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Old 31-05-2019, 11:21   #1
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Autopilot Hydraulics

Hello all,

We have a Hynautic RAM (not sure of model) and RV-60. The ram on the autopilot sometimes oscillates, see this video towards the end:

https://photos.app.goo.gl/ikLptxq1kjzxd2gr5

A few more pictures: https://photos.app.goo.gl/1xsN3cACXyboPwyy6

The motor: https://photos.app.goo.gl/6zvyPN2S7dLDcg5r9

It is paired with a new Raymarine EV4 autopilot. I note in the last 12 months the pressure has dropped from about 22 to 18psi.

Any ideas what might cause this? It otherwise works great.

Cheers

Al
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Old 01-06-2019, 11:32   #2
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Re: Autopilot Hydraulics

Probably some air in the system. Air compresses allowing movement.
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Old 01-06-2019, 13:46   #3
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Re: Autopilot Hydraulics

I’m thinking it might be either leaking seal in the cylinder, or leaking oil, or possibly water ingress. Air in the system causes uneven movement and ‘bumps’, but usually not a slow fade, except when the oil level is very low.

First, thoroughly bleed the system to rule out the simplest fix. Crack your high point reservoir, then turn your rudder to full lock one way. Open the bypass valve on or near the steering cylinder and manually move your rudder back and forth through full range of motion. Close the bypass valve, turn your rudder to full lock the other way, then repeat.

Work better now?

Next check is your oil level - check your header tank - it should be not empty and hydraulic oil should be visible. If not, you may have an oil leak somewhere in the system. Most likely at the cylinder, but could be anywhere. Is your oil level decreasing slowly? The Platino disaster a few years ago was caused by leaking oil.

If oil level is fine, then it could be a cylinder seal leak. A cylinder seal leak will let it work normally at first, then it will get worse as oil leaks from high pressure to low pressure. Try just cracking your bypass valve - does the same thing happen, but faster? If so, check the cylinder shaft seals - this may need to be done professionally.

Finally, if you’ve removed the cylinder and checked/repaired it, before replacing it drain all the oil out and replace it. Then bleed the system as above.
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Old 01-06-2019, 13:51   #4
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Re: Autopilot Hydraulics

Quote:
Originally Posted by fxykty View Post
I’m thinking it might be either leaking seal in the cylinder, or leaking oil, or possibly water ingress. Air in the system causes uneven movement and ‘bumps’, but usually not a slow fade, except when the oil level is very low.

First, thoroughly bleed the system to rule out the simplest fix. Crack your high point reservoir, then turn your rudder to full lock one way. Open the bypass valve on or near the steering cylinder and manually move your rudder back and forth through full range of motion. Close the bypass valve, turn your rudder to full lock the other way, then repeat.

Work better now?

Next check is your oil level - check your header tank - it should be not empty and hydraulic oil should be visible. If not, you may have an oil leak somewhere in the system. Most likely at the cylinder, but could be anywhere. Is your oil level decreasing slowly? The Platino disaster a few years ago was caused by leaking oil.

If oil level is fine, then it could be a cylinder seal leak. A cylinder seal leak will let it work normally at first, then it will get worse as oil leaks from high pressure to low pressure. Try just cracking your bypass valve - does the same thing happen, but faster? If so, check the cylinder shaft seals - this may need to be done professionally.

Finally, if you’ve removed the cylinder and checked/repaired it, before replacing it drain all the oil out and replace it. Then bleed the system as above.

Awesome reply. Yes pressure is very slowly dropping over last 12 months from 24psi to about 18.

Will let you know how it goes.
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