Regarding this quote on the trv from the Oildyne brocure;

“It is a fixed relief valve with a pressure

setting approximately 100-140 bar (1500-2000 psi)

above the system relief valve pressure.”

As I read this, if the pump is rated to produce flow at 3000 psi, the TRV is set for 4500 – 5000 psi. That seems way too high for our systems.

The third set of pressure switches on my 360 are acting up. I am thinking about a spring project to upgrade them. I bought two new/old stock pressure switches for about $75 including shipping.

http://www.ebay.com/itm/DIRECT-AUTOMATION-PSD25-0P-1450H-PRESSURE-SWITCH-/220904940181?_trksid=p3286.m7&_trkparms=algo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D6005931030562248892

They are limited to 250 ma load current and a max overload of 2900 psi. My plan is to reset the TRV’s to the neighborhood of 1200 psi. At that pressure motor current is less than 30 amps.

I found 50 amp PNP Darlington transistors to replace the big power relays. They have enough gain to be driven directly from the pressure switch through an appropriate resistor.

http://www.ebay.com/itm/MJ11032-Darlington-Power-transistors-NPN-Audio-Amp-x2-/180663839378?pt=LH_DefaultDomain_0&hash=item2a10676a92

I would appreciate some information from those who have installed pressure gauges.

1… At what pressure does your up pressure switch close and open?

2… At what pressure does your down pressure switch close and open?

3… Does the momentum of the motor cause the pressure to spike well above the pressure setpoint?

4… In high G pull-ups and/or turbulence, do you see fluctuations in pressure, from what to what?

Thanks for your feedback.

From: Bruce <BGray@glasair.org>
Subject: [LML] Re: IV-P Hydraulic Pressure Switch
To: lml@lancaironline.net
Date: Monday, January 30, 2012, 12:05 PM

You might look at,

 

http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Pressure_Sensors_-a-_Pressure_Gauges/Pressure_Switches/PSD25-0P-5800H

 

Solid state and adjustable, don’t forget the matching cable

 

Bruce
WWW.Glasair.org

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Craig Berland.
Sent: Monday, January 30, 2012 10:53 AM
To: lml@lancaironline.net
Subject: [LML] IV-P Hydraulic Pressure Switch

 

A few weeks ago when returning home my main landing gear failed to extend.  I have determined the pressure switch that controls the hydraulic pump relay has failed. The kit supplied switch has a minimum temperature rating of -22 deg F.  Since my switch failed with about 110 hrs on it, has anybody found a better switch?

On a personal note: When building N7VG, the only thing my wife wanted was her own personal landing gear lights. She was all over the fact that the mains did not lock down. The emergency pump worked and all is well.

Craig Berland

IV-P N7VG