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Thread: Home made propeller

  1. #1
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    Default Home made propeller

    Hi all,
    I am giving making a tubed cleaver for a 8hp Tohatsu a go.
    Chopped blades of one of my Johnson 25hp stainless props and re-shaped, still a bit of fine tuning on blade shape to go.
    Will make a jig and pitch block to weld blades on at 13 pitch and low rake.
    Will keep pictures comming.
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    Default Home made propeller

    Hi all,

    I Have added a trailing lip to the blades, they all still need to be sharpened and polished.
    I have also started on a pitch block (I decided it does not need to be that pretty as I will only be making one of these props)
    I have weighed each blade and they are within 1gram (I will also ballance the prop once it is all together somehow)
    I am gauging my pitch block off 3 props I have here which are all 13 pitch.
    Although I have played, re shaped, modified heaps of props I have never made one from scratch so I am no expert at this, I know full well this could fail but would love any information or help from anyone who has done this before.
    Just something I am enjoying playing with.
    Cheers,
    Glenno
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    Another nut like me! (Made several that way.) Be sure to leave LOTS of fillet where the blades are welded to the hub. (I didn't once and--whamo!--the blades broke off.)

    Jeff
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    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Awesome project

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    Quite a nice project. Do those blades have progressive pitch from leading to trailing edge at any given radius or a constant pitch at any given radius? If progressive pitch how will you get your desired 13" pitch?
    " Three may keep a secret if two of them are dead" Ben Franklin
    " ------- well Doctor what have we got a Republic or Monarchy? A Republic he replies if you can keep it"
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    Hi mate,
    Yep the blades are progressive pitch the whole way up the blades.
    It will be 13 in the centre. I have three props here that are 13 pitch which I am modeling my pitch off, two of those props are progressive pitch.
    If I get the pitch a bit wrong hopefully I go down not up, 12.5 would be fine but I am not sure how above 13 would go without modifying the little motor a bit.
    If this prop is a failure, hopefully it looks cool and I will put it in my wife's display cabinet to man it up a bit!
    Cheers,
    Glenno

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    Default Home made propeller

    Hi all,
    Just finished the jig for holding the blades as I weld. We will see if it works, I know as soon as you tack weld stainless it moves, I am hoping to get this thing really accurate but at the end of the day if I fail at least I have learned a few more things.
    I am wondering if I should polish the hub and blades before I weld it all together so I only have to clean up the welds and splatter. It would be easier while it's apart as it is only a small prop at just under 9 inch diamiter.
    Thanks for the input so far.
    Any input would be appreciated
    Will keep you posted
    Cheers,
    Glenno
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    You'll have a tough time getting a grinding wheel in there no matter how you do it. Be sure to leave at least a 1/4 inch radius fillet weld AFTER grinding or the blades could snap off. (In other words, avoid excessive grinding.) A 1/2 inch fillet would be even safer.

    Jeff

    PS: Nice fitting of the blades to the hub! You might want to bevel that straight edge on both sides of the blade to improve weld penetration.
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  9. #9
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    Default Home made propeller

    Hi,
    I will make sure to leave a good amount of weld on for sure, good info Jeff, last thing I want is for it to tear apart.
    Just gave all members a quick buff to make final finish easier.
    Cheers,
    Glenn
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    One more thing I forgot to mention: I weigh each blade on a digital scale before welding. The heavy one(s) are ground (over a large area) on the back side to lighten them.

    On angular positioning (since we don't own a machine shop!) you can use a large hex nut tack welded to the hub. A pointer aimed at every other flat (where they peak) will give you accurate results.


    Good luck!

    Jeff

    PS: No one is gonna put Ron Hill out of business this way, but it sure is an interesting project. I've built five to date, two of which are successful.
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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