Fizgig Stirling Engine

Engine build and author: Dick Barnes

Having now reached that moment of retirement and with a fully kitted out workshop, this Fizgig stirling engine looked like an ideal subject to commission the new lathe.

Fizgig

Fizgig is a Gamma Stirling engine in which the power piston is not mounted coaxially to its displacer piston. The advantage of this design is that it is mechanically simpler and the disadvantage is the lower compression ratio. This design is often used in multi-cylinder Stirling engines.

During the build I did quite a few modifications to it, fitting ball bearings where ever possible, and making improvements as I saw fit.

fizgig stirling engine

The end result is an engine that runs unbelievably smooth and needs hardly any heat at all.

Fizgig

Plans for this engine are online: water cooled stirling engine

This is a really simple design that would allow the model maker to build it as per the design or with confidence modify a number of different aspects. Even if you just change the water cooler the design would change. Or a chimney could be built around the heater. This makes it a great design to start and learn from.


model of the stirling engine

Stirling Engine

The Stirling engine was invented in 1816 by a Scotch clergyman, Robert Stirling, as a competing technology to the steam engine.

Stirling engines work by subsequently heating and cooling a gas inside a closed volume. As the gas is heated it expands and as it is cooled it contracts. This expansion and contraction works forces a working piston which in turn drives a crankshaft. A Stirling cycle has two pistons: one that drives the crankshaft known as the power piston and one that moves the gas between the hot and cold ends of a cylinder known as the displacer piston.


low temperature stirling engine

Low Temperature Stirling Engine

A stirling engine that operates with a very low temperature differential across the displacement cylinder.

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