A Tripoli Technical Advisory Panel Document

By Alan D. Davis TRA L3 #5935

Electronics

The PHASAR will incorporate dual Olsen FCP-M2 altimeters. I have used the Olsen FCP-M2 in my previous Phasar project and have had nothing but excellent performance with this unit. The ease of use, programmability and data downloads made this choice a no-brainer. The FCP-M2's have a nice feature that allows for a delay at apogee detection for the backup unit so both charges will not fire simutaneoulsy. The main unit will have a charge set for 750' and the backup unit set for 650'. Another good reason for using the FCP-M2 is there ability to set main chute deployments in 50' increments as opposed to 4 or 6 main chute settings.

The design of unit is from my good friend Steve Baughman, a completely modular unit which can be incorporated in any of my 4" rockets.

The construction of the unit was fairly straight forward with the exception of the Olsen's being mounted in a modular way to allow for easy access. So after my 1st design I wanted to incorporate a "inner frame" which would hold the Olsen's. The primary problem with the design was the limited space in a 4" tube for dual electronics plus all the associated wiring involed to remain modular and accessabile. The result was the inner cage which would hold the Olsen's.

The next part was to design the board unit on which the Olsen's would mount and slide over the all-thread rods. This was accomplished with a piece of .125" G10 cut to width and height to fit in the avioncis section. Now, how to attach the unit to the all-thread rods running through the avionics section and still be removable. Another good friend of mine Mike Hudgeons came up with the design of using aluminum arrow shafts as the guides to slide over the all-thread rods. This unit will now slide over the all-thread rods and allow for easy removal. Carefull planning and a template allowed for drilling the holes in a pattern that would allow for all the components.

Now the next part was to mount the Olsen's on the G10, no problem here just used the hole template sent with the units with some standard nylon stand-offs. The other item I corporated was drilling holes in the G10 for the wiring to pass through plus the addition of nylon tie straps for battery retention.

The next problem to overcome was managing the wiring and making that portion modular. The solution was using computer part wiring harnesses, the wire guage was perfect and the connectors would allow for easy removal without having to undue the actual connections to the screw termimals on the Olsen's. The wiring harness is held in place on the G10 with plastic wire holders.

The next consideration was how to external arm the units at the launch pad. Again, another great friend of my, Ed Jacoby turned me on to key switches, the only problem with the previous units where the length would not allow for the unit to slide into the bay area. The solution was solved from Hawk Mountain which sells some great key switches that are fairly short and would allow for the unit to slide into the bay area.

The last problem was the amount of real estate on the bulkheads to mount 2-sets of terminal connectors, an eyebolt attachment and the ejection canisters. A carefull hole pattern and design solved this concern.

All in all the desgin and construction required some careful fore-thought and a lot of inspiration from my fellow rocketeer's that culminated into a great desgin that I feel very confident in achieving my L3 status.