THE HISTORY

The Stirling engine was invented by Rev. Robert Stirling in 1816.
He was a Scottish minister. At that time, Stirling engines
were recognized as a safe engine that could not explode
like steam engines of that era often did.

Nei motori a ciclo Stirling il fluido motore (gas) non ha
contatti o scambi con l'esterno, ma è ermeticamente
confinato all'interno del motore, quindi non vi sono emissioni
inquinanti. Il ciclo di funzionamento è molto simile al ciclo
di Carnot, quindi in questi motori il rendimento approssima
il massimo ottenibile da un motore termico che funzioni
fra le stesse due temperature estreme. I motori Stirling
possono funzionare fra temperature molto vicine:
anche solamente con 7°C di differenza. Sono diventati
interessanti in questi ultimi anni come possibili motori
puliti ed ecologici per la conversione diretta dell'energia
raggiante solare. Il ciclo Stirling inverso ha applicazioni
nei liquefattori di gas come l'aria e l'azoto.

My friend Adolf Cortel from Spain shows two models
of Stirling motors to VIP's at POS2 (Physics on Stage 2002)
in Noordwijk (The Netherlands). The motor on the left
is of the kind illustrated in the following sketch.

THE STIRLING MOTOR WORKING PRINCIPLE:

The cycle of a generic Stirling engine is as follows:
Air at the bottom of the cylinder (E) is heated,
thus expanding and forcing the piston (A) upward.
At this time the displacer (B) is driven downward
to the bottom of the cylinder. Since the displacer
is of a smaller diameter than the cylinder, the
hot air rushes around the displacer to the cool
end of the engine (F). Once in the top end of
the cylinder, the hot air begins to contract,
sucking the piston downward. Now the displacer
moves upward, forcing all the cool air from
the top end of the cylinder into the bottom end.
Here the air is heated and the cycle begins again.
Note the 90° phase shift between the displacer
and the active piston. Furthermore, this motor runs
completely silent!

SEE HERE AN ANIMATED STIRLING ENGINE
Thanks to M. Abendschoen and its web site:
http://michael.abendschoen.bei.t-online.de/hauptmenue.html

YOU MUST SEE ALSO IMEDIATLY:
http://www.newenergyshop.com

This is the beautiful Stirling engine from EXERGIA GERMANY
(WWW.EXERGIA.DE)  which incredibly runs on unconcentrated
solar radiation on its top surface. The same firm sells
also other interesting engines both in kit and fully assembled.

AN EXTRAORDINARY STIRLING MOTOR
WITH THE  "RINGBOM" TECHNOLOGY: SEE.

THE TEST TUBE  STIRLING MOTOR

This test tube Stirling engine is likely the simplest to construct.
It makes an ideal gift for that budding scientist or engine
enthusiast. Ideal as science project and teaching aid.

A BEAUTIFUL SELF EXPLAINING
ANIMATION

Note the 90° phase shift between the displacer
and the active piston. Heath is on the left cilynder.
By courtesy of: Steffen Tschirch, CAD Zeichen Büro
Hildesheimer-Str. 401, 30880 Laatzen
Fax.:  49 5102 914732
http://www.cad-zeichen-buero.com
E-Mail: info@cad-zeichen-buero.com

ANOTHER INTERESTING
CONFIGURATION
symilar to that of the above animation:

Owing to the simplified mechanism of the 90° shifted
displacements of the pistons, this structure could be
easier to make.

CONSTRUCTION TRICKS AND HINTS

1. In small engines the connecting rod small end  from
the piston or displacer to the crankshaft may be done by means
of an intermediary small piece of flexible rubber tubing.
2. In small engines the piston may be in the form of a thin flexible
rubber membrane, like in those barely visible in the above photography
of Adolf Cortel from Spain and in the following image:

as is used in  the following fine "cofee cup" engine
(sold also in kit form):

3. Long life, self lubricating and very low friction pistons are made of
grafite, with the cylinder made of glass tube. Suitable cylinders
are made by a glass syringe.
4. As in the above "cofee cup" model Stirling motor, the bushes and the axle
bearings are suitably made by teflon. Remember to keep frictions as small
as possible.

MY STIRLING MOTOR

This is a detail of a Stirling motor constructed in the Laboratory
of the Museum of Physics of Cagliari University.
Cylinder: glass; piston: graphite; displacer: styrofoam. Under
a working temperature difference of  20 °C it turns at 150 rpm.
Note the couplig between the piston and the connecting
rod made by a spring of inox harmonic wire.
 

STIRLING ENGINE SCHMIDT THEORY
See the site of Koichi Hirata
See also the Alan Altman site
for a calculation program.