Firestorm AV Bay

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The Avionics Bay in a rocket provides a place to mount all electronic equipment while protecting it from any pyrotechnics used during the flight of the rocket. The most basic AV bay used by SSI is the firestorm AV bay, which is primarily used to house an altimeter for duel-deploy for an L2 certification flight. (Need to add a nice picture of an AV bay here)

Structure

The picture to the left shows the general structure of an AV bay. The mounting rack provide the surfaces for mounting hardware. The bulkheads (also called end caps) protect the equipment from ejection charges and provide a surface for mounting charge wells and connection points to the shock cord. The all threads clamp the AV bay together and provide the rigid elements that prevent to AV bay from being ripped apart during ejection. The coupler encapsulates the AV bay while providing a structural element to connect the two halves of the rocket's air frame.

Bulkheads and mounting rack

The solid works files of the AV bay, and an already made SLDDRW file for exporting the parts to be laser cut can be found here: GrabCad Files

The bulkheads and mounting racks are typically made of laser cut duron. This is for easy of manufacturing, low cost, strength, and resistance to cracking. Each bulkhead consists of an inner and an outer piece to ensure that so that the securely fit into the coupler. The inner and outer pieces for each bulkhead are epoxied together, as shown in the images to the left. The pegs of the mounting rack fit into the slots on the inner bulkhead. On one side, the bulkhead should be epoxied to the bulkhead (this is typically the end of the AV that is facing the ground when it is mounted in the rocket). Also attached to each bulkhead is a an eye bolt, for attaching to the shock cord on either side, and a charge well. Two more holes should be drilled through each bulkhead for igniter wires to be routed through.

NOTE: Completely assemble the structural components of the of the AV bay, with the mounting rack, bulkheads, and coupler put clamped together, and all of the holes on the bulkheads lined up before epoxying anything, to make sure that every piece is oreiented correctly, then disassemble and epoxy. This is easier than you might think to mess up.

Mounting Avionics

NOTE: The specific electronics used in an AV bay often differ, so there is no single best way to mount everything. Before drilling holes or permanently attaching anything, lay out all of the components and make sure that you have enough room. Remember that there are all threads running on each side of the mounting rack, so make sure there is space for them when mounting electronics. Also, remember that wires are actually a thing, so plan space for them. Think about how you will close up the AV bay with wires attached to the top and bottom bulk head. Think everything through before mounting stuff.

Altimeter

While each type of Altimeter are mounted slightly differently, they should all be mounted with screws and spacers, or standoffs. To get the correct hole pattern on the mounting rack, place the altimeter on the mounting rack in the correct position, mark where the screw holes in the altimeter PCB are, and drill them out. The holes should be sized such that the screws you are using can thread into the duron. Make sure that you use spacers, as shown in the diagram, between the altimeter and the mounting rack. Otherwise, the barometer may be pressed against the duron and not take accurate readings.

Batteries

Mounting the 9 volt batteries is relatively simple. Use snap on connectors to connect wires to the batteries. Both batteries are typically mounted on the same side. Use double sided foam type or PCB mounting tape to attach the battery to the mounting rack, then clamp the batteries in place using zip ties that run through the horizontal slots in the mounting racks.

Pin Switch

The pin switch is used to keep all avionics in the rocket powered down until the rocket is on the pad an ready for launch.

See: How to Build a Firestorm