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  1. #1
    Join Date
    Jan 2011
    Location
    Far West Wimmera
    Age
    63
    Posts
    4,049

    Default Suitable Sheave Diameter

    I am thinking about knocking up some mutiple sheave pulley's to add some lifting capacity to my lifting trailer. I have been pulling out posts and want to try for something better. Most posts come out easily, but I thought it could be useful. I was using the 8 tonne ram to do the pulling, but this got boring real quick, so I hooked up a couple of pulley's to the 3000lb 12v winch and found it did the job. I have not tried anything big tho. 6" x 8" redgum is the biggest. Mostly it will be little CCA posts I will be doing. They are needed for new fencelines.

    I looked up recommendations for cable radius and found a suggestion of 10.5" diameter for pulley's used for 1/4" 7 x 7 cable. I think my cable is 6mm 7 x 7. I have the choice of 50mm diam solid, 65mm diam solid or 80mm thick walled tube which would need a hub fitted. The winch drum would be 65mm max when full. I currently have 2 pulley's at the top and 1 at the bottom. One of the top pulley's is only directing the cable tho. I am thinking of turning 6 sheaves for 2 pulley's.

    What diameter would people suggest for the sheaves? The winch has a pulley that came with it that would only be about 50mm diam. This setup would not get a huge amount of use.

    Dean

  2. #2
    Join Date
    May 2008
    Location
    Perth
    Posts
    241

    Default

    Going by the table in my crane training book, if you decided to call it light duty work, the ratios of the parts to the rope diameter would be as follows; Drum=11.2, Sheave=12.5, Equaliser sheave=11.2.
    If you feel like considering it medium duty work, you'd have ratios of Drum=18, Sheaves=20, Equaliser sheave=14.

    If you're curious about the sheave grooves, the recommended depth is 1.5 x rope diameter, though 1 x diameter is allowed if the rope is positively prevented from leaving the groove.
    The flare angle is a minimum of 42 degrees and a max of 52 degrees. And the grooves should be slightly larger than the nominal diameter of the rope.

    Hooray, my training came in handy

  3. #3
    Join Date
    Jan 2011
    Location
    Far West Wimmera
    Age
    63
    Posts
    4,049

    Default

    Thanks heaps for that info. I had not even thought about details like you have given. Light duty duty it will be. This looks like the 80mm would be best. I hope it is alright. The end is rough gas axed and the inside is very rusty. I am hoping it will be better further down. It used to be a vertical pin to hold logs onto an ancient timber forwarder. It got left behind when scrapping it for some reason. Maybe I just decided to keep one. Think Beijing Olympics period. I am hoping it will clean up to 50mm inside.

    It is good when your knowledge can help others. I know what you mean. Then you meet up with some smart ar5e who tries to tell you you're wrong.

    What is an equaliser sheave?

    Dean

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