Mounting Your Eggtimer Quasar
The Quasar is relatively small and light, and can be mounted several ways. The most common
way of mounting it is using four #4 screws, either self-tapping screws for wood sleds (put a drop
of CA glue in the pilot hole first to prevent the screws from loosening in flight) or machine
screws (we recommend using Nylon-insert nuts so they don’t come loose). We STRONGLY
recommend that you use Nylon washers between the board and the screw heads and nuts to
prevent any possibility of shorts. You’ll also need to put some kind of spacer between the
bottom of the board and the sled, about 3/16” high… you don’t want the parts on the bottom of
the board getting pushed against your AV sled. There’s a mounting template on the Eggtimer
Rocketry web site to help you plan your installation.
We do NOT recommend using double-sided foam “servo” tape to mount the Quasar to your AV
sled. There are parts on both sides of the board, so the bottom isn’t flat. You won’t get 100%
coverage with the servo tape, so there’s a potential for it coming loose in flight, which is bad.
However you mount it, be careful not to overtighten the screws and possibly bend the circuit
board. Parts on the bottom of the board can break if you force them against the bottom of your
sled… don’t ask us how we know. We recommend that you leave a little space between the
components on the bottom of the board and the sled… about the thickness of a credit card.
The Quasar can be mounted in any direction, there’s no “up” or “down” side. Since it’s longer
than it is wider, you’ll probably mount it parallel to the centerline of your rocket. We do
recommend, however, that you don’t mount it so that the pressure sensor is directly across from
the vent holes in your AV bay. You can get funny currents during flight, which may
compromise the accuracy of the altitude readings.
Since the Quasar uses a barometric pressure sensor to determine altitude, you’ll need to drill a
few holes in your AV bay to vent it to the outside air. There’s a lot of debate about what the
right size for the holes is, how many, etc., but the most accepted rule of thumb is: One ¼”
diameter hole for every 100 square inches of AV bay volume.
Now the tricky part is that you don’t want ONE vent hole… the optimum number is THREE,
equally spaced along the AV bay perimeter. This works out to about three 5/32” holes for every
100 square inches of volume. That’s just about the size of a 4” diameter AV bay that’s 8” long,
so you can work up or down based on that. We’ve found through experience that the actual size
of the holes isn’t terribly critical… just drill the three holes and you’ll be fine.
Wiring Your Eggtimer Quasar
The Quasar is designed to have the power connector directly soldered to the board.
This prevents the battery connections from coming loose in flight due to vibrations and G-forces.
The output wires can be similarly soldered to the board, or you can use the included screw
terminal block with them.
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