Triple Expansion Marine Steam Engine

Built by Peter Cowie of Sydney


The 26' counter-stern launch "Witch of Endor"




A John Davis Engineering "keyhole" boiler  (see links page)

Propeller 20" x 36" RH


Triple expansion engines, whereby the steam is expanded three times, provided the power of most of the world's ships until supplanted by turbines in warships and fast passenger ships in the period 1910 - 1920. They still powered much of the world's cargo ships and ferries until the 1950's.

They power such famous ships as the Titanic, the Liberty ships, and Sydney's own Lady Hopetoun, South Steyne and John Oxley.

Chosen for their economy over compound engines they were were rare in small sizes (less than around 60 IHP).

With six power strokes per revolution they are extremely smooth in operation. Most of the large triples ran slowly. The Titanic's two reciprocating engines running at 76rpm each developed 16,000IHP. The Lady Hoptetoun's 260IHP engine runs at 250rpm. This small triple is designed to produce 10IHP at 300rpm. Although relatively small in horsepower the engine produces a lot of torque, the equivalent of a five litre 300HP V8 in a modern car.

For more information  contact:

I posted a comprehensive website while I was building of the engine

Unfortunately Telstra removed their webhosting from my subscription package and the website disappeared for a few years.

The original site is back again slung off the SBAA's site but some of the links are rusty and won't work (especially the movies) but there is a lot of information about building the engine that is still relevant.

Link to Old Triple Site



Click on these thumbnails for a larger view

115 Bronze and Iron Castings

Valve gear, intermediate pressure cylinder

Valve Gear Components, one set for each cylinder

The boiler on order

Progress on the half model of the hull 3.7.03

Ready for steam 17.10.03

The Finished Engine 26.2.04

The engine being steamed for the first time November 2003


More details about this project can be found at the builder's web site