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01-23-2012, 10:01 AM
Russ Kotlarek | Mechanical Valves vs Manifold Block
As many were aware I have replaced the solinoid driven Manifold Block with Mechanical Hydrualic Valves. The Valve I elected to use happens to be the same one used in the Lake Amphibian oddly enough.
This past weekend was the magical fill up and test of that system. Without so much as the slightest issue the hydrualic system performed perfectly first time out of the gate. No leaks, no mis-plumbed lines, even the new retractable Manual emergency pump worked perfectly. No real award needed here as the system is so straight forward it is just that easy to do.
I also moved my Zinc Chromated Aluminum Hydraulic lines up under the door Jam rails. Creating a shroud over them protects them nicely from the environment of the tunnel and the hazards of passengers. Towards the back seat they pass into the rail and through to the rear of the plane in a perfect location to hard point the lines and run hoses to the Gear and flap accuators. I also placed my break lines here as well.
Although I built the system from scratch, I believe the system would be fairly easy to adapt to the existing Seawind system using the Manifold block. Please feel free to contact me for details and Hydraulic system schematic or further info.
Bottom line I made three changes to the system.
1) I replaced the electrically driven Manifold block with two Mechanical valves made by Parker (Parker 8441). Available in retail for $500 to $700 each or ebay new in a box for $45 - $90 each. Mine ($45 New in a box). They are easily rebuildable with a set of O-Rings commonly available.
2) I Replaced the Small accumulator with another Ebay buy off of I understand a Black Hawk Helicopter. $9000+ Retail to the Govt. New in a box about 11" long accumulator $45. This is optional. I wanted a charge large enough when full to Cycle the gear down and lock it without any additional pumping. That worked perfectly with about 500 lbs of pressure still left in the system.
3) I elected to increase the volume of fluid in the tank and made another aluminum Tank to replace the plastic one. That was a pretty easy task as well. Our pumps have a one screw option through the bottom of the tank and a 4 screw option from the top down. I elected not to put a hole in the bottom of the tank which seemed like a problem waiting to happen and went with the four top scews. Somehow the loss of a plastic tank I know will harden and crack at some less than entertaining time worked for me. It is a very simple design I can give details if you wish to email me.
Benefits:
a) The system does not self Bleed! the system holds presure for days. The Electric pump only runs when you use the system. No cycling of the electric pump every 20 Seconds. This is NOT by nature of the the larger accumulator but by the fact the mechanical valves do not leak.
b) It does not fail easily! At least not like the manifold block. The Mechanical valves if they get dirt in them will simply crush the dirt and it is then free to be picked up by the filter. It will not stop the valve from operating properly. In my Lake Amphib. having owned it now 20 years (ouch) has never come close to failing. In that, if it were to leak one can rebuild the valves very easily in about an hour and a half including taking them out and re-installing them
c) The system Holds a charge large enough to fully cycle the Gear. We are instructed in the Lake to verify a full charge before touching the Gear handle hence you know it will make the full down and locked position.
d) Only one system need be functioning. As it stands for the original system with some oddity the electric system and Hydraulic system both need to be functioning to cycle them. In this case the system once charged will act on its own without electrical needed to move the actuator. They are fully mechanical. The Valves themselves consist of a handle on the side of an aluminum block that is about 2.5" square and about 1.25" thick. Small, light weight and hugely dependable.
e) The hand pump and electric pump both pump fluid from the tank to the accumulator. If the electric pump fails you simply pump up the accumulator to pressure with the hand pump and cycle the gear or flaps as normal. It takes about 50 strokes with my remotely mounted hand pump to take the Accumulator from full empty 0 PSI up to 1200psi. The final couple of strokes are stiff but very doable and are not really needed to fully extend and lock the gear. I need about 850 PSI in the accumulator to fully move the gear which is very easy to pump up to and it requires about 40 easy strokes from zero up to 850psi.
f) The manual valves have up and down positions but they also have a bypass position to bleed the system down and an "off" position that the flaps use but also should you have a leak or cylinder bypass you can actually troubleshoot the problem while flying to determine which systm is compromised. Normally an electric pump running when not in use warns you of this fact as the system again does not naturally bleed off and you can shut off all systems and activate one at a time to determine if it is flaps or gear. Also saving precious fluid if it is being lost from a leaking cylinder that is pumping fluid overboard.
g) The levers have a tactile feel and self locking for further safety. The Gear has a round handle where as the Flaps have a square type feel. They need to be pulled out to move them as the mechanism is shown in the fourth photo for the Gear is lockable up and down.
Russ Kotlarek
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