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The recent discussions about the inadvertant deflation of a
door seal by apparently switching off the toggle valve has inspired me to relay
a different approach we've taken to operate the inflatable seals. Instead
of using the Clippard MJTV-3 toggle valve we are using a small electric solenoid
valve, ETO-3, also made by Clippard. When no electric power is supplied to
the seal pump assembly the seal is vented through the valve. When power is
applied the valve directs compressed air to the seal and closes the vent
line. So, whenever the "cabin seal" switch is turned off the seal
automatically deflates. Or if the master is turned off it also goes
limp. Recently we did a retrofit installation of an inflatable seal
on John Halle's Legacy and decided to make it even more idiot proof by putting a
simple micro switchwired in series, behind the canopy lever in the closed
position so that when the canopy is unlatched the seal also deflates.
Works great and is easier than reeducating the idiots. I'm sure there are
any number of small pneumatic solenoid valves that will do the job as
well.
On the subject of the seal pump assemblies, we've noticed that
the pressure switches that come with them have been arriving set at about
22 psi which is too high and will cause the canopy or door to be forced
outward. Somewhere between 5 and 10 psi seems about right. There is
an adjusting screw between the spade terminals on the pressure switch, although
my first attempt at finding it caused some head scratching as it was covered
with a black coating of some kind. Scrape it off and the screw can be
turned counterclockwise to reduce the pressure setting. I use a simple
mechanical gauge with a small hose hooked to the air output to set it.
Someone recently was looking for a toggle type air valve to
use as an alternate static source and said the MJTV-3 wouldn't
work. However, it should work fine if the exhaust port is plugged
making it a two way valve.
Leighton Mangels
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