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  1. #1
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    Drogue and main terminals on same side of e-bay?

    I purchased a pre-built rocket with a nice e-bay for dual deployment. But please see the attached pic, why would the drogue and main terminals be on the same side of the e-bay? Shouldn't the drogue be on one side and the main on the opposite side? There are no terminals on the opposite side. Must be an explanation, as this is clearly a quality build, doubt it was just a mistake.
    Thanks for any info,
    Bill

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    L1 3/25/17 H135
    L2 8/12/17 J180

  2. #2
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    If the guy used a tender descender or cable cutter, you'd have terminals on the same side.


  3. #3
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    +1. The clue is that there is only one charge container. That is the drogue charge and then another charge containment device (Defy-Gravity, Tender Descender, etc.) releases the main.
    L3, TRA #11847
    Tripoli Indiana #132
    Tripoli Central Illinois #59
    Central Illinois Aerospace (NAR) #527
    Chicago Rocket Mafia, "Big Bucks" Dixon
    ___________________________________

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  4. #4
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    Thanks for the replies. I had never heard of Tender Descender, etc., but I looked them up and they look interesting. Are they used very often?

    L1 3/25/17 H135
    L2 8/12/17 J180

  5. #5
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    I've never used one. I've got a cable cutter that I procured not long before Jolly Logic came out with the Chute Release, so I never ended up using the cable cutter either. The charge flopping about in the wind always made me a little nervous.

  6. #6
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    I've used a cable cutter a few times, but it was mostly for fun, and the challenge.
    Matt, Tripoli #14257
    L1 11/13/16
    L2 2/25/17
    L3 @ LDRS36
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  7. #7
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    10th July 2007
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    You can run one of them (drogue) on long wires, past the chute, so you blow the nose off, and then blow the main out with the second charge in the canister.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  8. #8
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    In addition to the "charge flopping about in the wind" issue, what about the main and the drogue being next to each other in the same tube? Isn't there a substantial risk of tangling?

    L1 3/25/17 H135
    L2 8/12/17 J180

  9. #9
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    Quote Originally Posted by billdz View Post
    In addition to the "charge flopping about in the wind" issue, what about the main and the drogue being next to each other in the same tube? Isn't there a substantial risk of tangling?
    With any chute-binding mechanism you only have one chute, the main. You use the drogue charge to blow the nose cone, the main channel fires whatever mechanism you have (cable cutter, Tender Descender) to unbind the chute. This is what the JLCR does, too... you still need something to blow the nose (most people I know that use them use motor eject, but you may need electronics if the rocket's apogee exceeds the limit of the delay).

  10. #10
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    Quote Originally Posted by OverTheTop View Post
    You can run one of them (drogue) on long wires, past the chute, so you blow the nose off, and then blow the main out with the second charge in the canister.
    Unless you use a piston or something else to seal the BT to get the main out, I wouldn't depend on just a charge to push out a chute. My experience has been that gases tend to go around and past things pretty easily and provide little "push" if there isn't a significant seal in the BT. YMMV
    Handeman

    TRA #09903 L3 :D 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

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  11. #11
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    "You can run one of them (drogue) on long wires, past the chute, so you blow the nose off"

    That's a good point, does the drogue charge need to go deep in the tube, past the chute on long wires, or is it OK for the drogue charge to be in a bulkhead-mounted container, as my e-bay has it? With bulkhead-mount, it would seem that the charge will push the chute deeper into the tube instead of blowing it out.

    L1 3/25/17 H135
    L2 8/12/17 J180

  12. #12
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    It could also be set up for the main to be deployed at apogee, with a back up charge fired later to ensure the chute does not hang up in the tube.
    more rockets then cents

  13. #13
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    Unless you use a piston or something else to seal the BT to get the main out, I wouldn't depend on just a charge to push out a chute. My experience has been that gases tend to go around and past things pretty easily and provide little "push" if there isn't a significant seal in the BT. YMMV
    I have a deployment bag blown out and the chute is then extracted by a drogue. Works reliably.


    That's a good point, does the drogue charge need to go deep in the tube, past the chute on long wires, or is it OK for the drogue charge to be in a bulkhead-mounted container, as my e-bay has it?
    I have run it that way in the past, without a canister at the front. Main worked well each time. Nowadays I run the deployment bag for the main and rather than run the central avionics eMatch forward I have a separate altimeter in the NC for apogee. I think it would be a little more reliable now. Maybe.
    Last edited by OverTheTop; 3rd September 2017 at 02:11 AM.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  14. #14
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    26th November 2009
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    I used a Prairietwister Rocketry cutter: http://www.rocketryforum.com/showthr...-side-of-e-bay
    to do a 38mm MD rocket. Made a long forward ebay for an EggFinder TRS. Cut off the base shoulder of the NC so a Linx antenna could project into the
    hollow nosecone with two terminals on the base of the "longish" ebay. Main 36" chute has a loop at the apex that I threaded a small puck of hard foam over. I attach
    a 10" drogue/pilot chute to the loop. I pack the chute so the foam puck is restrained underneath the chute protector by the cutter's zip tie. I have the main chute
    close to the eyebolt and there is strain relief for the cutter ematch wire.

