Friday, January 8, 2010

Silly Putty Timer DT (Dethermalizer)

The silly putty timer has been around for well over a decade in free flight aeroplane model making.

Over the last few months, Tony Mathews, free flighter extraordinaire, has been experimenting with micro versions of the timer. He has come up with a timer that is amazingly small - 1/8" x 0.7" (3 x 18 mm) - and light at about 0.3g.

Here is a photo of his excellent Stinger 8" CLG with a micro silly putty timer installed. It operates an aluminium drinks can foil DT. Notice that the foil is on the inside of the circle turn, causing a steep downward spiral. When I saw that, my initial reaction was more "Death Trip!" than De-Thermaliser! Encouragingly, he reports that small gliders like this suffer no damage on DT deployed landings.

Tony has put together an absolutely superb pictorial build guide here. You must look at it. I've made some timers according to his plan and found them to be quick and easy to build. Cutting aluminium tube with a scalpel is fun! You need to roll the blade over the tubing to make one cutting groove around the circumference and perpendicular to the axis. As you continue to roll, it then pings off at air pistol speed, so one trick is to thread some wire or string through the aluminium tubing before cutting it, to catch the piece.

I have some ideas to try to improve the consistency of the timer, which is not as good as a commercial viscous button timer. If I find success I will report it.

Here is more background on silly putty timers. Useful sources of information include articles by Peter Michel (on Ramon Albon's great free flight site) and Pensacola free flighters. Thayer Syme's super page and diagrams dating back to 1996 are here. Martin Gregorie has posted some useful and detailed information here.

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