Edson Simplex steering gear

Discussion in 'Metal Boat Building' started by pdwiley, Dec 30, 2010.

  1. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    One advantage to hydraulic is that its very compact, only two hydraulic hoses
    need to be run and a hydraulic ram mounted. The hydraulic piping can be mounted in any location that is convenient. In future when your save up enough fun tickets for an autopilot or a second inside steering station, its installation will be simple because you must only Tee into the hydraulic system. Some good info on pump size and ram geometry is available in the VETUS catalogue. You might ask your designer what the load, force... scantlings are for your steering system .

    How much space do you have ? Will the steering gear be serviced thru a cockpit lazarette ? The problem with mechanical steering is that the cable runs or drive shaft runs require protected, dedicated space and it run geometry is fixed. .

    Each system has its merit.

    Conventional Cables, blocks and a steering quadrant is the simplest, cheapest, most reliable, easiest to service system.

    http://www.vetusweb.com/manuals/files/Hydraulic_steering_systems/020108 r02 07-00.pdf

  2. wardd
    Joined: Apr 2009
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    wardd Senior Member

  3. eggman918
    Joined: Jan 2011
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    Location: Bakersfield Ca.

    eggman918 Junior Member

    Hi ,I am new here just starting to plan the start of a project.
    Could you build a hydraulic system without a pump using two cylinders
    using one as master the other as slave as in a clutch/brake system
    except using double action cylinders?
    I am a machinist in the heavy industrial repair field and am just thinking out loud.
  4. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    I'd say that cable systems are the least reliable if they are not regularly serviced. So they need to be accessible which makes them simple to service ! But from experience it can be far from simple to replace a cable in rough weather.

    But failures of cable systems is still very common. They often have to be repaired at sea and you should carry spare cables and sheaves on a voyage which adds more weight unless your fall back position is the emergency steering.

    Lightweight sailboats use cable because it's the lightest option after a tiller but for reliability just look to steering systems used by commercial craft. You could never sell an experienced coastal fisherman here a cable and quandrant ! They have moved almost totally to hydraulics now for strength and reliability in adverse conditions. Hydraulics fail gradually give fair warning of air in the system or leaking seals, and on larger vessels it's very easy to add redundancy to a hydraulic system.

    When your steering breaks it's nearly always in the worst conditions. Cable systems are prone to eventual fatigue and are compromised by linkages crimps and less than perfect cables. If you design with the stresses really low in a cable system the weight is high, it's a Catch 22.

    One mechanical system I like is the 'Lewmar Mamba' (ex-Whitlock) and it's a very robust setup using torque tubes, gear box and bevel gearboxes.
    Edson screw type arrangements abound on old boats and are still in excellent condition after 80 years of hard use. How could cable ever match that for reliability?

  5. pdwiley
    Joined: Jun 2008
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    Location: Hobart

    pdwiley Senior Member

    A concluding picture...

    Many threads get left hanging so I've resurrected this one just to provide a picture of the finished article.

    As I said some months ago, I planned on making my own steering gear.

    Attached is a picture of the final result ready to fit to the hull. There's a bit more of a mix of metals than I consider desirable but it's all inside the hull space and fully accessible for maintenance. I've added a ton of grease nipples for every moving joint, all the steel holes are bronze bushed etc. I now have to paint the various bits with some epoxy paint and call it done.

    The bottom turning plate bolts to a plate on the rudder stock fabricated using a taperlock type 1615 weld-in hub to 12mm plate then machined flat. The 2 pieces bolt together using 4 of M10 bolts. The entire assembly could be removed by unbolting the end bearings and the 4 M10 bolts and lifting it out of the way, leaving the flange on the rudder stock exposed for attachment of any other sort of steering gear.

    Only time and use will show if I've done an adequate job, but I think it's good enough.


    Attached Files:

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