Hydraulic Steering Question

[Celestialsailor]

Thanx John...well you know that this boat has been a project...whats new...right? this is all the little stuff that I am ironing out now before we take off. Right now...the steering sounds like it may have a little air still. The stuffing box is misaligned and a few other odds and ends.

[maersi]

I have to say up front that I know nothing about hydraulic steering, never owned or sailed a boat with it, but I can only think of 3 possible causes.
1) Air in the system.
2) Mechanical play, which could be at either end of the system. Is there a chain running down the pedestal to the pump?
3) Expansion. Are there any flexible hoses? If so, and they are not adequately reinforced, they could be expanding.

Eric

[Celestialsailor]

Ok...Kick starting this thread again. Today a friend and I bled the system as Sea Star stated. No change. you can still turn the wheel 45 degrees, starboard and port. I open the bypass valve to exclude the ram. It still feels like the pump wants to take up slack turning 45 degrees from center to one side and the same to the other. There is a flow control valving in the system as well as check valving in the pump itself. I'm wondering if the valving is in question. Maybe I'll try to find a rebuild shop and have them go through both the pump and ram. Anyone knows what this costs?

[delmarrey]

Is your wheel hooked directly to the pump or is it chain driven? With a chain there maybe backlash but that much would be noticeable.

Another possibility is if there is a gear missing a key and slipping on it's shaft (chain drive).

Maybe the inside of the pump is slipping on a shaft somewhere. Try capping both sides of the pump while keeping oil in it and then try turning. This can work all the way down the line. Cap at each joint. If the pump is a top fill, by loosening the cap you can bleed the air out. You just have to make sure the pump stays full.

[Celestialsailor]

Thanx Del...Here's the deal...it's a direct drive. The ram is disconnected from the rudder post arm.
There was something else I was incorrect about. I said that there was a check valve in the system. Actually it's a "Pressure lock valve". There were 2 of them. One was at the old Benmar Hydraulic auto pilot which was dead and the other 3 feet away from the drive ram. I'm not quite sure what it does as I think the pump has check valves in it to prevent the pump from motoring when the rudder is hit by a wave.

[Celestialsailor]

I should have included this picture of a "Pressure lock valve".

[delmarrey]

Originally Posted by Celestialsailor

I should have included this picture of a "Pressure lock valve".

It looks like a relief/bypass valve. If you loosen the screw on the end it should bypass and the oil, which will just go in a circle thru the pump.
Here's mine, the piece in the middle.

.

[delmarrey]

And here is my pressure lock valve for on or off. When on, there is no feed back on the wheel.

.

[Celestialsailor]

Originally Posted by delmarrey

It looks like a relief/bypass valve. If you loosen the screw on the end it should bypass and the oil, which will just go in a circle thru the pump.
Here's mine, the piece in the middle.

.

Actually, mine is not exactly like the picture I provided. It is the same casting with only caps on the end. I suspect large springs and check balls under them. Is it not rue that there are check valves in the pumps? mine is an old Vetus...

[delmarrey]

Generally pumps don't have relief valves attached. On most hyd. systems, like on work trucks, they have a relief valve inline. W/o it the pump could deadhead and blow apart. I don't think you could do that with a hand driven pump unless you had a really big wheel and spun it real hard to a deadhead.

Originally my pump had a wheel lock attached to the back of the pump (see picture above). But on hot days both sides of the system would push against each other, creating as much as 1200 psi in the hoses. So I complained to Kolbet and they sold me a manual wheel lock/pressure lock with a kit to bypass the one on the back of the pump.

Unless you have some kind of mechanical back lash then it has to be air in the system. These steering pumps is whats called a piston pump and they generally last a long time and usually don't bypass like a positive pump will.

[delmarrey]

Doing some research it appears that Vetus does put in relief valves internally now, in the newer pumps. And from the pictures it looks like they are sealed unites. Once they go bad you have to buy new, no repairs.

[Celestialsailor]

I'm pretty sure my pump is an original 1974 pump. If you look inside the filler hole you can see the roller type pistons moving around. I was wondering if their fit might be out of tolerance. But it seems if they were, when I was hard over, they wheel would want to keep turning at the end of the ram travel. Am I correct? So maybe, it's this "Pressure lock valve that is the problem. I mean it has to switch flows for direction. Maybe I can find a shop that knows this stuff. Being European, I'm not sure I'll be able to find parts. This pump is discontinued by Vetus.

[delmarrey]

When your hard over do you feel any spongyness (not a word ) If so, then there is air still in the system. Providing there are no leaks in the system, when hard over, if you can hold the wheel and it doesn't creep then the pump is OK.

A locking valve has a sling piston in the middle with a spring loaded ball check at each end. If there is back pressure the ball is forced against a seat. But I don't think this would affect the 45º slop in your wheel.

[Celestialsailor]

Well...I'm not sure about sponginess. Maybe like hitting a die spring with short travel. But the wheel does creep slightly with moderate pressure. Putting about 5 pounds force on it would take the wheel maybe 5 minutes to do 360 degress. Can a hyraulic shop test each piece of equiptment and determine if the Pressure lock valve, ram or pump need work?

[delmarrey]

Yeah! That's too much creep! That's why piston pumps are used on boats, due to the close tolerance and lack of bypass. 1974, it may have some corrosion set inside there by now. But that could be your pressure valve leaking/bypassing.

Each piece can be checked individually by a hyd. shop. But one that deals in metric fittings, assuming the parts have metric fittings. Some places do carry adaptors. Cylinders should never bypass.

A system that old, I think I'd have the pieces checked.