The road to L2 is paved with practice. PSII trainer fleet

Discussion in 'Mid Power Rocketry (MPR)' started by Nytrunner, Jun 4, 2017.

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  1. Jun 22, 2017 #31

    OverTheTop

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    I usually put some Velcro under the battery to take the shear forces. Then the cable ties just hold the Velcro together. Don't overdo the tension on the cable ties or the LiPos can be damaged. The stop block is a good idea too and I usually put one in for high-G boosts.
     
  2. Jun 22, 2017 #32

    Nytrunner

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    I really need to go review some of your builds because I recall you've had some great bay setups.

    And I can probably get Velcro at Walmart or Hobby Lobby! (unlike resistors or 9v connectors.....)
     
  3. Jun 23, 2017 #33

    dhbarr

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    http://data.energizer.com/pdfs/lithiuml91l92_appman.pdf , fig. 9 for LiFeS2 AAA.

    A little under 200milliohhms, less than nimh or alkaline, more than vanilla lithium.
     
  4. Jun 23, 2017 #34

    Steve Shannon

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    Something you might consider instead of putting a resistor in series with your match is to put two matches in series and put both in your powder charge. You increase your reliability.
    I've only had two matches fail to light. Both showed continuity afterwards.
    If either of the matches works you'll light your powder.


    Steve Shannon
     
  5. Jun 23, 2017 #35

    Nytrunner

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    Another interesting suggestion. My only worry there is that if Both short, the Hi current will still be having a party with the Stratologger internals.
    I'll be carpooling with a couple HARA guys, one of which is an L2 Elec. engineer, so I'm sure we'll be able to hash out solid path forward at the end of the day.

    Should be able to fit two in there with taped contacts (too bad the red caps won't fit, those were great insulators)
    IMG_20170623_103818455.jpg IMG_20170623_104648374.jpg


    And its done just in time!
    IMG_20170623_104815524.jpg IMG_20170623_104845823_HDR.jpg
     
  6. Jun 24, 2017 #36

    OverTheTop

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    Get some heatshrink tubing, and carefully shrink it onto the metal parts of the eMatch. This is how I do it, and it doesn't add significantly to the size. Never triggered one during shrinking yet, but use safety glasses, and don't try to shrink with a bare flame :wink:
     
  7. Jun 25, 2017 #37

    Nytrunner

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    Perfect success! Thank you to anyone chiming in with electronics wisdom!
    Flight 1.PNG

    First flight on a G118, with a peak of ~160 N's against a 22 oz rocket! I would post a video, but its rather boring because the rocket is gone in three frames and didn't reappear till ~1000 ft.

    Turns out my friend's "I have resistors and a 9v connector" did not translate to "I will Bring resistors and a 9v connector to Southern thunder", so I was forced to go with Steve's idea of ematches in series. The main popped perfectly, and when I got to the rocket, the altimeter was still beeping which I take as a sign that its not fried! (although it did land half in a puddle...friggin rogue tropical system....the field was a swamp.

    I will declare victory and let Vertigo II rest until the next launch. Its time to see how many RSOs I can freak out with the Great Big Inductor mk. 18 tomorrow!

    Next L2 training project: The Fissile Missile. An Argent set up for electronic apogee deployment with a bay similar to the Vertigo II.
    (Fun fact: if you ship work equipment to an Air Station in an Orange Crate, there is a high possibility you will be interrogated by a man with a Geiger counter......let's just say property management wasn't aware that Orange was the sign for "Fissile Material"......)
     
  8. Jun 25, 2017 #38

    Steve Shannon

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    Great job

    Why did you worry these matches would either or both truly short? Some may be designed to do that, I don't know. Ive had two failures that still showed continuity but didn't go low impedance. Did you test some and see some short? If that were truly a concern couldn't you get better ones once you were at Southern Thunder?
    Sorry for all the questions.


    Steve Shannon
     
  9. Jun 26, 2017 #39

    Nytrunner

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    Thanks Steve! Questions can be enlightening.

    In short:
    Mitigate!.jpg

    I'm a Systems engineer by current job. Risk mitigation is just part of how I do things.

