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This can be done very easy
with a simple T-shuttle valve. I got one but haven't felt like putting the pump
out yet. The problem is that when the pump stops the shuttle valve, in the
pump, closes. This stops the fluid from retuning to the reservoir when it
expands from the heat. By adding a small T-shuttle valve in the low side (down)
of the system, it would return the fluid to the reservoir automatically. The low
side of the pump connects to one side of the T (Top), drill a hole in the
reservoir and connect the other side of the T (Top) to the reservoir, the bottom
of the T goes to the actuators (down side ). Now when you run the gear down is
closes the T-shuttle valve and flows the fluid to the down actuators. when the
gear runs up, the fluid from the down side flows back through the pumps shuttle
valve until it closes. When the fluid expands and the pump valve is closed the
T-shuttle valve opens and flows the small amount of fluid back into the
reservoir.
I haven't had a chance to
connect this up to my pump and it might take a little adjusting to get it to
work just right but this should completely solve the "No gear down" problem on
hot days. And do the job in the background with no buttons or extra levers, etc.
Randy
Stuart
LNC2
----- Original Message -----
Sent: Wednesday, February 06, 2008 9:28
AM
Subject: [LML] 235/320/360 gear dump
valve idea
I have been thinking about this for some time.
With the
way the hydraulic system is currently designed, you equalize the pressure on
the high and low sides when it is opened. For those of us who have pressure
gauges, you can see that you can have significant pressure on the system even
when the valve is opened. I want to be able to not only equalize the pressure
between the high and low sides of the hydraulic system with the dump valve but
also release the pressure on both sides.
Today I purchased a 3 way
valve to do just that. The idea is to open the valve
connecting the high and low sides and also releasing the pressure back
to the tank.
I will most likely run a low pressure line like nylaflow back
to the pump and make spin up a custom fitting on the lathe out of aluminum to
go into the dipstick hole and terminate the return line there. I will make a
needle dipstick checker that will screw into the same fitting for checking
fluid level.
If you wanted to do it the easy way, you could always just
dump the low pressure line out the belly of the airplane onto the ground. It
would take very little fluid to drop the pressure and there would be no need
to deal with connecting the low pressure fluid line to the tank.
I hate
pulling the airplane out of a cool hanger into the warm sunshine and watching
the gear pressures rise to 6-700 lbs before the master switch is turned on! We
all know what happens when they hit 900. Yep no gear retraction as the upper
limit has been tripped by the system pressure.
My new valve would fix
that!!!
I hope...
Chris Z and others who are much smarter than me
please chime in with your input....
Am I missing
something???
Thanks!!!
Randy L. Snarr
N694RS 235/320
Salt
Lake City, Utah
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