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Re: [MedievalSawdust] RE: Bellows -- was Hinges

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  • conradh@efn.org
    ... No plans or article yet, but the valves are simple flap valves. For this kind of improvised rig, just use a scrap of cardboard or stiff plastic over a
    Message 1 of 10 , May 19 3:23 PM
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      > On Sat, May 16, 2009 2:08 pm, leaking pen wrote:
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      >> id love theplans for that fruit carton bellows, how the valve is set
      > up?
      >>
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      No plans or article yet, but the valves are simple flap valves. For this
      kind of improvised rig, just use a scrap of cardboard or stiff plastic
      over a hole in the box. The hole should be 3-4 inches across to bring in
      enough air, and the flap needs to be stiff enough to not distort over such
      a hole during the output stroke. A scrap of 1/8 inch thick modelmaker's
      plywood is ideal, or thin aluminum plate. Whatever you use, be careful
      not to distort its flatness while you cut it out. It should overlap the
      hole by an inch or so all around, be light enough you can lift it by
      blowing on it sharply. Duct tape will do fine for a hinge.

      I prefer to lay out the bellows so that the intake valves are closed by
      default, and lift open when the intake stroke begins. Sometimes this means
      you have to leave an air channel along the bottom of the bellows.
      (Mounting the rig on a complete or partial cargo pallet is an easy way of
      doing this)
      Also: you may need to rig some kind of thread, glued stick or flap over
      the valve as a limiting stop so that it cannot flip all the way over; if
      it does a full 180 in there it's not going to close again!

      If your situation calls for intake valves at the top, they'll hang open by
      default, and you'll need to make sure they don't hang so far open that the
      beginning of the output stroke can't blow them shut and seal them. Try
      sewing through the cardboard with stout thread or monofilament, from the
      edge of the hole to the lip of the valve flap, and stitching or gluing it
      so that the valve can only open a couple of inches. That will insure that
      the rush of air will be able to catch and close it properly.

      If you find you get too much leakage around the edges of your valves, glue
      scraps of felt or suede around the hole by way of a gasket.

      For more permanent, period-type bellows I like to mount each valve on a
      removable wooden frame held in place by turnbuttons. Taking the leather
      or canvas off a bellows for repairs is major surgery, and trying to fix an
      intake valve in place is worse than building a ship in a bottle (You can
      see through a bottle!) With the removable valve, you can "unbutton" it in
      a moment for troubleshooting, and the hole it mounted in becomes an access
      port for jobs such as sewing a patch on the leather. Access is good; I
      heard of a smith once who sewed a patch over a hole a mouse had gnawed in
      his bellows, and thought he was done. Later the bellows stopped working.
      He took it apart and found the mouse had died in there, and the corpse had
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