Hydraulic Steering design

Discussion in 'Boat Design' started by 7228sedan, Jun 5, 2016.

  1. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    Hi All,

    I'm the proud owner of a new old stock Hynautic K-2-B steering cylinder. I understand this to be an obsolete unit, replaced by PN HC5373- Cylinder Model BA175-9TM (Teleflex/SeaStar). However, as this one is new in the box, I'd like to research completing the components around it. A few questions to anyone who is familiar with the Teleflex hydraulic steering line:

    1) This cylinder is overkill in size a bit for my application 28 ft planing cruiser, are there any concerns with that assuming that I can correctly attach the cylinder to my rudder?
    2) I understand that the helm pumps need to be matched to the cylinder based on volume of fluid moved. Does that determine how many turns lock to lock?
    3) Can anyone recommend an appropriate helm pump to match this cylinder?

    As always thank you for your expertise.
     
  2. gonzo
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    gonzo Senior Member

  3. 7228sedan
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    7228sedan Senior Member

    Thanks Gonzo, I have looked here, and it's not real clear if the HC5373 is still on their application guides. I've reviewed both the standard and the capilano series guides and don't find it. The actual cylinder model is BA175 9TN which I also no longer find. I am assuming that the displacement of the helm pumps define the volume of fluid moved, and therefor the speed at which the cylinder will actuate. Am I correct in that assumption based on your understanding? It appears that the H-41 pump would have been correct however I can't find an appropriate cross reference to that pump when compared to their new models.
     
  4. gonzo
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    gonzo Senior Member

  5. serow
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    serow Junior Member

    I looked online and these are obviously hydrostatic steering systems, some with a boost pump and some with the steering unit simply providing the drive to the actuator with the oil supply delivered from a pressurised can so eliminating any suction on the input. My experience of these systems on mechanical plant is that unlike power assisted steering after a short while the steering wheel invariably looses register with the wheel position because of unavoidable internal leakage; it doesn't mean that the steering fails to work of course that just if you start with a spoke at 12 [to use the clock analogy]for straight ahead half an hour later the spoke can be at say 1 for straight ahead [Some operators find this irritating, by the way, especially if the driving involves a lot of reversing]
    I presume the same thing happens here. I can imagine it might be a nuisance on a sailing ship.
     
  6. 7228sedan
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    7228sedan Senior Member

    That is correct Serow, you have to use a wheel with spokes equidistant from each other. Gonzo, which component is designed for outboards?
     
  7. gonzo
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    gonzo Senior Member

    I'm wrong. I confused it with the 5370. It is OK for inboard.
     
  8. 7228sedan
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    7228sedan Senior Member

    Thanks. For a dual station installation, do I need to use the same helm pump at both stations? or can I use 2 different pumps with the same capacity? I would like to install a tilting helm on the bridge & standard downstairs...
     
  9. gonzo
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    gonzo Senior Member

    The difference between the tilting and standard is only on the exterior tilt mechanism. There are the same otherwise. Make sure you get the helms that can be used for dual station.
     
  10. 7228sedan
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    7228sedan Senior Member

    Sorry to resurrect this post, however I'm getting back to putting this together. I've decided to go with the H25 helm pump which is a 2.75 cu. in. / rev. pump. I am currently working out which type of hoses/lines to use. I am leaning to 1/2 copper tubing for the primary runs with nylon hoses from the reservalve to the cylinder. My question is regarding the fittings. What type of fittings are appropriate for connecting the Copper tube to the components? Would these be compression fittings?
     
  11. serow
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    serow Junior Member

    Copper is not common on hydraulic systems as it a bit soft, ditto nylon unless its nylon braided hose. What pressure does this run at?
     
  12. 7228sedan
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    7228sedan Senior Member

    The Sea star page recommends it:

    TUBING / HOSE OPTIONS

    Use soft refrigeration type copper tubing for optimum performance. For tube-to-cylinder flex hoses, select a hydraulic hose rated for 1000 PSI (70 bar) working pressure, and with a very low volumetric expansion rating.
    HELM TYPE DISTANCE—CYLINDER TO FURTHEST HELM
    40 FEET OR LESS MORE THAN 40 FEET
    All 1/2″ O.D. Copper Tubing 5/8″ O.D. Copper Tubing

    1000PSI is the working pressure rating of the hose or tubing.
    The nylon would be reinforced with braid.
     
  13. serow
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    serow Junior Member

    Interesting, thanks. Quite low pressures for a hydraulic system.
     
  14. 7228sedan
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    7228sedan Senior Member

    Coming back to this one...

    I've got 2 H-25 helm units and the Reservalve RV60 relief valve/fluid reservoir. I am struggling to fond the appropriate bleeding "T" fittings for the cylinder. My question is, does anyone know if I need the bleeders with the reservavle? Is anyone aware if the bleeder t's are required assuming the proper procedures are followed? I assume that as the fluid is cycled through from port to starboard hard-over any air would wind up in the reservoir (like bleeding the power steering in an auto). Any thoughts or experience with this system?
     

  15. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    Bumping this one for a fresh look.
    The steering cylinder, and helms are mounted. I'm In the process of running the copper tubing. I opted for type "K" 3/8" OD tube with .035 wall thickness. Working pressure is 1084PSI so I'm good there.
    Also, I am looking for recommendations for the fluid. Sea Star fluid runs 25-30 USD/qt. I have read that any MIL-H-5606 spec fluid will work. Does anyone have any other input on the fluid options?
     
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