Autopilot Hydraulic Ram Bypass

[gmorel]

Sorry very late post on this thread...

The bypass/clutch valve (normally opened to allow manual mechanical steering) installed on the hydraulic RAM of my autopilot seems to work well only in one direction!

When the autopilot actuates and closes the valve to drive the RAM, it can perfectly actuate the RAM in one direction.

When exercising significant force in the opposite direction, the autopilot (Furuno FAP-7002/711c) generates a Rudder drive error because the RAM does not move the rudder as intended. At very low rudder angle increments it is still possible to steer.

The root cause seems that the installed bypass/clutch valve is NOT bidirectional, so it does not succeed in blocking the oil when the oil pressure is pushing the pintle against the solenoid magnetic force.

I am now looking for a symmetric valve in the range of 150bar in both directions, possibly with a reduced steady-state consumption.

I have also heard of electro-actuated "motorized" valves that do not draw any steady-state current, but take 10-15 seconds to close or to open. They also require a specific drive circuit that the Furuno FAP-7002 TB3 port does not support.

Any hint?

[donradcliffe]

To me, it is more likely that the problem is a failure of one of the check valves in the pump. Here is a flow diagram of the Simrad hld2000.

[gmorel]

That was effectively our first guess, but when the bypass valve was opened (disconnecting the valve and closing the two pipes) the problem went away…
The good thing is that it is easy to reproduce the problem in the harbor by manually actuating the ram with the autopilot manual steering mode.

[Tikitour]

Hi I have a problem with my Raymarine Tupe 2 hydraulic linear drive. When Auto is engaged the steering does not lock and the steering is able to be moved freely. I confirmed that there is 12V at the clutch/coil and plugs are free of corrosion. I checked the fluid level it and it was on the minimum line or just below. I topped it up and still no changes. There also appears to be a fine sediment at the bottoms of the hydraulic reservoir. The entire system was new from 2018 not sure if should be failing so soon. Has anyone removed and replaced the coil on their linear drive?