    Rocket flies to apogee and the apogee charge fires. Rocket breaks in two pieces like a single deploy. I pack the pilot without a protector in front of the restrained
    main chute as it "protects" it from the apogee charge.

    Now the drogue/pilot is out in the open to fill and lines up the main chute for deployment. It can't pull the main out of the protector because the hard foam "puck"
    is restrained against the ziptie. Now I also have the chute protector attached solidly down the harness and there is a bit of slack between it and the chute.
    When the main charge fires, it breaks the ziptie, the pilot/drogue is free to pull the chute free plus the harness now extends passively, between the pilot/drogue
    pulling on the chute and the positioning of the chute protector to pull it off the chute, I get the main deployment.

    This is not my doing, I read it on a link here years ago but unfortunately the excellent pictures disappeared sometime thereafter.

    It's not too hard to visualize: 1. sewn loop at apex of main chute. 2. Small "hard foam" puck (I cut mine from foam I saved from some items I had shipped to me) 3. Positioning the chute protector down the harness a bit and lining up the main chute pack close to the eyebolt. I used a short bit of harness material
    with the 38mm MD rocket. 4. Custom cut and strain relief on the ematch leads.

    Yeah, the JLCR changes everything now but in a 38mm rocket it's a tight fit. I did the project a long time before the CR was available. Plus over 8k' on a cardboard/plywood appropriately laminated finned rocket on a venerable J350 makes it a nice rocket to practice out of sight GPS tracking on a budget.

    Now if Mr. Beans can get a CR to fit in a 29mm airframe, an easily had "Apogee Aspire-like" with an EggFinder mini would be practicable and could routinely
    fly to 5k or more with a reasonable prospect of routinely finding it. I have one partially built with a forward ebay with the antenna projecting into the nosecone.
    Am going to laminate the fins with glass cloth in a tedious 1/3rd, 2/3rds and full span fashion like the 38mm project described above. Should be fun.
    Kurt

  15. #15
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    So it seems the JLCR has pretty much rendered obsolete the cutter and other chute binding mechanisms? I have a JLCR and love it but for fun would like to try traditional dual deploy, guess I'll just have to move one of those terminals to the other side. But before I move it, if anyone has an old cutter they are no longer using and would like to sell it for a low price, please PM me.

    L1 3/25/17 H135
    L2 8/12/17 J180

  16. #16
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    Quote Originally Posted by billdz View Post
    So it seems the JLCR has pretty much rendered obsolete the cutter and other chute binding mechanisms? I have a JLCR and love it but for fun would like to try traditional dual deploy, guess I'll just have to move one of those terminals to the other side. But before I move it, if anyone has an old cutter they are no longer using and would like to sell it for a low price, please PM me.
    As far as obsolete goes, yes it certainly changed the field but with small diameter projects the JLCR is simply too large. Secondly, electronic deployment at apogee results in the lowest energy deployment possible. With a cardboard rocket and late motor ejection
    one gets into the "zipper zone". True, with the JLCR the restrained chute is less likely to result in a zipper but the risk is still there. There are some small electronic deployment devices for 38mm DD rockets and the Pico AD-4 (oop?) can be used for even
    smaller DD rockets. Kurt

  17. #17
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    +1, JLCR is awesome above 39mm. It is a tough fit in 38, obviously no-go below.

    Cutters can do 13 :-)

  18. #18
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    The Tender Descender is still a very viable option is heavy rockets that need large parachutes.

  19. #19
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    There's also the ARRD. Nate Lowrie is our resident expert.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067 ---- BARC #028
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  20. #20
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    I fabricated a chute release cutter out of a spent .45 shell and a hardwood dowel. Drilled out the primer, and cross-drilled through brass and dowel after setting a bit of room (8-10mm) for the match head and powder. Feed ematch in (tight fit), hot glue the primer well to seal the hole, load .34g powder, fit dowel. Stick zip tie through cross-drilled hole, around chute, and secure. The dowel and brass are connected by a braided steel fishing leader, to which is also tied kevlar cord. The cord is tied to the av bay so the assembly doesn't put any strain on the ematch wire (kevlar is shorter than lead for eMatch). I'm sure I didn't invent this, saw it somewhere, but it works remarkably well for being essentially free. I'll post a picture when I get home, since it's tricky to describe for those who haven't seen it.
    NAR 96681
    L1 - May 29, 2014 LOC Norad ProMax, H120
    L2 - Feb 21, 2015 Fiberglassed Madcow Frenzy, J280

  21. #21
    Join Date
    23rd January 2009
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    Quote Originally Posted by OverTheTop View Post
    You can run one of them (drogue) on long wires, past the chute, so you blow the nose off, and then blow the main out with the second charge in the canister.
    Your charge doesn't need to be behind the chute, though it 'might' help. I frequently have the main airframe stacked motor-drogue-drogue charge on bottom of ebay,main charge on top of ebay, main, nose. As long as your drogue fit is loose, you just need to blow it apart with momentum (some mass in the ebay/nose section helps), and the drogue has always come out fine.

    -Ken

  22. #22
    Join Date
    10th July 2007
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    There's also the ARRD. Nate Lowrie is our resident expert.
    I flew one of these for my L3 flight. Worked predictably well.

    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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