uer16

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Posts posted by uer16

  1. Quote

    No, I don't believe it. Someone tell me this is not true. Not even BPA would do that. It's probably mostly run by men much older than that!



    Quote


    Maximum age Analysis of statistics compiled over many years indicates that incident rates tend to increase as student jumpers get older. This may be due to slowing reaction times and sometimes less acute senses as the years go by. Risk assessment suggests the tipping point to be when a person reaches their mid-fifties. On this basis, to avoid increased risk, the maximum age at which even a hale, hearty and healthy person can be admitted to start training under BPA rules for solo parachute jumping is before they reach their 55th birthday, although some BPA Affiliated Parachute Training Organisations may set a lower age limit than this based on their own risk assessments. This restriction does not apply to tandem students, where the descent is in harness with a qualified instructor - although health requirements continue to apply.

  3. Hajo

    important parts of your lifesaving devices are "worn to shit"


    That was a bit of a hyperbole.
    Hajo


    140 jumps, A-license.
    buying and installing risers


    Not sure how it is in Germany, but basic gear maintenance is part of getting an A-license here.

    betzilla

    Item m3345 is the hard riser housing pair ...


    So the D224 risers don't come with hard housings installed? I assumed they already had them.

    skytribe

    You can pretty well ask any manufacturer to build velcro toggles/risers


    Thanks for the suggestion, this is probably what will end up happening.

  4. Sorry I wasn't clear. The velcro and toggles are fine, it seems to have been replaced at some point. The risers themselves are worn (especially where the harness ring loads the ty-17 webbing, and the white loop).

    Are paragear D224 velcro risers? I like how secure velcro is, hence why I'm looking for the out-of-fashion risers.

  6. https://www.youtube.com/watch?feature=player_embedded&v=ODhBajI4JaI

    Should be required viewing to whoever thinks that yelling CUTAWAYY at a bunch of people is a good idea.

    To be fair, the guy apparently was a lieutenant colonel, and in true military style, he executed the order immediately without thinking.

    Moreover, the guy on the ground was yelling at a cutaway'd canopy that was spinning, not a person, which makes the whole thing even more ridiculous.

  8. Most of the time that's not a very accurate method. Very good batteries (like Maxell) maintain rated voltage regardless of them being at 5% or 95% capacity. You can't determine anything useful from a voltage measurement.

    If the voltage does drop substantially as they are drained (Panasonic ones do, for example), then you can load them at rated load (15k ohm for Panasonic) and measure voltage at one of the temperatures that the cell was tested at (-10C, 20C, or 60C). Then try to match the measured voltage to the discharge curve from the datasheet. Basically too much work to be worth it.

    Best bet is to just replace them every X amount of hours, they're basically free compared to jump tickets anyways.

  9. Unless they are fake batteries.

    I bought a few Chinese 6000mAh 18650 cells once, after characterizing one of them at rated current, the capacity turned out to only be around 250mAh.

    Not sure if there's a large market for fake coin cells, but it's certainly a possibility.

    Regarding performance, Maxell's CR2032 datasheet suggests that they have the flattest discharge curve of all, staying at 3V till the very end.

  14. Last year I made one with a 7-segment LED display, which, even though it was the brightest on the market, was too dim in the sun. And at 100mA current draw, the battery couldn't last a day.

    I'm now interested in making one with a big 2.7" Sharp Memory display. Will work on the hardware over the next couple months, will let you know of the progress.

    Software-wise, writing render code for the 400×240 (or any other really) display would be a first for me, so help would definitely be appreciated.

    I'll put all the stuff in a bitbucket repo and link it later here.

  15. Quote

    Wouldn't the MicroSD port make the unit very susceptible to water damage?



    I meant a hinge-type microSD holder inside the device (i.e. you can't take the card out without taking the device apart). Basically as an alternative to on-board memories.

    The bigger issue with making it water-resistant is probably the membrane for the pressure sensor(s).

  16. I've used the MPL3115A2 with great success, has internal temperature compensation and altitude calculation, simplifies firmware a bit. The SCP1000 seems obsolete as of now.

    And +1 to whatever Gary said, implementation details like what exact hardware to use aren't that important.

    There's also no point in limiting the amount of sensors for the initial device for data acquisition. I'd go with a gyro, an accelerometer, magnetometer, an altimeter or 2 (which includes a temp. sensor internally), and perhaps even GPS, although this one would severely constrain a bunch of stuff like battery and case size.

