January 10, 2013 at 9:09 am #3359
Venner Time Delay Switch (reference 27N/56).
A fire suppression time delay switch, this one is from around the early to mid 1950s.
Extracts from ‘FLIGHT’, 12 January 1950, article “Delays For Safety. Less Haste, More Speed in Fire Suppression”
“If a fire breaks out in a piston-type aircraft engine during flight, it is highly desirable that the engine should be stopped as soon as possible, in order that the fire may be deprived of “forced draught”. -//- Clearly, if the fire-suppressing system is to operate at its maximum efficieny in such circumtances, an artificial delay should be imposed to ensure that, within certain limits, the suppressing agent is not discharged until the airscrew is feathered.
A device to ensure such a delay is manufactured by Venner Time Switches, Ltd., New Malden, Surrey. Known as the Venner Time Delay Switch (reference 27N/56) it also ensures that eventually, whether the engine has come to rest or not, suppressent is released after a maximum delay of 20 seconds. The switch has been produced to the requirements of the M.o.S. Directorate of Instrument Research and Development, and embodies a clockwork mechanism in conjustion with a solenoid-operated release.
The solenoid has been designed to pass a current not exceeding 2.5 amps at 28.5 volts D.C., and to have a minimum operating voltage of 16 volts at 20 deg C. Loading is effected by depressing a button protruding through one side of the switch casing. The sequence of operation is as follows: Through the feathering button, a circuit from the positive and earth terminals is supplied to the main coil of the relay. This opens the main extinguisher-bottle contacts and closes a circuit to energize a holding-in coil for a period of eight seconds; simultaneously, the relay starts running.“-//- etc.
January 13, 2013 at 10:30 am #3375March 8, 2013 at 5:21 am #3618March 13, 2013 at 1:32 pm #3660
Greg DietrichModeratorMarch 14, 2013 at 3:12 pm #3662
Hi Greg, yea I’ve seen that pic. I ran the numbers for a few weeks, constantly searching part number lists and still nothing definite to ID it.
However, here’s a shot of another type of unit I had thought of that could contain it – a modular rack mounted item that snaps into place. Notice the card slots at the top of the boxes, approximately the right size for the circuit board to stick out of, maybe?
I’m still looking for it, even if it’s just for personal satisfaction lol.
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