autopilot hydraulic linear drive noise

[Capn C]

I have a center cockpit Cheoy Lee with an Autohelm 3000 computer controlling a Navico hydraulic linear drive (LHA:12A). Everything works fine as far as tracking / response, etc. however the control valves are constantly making noise (opening & closing I think). It wouldn't be so bad except that the hydraulic pump and cylinder are under the aft berth.


Anyone have suggestions for reducing the noise (apart from buying an electric linear drive)??



Thanks!

[atoll]

get longer hoses and move the pump from under the bed

[Capn C]

Is there any limitation to how far away i can move it. The nearest suitable place is probably 4 meters away. the volume of fluid in the hoses will probably be several times what is in the cylinder. Will this affect performance / response?

[DeepFrz]

With longer runs it is better to use copper tubing rather than hose. But is that going to solve the problem? Before going to a lot of trouble you should be sure that you know where the noise is coming from. A mechanic's stethoscope can help you determine what exactly is making the noise. If you can't get one of those sometimes a screwdriver placed on a component and your ear pressed against the handle can help but a stethoscope is much better.

[atoll]

Originally Posted by Capn C

Is there any limitation to how far away i can move it. The nearest suitable place is probably 4 meters away. the volume of fluid in the hoses will probably be several times what is in the cylinder. Will this affect performance / response?

it should not make any difference to the pump as it will be pushing or pulling exactly the same amount of fluid to get the ram to move.

you will have to be careful filling and bleeding the ram initially so as not to run the reservoir dry/empty and introduce air into the system but once it is full and bled it should operate exactly the same.

as deepfrezz noted using copper tubing will make the system more robust for the longer run.
you will still need to use hoses to connect to the ram so if they are in good condition they can be reused,the copper tubing can be connected directly to the pump.

ideally the reservoir should be above the height of the ram

[capt jolly]

Not sure if I read this correct but you have the actually steering hydraulic control block under the bunk? You may be able try proportional solenoids instead of direct on/off type, worth a mention..

[msponer]

We had the same problem in our previous boat. We remounted the pump assembly with vibration dampening mounts and put foam sound insulation all along the wall that it shared with the aft berth. We could still hear it after this, but it was much quieter and no longer annoying.

[brianb00]

Originally Posted by msponer

We had the same problem in our previous boat. We remounted the pump assembly with vibration dampening mounts and put foam sound insulation all along the wall that it shared with the aft berth. We could still hear it after this, but it was much quieter and no longer annoying.

Be careful with insulating the electric pump. In big seas it draws lots of current. You could overheat the motor. Check with pump manufacturer.

[Captain Yiannis]

Originally Posted by msponer

We had the same problem in our previous boat. We remounted the pump assembly with vibration dampening mounts and put foam sound insulation all along the wall that it shared with the aft berth. We could still hear it after this, but it was much quieter and no longer annoying.

This is my suggestion too.