Pulleys for Cable Steering system

Discussion in 'Boat Design' started by Dhutch, Feb 9, 2012.

  1. kenJ
    Joined: Jul 2005
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    kenJ Senior Member

    Edson should give you some ideas. For what you need I think shopping locally will save you quite a bit. Any pictures or diagrams avalible to help us give advice?
     
  2. Dhutch
    Joined: Oct 2008
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    Dhutch Junior Member

    To a certain extent I agree, however it is still a LOT of money, when all considered, although very good to have a look at whats available and what others are doing to take ideas from it. As said, the boats a narrowboat so onthe UK freshwater canal system, maybe two days a year on brackish max! The pulleys also wont be seen so dont need to look nice, just work reliably.

    I've been posting from work, so dont have any photos with me, although I have plenty of the system at home, so I'll have to get some up next week (im away all weekend) with a diagram.



    Daniel
     
  3. michael pierzga
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    michael pierzga Senior Member

    Steel sheaves will work...messy because they need to be grease covered.

    I say ask your local machine shop for advice. Delrin is not expensive and is widely used. I just had a Jumbo chain turning sheave custom fabricated on demand for 75 euro
     
  4. Dhutch
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    Dhutch Junior Member

    The whole boat is steel! If suitably painted the only area that should become exposed is the working face which the cable will kepp bright... And as I say, they are not in an exposted location, or on a saltwater boat.

    I will look into have some made up from Delrin and get a price from one of our machine suppliers (I work in a designer in an engineering company) I would make them byself but time limitation and a new house dictate otherwise!


    Daniel
     
  5. Stumble
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    Stumble Senior Member

    Dhutch,

    There are a lot of boats using dyneema for stearing now, and assuming there isn't a really sharp area to abrade against it will more than last that life time. We are seeing 3 years lifespan for main tow hawsers in use 365 days a year, logging companies are using it to drag trees out of the forest, heck OSHA has approved it for catagor 1 cut resistant gloves (the same rating as steel mesh).

    Part of the reason it is becoming popular is because it has a friction coefficient of .04, as compared to Teflon at .1-.05, which actually greatly reduces abrasion, since it just slides over stuff, even knifes. This reduced friction is like having everything is touches permanently greased, so there is less resistance in the system, giving a better feel for the boat at the wheel.

    Add in the fact that it bends around sharper radiuses so you can use small blocks, and is twice as strong as steel for the same diameter, so even a little abrasion doesn't kill it. I have been using it on my boat for 3 years, and when I pulled it for a new bottom job I had everything checked, all of the other lines are getting close to replacement, but the dyneema stuff still looks new.
     
  6. Submarine Tom

    Submarine Tom Previous Member

    Dhutch,

    I used ~2 1/2 inch nylon pulleys from an old Boston Whaler on my 25 foot houseboat, but my cable was only about 3 mm, plastic coated (5 mm max), stainless steel. It worked out really well. I've used 8 hp all the way up to 25 hp four stroke. About 5 turns lock-to-lock.

    I haven't read the whole thread... have you considered making some out of hardwood on a lathe? Larger diameter of course.

    -Tom
     
  7. kenJ
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    kenJ Senior Member

    I was suggesting pulleys designed for the marine environment because the last thing you want is to have to fight friction when you turn the wheel. As you have said, they don't need to be huge. Check Craigslist (if you have it in the UK) or Ebay for used ones off a small racing skiff. They upgrade quite often in the name of performance. Or check with a local marine second hand/salvage store.
     
  8. Stumble
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    Stumble Senior Member

    Ken,

    The problem with the sheaves you can find from dinghys is that they won't be large enough for wire. Depending on the type of wire you need at least 20 times the wire diamater for the sheave diameter, though the life span and breaking strength goes up untill you reach around 40 times. So yes if you are using 1/4" wire you ideally would have a 10" sheave, and need at least a 5" sheave. Line handling sheaves are no where near this size, untill you get to true mega yachts. That are using 1" spectra halyards, and where each block can be over $1,000 a piece.

    This is part of why dyneema is so desirable. It only needs a minimum radius of 5:1, so that same 1/4" line only needs a 1.25" sheave. And if you get really worried about size, you could go to 5/32 dyneema for the same breaking strength and use even smaller sheaves.
     
  9. kenJ
    Joined: Jul 2005
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    kenJ Senior Member

    I understand the need for larger sheaves for wires. I was assuming the decision to go with rope was a done deal.
     
  10. bertho
    Joined: Aug 2006
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    bertho bertho

    for sheave, i find the tufnol, used for electric insulation, (phenolique resin + cotton )cheap and very good in marine environment , can find in large diameter think tube, ready for machining, almost nothing wasted, not to heavy, clean..
    i insert a SS bearing in , look ok !!
    cheer's
    bertho
    fusionschooner.blogspot.com
     
  11. michael pierzga
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    michael pierzga Senior Member

    Yah, that resin impregnated brown stuff is perfectly suitable for sheaves. Both delrin and that brown stuff suffer when exposed to UV.
     
  12. Dhutch
    Joined: Oct 2008
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    Location: Cheshire UK

    Dhutch Junior Member

    I was at one point going to make a set from tufnol, namely when someone offered me a large block of it for free, however i never had the time and the offer passed on untaken.

    However I have got some photos of the current equipment for you, sorry for the delay on that.

    Here is a schematic of the system. The boat is 7foot wide and pulleys B-E are install under the back deck which is around 7ft square, with A-B running forwards at the side of the wheelhouse and then the chain running up to the back of the wheel from there:
    [​IMG]

    Quadrent
    [​IMG]

    Close up
    [​IMG]

    Pulley C
    [​IMG]

    Back of wheel
    [​IMG]



    Full album of photos
    http://img51.imageshack.us/img51/1544/image1tuo.png

    Daniel
     
  13. SamSam
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    Location: Coastal Georgia

    SamSam Senior Member

    Where is the tension spring located?
     
  14. Dhutch
    Joined: Oct 2008
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    Location: Cheshire UK

    Dhutch Junior Member

    Between b and c, obviously the photos show the system with cable off and a few years apart, before and after painting if the area.

    Daniel
     

  15. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I'd put another spring between D & E to keep tension. As for pulleys and all other mechanical gizmos you might need, you must have an industrial supply house over there. We have a few here, this is McMaster-Carr and their pulley page...
    http://www.mcmaster.com/#cable-pulleys/=gbsbpm

    Click on "wire rope pulleys" for what you might need, on the left click on "additional pulleys" for more. Go up to where it says "over 490,000 products", it will change to "home" click there for the main page.
     
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