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Re: PYRO SECRETS OR QUESTIONS

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  • tsklebar
    Put your pistil inside another set of shell halves. If you have the pgi anthology, jim widmann s article has pictures and descriptions. Barring that, take
    Message 1 of 5 , Jan 21, 2013
      Put your pistil inside another set of shell halves. If you have the pgi anthology, jim widmann's article has pictures and descriptions. Barring that, take some cardboard hemis the size of your pistil, using a punch, punch some holes in the shell halves to make it look like a colander. Also glue a passfire tube from one half of the pistil casing that will reach to the outside of outside casing. This is done so that when the fuse burns, it first ignites the pistil burst charge while also passing fire to the burst of the rest of the shell. put in tissue paper on pistil halves, put in stars, add burst for pistil, close pistil (tape the halves together if you must), spike pistil with string in an off center pattern to hold the pistil halves in position, glue assembled pistil halves and passfire tube to the outside casing, then put in stars and burst for outer pistil as is usually done. If anyone wants a demo of this process at our next build, just let me know.

      Tom S.

      --- In PrairieThunderPyrotechnics@yahoogroups.com, "deanw3576" wrote:
      >
      > I have some questions that i would like to throw out to the group.
      >
      > #1 Does a strobe rocket produce thrust in the STROBING stage of the burn?
      >
      > #2 How do you maintain a symmetrical pistil in a ball shell?
      >
      > #3 what do you think would cause a PROVEN whistle rocket to cato after storage(3 months)?
      >
    • Andy Holcomb
      Hi Dean 1. A strobe rocket does produce a small amount of net thrust during the strobing stage, but not enough to really be meaningful. The original creator of
      Message 2 of 5 , Jan 23, 2013
        Hi Dean

        1. A strobe rocket does produce a small amount of net thrust during the
        strobing stage, but not enough to really be meaningful. The original creator
        of the strobe rocket, William (Doc) Barr (not ex PGI president Bill Bahr)
        actually made his rockets with the entire fuel grain being strobe comp. They
        didn't have much thrust, so you couldn't really even put a small header on
        them. Steve LaDuke and a few other guys came up with the idea to use whistle
        fuel as a "booster".

        2. The first trick is to pack the shell so full that the contents can't
        shift around during pasting/handling; I think that's the important part, and
        use a layer of tissue paper across the top of one of the hemis to keep
        everything solid when you close the two parts together.

        On shells 5" and above, most guys use a perforated inner paper hemisphere.
        The best results come from "pasting" (2-3) layers of gummed paper tape on a
        plastic shell of the appropriate size for your pistil, the first layer
        sticky side out, and the others sticky side in. After it's dry, you slice
        the shell in half to form a thin set of hemis, perforate them with whatever
        your chosen method, and assemble the inner petal just like you were making a
        smaller shell inside. The perforations let the fire propagate more evenly.

        Jim Widmann was selling commercial perforated hemis from 4"- 8" a few years
        ago, that had 5/16" holes punched in them, so I suppose you could use a step
        drill to recreate those. Ned uses one of these to perforate his inner hemis:
        http://compare.ebay.com/like/290407649600

        If you want some inspiration as to what's possible, check-out this guy's
        video of his 4" shells: http://youtu.be/Ypm6kP7XSrc , and
        http://youtu.be/R59unyXC3vQ Amazing!


        3. Low humidity been my issue lately. The paper tubes shrink when they dry,
        and everything is stressed. I've even had the tube split/crack on the
        outside. I keep motors sealed in Ziploc bags now.



        -----Original Message-----
        From: PrairieThunderPyrotechnics@yahoogroups.com
        [mailto:PrairieThunderPyrotechnics@yahoogroups.com] On Behalf Of deanw3576
        Sent: Saturday, January 19, 2013 4:20 PM
        To: PrairieThunderPyrotechnics@yahoogroups.com
        Subject: [PrairieThunderPyrotechnics] PYRO SECRETS OR QUESTIONS

        I have some questions that i would like to throw out to the group.

        #1 Does a strobe rocket produce thrust in the STROBING stage of the burn?

        #2 How do you maintain a symmetrical pistil in a ball shell?

        #3 what do you think would cause a PROVEN whistle rocket to cato after
        storage(3 months)?



        ------------------------------------

        Yahoo! Groups Links
      • andys_junk_address
        Here s a photo of one of Ned s perforated hemis for the inner pistil:
        Message 3 of 5 , Jan 25, 2013
          Here's a photo of one of Ned's perforated hemis for the inner pistil:

          http://www.fireworking.com/sites/default/files/Articles/double-petal/perforated%20hemi.jpg


          --- In PrairieThunderPyrotechnics@yahoogroups.com, "Andy Holcomb" wrote:
          >
          > Hi Dean
          >
          > 1. A strobe rocket does produce a small amount of net thrust during the
          > strobing stage, but not enough to really be meaningful. The original creator
          > of the strobe rocket, William (Doc) Barr (not ex PGI president Bill Bahr)
          > actually made his rockets with the entire fuel grain being strobe comp. They
          > didn't have much thrust, so you couldn't really even put a small header on
          > them. Steve LaDuke and a few other guys came up with the idea to use whistle
          > fuel as a "booster".
          >
          > 2. The first trick is to pack the shell so full that the contents can't
          > shift around during pasting/handling; I think that's the important part, and
          > use a layer of tissue paper across the top of one of the hemis to keep
          > everything solid when you close the two parts together.
          >
          > On shells 5" and above, most guys use a perforated inner paper hemisphere.
          > The best results come from "pasting" (2-3) layers of gummed paper tape on a
          > plastic shell of the appropriate size for your pistil, the first layer
          > sticky side out, and the others sticky side in. After it's dry, you slice
          > the shell in half to form a thin set of hemis, perforate them with whatever
          > your chosen method, and assemble the inner petal just like you were making a
          > smaller shell inside. The perforations let the fire propagate more evenly.
          >
          > Jim Widmann was selling commercial perforated hemis from 4"- 8" a few years
          > ago, that had 5/16" holes punched in them, so I suppose you could use a step
          > drill to recreate those. Ned uses one of these to perforate his inner hemis:
          > http://compare.ebay.com/like/290407649600
          >
          > If you want some inspiration as to what's possible, check-out this guy's
          > video of his 4" shells: http://youtu.be/Ypm6kP7XSrc , and
          > http://youtu.be/R59unyXC3vQ Amazing!
          >
          >
          > 3. Low humidity been my issue lately. The paper tubes shrink when they dry,
          > and everything is stressed. I've even had the tube split/crack on the
          > outside. I keep motors sealed in Ziploc bags now.
          >
          >
          >
          > -----Original Message-----
          > From: PrairieThunderPyrotechnics@yahoogroups.com
          > [mailto:PrairieThunderPyrotechnics@yahoogroups.com] On Behalf Of deanw3576
          > Sent: Saturday, January 19, 2013 4:20 PM
          > To: PrairieThunderPyrotechnics@yahoogroups.com
          > Subject: [PrairieThunderPyrotechnics] PYRO SECRETS OR QUESTIONS
          >
          > I have some questions that i would like to throw out to the group.
          >
          > #1 Does a strobe rocket produce thrust in the STROBING stage of the burn?
          >
          > #2 How do you maintain a symmetrical pistil in a ball shell?
          >
          > #3 what do you think would cause a PROVEN whistle rocket to cato after
          > storage(3 months)?
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
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