User`s manual

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Building Your Rocket to Use the Eggtimer
Mounting
First things first… the Cardinal Rule of tracker mounting is KEEP THE ANTENNA AWAY
FROM METAL OBJECTS. More on this later…
In order to use your Eggtimer TRS with a rocket, it will need to be properly mounted and
secured. The Eggtimer TRS is designed to be used with just about any rocket with a 1.35” dia.
(BT-55) or 38mm payload bay, so any rocket that will take an egg will easily take the Eggtimer
TRS. However, there is some preparation that will be need to be done to secure it properly. If
you’re familiar with egg-lofting, you know that you can’t just throw an egg in the payload bay
and expect it to come back unharmed. The Eggtimer TRS is no exception, like an egg it needs to
be properly protected from the forces of flight.
The easiest way to do this is to build a “sled” for it, a piece of 1/8” plywood or basswood that
can simply slide into the payload bay. If properly done, a sled can be easily removable for post-
flight downloading. Better yet is to build a payload bay out of couplers that fits into the rocket
between the booster and the main parachute sections, there are some excellent references for
constructing payload sections in the Appendix.
If you have a L2 size rocket, it will probably come with a payload bay. If you’re lucky, it might
come with the sled too, but if it doesn’t you’ll probably need to make one. 1/8” plywood or
1/16” G10/G12 fiberglass works well.
The minimum size sled that will work with an Eggtimer TRS is 7 ½” long, if you are using the
wire antenna. If you are going to use an external antenna, that takes about 3” off of that, but
you’re going to need an RP-SMA extension and an antenna. We recommend, however, that you
make the sled as long as the payload bay will allow; if you have a 6” payload bay, for example,
your sled should be the entire 6” in length. You do not want the sled moving around in the
payload bay during flight!
Mount the Eggtimer with at least two, preferably four, 4-40 screws and nylon washers, and use
nylon washers on the top of the board if you are using metal screws. You can use self-tapping
screws if the sled is wood, but we recommend that you put a dab of CA glue in the holes to keep
the screws from coming loose. You can also use a small strip of ¼” plywood to stand-off the
board. If you use machine screws, put a dab of Loctite® on the threads before you install the
nuts, or use Nylock-type nuts. You can also use nylon screws, they are a little lighter but they’re
more expensive too. NEVER use Velcro to mount your Eggtimer TRS, it will generate static
electricity when you remove it and you may damage your Eggtimer TRS permanently.
OK, remember the Cardinal Rule? What this means is THAT YOU CANNOT MOUNT THE
EGGTIMER TRS IN AN AV BAY IF YOU HAVE ALLTHREADS RUNNING THROUGH
IT. OK, so all of the AV bays that you’ve ever build are held together with allthreads, how are
you going to put an Eggtimer TRS into them? The answer is simple… just mount the antenna