    LiPo's and their quirks are untrod ground for me, so I was trying to cover all the bases.
    Hearing that the Stratologger "can" be fried if a high mAh/C-rating LiPo shorts through it, I wanted to take precautions.
    I had no reason to suspect a short from my ematches (they'd been 6/6 and uniformly measures 1.05 ohms), but IF something happened, I wanted some insurance against a toasted alt.

    And this process of working out the kinks and challenges is EXactly what I aim to do with these trainers. Build them strong, but not bricks. Learn to fly the field and conditions. Become familiar and skilled with the available electronics. When L2 comes around, I want the only new thing to be the size and strength of the rocket. My background is Mech. engineering, so building something to survive the motors I plan to fly in it will be the easiest part of the process.
     
  10. Jun 26, 2017 #40

    Steve Shannon

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    I absolutely understand. I'm an engineer also. Understanding risk and mitigating proportionally is really the most important part of our profession.
    Unless designed to short after firing the risk should be very low. In that case having two of them in series makes it even lower but also reduces the risk of having an electric match fail to fire, which I consider a higher risk than experiencing a short. Crashing a rocket of course is worse than zorching the output of your altimeter.
    Having a current limiting resistor as you previously discussed would be one solution but an even simpler solution would be to wire the correctly selected fuse in series with your electric matches.
    I think it's great that you're considering all of these things. That's my favorite aspect of this hobby: learning all the different ways to do things.


    Steve Shannon
     
    Last edited: Dec 3, 2017
  11. Jun 26, 2017 #41

    OverTheTop

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    Another way of limiting current (sometimes considered a bit agricultural) is to use a thinner wire for the connections. This can work if the wire is long enough. It saves weight too.

    I prefer using other ways in rocketry however (normally the smaller battery approach).
     
  12. Jun 27, 2017 #42

    cbrarick

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    I don't know about putting resisters on ematches. The electrical problems and increased complexity should be seriously considered.
    I've been using 2 NiMh batteries in parallel to PerfectFlight HiAlt, MWAD, Stratologger and Stratologger CFs. Never had a problem and I'm not messing with resisters.
    Don't forget every connection you make is a potential failure point. that means every resistor is 2 failure points.
     
  13. Jun 29, 2017 #43

    Nytrunner

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    Hehe, this is bringing back memories of Phys II lab while testing sequentially longer coils of wire to chart the increase in resistance. There may be room in the 5.5" L2 bay for such a method, but I don't think I'll try that in my little PSII transition bays.

    Join the club, I don't know anything about it either :eek:! But it won't hurt to try it if proper precautions are taken. I use a meter to check any igniter wire circuit before plugging it into the altimeter. Although I don't like blowing two e-matches at once, I'm slowly coming around to the redundancy boost it provides (thanks Steve!). That being said, adding a 2nd e-match in series is just as 'complex' as adding a resistor. +1 connection/failure point.

    Have you gotten the idea that I thrive on complicating things yet?
     
  14. Jun 29, 2017 #44

    Steve Shannon

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    You're exactly right. For years I've heard the argument that adding connections/switches/components/etc. increases risk. I suppose there's some marginal statistical truth to it, but that's way too simplistic and ignores the benefits gained by the addition of each. If adding a connection really does substantially increase risk, there's something wrong with your soldering or you've chosen poorly when selecting components. Each component in a series circuit must be considered in terms of its statistical reliability, mean time between failures, increased functionality or some other metric.
    When I hear these simple "every connection increases the risk" pronouncements by people who insist on avoiding switches, my first thought must always be this:
    [​IMG]


    Steve Shannon
     
  15. Jun 29, 2017 #45

    MikeyDSlagle

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    I'm with Steve on this. I dont really see how a connection is another point of failure. Some folks make problems where there are none. Adding a resistor is super easy and there are a hundred ways to do it securely and reliably, with or without solder.

    Two batteries in parallel? That is an extra connection that could be avoided with a larger battery. I don't know your setup so the dual battery may be your only option.

    I am horrible about making things complex. My first sled had aluminum conduit and a vacuum formed cover to hold wires rather than using zip ties. That all got scratched. I am simplifying a lot of things now but still tend to over engineer most things.
     
  16. Jun 29, 2017 #46

    Nytrunner

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    A vacuum formed cover? It sounds really neat in theory, but I'm imagining endlessly poking wires until they align properly underneath it.
     
