Chain drive,Universal joint,Direct drive

Discussion in 'DIY Marinizing' started by Ed-H, Mar 11, 2010.

  1. Ed-H
    Joined: Mar 2010
    Posts: 18
    Likes: 1, Points: 0, Legacy Rep: 13
    Location: Montana

    Ed-H Junior Member

    I have been reading the threads, and there seem to be proponents of each method of power transfer from the engine to the prop. I thought the U-joint could be good, but it appears they do not last long. I see the advantages of the chain drive, however, I wonder how much longer that chain and the sprockets would last under such loads? And the direct drive also has its advantages, perhaps the most in its simplicity. If anyone out there has some input from their experiences with these modalities, I'd sure like to hear them, as I just acquired a 4hp BS for free today, and WILL be building a longtail this summer! Thanks in advance guys.
  2. marshmat
    Joined: Apr 2005
    Posts: 4,127
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    Location: Ontario

    marshmat Senior Member

    All of these options can be very reliable and long-lived, if they are set up properly.

    Regarding universal joints- the simple Cardan joint is the easy choice, and if you're careful about the loads you transmit through it (torque OK, but try to keep lateral and axial small) they can last for decades. More sophisticated types are also options; many high-end installations use double Rzeppa joints. Obviously, a thrust bearing on the prop shaft would be called for.

    As for chain- look at motorcycles, snowmobiles, the timing chains of some car engines, all sorts of industrial systems- with well designed bearings and good sprocket alignment, chain drives can be made to reliably transmit quite a lot of power.

    I'd say it's a fair generalization that most complaints about "such and such a drive system doesn't last long" are the result of a system that wasn't properly engineered for the loads it was expected to handle, rather than being due to any fundamental flaw in the idea.
  3. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    chain is very common in Thialand only they put it behind the engine as they have availability of left hand props .... what you dont have carnt go wrong so the best way is direct drive if if if if if you can get he right prop.

  4. Frosty

    Frosty Previous Member

    Its a kit they are in every hardware shop --approx 5 to 1 in duplex chain.

    Props are 2 blade made by AAA in ally machined to taper with key.

    The smallest is 30 baht there is 32 baht to a US dollar.

    My friend used to buy them as decorations to take them back home to UK.
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