PASCO SE-8575 VISIBLE STIRLING ENGINE - Manual (Page 13)

9
012-06055A The Visible Stirling Engine
®
Troubleshooting
There are three general reasons why the SE-8575 Stirling
Engine might not run.
➀
Not enough temperature difference between the hot and
cold side of the engine. This Stirling engine needs about a
40°F (23°C) difference in temperature to run. If the room
is at 72°F (23°C) and the ice temperature is 32°F or
cooler the engine should run at 100 rpm or faster.
If ice is used as the “cold” source, it is possible to have
the bottom of the engine rest on only a few high points
on top of the ice cubes. The best solution is to pick up
the engine and rub an ice cube vigorously around its
bottom. Then place the engine on a pile of ice cubes
(ice chips are best). Push down on the LCD thermom-
eter with your warm hand to help establish contact
with the ice. This will simultaneously warm up the top
of the engine and help establish better ice contact with
the cold side of the engine.
➁ The engine may have developed a leak in the system.
The Stirling cycle engine is a sealed system. It can
only tolerate one tiny leak. If there are any obvious
holes in the grey diaphragm (which is the piston) the
engine will not run. Contact the Magic Motor Com-
pany 1-800-503-2906 for replacement parts or service.
➂
There might be internal friction in the system. Every
engine ever built has internal friction losses. However
this engine when operating between such small tem-
perature differences does not have room for much
wasted power.
There are two things that have been observed to some-
times cause problems. There must be about slight loose-
ness in the collars where the crankshaft goes through the
aluminum upright near the propeller. In other words, If
the engine is held in one hand and the prop is moved back
and forth along the axis of the crankshaft it should be
possible to hear the collars make a clicking sound, and
see the bushings which hold the crankshaft in place move
back and forth about the distance of 2 to 4 sheets of
notebook paper.
This looseness is essential to proper operation of the
engine. If one of the bushings has moved slightly and
becomes a tight fit on the aluminum upright, the engine
will run poorly or not at all. The solution to this problem
is to use a knife blade to move one of the collars slightly
away from the aluminum uprights.
Also, the piston must move freely without binding at the
top or bottom of its travel. This should never need
adjustment, but it can be adjusted if someone accidentally
moves it out of its range. The piston (grey rubber dia-
phragm) should, at the bottom of its travel, be almost (but
not quite) tight. At the top of its travel it should also be
almost but not quite tight. If the piston is tight at either
end of its travel it can be adjusted slightly by hand.
The black tubing that covers the rod connecting the piston
and the crankshaft is a slip adjustment mechanism. If the
piston is too tight at the bottom of its travel, shorten the
connecting rod by pushing in (ever so slightly) on the
piston end and the crankshaft end. Hold one hand at the
crankshaft end of the connecting rod and the other at the
piston end and push these ends together. If the piston is
too tight at the top end of its travel then lengthen the
connecting rod (very slightly) by pulling down the piston
and pulling up on the crankshaft end of the connecting
rod. In other words, reverse the previous process.
Adjusting the Regenerator
The regenerator is the yellow piece of foam inside the
engine that moves the air from the hot side to the cold
side. In normal use this should never need adjusting.
However if someone grabs it and pulls on it, the regenera-
tor can be moved out of adjustment. Ideally the displacer
should just barely touch (or not quite touch) the top side
of the engine when it is at the top end of its travel. It also
should not quite touch (or barely touch) the blue plate
when it is at the bottom end of its travel.
Turn the propeller slowly through by hand and watch the
regenerator. If it is adjusted as indicated in the above
paragraph then don’t do anything with it. If it hits the
bottom enough so that the flexible rubber linkage tubing
bows out when the regenerator is at the bottom of its
travel then push the black tubing slightly down onto the
regenerator shaft. The regenerator shaft is the shiny piece
of wire that goes down into the engine and attaches to the
yellow foam.
If the LCD Thermometer Turns Black
LCD thermometers of this type have specific operating
ranges. When the temperature is within their range they
display colors. When the temperature is out of their range
they turn black.