  17. Jun 29, 2017 #47

    MikeyDSlagle

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    That is exactly right. It worked great once all was in place, no zip ties only a few screws. I was looking for alternatives to using consumables. Started out just for the battery then I thought "What the heck?" I have been gonna try to vac form just a battery cover but my chamber needs improved and reassembled...my daughter thought the hinged lid and all the holes were fun to play with.
     
  18. Jun 29, 2017 #48

    OverTheTop

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    Wires can be tacked down to the sled using CA glue. I do this a lot on my sleds, using Loctite 401. Just a little drop at key locations keeps everything from flapping around. It avoids having to make extra holes for cable ties or other hold-down methods. If I am really desperate I can remove the wiring with a chisel and rewire (exceptionally rare event).
     
  19. Jun 30, 2017 #49

    Kallahan11

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    There's no reason to add resistors to a stratologger, the output is limited to 5 amps on the board, even if they did short the relay closes for 1 second. Also the big can is a capacitor that keeps the board powered so a momentary voltage drop from the battery (max 1.25 seconds conservative, 1 seconds relay on + time for voltage to rise after relay off) will not turn the unit off. This is why disconnecting power doesn't shut the unit off immediately. The only thing adding a resistor will do is drop the current to the igniter, reducing it's reliability, though even that is not an issue with most igniters and ematch's going off at less than 2 amps with your resistor setup wont drop the current enough to effect that.
     
  20. Jun 30, 2017 #50

    Nytrunner

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    I really want to believe you, but there are testimonials about fried altimeters in addition to this very statement by PerfectFlite themselves:

    Now my background is Mech., but what I do know about electronics tells me that 1 second is an eternity in terms of current flow.
    Again, its all risk mitigation. I'm confident in my wire connections and have a meter to check continuity.
     
  21. Jun 30, 2017 #51

    Kallahan11

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    I read the 5A output as if they were current limiting it, not as a maximum value, then I assumed they would short test it to verify that was ok. You are right this is my mistake.
     
  22. Jun 30, 2017 #52

    Nytrunner

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    Gotcha. There's a ton for me to learn about commercial flight electronics, so the questions and suggestions help to keep me researching and double checking.

    Occasionally I've thought of investigating making a homegrown barometric sensor/microcontroller/(transistor/relay) setup and comparing behavior with the commercial ones.
     
  23. Aug 14, 2017 #53

    Nytrunner

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    Long time no post. been traveling for work and weddings, building a QCC explorer, and preparing to transfer to a new program with my company.

    There has been a little progress on the Fissile Missile (PSII Argent). Someone sold me a few 2.5" PSII couplers and left a bulkhead with an eyebolt epoxied in one of them.....
    I was quite baffled as to how to address the issue and in my frustration ended up gluing another bulkhead on the back end and drilling a bunch of holes in it.
    Likely got the idea from some of Qqake2's threads. I like how it turned out and am debating whether I want to adapt one into my L2 design, but I'd have to make an extra cut on the airframe, and I'm hesitant to do that.

    IMG_20170812_214532636.jpg IMG_20170812_214548905.jpg IMG_20170813_191142782_HDR.jpg

    As per usual with these, I put both lugs and buttons on to maximize flight options.
    Fins are foiled as best I can by eye on the belt sander, and the TBII fillets are drying. Next comes a few rounds of TB Q&T to increase the radius.
    There's also some pretty solid TBII coverage of the seams and joints inside since I left the rear ring off for the time being.

    IMG_20170813_191215712_HDR.jpg

    Here's a topic of thought: HPR and wood glue.
    At Southern Thunder, Vertigo II flew on a G118 with an initial Thr/Wt of ~18 and reaching ~.6 M. The only epoxy was on the retainer, the nose weight ring, and the sled.
    This isn't an extreme flight, but its not bad for a PSII rocket (with the thinner Estes MPR tubes). However, my club friends were incredibly ........dubious of its chances with the G118.
    I'm happy to have proved them wrong B) . At that same flight, I heard someone telling a college flier "Hi power Needs to be built with Epoxy!"

