HOMEMADE STEAM ENGINE

FROM TWO DOOR CLOSERS

   A door closer is extremely robust and has a precison cylinder and piston
which can make a steam engine.  They have a long piston with a rack down the
side that engages the pinion which operates the door-closing arm.  In normal
use, a spring closes the door that was pushed open, compressing the spring.
Basic parts of a door closer.
  The spring was removed using a 1 & 1/4" hole saw to cut into the back.  The
closer is full of oil which will run out, so be ready for that.  For steam use
the cylinder is oiled externally. Wash it well with dish soap, hot water, a
bottle brush and an old toothbrush. Turn adjustment screws in tight.
Modifications.
  The U-shaped pin wrench was made in order to remove the end cap above the
piston.  A 1 & 1/4" hole saw was used to cut into the pinion bosses on the
sides.  Stop when you see a ring turning with the hole saw.  A pipe wrench
unscrews the pinion bearings.  Remove the pinion.  Wash the cylinder again.
  The piston has a diameter of 1 & 7/16" (1.62 sq. in.) and a stroke of 2".
A door closer can take very high pressure, but the airguns used for valves can
only take air compressor pressures.  Our test boiler for steam was a common
kitchen pressure cooker.
  Remove the piston and cut the housing 1 & 3/4" from the back vertically
down. Stop at a point 1" from the bottom.  Now cut horizontally from the back
to the vertical cut.
  Drill down to the ball valve in the piston and then push the ball out from
the back with a coat hanger.  Now drill all the way through 1/4" for the
central rod.  A 1/4" rod is welded to the piston flush with the boss on the
top of the piston.
  The end disk is cut out of 1/8" steel using a 1 & 1/2" hole saw, which also
drills a 1/4" hole.
One piston with end disk and pushrod.
  The end disk with the pushrod ears is tack-welded to the other end of the
1/4" central rod.  The wrist pin is 3/8" stainless round rod.
Air gun used for valves.
  Common airguns are used for the poppet valves.  The springs are removed
and the O-rings replaced with silicone ones which can take the higher heat.
They are lubed with silicone grease.  The end of the valve plunger is drilled
3/32" for securing to the valve rod.   The removeable part of two air gun
nozzles is drilled 1/4" for 1/4" copper line which is silver-soldered to it.
The nozzle piece with the copper line is then threaded back on with pipe
joint compound.  The inlet end of the gun takes a standard 1/2" pipe fitting.
Two inches of 1/4" copper line is JB-Welded (epoxy) into each cylinder cap.
The valve rod.
  Springs hold the valve rod against the connecting rods so that the pushrod
ears bump the valve rod to the opposite position.
The valve plungers are held in place by wire.
  There should be very little free play.  When a valve closes (out), the
pressure holds the plunger tightly closed.  But a plunger that is pushed in
(open) does not have to be fully in to work perfectly.
The door closer steam engine.
Operation of the door closer steam engine.(3.5MB)
The modified pressure cooker boiler.
  We did not know what pressure the steam engine would require, but it turns
slowly at 15 PSI and spins almost too fast at 30 PSI!  So we modified this
thrift shop 4 quart pressure cooker.  The steam comes out the central fitting
that had the pressure-regulating weight.   Corks were placed in one hole that
is under the lid handle and the other hole that was where the missing pressure
gauge would have been.  They are pushed into the holes from the inside.  We
stop the pressure at 30 PSI, the usual canning pressure.
The pressure cooker boiler assembled.
  Put silcone grease on the gasket where it contacts the pot rim for ease of
opening. The mark on the gauge is at 30 PSI.  WARNING: At some point above
that the corks would be BLOWN OUT and the water inside would FLASH-BOIL!
  As it is this steam engine is just a school shop demo unit. If the steam
engine was to be used for serious work, two things need to be changed. The
pressure can be as high as the air gun valves are rated, 150 PSI.  And the
steam should be allowed to expand in order to extract the most work from it on
each stroke.  As it is the valves are fully opened (or fully closed) at the
ends of the strokes. The inlet valve should be opened for about a fifth of the
stroke while the exhausting valve is open for the complete stroke for maximum
efficiency.
PARTS:
  The door closers are Medium Duty Commercial units from Home Depot.
  The air guns are from Harbor Freight.
  The 5/8" shaft bearings are from a pneumatic wheel hub from Harbor Freight.
  The 1/2" flanged crank bearings are Grainger 1ZGE8.
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SILVER-BRAZING:
Alpha-Fry 45%-silver-braze & flux.  (Ace Hardware)
  This is 45% silver and so is expensive, but the bond it forms is nearly as
strong as a weld at half the temperature. Clean the joint to bare metal, flux
ONLY where you want the braze (important).  Heat with a torch ONLY enough for
the braze to flow (dull red) and then remove the torch immediately.
Copper line brazed into the air gun muzzles.