Safely removing powder from CTI?

Discussion in 'Propulsion' started by Andrew_ASC, Sep 13, 2018.

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  1. Sep 13, 2018 #1

    Andrew_ASC

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    If somebody has a min diameter rocket for example and wants to use a CTI motor without an motor ejection charge for electronic deployment charge only for cases where Apogee happens way after the maximum delay length and a motor eject backup is impractical. What steps to remove the stock ejection charge from a CTI product? What steps to put dog barf where? Pictures please. With AT motors we simply don’t include the powder and I am familiar with that process for AT not for CTI. Thanks.
     
  2. Sep 13, 2018 #2

    timbucktoo

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    Get a sharp Xacto knife and cut away the white paper. Do this over some newspaper. The BP can then be easily poured out. You might have to poke at it a bit, sometimes its clumped together but use a tooth pick or something non metallic. Make sure you get it all out of the touche hole too. Then stuff it with dog barf & cover with masking tape. I have also seen people just fill it with 5 minute epoxy.
    This is from a 38mm motor with BP removed. image1.jpeg
     
    Last edited: Sep 13, 2018
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  3. Sep 13, 2018 #3

    jimzcatz

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    What Tim said. Pics are not really necessary, it's just a paper cap. I use a small screwdriver.
     
  4. Sep 14, 2018 #4

    OverTheTop

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    I try to not use metal tools around BP. Chance of sparks if I slip and hit something else. I use a sharp wooden skewer to puncture into the paper cap and flip the cap off. Then the BP can be poured out.
     
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  5. Sep 14, 2018 #5

    jimzcatz

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    There is nothing in the BP well to create a spark. Nothing against caution, just saying.
     
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  6. Sep 14, 2018 #6

    OverTheTop

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    I understand, but if I slip with the scalpel and hit a nearby tool, or drop in on the metal bench? I'd rather not have any unnecessary frights thanks! They use wooden tools around fireworks for a good reason I think.
     
  7. Sep 14, 2018 #7

    dhbarr

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    Nylon spudger seems like something good to add to my range box anyhoo.
     
  8. Sep 14, 2018 #8

    Andrew_ASC

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    Thanks.
     
  9. Sep 14, 2018 #9

    grouch

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    I've always used a lit cigarette. Have I been doing it wrong?
     
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  10. Sep 14, 2018 #10

    Kallahan11

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    Yes, a cigarette is bad for your health and probably doesn't have the thermal capacity to burn all of the paper. Try using an Oxy-acetylene torch, it's finicky work so forgo a face shield so you can see it better.
     
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  11. Sep 14, 2018 #11

    Nytrunner

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    The couple times I've done it, I put some masking/electrical tape over the tip of a small flat head.
     
  12. Sep 14, 2018 #12

    dshmel

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    Thermite works well too.
     
  13. Sep 15, 2018 #13

    OverTheTop

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    I always wondered what "head end ignition" was :eek:
     
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  14. Sep 15, 2018 #14

    snrkl

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    IMG_9992.jpg
     
  15. Sep 15, 2018 #15

    OverTheTop

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    Set fire to your hair
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    Eat medicine that's out of date
    Use your private parts as piranha bait.

    Dumb ways to die
    So many dumb ways to die...


    Love that song :).


    BTW I wrote those words from memory.
     
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  16. Sep 15, 2018 #16

    snrkl

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    Invite a psycho-killer inside

    Scratch a drug dealer's brand new ride

    Take your helmet off in outer space

    Use a clothes dryer as a hiding place
     
  17. Sep 15, 2018 #17

    Andrew_ASC

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  18. Sep 15, 2018 #18

    Steve Shannon

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    I jab the two jaws of a needle nose pliers through the paper cap covering the ejection charge and then peel it off. Then I add the powder to my medicine bottle full of BP. I wear safety glasses while doing anything with BP. I put a little grease into the well.
     
  19. Feb 12, 2019 #19

    kjkcolorado

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    Was looking at some older threads and came across this one. Just curious, why do you ‘cap off’ (dog barf and tape, epoxy, etc) the ejection charge well after removing the BP? I took a look at the online instructions for CTI Pro54 and I didn’t see anything about covering the well if removing the BP.
     
  20. Feb 12, 2019 #20

    Nytrunner

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    In case anything untoward happens. Delay blowbys have happened, forward closure issues have happened, etc...
     
  21. Feb 12, 2019 #21

    Steve Shannon

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    It’s probably not necessary and honestly probably doesn’t do anything. If there is blowby the grease, dog barf, and tape won’t do anything. You would have a forward closure failure. However it does inhibit the forward end of the delay grain so if you want to use that motor as part of a cluster you don’t have to worry about it igniting from the forward end. Admittedly that’s an extremely unlikely thing to worry about.
    Epoxy or a screw through the touchhole would prevent a forward closure failure though.
     
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  22. Feb 12, 2019 #22

    GrouchoDuke

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    I always put some 5 minute epoxy in the BP well just to make sure no gasses go were I don't tell them to.
     
  23. Feb 12, 2019 #23

    cerving

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    I don't do anything with the well once I dump the powder. The delay charge is a slow burning smoke charge, and really isn't going to flare up. Like Steve said, if you get blow-by, nothing is going to stop it... probably not even filling the well with epoxy.
     
  24. Feb 12, 2019 #24

    GrouchoDuke

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    Good point Cris. Thinking about it more, the main reason I got in the habit of sealing it is that in some of my MD rockets, I don’t have a sealed bulkead between the motor and the avionics bay. A hole there with a path to the open nozzle could potentially really mess up altimeter data on the way uphill.
     
  25. Feb 13, 2019 #25

    OverTheTop

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    The hole through to the charge well is quite small in diameter so even at high pressure there is not excessive force. I think you will find epoxy would survive quite well there, in the well ;).
     
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