    And also slap a microSD holder for logging all the stuff, since eeprom/flash or whatever ICs have worse byte/$ ratio than an SD card and are easier to use. And data can be retrieved from a broken device this way too.

    Something like an N3 with all of the above sounds pretty interesting.

  18. I'm willing to put time into it.

    Reverse-engineering is a waste of time, especially with the old cypres with its' external ADC and other obsolete stuff.

    Designing from scratch is complex, but mostly trivial. Anyone who knows C and can read a manual can follow MIRSA-C or the shorter JPL standard. PCBs are $5 per square inch nowadays, i.e. basically free. Machining an enclosure is free if you have access to a shop. Really, the only thing that one can't make themselves is the cutter. In any case, a prototype would run at most a couple grand with the above, large-ish scale production is a completely different story though.

    Imo, the regulatory and validation issues are bigger than the technical ones. (i.e. who will let me, or anyone else test-jump, or maybe drop-test a homebrew AAD?).

    In reality, starting with something a bit less serious like an open source altimeter that would integrate AAD code to watch for inadvertent fires would probably be a good first step to see how it goes. Basically a risk-free test platform. Actually that sounds like a good winter project, any volunteers to test-jump one-of-a-kind altimeters?

  19. Man this is funny.
    "A is better than B because facts"
    "what facts?"
    "Google it" :D

    Unless both companies give away all the C code/hardware design/mechanical design to a 3rd party for analysis all this yelling is senseless and feels like brand loyalty for subjective reasons.

    Nobody outside the manufacturer (potentially not even) will ever really know what is going on inside an AAD's brain, and seems like people can't make peace with that.

    Besides, describing an AAD as "safety critical" is doing a disservice to it's users imho. It's a consumer electronics device that's made to consumer electronics standards, just like your shitty iPhone. It's not like this crap is certified to DO-178/DO-254/IPC610-class 3, etc...

    Wouldn't it be nice if someone made an open-source (both software AND hardware AND mechanical design) AAD, so when it inevitably malfunctions, everyone can take a look at the design and see exactly where it went wrong. And fix it.

    // end rant

  21. Quote


    Oh man, don't we know it! We spent a solid three months just on battery selection and design. :)



    Heh, I believe that :D. Thanks for going through all the questions, pretty rare nowadays to see the engineers that involved with end users.



  22. Finally found a perfect rig for the right price.

    Was sent out on the 24th of July.
    A week later it did not arrive (last known location was warehouse 10m away from destination >:() and got reported as lost by the shipper.

    3 days later it surfaces literally on the opposite end of the U S of A. Fine I think, shit happens, can wait an extra week. Another week goes by and it shows up at the final warehouse. Happy knowing I'll get it soon, right? Wrong, these fucks have lost it again the second time at the exact same warehouse.

    It's now been a total of 3 weeks since shipment and UPS has no idea where it is. When I called they basically told me to fuck off and refused to give out any info (let alone take any action) since I'm not the shipper.

    Fuck UPS >:([:/]

  23. Now that reminds me (was a while ago). I didn't actually sew any zippers, but was planning originally. I sewed the side and bottom flaps together on both reserve and main (was awkward due to stiffeners). Put 3 fastex clips on top main flap, and one clip on the top reserve flap. Then cut off the legstraps without replacing the heavy webbing. Basically exactly like you're describing.

    It can probably be done to look nice, if one has skill/talent (I don't).

    Also, not sure how one would put a rig on with no legstraps, but then again, people jumped after forgetting to put a rig on at all :S..

  25. All I'm saying is it's good to be cautious when putting something that might burn like thermite right against your risers, even if the chance of that happening is remote.

    If you wanna get technical:
    There are lots of different kinds of Lithium batteries. AADs have hard-shelled low-current ones not known to spontaneously combust. Newer laptops, tablets, and phones have flat vacuum-packed lipos that blow the fuck up if you bend them or if you puncture the thin plastic casing.

    Unfortunately, looking at the battery pic https://res.cloudinary.com/indiegogo-media-prod-cld/image/upload/c_limit,w_620/v1438124823/g6j1dg71pubyo2j1oxyv.jpg, it looks like they opted for the latter (not 100% sure though).

    Apart from that, the thing seems well designed, really like the fpc antenna, would be nice to know more. And no, I don't dislike AADs, but do wish that they were cheaper.