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  1. #31
    Join Date
    11th April 2017
    Location
    Brisbane Australia
    Posts
    531

    Why would my Jolly Logic Altimeter 2 say I went Mach 29?

    Quote Originally Posted by scsager View Post
    For the best performance from the 3-axis accelerometer ... check out this ... https://www.apogeerockets.com/educat...sletter293.pdf
    LOL.. from the article:

    "But for lightweight rockets with high-thrust motors, this limit of 23 Gs can easily be exceeded. What this means is that the maximum speed shown on the AltimeterTwo after the flight will be too low. "

    You see: the REAL problem is that your rocket was actually travelling FASTER than MACH29!!

    NASA called - they want their secret research rocket back... 😜

    Interesting in that article: using prototyping board as a sled - I'd never have thought of that..

    Reasonably new to rocketry and hailing from the land down under.. I speak metric... I know not of these feet and inches you speak of...

    QRS: #193
    AMRS: #148

  2. #32
    Join Date
    11th April 2017
    Location
    Brisbane Australia
    Posts
    531
    Out of interest, did you ask John Beans via the JL contact page?

    He has always been very helpful support wise via email in my experience.

    Reasonably new to rocketry and hailing from the land down under.. I speak metric... I know not of these feet and inches you speak of...

    QRS: #193
    AMRS: #148

  3. #33
    Join Date
    9th December 2015
    Location
    Fullerton, CA
    Posts
    74
    Quote Originally Posted by snrkl View Post
    Out of interest, did you ask John Beans via the JL contact page?

    He has always been very helpful support wise via email in my experience.
    No, I hadn't. I'd kind of hoped he'd chime in here. It wasn't that big of a deal to me and didn't want to specifically bug him over this. I assumed it was just a quirk, some data somewhere threw the equation way out of whack.
    TRA 16109
    L1 - 07/09/2016 - Wildman Demon Sport on an Aerotech H195
    L2 - 07/08/2017 - Wildman 3" Punisher on an Aerotech J450DM

    Personal records
    Altitude - 15,556' AGL
    Speed - 1,272 MPH

  4. #34
    Join Date
    5th June 2010
    Location
    Danville, CA
    Posts
    714
    Quote Originally Posted by SoCalChris View Post
    No, I hadn't. I'd kind of hoped he'd chime in here. It wasn't that big of a deal to me and didn't want to specifically bug him over this. I assumed it was just a quirk, some data somewhere threw the equation way out of whack.
    Sorry for being slow to this thread. Thank you OneBadHawk for bringing my attention to it. I'm instantly reachable at john@JollyLogic.com, but unless you use certain keywords here or an exact product spelling, I might not see it, or at least not for a while.

    Some of these answers are correct, or pretty close.

    1. Speed is by accelerometer. Orientation doesn't matter. During boost this is a great method for max speed. Baro is not a good method at all, except for gross average speeds over a time period with no venting issues at play (like from ground to ejection, but that average speed is only so meaningful, since there's coast in there, too).
    2. The crazy result is simply a software bug. Ouch.

    It's a bug that I don't recall seeing or at least not often enough to come to my attention (thanks for doing so). The acceleration readings are supposed to be capped at 23G (23G being rocket relative accleration to the earth, 1G is just gravity; save your breath if you feel a physics argument coming on). At 23G and 4 second burn, it should be good to about 4000 MPH if I'm doing math in my head right.

    It's easier to diagnose a bug like this with AltimeterThree, because there's data to study in the spreadsheet. With AltimeterTwo, there's no other data to really dig into. But let me know if it reoccurs, please?

  5. #35
    Join Date
    9th December 2015
    Location
    Fullerton, CA
    Posts
    74
    Thanks for the reply. No worries about it, I wasn't too concerned. I just assumed there was some odd data that was captured that got me the weird result. If it happens again, I'll see if I can get you some more information. Thanks!

    TRA 16109
    L1 - 07/09/2016 - Wildman Demon Sport on an Aerotech H195
    L2 - 07/08/2017 - Wildman 3" Punisher on an Aerotech J450DM

    Personal records
    Altitude - 15,556' AGL
    Speed - 1,272 MPH

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