Hynautic AP - changing hydraulic fluid

[BigAl.NZ]

Hi All,

We have a linear Hydraulic system on our AutoPilot. The cylander and resevior are made by Hynautic.

The manual for changing the fluid over is clear enough (
https://www.samsmarine.com/Manuals/hynautic2.pdf
)

However, it calls for the wheel to be turned 60-100 times.

We have a Autopilot On/Off leaver on our boat near the helm. This leaver turns the hydraulics on/off.

I presume during the bleeding/turning of the wheel the hydraulics needs to be on, but when its on, I am not able to manually turn the wheel - I could try applying a lot of force to overcome this resistance when the hydraulics are engaged - but can someone enlighten me is this normal or am I missing something? (the wheel being unable to be turned manually).

Cheers

AG

[Bycrick]

Your description leaves me with questions. You say that the Hynautic cylinder is used for the AUTOPILOT. What do you use when you’re steering with the wheel? From your description, I’d guess that you are NOT using the wheel to drive this cylinder. That’s a guess based on your saying that you have a valve in the cockpit to enable/disable the autopilot.

If all that is true, then the valve in the cockpit should be open (thus bypassing the hydraulic pump) when you use the wheel. If the valve is closed, the the AP pump can drive the cylinder.

Most AP hydraulic pumps have an electrically controlled bypass valve rather than an external, manual, valve.

If it’s set up so that only the AP uses the cylinder, then you don’t purge the AP hydraulic system by turning the wheel. Instead, disconnect the piston from the rudder and use the AP to drive the cylinder back and forth. The cockpit valve should be in the autopilot ON position.

[BigAl.NZ]

Hi Bycrick

Thanks for the reply.

The other manual is here : http://www.boatsteer.com/assets/Hynautic_1987.pdf

Page 11, point 5 : Disconnect the clevis road (is that what you mean when you say disconnect the cylander?)

Also on that page are the instructions for purging the air, but it does not mention disconnecting the cylander.

Yes I am thinking that only the AP uses the cylander at this point - but will get some better photos tonight.

AG

[BigAl.NZ]

I have drawn the steering hydraulics setup. It looks like this:

https://photos.app.goo.gl/EghgTDcasEqoW5Po8

[BigAl.NZ]

The instructions in the manual are:

FILLING AND PRESSURIZING THE SYSTEM
1. Locate the two screws with pinned 112" hex nuts on the top of the relief valve. Loosen and back off by hand. turning Counterclockwise until they Stop.

2. Remove the hex plug from top of the reservoir and fill with oil to within 112" of the top and replace the plug.

3. The reservoir is equipped with a tire type air valve. Any tire air pump or compressed air supply can be used to pressurize the System. Slowly pressurize the reservoir to 40- 45 psi. As pressure is applied. oil will flow into the System. Then the oil level drops to within 2 inches of the bottom of the reservoir, stop pressurizing. Exhaust the air pressure through the air valve. remove the hex fill plug. refill. and replace the fill plug. Repressurize until the reservoir oil level stabilizes and gauge pressure reads between 40-45 psi. Check all connections for leakage. the fitting connections. Allow the air to escape until oil appear. and then retighten.

4. Go to the highest helm and bleed the air out of the (P) port and (S) starboard lines by cracking Open the fitting connections. Allow the air to escape until oil appears and then retighten.

5. Disconnect the clevis or rod end of the cylinder from its engine or rudder mounting if at all possible, making certain it is free to stroke without interference. This will assist in purging the air from the cylinder.

6. Bleed both ends Of the cylinder by backing off the socket head cap screw bleeders one turn. If the cylinder is not equipped with bleeders, crack open the fitting Connections. Hold the cylinder so bleeding will be performed on the highest end of the cylinder. Allow the air to escape until oil appears and then close.

7. Verify that the reservoir is at least 3/4 full and the gauge reads between 40 and 45 psi. If oil level is below 1/2 full, exhaust the air pressure through the air valve, remove the fill plug, refill. and replace the fill plug. Repressurize to 40-45 psi.

PURGING THE SYSTEM OF AIR
The following procedure is a process by which helms and autopilot are sequentially operated to pump oil into the (P) port and (S) starboard hydraulic lines. displacing the air - infiltrated oil out through the relief valve and into the reservoir where the
air Separates from the oil. Solid oil from the bottom Of the reservoir is then fed back to the helm and autopilot through the (R) line as needed. The number of wheel turns specified below have been established for average tubing lengths Of 20 feet between components. If tubing lengths exceed 20 feet. increase the number of turns by 2 for every extra foot of tubing length.

