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  #31  
Old 05-06-2011, 11:27 AM
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Bill Bill is offline
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Default Parallel Staging Design 101, part 5

...and here is the design...

Forward Attachment.

On the core stage, near where the front end of the booster would be, mount a staple. Not the familiar rectangular office staple, but a U-shaped one like those used to run wiring along a wall. For a small model, the staple should protrude just over 1/2" from the tube. It must be perpendicular to the length of the tube so that viewed from the end, it looks like a miniature croquet wicket. A small piece of wood or a thick centering ring will be needed on the inside of the tube for a secure mount.

Cut a small slot near the front end of the booster tube just large enough to slide over the "wicket." Glue two short pieces of launch lug on the inside of the booster tube, one just in front of and the other behind the slot. A short length of dowel or wire attached to the nose cone slides into the "wicket" (and through the guiding and reinforcing launch lugs) to hold the front end of the booster in place for launch.

Glue a short piece of compression spring to the outside of either the booster or the core stage near the attachment so that it will be caught between the booster and the core. An easy source for this part is the common retractable ball point pen. A small piece of soft foam may be substituted. This tiny part is vital so that the front of the booster pivots away from the core when it is released.


Aft Attachment.

Get a small cup hook. If that is not available, get a screw eye. Cut the open end of the hook or eye with a hacksaw so that you have about a 150 degree opening relative to the surface the hook or eye is to be attached. Use some emery cloth to smooth rough edges from the cut. Insert this hook into the base of the booster with the opening facing down. If the booster is based on a BT-55 or BT-50, an AR-2050 or AR-5055 style centering ring may be enough to serve as an anchor on the inside of the booster tube. Otherwise, back up the tube with a small piece of wood.

Attach two staples at the aft end of the core stage. They should be separated by slightly more than the thickness of the hook on the booster. The rearmost staple should protrude just enough so that the booster hook can fit onto the "wicket." The other staple should stick out a little further as it will bear the thrust of the booster. As with the forward attachment, backing is needed inside of the tube.

Construction notes.

The attachments have been described starting with the front one to aid understanding of how the system works. In practice, I strongly recommend that the aft attachment be installed first. It is much easier to ensure that the staple and slot of the front attachment are properly aligned if the aft attachment is complete.

Flight preparation.

Prepare the booster as you would an ordinary rocket. Before sliding the nose cone into place, point the front end of the booster away from the core and insert the hook into the lower of the two "wickets". Pivot the booster into place and slip the slot over the front "wicket." Seat the booster nose cone making sure that the retaining dowel or wire is in the "wicket." That is all there is to that.

Unless parts are laser cut or extreme care is used in construction, it is likely that the spacing between the attachments will vary enough between different sets of boosters and their attachments so that a booster can only fit in one set of attachments. Mark the booster and attachments as they are installed for reference during flight preparation.

Because of the unique geometry involved, a Vostok booster cannot simply blow its nose, so there is more work left to do...


Bill
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Last edited by Bill : 05-09-2011 at 10:28 AM. Reason: Corrected a dimension in the forward attachment
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  #32  
Old 05-08-2011, 07:51 PM
mkrobel mkrobel is offline
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Seems to me that these would work, especially if they were placed inside the body tube so that only the "hook" portion protrudes and the slit is properly aligned.

http://www.apogeerockets.com/glider_pod_hooks.asp
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  #33  
Old 05-09-2011, 10:27 AM
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Default

Quote:
Originally Posted by mkrobel
Seems to me that these would work, especially if they were placed inside the body tube so that only the "hook" portion protrudes and the slit is properly aligned.

http://www.apogeerockets.com/glider_pod_hooks.asp



That is a good idea for gliders, but I wonder whether the added weight may be a problem. If the glider half replaces nose weight which would have been needed anyway for trimming, it would not be an issue.

However, one of the goals is not to depend on rare parts. There is no way to guarantee that Tim does not decide to stop making these. Plus I really want the booster to swing out before dropping off.

While buying parts for my prototype, I discovered that either the round end of a cotter pin or the loop spring end of a safety pin may be a good replacement for the lower wicket of the aft attachment, so I bought some of each to try.


Bill
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: countdown begin cr dup . 1- ?dup 0= until cr ." Launch!" cr ;

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