advice on hydraulic steering

[tkeithlu]

My steering system for my 60,000# 44' steel trawler is a Lecomble & Schmitt helm pump, probably a 70 HB or predecessor, definitely with a lock valve, a full meter diameter destroyer wheel, 1/2 inch copper tubing running about forty feet, and then a double acting balanced cylinder pivoting the rudder bar 45 degrees each way. The only side attachment is the autopilot motor just below the helm.

I need some advice from people well versed in hydraulic steering. I'm getting leaks at the cylinder no matter how much I beef up the connectors from flare, 90 degree turn, and pipe threads. My suspicion is that I am over pressurizing the cylinder by the top stern tip of the rudder hitting the plates used for removing the rudder at the end of travel to each side, and then still being able to add a bit more oil given the large wheel and springiness in the system.

Do these helm pumps have internal pressure release? Am I overpowering it with the large wheel? Should I stop the cylinder with chains from being able to take the rudder quite so far? Stop the cylinder by clamping angle on the rod ends? Install a relief valve (I own one, but have no idea how to install it)? Logic says I need to stop over pressurizing (if that's the problem) at the helm, so the entire rest of the system stays at lower pressure, rather than stopping it at the rudder, but I don't know how. Any words of wisdom or just ideas would be welcome.

[undercutter]

So you are saying that the fittings are leaking not the cylinders?

Can't believe that it is a pressure problem.

Pipe thread is only rated for 2000psi I believe but usually suitable for hydraulic steering. Your auto pilot pump will have a relief for sure.

If you have a large movement of the hoses when the cylinder moves then this could result in the fittings working themselves loose in the cylinder or at the adaptor(s) to the female flange fittings on that end of the hose. Flange and Boss O fittings can be a problem where there is lots of movement in the hoses.

Male pipe fittings on the end of the hose into the adaptor on the cylinder may not work themselves loose like JIC/SAE and boss O female fittings will.

Male pipe fittings on the hose end can be a pita as you have to spin the whole hose to make this joint but with proper thread tape on the adaptor into the cylinder and the hose end you should eliminate any problems associated with leaks at these positions.

Bad hose runs that cause strain on the fittings due to cylinder movement should be checked for as well while someone is operating the helm. Modifying hose lengths to provide larger radius and remove sharp bends will prevent damage to fittings and hoses as well as reduce leak potential.

Adaptor fittings in the barrel should be of the same material as the barrel of the cylinder.

[undercutter]

[QUOTE=tkeithlu;2229832 I beef up the connectors from flare, 90 degree turn, and pipe threads. [/QUOTE]

Do you mean you have a swivel connector that moves with the cylinder. If so they are always a problem and should be eliminated if possible.

[edmundsteele]

I thought the hose connectors were leaking on my Lecomble and Schmitt steering cylinders. I used paper towels wrapped around the fittings etc. to diagnose that it was in fact the cylinder seals that were leaking. I have a 2009 Leopard cat and both cylinders needed a rebuild with new seals etc.

[HappyMdRSailor]

Originally Posted by tkeithlu

My suspicion is that I am over pressurizing the cylinder by the top stern tip of the rudder hitting the plates used for removing the rudder at the end of travel to each side, and then still being able to add a bit more oil given the large wheel and springiness in the system.

Do these helm pumps have internal pressure release?
Dunno... Should though... AND... Should be adjustable... If you look at these diagrams, it looks like the relief valve is right on the back of the pump...
https://www.dropbox.com/s/wx8tjo5pl0...ES-LS.pdf?dl=0

Am I overpowering it with the large wheel?
Methinks so... is the wheel new(er)???

Should I stop the cylinder with chains from being able to take the rudder quite so far? Stop the cylinder by clamping angle on the rod ends? Install a relief valve (I own one, but have no idea how to install it)? Logic says I need to stop over pressurizing (if that's the problem) at the helm, so the entire rest of the system stays at lower pressure, rather than stopping it at the rudder, but I don't know how. Any words of wisdom or just ideas would be welcome.

It doesn't matter HOW you stop the cylinder... be it your quadrant limiting stops, any number of physical limiting devices, OR... End of travel of the cylinder...

You are still going to develop the same pressure... Not leaking at the helm or any manifold blocks you say??? Sounds like we could simply beef up the cylinder connections... But before you do, maybe a Tee and a $15 ebay pressure gauge would be a good experiment...

An external relief valve will take care of your issues... But obviously you need to adjust it stronger than any sea conditions are going to throw at it... Knowing what pressure you are developing with your tee'd in gauge seems like a no brainer... example of external relief valve pic attached...

Show us a pic of your cylinder connections...

[HappyMdRSailor]

Don't know what you have for a pump, but here's a pic I copied from the L&S manual

[Russ]

Have similar and copper fuel system. I have found the flares nuts a huge prob if 1 flare is not perfect 2 you do not use a flare wrench nut vs reg open end wrench and 3 most important you do not put some goop (. Yes I know shouldn't need too. ). I use a fuel proof black stuff called Joint Seal #6.Devil is in the details. Russ

[cjsfsm]

Couldn't help but to chuckle at the question

[Lancerbye]

Is there a possibility that the fittings at the cylinder are the wrong type. I have worked on a number of hydraulic systems and have come across this a number of times. An NPT fitting will fit and even tighten in an ORB female fitting but it is will leak. Some cylinders have npt female fittings but most quality cylinders have ORB fittings which do not use sealants or any kind of pipe dope . A proper fitting can withstand pressures over 15000 lbs.

[tkeithlu]

Wow! Thanks. I'm off being a dutiful grandfather at Harry Potter Land for a few days, but will start chasing these ideas down on my return. One point - my cylinder barely moves, and is a the end of two tubing (copper) loops to allow for that.

[Rduncanson]

You need an adjustable relief valve in the system and proper stops on the rudder. The relief valve would be an easy install the stops maybe or maybe not

[undercutter]

Originally Posted by tkeithlu

Wow! Thanks. I'm off being a dutiful grandfather at Harry Potter Land for a few days, but will start chasing these ideas down on my return. One point - my cylinder barely moves, and is a the end of two tubing (copper) loops to allow for that.

You don't mean that the copper tubing is attached directly to your cylinder?

The last thing you want is hard piping attached to the cylinder as this will surely leak/crack/break. If this is the case then you need to have these loops in flexible hose to match the pressure of your system. Should be like a 3/8 single wire hose.

Send us a picture.

[tkeithlu]

AND THE WINNING CLUES ARE....

[tkeithlu]

Lancerbye, for pointing out that I might have put the wrong threads together - I thoughtlessly put a 1/4"NPT into a SAE-6 hole. Also to Happy MdRSailor for pointing out the adjustable rlief valves on my pump. I can limit travel at the rudder post. Thanks so much to everyone for help and a good education as well. --Tim.

[HappyMdRSailor]

Bravo!!!

Awesome news Tim!