It was decided after a bit of risk analysis regarding the parachute that it would be advisable to have a gimbal arrangement to ensure that the SPOT Messenger antenna is pointing directly up at all times. This is because Spot Messengers need to be orientated correctly; and if for whatever reason the parachute did not deploy and the HAB did not maintain this orientation for sufficient time, then we may not get any measurements on its decent. [That being said, I did perform a few tests with the Spot Messenger around the wrong way and it did seem to function OK. But we cannot take chances.]
There are several designs that can be found on various sites using hamster wheels and various ways to “attach” a spot messenger. I decided to design one from scratch.
Firstly, I got some 90mm PVC pipe and cut out a 1/3 circle segment about 20mm wide. I was able to fit this snug into the Spot Messenger III slits at each end. The 90mm PVC pipe was just the perfect thickness and the “spring” in the PVC pipe helps to keep the pipe segment “attached” to the Spot Messenger. Then a hole was drilled through this pipe segment and a skewer was passed through. This was all mounted inside a 110mm sewer PVC pipe. This 110mm sewer pipe is cut in various places to allow the easy rotation of the Spot Messenger and to reduce weight. Pieces of wire are inserted in VERY small holes drilled through the skewer to stop
The 110mm sewer pipe segment happens to sit very neatly into a tissue box which we will use to build a fiber-glass device to allow rotation of the whole system inside the payload.
I’ve taken a few pictures of the device and attached them below.