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Thread: Pump Drill

  1. #1
    Never Alone In The Bush
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    Pump Drill

    20181104_170651 (Medium).jpg

    I started with a piece of eucalypt as a fly-wheel. Its a dense, relatively heavy wood. I also found a straight branch to use as the spindle:
    I found a fallen tree and cut one end off a branch to give a working surface.
    20181104_135005 (Medium).jpg

    I marked the center as best I could judge it, then used the auger to cut a decent diameter hole into it
    20181104_135911 (Medium).jpg 20181104_140616 (Medium).jpg
    The wood was still attached, so it was firmly held in place while I drilled. Once the hole was deep enough, I cut a section of the branch off; so I had a fly wheel with a center hole.

    Next I found a dry wattle and split out a "plank" for the cross bar:
    20181104_142720 (Medium).jpg

    Here are the bits and the tools I have:
    20181104_151748 (Medium).jpg

    Next steps were really just assembly and tuning.
    I went through several "rounds" of making adjustments to get it running smoothly
    20181104_170707 (Medium).jpg 20181104_170244 (Medium).jpg 20181104_170231 (Medium).jpg 20181104_180434 (Medium).jpg

    I was very please and somewhat surprised how easy the overall project was !
    The drill worked really well for what it was, although it still needs more tuning.


    One major issue was the spindle was not really straight enough and that was a limiting factor. I probably need to throw it out and get a new one, but I wasn't able to do that.
    I also found that having a longer string allows the cross bar to sit lower which is more stable, and gives more spin per "pump" and is therefore better.
    In fact I think I'd recommend a much longer spindle than the one I used, although you may wish to consider storage and transport options.

    Removing as much mass from the cross bar as possible was a good move, a heavier cross bar acts as a fly wheel itself and destabilizes the motion.

    I could see that the fly wheel itself needed tuning, but without a straight spindle, that seemed a bit pointless

    I made a "chuck" with a cross cut in the base of the spindle so I could insert bits for drilling. I made some wooden bits just to test with, but bone, stone or metal could be used.
    You can wrap twine around the cuts in the spindle to tighten it, but I had a snug fit and didn't need to, although with use it may loosen a bit and may need it.

    I made the chuck cuts a bit skew which lead to s somewhat wonky action - I wasn't paying enough attention; so that's another reason to replace the spindle.

    As well as using the pump drill to make holes, a suitable "drill" cold be fitted to allow friction fire.

  2. The Following 6 Users Say Thank You to Aussie123 For This Useful Post:

    Askew (09-11-18),biggles1024 (09-11-18),Chigger (09-11-18),MongooseDownUnder (08-11-18),sami12 (10-11-18),Thrud (08-11-18)

  3. #2
    Mors Kochanski

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    Great write up mate, thanks. Very interesting alternative.

  4. #3
    Richard Proenneke
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    Great stuff!

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