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  1. #1
    Join Date
    11th April 2017
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    Brisbane Australia
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    372

    AV bays in small rockets

    ok: so I am planning an Apogee Aspire for supersonic flight - now a 29mm MD rocket going to 1300m means I will definitely need a tracker.. I also want to jam my JLA3 in, there is no point going fast and high without getting the data to know how high/fast we went..

    So the payload I am looking to carry is a JLA3 and an eggfinder mini..

    Initial planning is for a G76G or a G77R - I am simming with both for the time being, but haven't made a hard choice and am open to other G class motors.. if I get to H that I see are available through my local purveyor, suddenly I am exceeding altitude ceilings and getting into places I don't feel I am ready for yet... While I am open to suggestions of other motors, my main focus here is on understanding and gaining the skills to design/construct the AVbay elements..

    So, to my question: How do people build / attach AV bays on to small diameter rockets that are using motor ejection charges? I can certainly build an AV bay that slots onto the top of my airframe under the NC, but I am not really certain how people actually attach the top end with the nose cone in a way that allows access to the actual AVbay...

    (an aside with the additional BT based AV bay, as soon as I add it to the sim, I'm losing my mach breaking capabilities on the 29mm G motors I can get my hands on... which kinda sucks..)

    I have also been pondering installing the EggFinderMini in the nose cone - I am certainly able to take the end off the nose cone, but then I am a little uncertain of how the whole thing is capped off at the blunt end to keep it all together and still allow for NC retention and access to the AV package. I note that HPR folks often have an allthread running between the NC tip and the back NC bulkhead and replace NC shoulders with a coupler and a bulkhead, but in such a small package, this doesn't seem feasible..

    I am interested on peoples thoughts here...

    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. #2
    Join Date
    19th February 2017
    Location
    The world, probably
    Posts
    135
    Throw some rivets in with your Apogee order. I use them all the time- you push the button and they expand, then pry it back up and they contract again so you can take them out.

    https://www.apogeerockets.com/Buildi...mndkfb0f5n93n1

    crmrc.org

  3. #3
    Join Date
    27th December 2012
    Posts
    265
    Click image for larger version. 

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    This is an Estes BT-60 nosecone with an Eggfinder. I don't have it in front of me so I'm going by memory. There is a 2" length of body tube (silver) that is glued 1/2 onto a 2" piece of coupler. I have a bulkhead glued inside the body tube and on top of the coupler. I drilled two holes in the bulkhead and tied a length of 1/8 kevlar for retention point. Sled is glued to bulkhead and along inside of body tube. Nose cone is attached with 2 plastic push rivets.

  4. #4
    Join Date
    21st March 2011
    Location
    central America
    Posts
    1,850
    You can use plastic push rivets, or you can drill holes through nosecone and body tube (so they're aligned) and epoxy nuts to the inside of the nosecone. Re-enforce the body tube around the holes with CA. I've got some short 8-32 mushroom-head torx machine screws I use for this (but regular square-sided ones would work, too).

  5. #5
    Join Date
    1st September 2010
    Location
    Tucson, AZ
    Posts
    1,030
    instead of removing the base of the nosecone, cut a "window" in the shoulder big enough to admit the tracker and battery. Squish in some foam pieces to keep things from jostling around, and cover the window with some tape. I've had luck tapping the Polypropylene material to accept a 4-40 screw or two as a retainer- would recommend that if you're going to increase the mass of the cone. Sooner.boomers advice to epoxy nuts in is solid, but probably not required...YMMV.
    NAR 96681
    L1 - May 29, 2014 LOC Norad ProMax, H120
    L2 - Feb 21, 2015 Fiberglassed Madcow Frenzy, J280

  6. #6
    Join Date
    26th August 2016
    Location
    Divide Colorado
    Posts
    95
    Have you thought about using the Altus Metrum Telemini? It would save you weight I think and provide for all the systems you need +

    Tinker

  7. #7
    Join Date
    11th April 2017
    Location
    Brisbane Australia
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    372
    Quote Originally Posted by Tinker View Post
    Have you thought about using the Altus Metrum Telemini? It would save you weight I think and provide for all the systems you need +

    Tinker
    Interesting... I just took a look. My initial thoughts are that the ham based transmission makes things more complex for me.
    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

  8. #8
    Join Date
    26th August 2016
    Location
    Divide Colorado
    Posts
    95
    Basic Ham radio is a pretty simple test here. (Not that I have gotten off my ass and done it yet, but in the very near future). I hadn't thought of that it might be more laborious there. That being said, weren't you looking for an easy PC connection and gps plotting of the flight? That would be bread and butter for this family of products, if not this one.

