gluing igniters to plugs

Discussion in 'Low Power Rocketry (LPR)' started by ActingLikeAKid, Oct 2, 2019.

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  1. Oct 2, 2019 #1

    ActingLikeAKid

    ActingLikeAKid

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    So it's fall, which means I'm doing Rocketry Club with the kids' school. We're building and launching the BMS School Rocket. Should be fun.
    One of the perennial problems with kids and rockets, though, is mastering installing the igniter in the motor. You need it all the way in, you need it so the wires aren't touching, and you need to put the plug in while holding the igniter. It's not complicated, but it's tough to explain and get kids to grasp it on the first try.
    What if I superglued some igniters to plugs ahead of time? Any reason why not? As long as I got the height right, any reason that wouldn't work? Then you could just plug the whole thing into the motor.
    Thoughts?
     
  2. Oct 2, 2019 #2

    ebruce1361

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    I tend to think that if the igniters were glued directly to the plugs, there's a chance that the action of inserting the igniter/plug could make a tight enough fit as to damage the igniter.

    That being said, I have an alternative idea that may accomplish essentially what you want. A tiny rubber or plastic stopper like what you find in the openings of chemistry glassware, but sized for the rocket motor nozzles. This doesn't get glued into place on the igniter, but rather can slide freely up and down the igniter leads just above the pyro tip. The igniter is installed like normal, but then the stopper/plug is slid down into place. With this setup, the plug is solid and therefore the wires cannot be shorted unless the igniter is actually broken.

    The main problems with this setup would be the time and effort to manufacture the plugs, and to put them on the igniters one by one. 20191002_151158.jpg

    To simplify the idea, maybe a small wad of clay or play doh mashed onto the leads that can be stuffed into the nozzle? This would still have the possibility of accidentally shorting out the igniter, but would be easier for younger kids to put together.
     
  3. Oct 2, 2019 #3

    BEC

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    Of course before there were plugs we used little balls of wadding. A bamboo skewer with the point blunted is a great tool for pressing wadding balls in tightly. I still do it that way when prepping a cluster model and using Q2G2 igniters.

    Super glue won't stick to polypropylene very well, and that's what the plugs seem to be made of.

    If I'm short of time at a launch with a group of first-timers (and I have the motors) I just prep them myself in advance and stick them in a piece of foam I've poked motor-sized holes in to store/carry them. Alternatively taking the time to make sure that they don't leave the little separator between the plugs still on the end of the plug, and that they turn the rocket nose down, drop the igniter in, press the plug in and THEN bend it over seems to work the best for me. I'm assuming A8s here where dropping the igniter in will get it all the way in. If using B6s then they might need a little push to go all the way down.
     
  4. Oct 3, 2019 #4

    BABAR

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    +1 for wadding balls.
    I use a Bic 9 mm mechanical pencil to shove the ball in. Sharp enough to get the ball deep but not sharp enough for a kid to get hurt (the ball should separate the wires to prevent a short, an added plus).

    For a typical low power bird, if done right, you can gently bear the weight of the rocket by the igniter wire without them coming out.

    Something I learned from der MicroMeister, John McCoy. Still miss him.
     
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  5. Oct 3, 2019 #5

    Gerald

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    We had some scouts this past weekend launching and their cub leader had glued igniters to golf tees at the right depth and they seemed to fit nicely into Estes B and C engines they were using.
     
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  6. Oct 3, 2019 #6

    BABAR

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    Wow I would not have expected that to work. Good thinking. Also gives you a built in stand off from blast plate. in fact the weight of the rocket actually helps keep igniter in place. Nice tip.
     
  7. Oct 3, 2019 #7

    Buzzard

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    I always put a small piece of masking tape between the igniter wires up by the tip. It prevents shorting, as sometimes inserting the plug will push the wires together. It also strengthens the area preventing the bridge wire from being pulled out. Simple, fast, and reliable.

    Chas
     
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  8. Oct 3, 2019 #8

    shreadvector

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    You said "you need to put the plug in while holding the igniter." This makes me think you are not installing them properly. There is no need to hold the Starter (or "Igniter" if you go back in time and buy motors with igniters).

    You hold the motor or rocket with motor vertically with the nozzle straight up.

    You drop the Starter into the motor nozzle. Gravity will keep it there with the tip touching the propellant.

    Insert the plug. The act of inserting the plug pushes the tip of the starter firmly against the propellant face.

    Only ways to fail are:
    1) Kids playing with the wires wiggling and twisting until the thick wires touch.
    2) Not looking at teach starter to ensure the thick wires are not touching or almost touching before they are inserted. If they are too close, they may be pressed together and short instead of being held firmly apart.

    https://estesrockets.com/wp-content/uploads/Educator/Estes_Igniters_and_their_use.pdf

    Not updated since igniters became starters, but this is still the same technique for installation.

    NOTE the words: Do NOT bend the igniter. Many people see the illustration and think they need to bend the starter once inserted. NO. bending it will pull the tip away from the propellant ensuring a very high failure rate. Inserting the plug will firmly press the starter tip against the propellant and also bend the lead wires over. DO NOT pre-bend.

    Estes invented the plugs in response to massive failure rates with bending and taping the "Solar Igniters". They surveyed many youth groups, educators and experienced NAR type fanatics. The NAR people showed them the wadding ball technique which was almost 100%. They then made the plugs which are easier and faster than wadding balls.

    The plugs are one of the best things they ever came up with. IF you read the instructions....

    I see thousands of rockets every year at our club launches and the youth group leaders who tell everyone to bend them when installing them have massive failure rates. Once I show them the correct way, the failures are near zero.
     
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  9. Oct 7, 2019 #9

    ActingLikeAKid

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    These are some great ideas, and really appreciated, thanks!!
     
  10. Oct 7, 2019 #10

    neil_w

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    I'm unclear if you need the kids to install the igniters themselves, or if you can just pre-install a bunch, which is super easy and solves the problem.
     

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