I will see if Air chrony get back to me, or see if anyone on here has the same Chrono......
     
  9. mikeyhall1

    mikeyhall1 Pepe Le Pew

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    Good luck mate:thumb:
     
  10. gargloit

    gargloit Posting Addict

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    To work out FPE you will have to somehow input the pellet weight into the chrono to get a correct readout. Could be a case of RTFM.
     
  11. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Yes, you do have to imput the pellet weight, this can be done on the chrony itself, via buttons, or via their own software installed on a laptop, (freely downloaded from the Air Chrony website). Obviously I did this and the chrony readings, on the chrony screen and on the laptop screen, both match with the same readings, all the readings are correct, apart from the FPE ones.

    These are made in eastern europe, possibly poland, and although there is a manual and its in English, its not the best guide in the world, and is a bit fiddly to follow, with mostly pictues of the chrony screens and which buttons to press. There are a couple of youtube clips (from Air Chrony) which shows how to use the screens / buttons, which make more sense once you have watched them. I don't think I'm doing anything wrong, this is not the first chronogrpath I have used. It may be a translation thing or something they have missed in the guide?

    Just found a youtube clip of a guy reviewing the air chrony, and he has the same high readings for FPE, see the link to the clip, the relevent bits with the high readings are at 8min30secs and 12mins30secs into the video. He also does not know how to explain them?



    So its obviously not just me.... :cool:
     
  12. terry1001

    terry1001 Major Poster

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    I’m going to have a wild guess, are you entering the weight correctly? Basically is the device expecting a weight in grams and you’re entering grains?
     
    Jeffsy likes this.
  13. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Pretty sure I double checked, imperial v metric, correct weight, etc.....

    TBH once I have the fps,it I can work out ft/lbs anyway, would just be nice for the device to do it for me...

    8-(
     
  14. gargloit

    gargloit Posting Addict

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    Just done the math and it looks like that's going to explain it. Putting grains in when the software is expecting grams. Factor of about 15.

    1 gram = 15.4324 grains. 170/11.3=15.04 ish.
     
  15. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Right, its definately a software eror, as I am definitely using imperial.

    I just checked the export (csv) you can save from the Air Chrony software, and it shows the speed (in feet per second - FPS) which is imperial, and it shows the pellet weight (in grains) which is imperial, but....

    It shows the energy as FPE, which is obviously metric, so the software is confusing itself, I have emailed Air Chrony, so maybe they have a software update?

    Thanx guys.....
    hw97 cal22 muzzle energy apr 2018 h and n ftt 14_66gr.jpg
     
  16. Dag

    Dag Very Active

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    Whether a Combro or a Chrony, both of which I have, I find it easier to use them to produce fps (aka ft per sec) and then just do the calculation away from the chrono. It reduces the risk of inputting an incorrect figure for the pellets and for me makes the whole operation much simpler.
    hth
    Jim
     
    Last edited: Apr 12, 2018
  17. pjgtech

    pjgtech If the Enemy is in range, so are You!

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    Not now cos everthings packed away, might give it another try at the weekend, but the data should all be in imperial or all be in metric, not a mixture of the two, so somethings gone wrong somewhere?
     
  18. terry1001

    terry1001 Major Poster

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    Metric would give an answer in joules and 12 ftlbf is about 16 joules.
     
  19. Ballisticboy

    Ballisticboy Busy Member

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    If you expand the width of the pellet mass column you may find is says "grms" instead of "grs". I have been caught out by that before now on spreadsheets.
     
  20. AirRifleSport

    AirRifleSport Well-Known Member

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    Could it be something like Feet Per Second and Metre Per Second?
     

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