    Counter to their doubts and that flier's opinion, I've heard several accounts on the forum of woodglue being used successfully on HPR models (not crazy flights that is). The argument for this position is that wood glue is specifically formulated for bonding .....wood! Wood (and paper/cardboard) are natural composites and respond well to the aliphatic(?) resins of the woodglue leading fliers to use it as a lighter weight alternative to epoxy on those rockets (that aren't doing super flights. which they'll probably fiberglass reinforce and require epoxy anyway).

    What does the reader think: How far would yo take wood glue?
    Since my L2 airframe is LOC tube and plywood fins and intended to be a show flyer that doesn't break records, I've been leaning towards using wood glues on whatever areas aren't plastic/metal (tubes/fins/couplers, etc.....). How much pushback should I expect from the the HPR=Epoxy crowd?
     
  24. Aug 14, 2017 #54

    Kallahan11

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    Bill from balsa machining did his level 2 on a 3 in cardbord rocket, all wood glue no epoxy, on a j570.
     
  25. Aug 22, 2017 #55

    Nytrunner

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    Transition e-bay (T-bay?) done thanks to another 1.9" sled from Apogee, sheer inserts epoxied and holes tapped, rivets installed in the fore end of the bay, sled mount holes tapped, baffle adhered firmly, Q&T fillets solid, and lugs/buttons installed. It's now entered in the paint queue right behind the QCC, so its time to order necessary decals/stickers. I'm going to have fun with this one.

    This came together quicker than expected, so I may be on track for L2 at NARAM. The Fissile Missile was originally intended to be an apogee deployment testbed, but I epoxied a forward charge well on the T-bay just for fun. May go and do the same to Vertigo II. I don't Haaave to use it.....

    IMG_20170821_205846355.jpg

    Final details are the switch hole, switch mounting, and preliminary CFD sims.
     
  26. Aug 22, 2017 #56

    Nytrunner

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    Well that's one vote for wood glue!
     
  27. Aug 26, 2017 #57

    Nytrunner

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    Ordering some lettering from stickershock for Vertigo II and the Fissile Missile. This time Mark's price beat sign-specialist.

    Also ordered a set of Hyperbolic Upgrade Stickers! I loved the idea of these things but never had a use until now.
    I'm considering contacting David Malki the creator and asking if he's going to do another run sometime soon, because I REEAlly want my L2 to have one of those "Gets Kind of Warm" stickers on the aft end.

    Edit: And Solidworks Flow toolbox is behaving itself today, so I've started running studies. Pressure distribution below will help me locate my vent holes for the T-bay.

    Pressure8.PNG
     
  28. Aug 28, 2017 #58

    Nytrunner

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    Speaking of Flow; I mentioned I've been having good luck with the simulator recently.
    For whatever reason, the geometry of the Argent hasn't thrown it any computational curveballs, and I haven't experienced a crash during any of my cases with it.

    That being said, I've been ramping up the velocity to see how the methods handle the CP, and the results have been cool if nothing else.
    Currently my poor little Acer is grinding away at Mach 2.4. At this point I had to turn on Flow Toolbox's "High Mach Number Analysis" and my laptop is Not happy.

    All the previous cases running full resolution took ~45 minutes. This one says it might be done in ~11 hours (if it doesn't hit its travel without convergence and decide to upgrade the mesh resolution for the 3rd time.....)

    I'll check back in on it at breakfast tomorrow......

    CP shift.PNG
     
  29. Sep 1, 2017 #59

    Nytrunner

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    Got my decals from stickershock!

    The Vertigo II now has its markings!
    IMG_20170831_224803998.jpg

    And the Fissile Missile's deal will wait till its painted. Which I will start as soon as Harvey's outliers and its humidity leave Huntsville.
    I also cut a Keying tooth out of the midsection to keep things aligned.
    IMG_20170831_225027546.jpg
     
  30. Sep 9, 2017 #60

    Nytrunner

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    Detailing is finished! I knew those leftover Mammoth sticker stripes would come in handy!
    IMG_20170908_232941895_HDR.jpg IMG_20170908_233422002.jpg

    Any missile that could involve Fission deserves a warning label.
    IMG_20170908_232950164.jpg

    I also epoxied on the switch to the T-bay sled and made sure the 2s battery and Stratologger would fit. It'll all be the same as Vertigo II's T-bay, just inverted.
    May get to fly it Sunday if I can grab some composite motors from the (overpriced) hobby store local! First mission is to attempt successful electronic apogee deployment!
     

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