1. Go to the highest helm and turn slowly (2 to 3 sec/rev.) 60 times in one direction.
2. Repeat Step 1 at each successively lower helm and autopilot
- NOTE Purging air from an hydraulic autopilot is accomplished by setting a course on the autopilot to the sane direction you are steering the helm(s). If you are steering the helm(s) to the Starboard (clockwise) direction, Set a starboard course heading on the autopilot and allow it to run for 1 to 2 minutes.
3. Once more. crack the bleeders at the cylinder. If bleeders are not available. crack the fittings at the appropriate ends and allow air to bleed out. Retighten when solid oil appears.
4. Check the reservoir pressure and oil level. If oil level is below the half full mark. exhaust the air pressue through the air valve. Remove the oil fill plug refill and replace the fill plug. Repressurize to 40-45 psi.
5. Go to the highest helm and turn the wheel slowly 60 turns in the OPPOSITE direction. Repeat at each helm.
6. Close the two relief valve screws with pinned hex nuts by turning clockwise, and snug with a wrench.
- LOSS of steering will occur if the relief valve screws are not closed. Do not apply heavy force or damage to the screw and relief valve will result.
7. Go to a helm Station and turn in one direction until hardover is felt.
8. 60 to the cylinder and open the bleeder or crack the fitting at the end of the cylinder that the rod is from. closing when solid oil appears.
9. Again go to a helm Station and turn now in the opposite direction until hardover 15 felt.
10. Go to the cylinder and bleed until solid oil appears at the opposite end Of the cylinder previously
bled and then reclose.
11. verification Of a complete purge is accomplished by rotating the helm and achieving, within 1/2 turn. the corresponding number of turns hard-over to hard-over shown on the chart below. An excessive number Of turns indicates air in the system and Steps 1-10 must be repeated.


So the question is should the Autopilot valve in the second link be On or Off?

If its On, how can I follow step 1 of the Air Purge since the wheel is now stiff and cant be turned?

[BigAl.NZ]

Which steps are turn by hand, which by AP control head?

[Bycrick]

The picture above shows the Hynautic system where the only pump is the electric AP pump. So any step in the instructions that talks about “turning the wheel” in your case means activating the AP pump in one direction or the other. You have no “helm stations,” just the AP pump.

As for “disconnecting the cylinder,” it is easier to do the purging if you temporarily remove the the end of the hydraulic piston from the rudder stock, however it’s attached. You can purge without disconnecting it, but often the rudder stock will hit the physical stops before the piston reaches the end of its travel in the cylinder. This can leave a little air in the cylinder and make it more difficult to purge.

Since you can’t count wheel turns to see if the system is purged, you have to see how long it takes for the pump to move the piston from fully one end of the cylinder to the other. IMO 10-15 seconds is OK. Faster is better.

[BigAl.NZ]

So, during pressurizing I should have the AP valve off?

During purging the AP valve needs to be on?

Cheers

[Bycrick]

When you’re pressurizing the reservoir, the bypass valve can be in any position. When you’re purging the air from the system the valve needs to be in the closed or Autopilot position.

[BigAl.NZ]

Originally Posted by Bycrick

The picture above shows the Hynautic system where the only pump is the electric AP pump. So any step in the instructions that talks about “turning the wheel” in your case means activating the AP pump in one direction or the other. You have no “helm stations,” just the AP pump.

As for “disconnecting the cylinder,” it is easier to do the purging if you temporarily remove the the end of the hydraulic piston from the rudder stock, however it’s attached. You can purge without disconnecting it, but often the rudder stock will hit the physical stops before the piston reaches the end of its travel in the cylinder. This can leave a little air in the cylinder and make it more difficult to purge.

Since you can’t count wheel turns to see if the system is purged, you have to see how long it takes for the pump to move the piston from fully one end of the cylinder to the other. IMO 10-15 seconds is OK. Faster is better.

Right, and so the piston must be moved (by the AP controlled pump) 60 times in and out (in lieu of doing it with the helm) ?

[Bycrick]

The 60 times isn’t sacrosanct. You need to do it until any air trapped in the system plumbing is eventually pushed into reservoir. That’s why the reservoir is there. You can sometimes speed up the process by slightly opening the connection at the end of the cylinders as you’re running the AP pump in that direction to let any air trapped in the cylinder out.