To start your Stirling engine, turn the crankshaft until
both cranks are tilted upwards at 45-degree angles
to the vertical. With the stopper removed from the
drain, fill each side with water, until a trickle runs out
the drain. Dry it and replace the stopper.
Designate one side as the hot side, then heat the
water on that side to boiling with a propane torch.
This takes a while, depending on the heat output of
the torch. Be patient.
When the water is ready, start the engine by
giving the flywheels a small push. The rotation is
determined by this rule: the cold side is 90 degrees
behind the hot side.
If built properly, your engine will dip and lift, dip
and lift, 20 to 30 times per minute to the chuff-chuff
beat of Robert Stirling’s ancient idea.
1. Make sure the engine is level. The crankshaft
must revolve freely, and the connecting rods should
stay in the middle of each crank as it rotates. Use
shims or cardboard to level the system. If the connecting rods will not stay centered on the cranks,
you can add a small wire loop or small nut to the rod
on either side of the eye screw, fastening them into
place with super glue.
2. You may have to experiment to find the best
flywheel weight. If the flywheels are too heavy, the
metal rod will bow, interfering with the crankshaft’s
rotation. But if the flywheels are too light, there
won’t be enough inertia to carry the crankshaft past
the volume compression phase and into the next
expansion stroke. If this happens, the engine will
pulse but not run cyclically. You can add weight to
the flywheel by simply taping bolts or other weighty
objects to its perimeter.
3. Large steel cans full of water take time to heat. Be
patient, and let the water heat to 200°F or more.
4. Minimize friction and interference. Friction is
your engine’s greatest enemy. Minimize rubbing
between pistons and water cans, between connecting rods and cranks, and between the crankshaft
and the metal support angles that attach it to the
5. Add a regenerator. A regenerator consists of a
small piece of heat-conducting metal gauze placed
in the air cylinder just behind the rubber stopper. A
regenerator will improve cycle efficiency and make
the machine turn faster. The copper gauze sold for
cleaning kitchen pots (“Chore Boy”) works well.