SEP 2006: Vacuum Bypass for Gyros when doing
Aerobatics
So you have vacumm driven gyros in your RV and
enjoy a bit of aerobatic now and then. Here is a simple, cheap fix...
Go to your nearest Home Depot / Garden
Irrigation Shop and buy a Gardena 2-way 90 degree tap fitting plus one
female hose connector fitting. Remove the O-rings and file / grind the three
ends to accept the rubber hose you use. Make up two actuating arms, I used
some scrap .040" 2024 T3 1/2" wide. One about 5" long the other about 2.5"
then mark out the shape of the raised portion of the orange ball valve
levers on the ends of the arms and drill / file / Dremmel the shape out.
From the centre of the ball valve shaft measure the same distance out
on both lever arms (about 1 3/8" to 1 1/2") and drill for a rivet or 6.32
screw. The connecting arm was made out of scrap .025" 2024 T3 is about 2"
long and has the pivot holes the same distance apart as the centre of the
ball valve shafts, thus forming a parallelogram.
The actuating arms were glued to the top of the
orange ball valve tap flange using quick set epoxy and the plastic
protruding above the .040 arm was melted down with a soldering iron for
extra security. The connecting arm was then fitted. To complete the job, the
second hose was routed to the vacuum filter, so that the vacuum pump could
pump clean air in the bypass position.
Now all you have to do is fit it in a position
where you can reach it under the panel or fit a push-pull cable if
inaccessible, then remember to switch the vacuum off before start up, as
your aerobatic session should be planned and not a spur-of-the-moment idea.
Regards, Chalkie.
