Hydraulic Steering Ratios

Our steering pump is mounted at wheel level in the pedestal, you know that gives very poor lock to lock. I noticed that pg 563 in the 1st Encyclopedia shows a pump mounted below the pedestal, with a chain drive to turn it. How do you fill a pump in that position? Can you use it sealed with a reservoir at a lower level? Do you have any better suggestions for solving this problem? – Mike B.

Hi Mike: Steering ratio is a function of helm pump size, hydraulic cylinder size, and tiller arm length.

It is usually hard to find helm pumps with enough capacity to get the ratio down to anything reasonable. Hence, the photo of the chain drive from the helm to "overdrive" the helm pump in Offshore Cruising Encyclopedia.

If you have a pressurized system, such as the Hynautics one we used on Beowulf and Wind Horse, it is possible to fill from the reservoir tank in the engine room. But getting air out at the helm pump can be difficult. So allow for bleed valves and/or a way to catch the oil as it oozes out in the bleeding process.

Otherwise, if filling the pump itself (at the highest point), there has to be an access door through the pedestal, or if the pump is below the cockpit sole, you need a way to fill through the plug on top. – Steve

Posted by Steve Dashew  (November 30, 1999)

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