Part 1 by Guenter Kallies

In the very early years of steam, most of the engines were of the stationary type. In 1736, Mr. Jonathan Hull was granted a patent to operate a steam engine to assist ships entering or leaving harbour using an arrangement of ropes and pulleys.

A lot of experimenting was done at the end of the 18th century, mainly in England and France. Finally, in 1802, the first usable steamship, the Charlotte Dundas, was launched and operated on the Forth and Clyde Canal to tow other ships to Glasgow.

The first permanent success was achieved in the United States, where in 1807 the Steamship Clermont began a regular goods and passenger transport service on the Hudson river from New York to Albany.

In subsequent years, ships increased in size and needed more powerful engines. At first, stationary beam engines with flywheels where installed on ships as specialized marine engines were not available. In 1814 the Boulton & Watt side lever engine was developed and become the standard marine engine of the time.

The complicated operation and great weight of this engine gave rise to the demand for a new type, the direct operating engine. Here, the cylinders were installed directly underneath the crankshaft, but, in this case, the connecting rods became very short. The disadvantage was the additional bending  load on the piston rods. Cross heads and slide bars were the answer but, again, with the inconvenience of additional friction and wear. Later, linkage systems, mainly the Evans system, become popular. This system, developed by Oliver Evans, an American engineer, consists of three levers, the main lever  “a“, the counter lever “b“ and the swivel element “c“ which give linear guidance to the cross head while the individual levers rotate counter wise. The benefits were low weight and a reasonable manufacturing cost as well as reduced installation space.

In 1837 the Royal Navy frigate HMS Gorgon was built by Seaward & Co. This ship was equipped with a new type of engine, a two cylinder direct operating engine. The name of the ship was also used for this new generation engine type.  A beautiful model of this engine is held at the Science Museum, London.

The model described here is a working freelance version of this engine. In many details it was simplified either for manufacturing reasons or to ensure safe function. For instance, all components are made from stock material instead of the castings used on the full size engine. Another example is the valve gear, where a Stephenson link system is used on the model version. Until 1843, this system was subject to a patent granted to a Mr. Howe. Whether or not it was used on a direct operating engine is not known, but it is conceivable.

The main design criterion for the model version was the ability to produce all components in a lightly equipped model engineer’s workshop. All that you need is a small lathe, a drilling machine and some hand tools. All dimensions given in the drawings are in the metric system. The design is broken down into 7 groups:

  1. The  framework

  2. The cylinders and steam chest

  3. The valve gear

  4. The crank shaft and connecting rods

  5. The condenser and pump

  6. The linkage system

  7. The steam pipes and equipment

Part one here  Part two  Part three  Part four