hydraulic steering with st 7000 autopilot issue

[Artic Warrior]

Hi All,

I have a sailing boat with hydraulic steering and st 7000 autopilot.
The autohelm tiller pilot operates next to the hydraulic ram steering the rudder.
For me to use the emergency tiller on top of the rudder stock, I switch the by pass valve over whch enables the fluid to flow so I can manualy steer the boat.

My question is, if I use the electric auto pilot surley the by pass valve has to switched over as well, for that operation too for the hand tiller to operate,,,,
Hope this is clear enough....

When I bought the boat the guy said switch over the by pass valve if the emergency tiller is to be used, but think it would be the same for the electric auto helm otherwise it must work too hard im thinking,

Colin

 

[impact30]

Hi Colin
From what you describe, you are correct in that the bypass valve must be open to allow the autopilot to work, otherwise it will try to drive the wheel backwards when steering. This would be OK with a mechanical linkage but a hydraulic setup would typically have checkvalves to prevent this happening.
A more orthodox system would simply have an electrically driven pump in parallel with your existing wheel pump allowing either to operate without opening the bypass valve. There would be just one hydraulic cylinder/set.

Hi All,

I have a sailing boat with hydraulic steering and st 7000 autopilot.
The autohelm tiller pilot operates next to the hydraulic ram steering the rudder.
For me to use the emergency tiller on top of the rudder stock, I switch the by pass valve over whch enables the fluid to flow so I can manualy steer the boat.

My question is, if I use the electric auto pilot surley the by pass valve has to switched over as well, for that operation too for the hand tiller to operate,,,,
Hope this is clear enough....

When I bought the boat the guy said switch over the by pass valve if the emergency tiller is to be used, but think it would be the same for the electric auto helm otherwise it must work too hard im thinking,

Colin

 

[Artic Warrior]

Its weird because ive been using the boat on auto electric without switching over the bypass valve and the autopilot seems to work
But I imagine its straining too much,,,,im out to the boat next month so will see,,,

 

[impact30]

Perhaps (as per previous phantom poster suggested) there is an electric bypass valve fitted. There is often a connection on the 'computer' for this. I'm not familiar with the st7000 specifically.

 

[Artic Warrior]

Perhaps (as per previous phantom poster suggested) there is an electric bypass valve fitted. There is often a connection on the 'computer' for this. I'm not familiar with the st7000 specifically.

Thankyou for that, I will see what happens next month,,,,
phantom poster hee hee

 

[claudio]

I would think that a correct implementation of the steering would be as described below.

When the autopilot is engaged it

1) operates an electrical bypass valve on the master hydraulic cylinder
2) operates an electrical valve to 'release' the bypass valve on the autopilot hydraulics, or engage a clutch on a mechanical drive.

In normal operation you would keep the manual bypass valve closed as the configuration above would select the correct sequence.

However should you need to operate the emergency tiller, you also need a method to disengage the master cylinder. This is why you open the manual bypass valve.

 

[Artic Warrior]

Ah I see Claudio,
my auto pilot is electric, so there must be a electric by pass valve on the master cylinder
but I don't remember seeing one,,,Mmmm

 

[claudio]

Ah I see Claudio,
my auto pilot is electric, so there must be a electric by pass valve on the master cylinder
but I don't remember seeing one,,,Mmmm

If you don't have an electric bypass valve on the master cylinder, the autopilot would be trying to move the rudder against a locked hydraulic cylinder. The only way that this can happen is if there are no check valves in the helm pump in which case the wheel will turn to accommodate the hydraulic fluid.
Does the wheel turn when the autopilot is on ?

 

[Artic Warrior]

No the wheel does not turn , and I can freely turn the wheel while the auto pilot is in operation

 

[Artic Warrior]

If you don't have an electric bypass valve on the master cylinder, the autopilot would be trying to move the rudder against a locked hydraulic cylinder. The only way that this can happen is if there are no check valves in the helm pump in which case the wheel will turn to accommodate the hydraulic fluid.
Does the wheel turn when the autopilot is on ?

Like you say, there must be an electric by pass on the helm pump otherwise it would lock up wouldn't it.

 

[knuterikt]

You can find manuals for old autopilots here http://www.raymarine.com/view/?id=1836&collectionid=10&col=1838
direct link to yours here http://www.raymarine.com/WorkArea/linkit.aspx?LinkIdentifier=id&ItemID=1833&libID=1977

 

[Artic Warrior]

Hi All, Thank you for all your help,
Just back from the boat and have seen what the set up I have now,
hydraulic steering unit, and ram with an electric type 1 pump for the autopilot, this has a pipe that runs back to the head unit which must be the bypass valve
The autohelm is a st7000 unit with a linear rudder indicator which piggy backs the hydraulic steering ram.

 

[Sandyman]

Hi All, Thank you for all your help,
Just back from the boat and have seen what the set up I have now,
hydraulic steering unit, and ram with an electric type 1 pump for the autopilot, this has a pipe that runs back to the head unit which must be the bypass valve
The autohelm is a st7000 unit with a linear rudder indicator which piggy backs the hydraulic steering ram.

Reading your comments & descriptions it would seem like you have an Electro-Hydraulic pump
with a reversible motor. What make is your helm pump unit ? Any photos available ?

On my set up the bypass valve remains closed except when using the emergency tiller steering. If it were in the open position all the time the fluid from the hydraulic pump,
when in auto-helm mode, would just go round in a circle & not pressurise the ram.

 

[bendyone]

Hi All, Thank you for all your help,
Just back from the boat and have seen what the set up I have now,
hydraulic steering unit, and ram with an electric type 1 pump for the autopilot, this has a pipe that runs back to the head unit which must be the bypass valve
The autohelm is a st7000 unit with a linear rudder indicator which piggy backs the hydraulic steering ram.

This is the filling / expansion overflow pipe.

 

[Sandyman]

This is the filling / expansion overflow pipe.

Correct. Bump

 

[Artic Warrior]

Reading your comments & descriptions it would seem like you have an Electro-Hydraulic pump
with a reversible motor. What make is your helm pump unit ? Any photos available ?

On my set up the bypass valve remains closed except when using the emergency tiller steering. If it were in the open position all the time the fluid from the hydraulic pump,
when in auto-helm mode, would just go round in a circle & not pressurise the ram.

My head unit is a Capilano pump, combined with the autohelm 7000 system and electronic drive motor, and linear indicator, and manual valve so I can use my emergency tiller