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larger image of it. |
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Two
Missile Works RRC2
altimeters will be installed into the Starfire altimeter bay.
Two are used for redundancy to help make sure the parachute really does
get deployed! |
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Some 3/4" wide aluminum
stock material from the local hardware store was used to create brackets
to hold the altimeter power switches. |
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The aluminum strip was
first cut to length and then drilled with at 1/2" diameter hole for
mounting the power-switch. |
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Next it was simply bent
into the required shape using a bench vise and a rubber mallet. |
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This is a good view of how
the power switch mounts into the bracket. The switch is actually a
voltage selector switch with a screw driver slot that allows it to be set
in two different positions. The switch has high detent force and
spring loaded contacts which makes it a good choice for rocketry so that
acceleration, shock and vibration do not open the switch. It also
has two sets of terminals that can be wired in parallel to provide extra
redundancy. The screw driver slot makes it very convenient to
actuate the switch with a small flat blade screwdriver through the
altimeter static ports in the body tube.
This switch is available
from Missile Works
for about $5. It is part number
MWC-SW-2. |
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A piece of 1x2 wood was
used as the main mounting surface for the altimeters and switch brackets.
A 5/16" hole was drilled through the length of the 1x2 block so that it
would slide over the threaded rod that runs down the center of the
altimeter bay. |
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Here we have all the
individual parts ready for assembly. Two altimeter circuit boards,
two switch brackets with switches installed, some #4 pan head sheet metal
screws and some #4 nylon nuts that will be used as spacers. The
sheet metal screws go into the wood block and hold the altimeter boards in
place. The altimeters are spaced above the surface of the block by the #4
nylon nuts to allow for the leads sticking out the backside of the pc
boards. Some #6 pan head sheet metal screws are used to
mount the switch brackets to the sides of the wood block. |
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All the parts are now
mounted on the wood block, the wiring has been completed and the batteries
are installed. The unit is now ready for final electrical
testing inside a vacuum chamber before the first flight. |
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Looking down into the
Starfire altimeter bay. The altimeter unit has been mounted onto the
threaded rod that runs down the center of the altimeter bay. A
washer and wing nut are added to the threaded rod to hold the altimeter
unit in place. The power switches on the brackets are "presented" to
the altimeter vent holes around the periphery of the altimeter bay. A
couple of angle brackets prevent the altimeter unit from rotating so that
the switches remain aligned with the vent holes. To power-up the
altimeters on the launch pad, a small flat blade screwdriver is
inserted through the vent holes and used to actuate the switches. |
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Design drawing for the
Starfire altimeter bay. |
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Here we see the structural
components of the altimeter bay. A coupler with internal fiberglass
re-enforcement is in the upper right. The forward bulkhead is a
sandwich of a wood bulkhead and a G10 disk. This photo also shows a
strip of fiberglass cloth that will be used to strengthen the bond between
the forward bulk and the coupler tubing. The aft bulkhead is
removable to allow access into the altimeter bay. The aft bulk head
has the U-bolt for parachute attachment and will also have the ejection
charge holders mounted on it. |
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Looking down into the
altimeter bay coupler where the strip of fiberglass cloth was used to
strengthen the bond to the underside of the forward bulkhead. |
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The aft bulkhead also
contains six small threaded inserts around its circumference to allow the
mid-section airframe body tube to be secured to the bulkhead.
The edge of the bulkhead was drilled and a brass insert installed.
The brass inserts are part
number 900164007 from
McMaster-Carr and accept a #6-32 machine screw. |
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Installing one of the
threaded brass inserts. |
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The brass insert is flush
with the edge of the bulk head.
The black stripe is an
o-ring that seals the joint between the bulkhead and the altimeter bay
coupler. |
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The completed altimeter bay
aft bulkhead along with the design drawing for it.
The two larger white pieces
are PVC pipe end caps to be used as ejection charge holders. The
smaller white piece is a threaded PVC fitting that serves as an igniter
wire seal when filled with clay and the threaded cap is installed. |
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