    But I get the impression that AM is like Apple, you buy into the family or you don't.

    Tinker

  9. #9
    Join Date
    6th September 2009
    Posts
    1,491
    Quote Originally Posted by snrkl View Post
    (an aside with the additional BT based AV bay, as soon as I add it to the sim, I'm losing my mach breaking capabilities on the 29mm G motors I can get my hands on... which kinda sucks..)
    Yes, this is the reality of the Aspire. Apogee claims 1 mile (and maybe Mach) on an F10. However, if you want to actually measure data and find the rocket afterwards, then an F10 isn't gonna cut it with all the extra mass for electronics. Nor is a G motor, as you are finding out.

    Lots of threads in the forum to give you ideas. I have done ebays in 38mm (Wildman Blackhawk), but not 29mm.

    All that said, I trust the simulation over the altimeter when it comes to speed determination, anyway!

  10. #10
    Join Date
    11th April 2017
    Location
    Brisbane Australia
    Posts
    372
    I've managed to sim the aspire to Mach 1.02 with the added weight of an eggfinder mini and LiPO plus the JLA3 using an aerotech g80...

    I'll be postulating on that in a new thread later in the week.

    For now, the suggestions here have me better understanding ebay construction techniques - I might look at starting a generic small BT60 ebay and / or nosecone mod while I have some time off work this week...
    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

  11. #11
    Join Date
    9th July 2014
    Location
    Phoenix, AZ
    Posts
    1,394
    You can pare the weight of the electronics down by using a small lipo (100mAh) for the Eggfinder and pulling the case off of the JLA3. Stuff all of it and foam into the nosecone. Probably the lightest way to get everything with what you've got already. Then a couple of dabs of hotglue to hold the last bit of foam in. That should hold it all in and still allow air through the foam so the JLA can do its thing.

  12. #12
    Join Date
    19th February 2017
    Location
    The world, probably
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    135
    Quote Originally Posted by Buckeye View Post
    Yes, this is the reality of the Aspire. Apogee claims 1 mile (and maybe Mach) on an F10. However, if you want to actually measure data and find the rocket afterwards, then an F10 isn't gonna cut it with all the extra mass for electronics. Nor is a G motor, as you are finding out.

    Lots of threads in the forum to give you ideas. I have done ebays in 38mm (Wildman Blackhawk), but not 29mm.

    All that said, I trust the simulation over the altimeter when it comes to speed determination, anyway!
    Are there any AT 29-180 G motors that would fit the bill? I know CTI has the G54 Red Lightning longburn in their 3G case but it ships HAZMAT.

    Sent from my LGL44VL using Rocketry Forum mobile app
    crmrc.org

  13. #13
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    2,985
    g75j comes closest, I think. Of course there's several H motors in that same case to do a Mach Mile.

  14. #14
    Join Date
    26th November 2009
    Posts
    4,368
    Quote Originally Posted by sl98 View Post
    Click image for larger version. 

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    This is an Estes BT-60 nosecone with an Eggfinder. I don't have it in front of me so I'm going by memory. There is a 2" length of body tube (silver) that is glued 1/2 onto a 2" piece of coupler. I have a bulkhead glued inside the body tube and on top of the coupler. I drilled two holes in the bulkhead and tied a length of 1/8 kevlar for retention point. Sled is glued to bulkhead and along inside of body tube. Nose cone is attached with 2 plastic push rivets.
    Yup, Nosecone payload bay just like sl98 shows. You use a coupler and a short body tube length. Or long bodytube length as the case may be.

    Click image for larger version. 

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    That long upper bay holds an EggTimer TRS with a Linx antenna projecting up into the nosecone with the shoulder cut off like sl98 shows. Two terminals on the aft bulkhead for apogee and a Prairietwister Rocketry cutter to unfurl the
    main. Single break deployment. Nice high flights on the venerable J350. Pricey glass nosecone, LOC tubes and 5 ply plywood for fins with 1/3rd, 2/3rds and full span 'glass cloth lamination on the fin can. 12 pieces of glass cloth that
    were a pain to apply but worth it.

    Click image for larger version. 

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    This is the result above when stupidhead used the mayhem rail guides on a dirty rod that bound up. Rocket blasted through and destroyed one half of the guide and still went 8500', Mach 1. I asked Bill if I could buy a replacement half
    and God bless 'em he sent me a new guide of the stronger material gratis. It was my fault and I woulda' paid but that's the kind of guy he is...... Plus it showed me how strong that laminated fincan is! Just a few paint chips.

    Kurt


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