A Miniature Triple-Expansion Marine Engine Model


Tuesday, 28 August 2007

Under the microscope

Finally, the time has come! I proudly present to you the pre-treatment digital photos, straight from the lab’s stereo-microscope! The miniature engine revealed some of its secrets as I was able to magnify it about 60x! The quality of Mr. Ewing’s work and his attention to detail at such a small scale are really incredible. I finally managed to see the reversing gear, the only part of the model which has screw threads.

A general inspection from every angle, shows dusty surfaces with minor iron corrosion, old lubrication mainly concentrated in the working parts of the model and some fibres (probably cotton).

There is also an etched mark on the metal base caused by the acidic action of a fingerprint, a constant reminder to never touch an object with bare hands!

In conclusion, I am still amazed by the complexity of the model and its details, which are visible only under the microscope. I am more positive that we can effectively remove the old lubrication and dirt layers and make it run again. Have fun with the pictures, more about the methods we are going to use for the treatment, next week!

Monday, 20 August 2007

Models as Historical Objects

Hello again from the Science Museum’s Conservation lab! The pre-treatment sessions are almost finished and I will soon post some condition and detailed stereo-microscopy pictures and a general schedule for the forthcoming treatment!
But before all these, I would like to introduce you first to a scale world, the world of the historical working models of the Science Museum’s collections.
You maybe want to know why we treat the models as historical objects, with equal value to the full sized original.

Britain is probably the paradise for models in any possible range and kind; Ships, locomotives or model engines in our case. “Rainy afternoons” is probably the first thing that comes to mind, but actually the answer is “Industrial Revolution”.
James Watt and his fellow steam engineers, used to apply their ideas on models first, then to the real thing. Thus, at the first years of the Industrial Revolution, models saved money, time and lives! The practice of model trials is still continuing today. You can always make a theoretical model of an airplane using modern computer technology, but you will never now how it is going to behave in the air, if you don’t build a scale model and test it.
During the Victorian period, the model construction reached its zenith. Model societies were founded in this period and, beyond their practical use as test beds, scale models were used as promotions for new industrial and marine technology -- kinetic advertising before the age of television! Model ships and marine engines were on display in the entrances of big shipping companies or exhibitions like the Great Exhibition of 1851 in Crystal Palace. The public could see a model when the real thing was simply too big or too remote for viewing. With scale models, you could even display a complete fleet in a single exhibition room!
Models are in many ways the best and most lasting record of a ship, locomotive or engine. Full-sized machines could be scrapped for profit at the end of their useful lives, a period of a few decades at most. So it is not surprising that models are the surviving artefacts.
Finally, model engines and models in general, have always enchanted and inspired museum visitors.

According to our historic archives, the miniature engine is a work of W.J.M. Ewing, an engineer from Kenya. It seems that he was a specialist in creating small scale fully functional marine engines and locomotives. He spent several years making this amazing feat of micro-engineering which has 3 cylinders with 3/64ths of an inch bore each, and 1/16th of an inch stroke. They are proper double acting fully functional pistons! The engine also carries real valves, bearings, even balance weights! Another impressive part of the model is the reversing gear (Stephenson’s link motion) which gives to the little engine the ability to run in two directions. It is the only part that has threads. All the other bolts are so small, that they are friction fit only.
Those details are visible only under the microscope. Be patient for the next post, which will include high quality detailed pictures from every angle!

Lavery, B., Stephens, S., (1995), Ship models, their purpose and development from 1650 to the present, London: Zwemmer, pp.7-8.
Dow, G., (1973), World locomotive models, Bath: Adams & Dart, pp. 5-8.
Science Museum, (1911), Catalogue of the Marine Engineering Collection in the Science Museum, South Kensington, London: H.M.S.O.

E. Tsolis (2007)
G. Dow (1973)

Monday, 6 August 2007


Hello, I am Stathis, the Metal Conservator of The Science Museum in London. We have made this blog to let you watch the treatment of one of the most spectacular and smallest artefacts of the Museum’s collections, a miniature working model of a ship’s engine which was built in 1936 and is no bigger than a 5 pence piece!

Full-sized engines of this type were enormous: the RMS Titanic had two of them, each larger than a double-decker bus. The triple-expansion engine was at the heart of shipping development from the 1880s to the 1920s. It was the ultimate in reciprocating steam power because it used the pressure of the steam three times over – triple expansion. Eventually the steam turbine and marine diesel took over. But when the Second World War broke out the Allies turned once again to the well proven and simply built triple-expansion engine. They had to build ships and engines faster than the U-boats were sinking them!
Our tiny triple-expansion engine works just like a full sized version, but on air rather than steam. Originally, the little engine was operated with a puff of air, coming from a rubber bulb. Unfortunately, rubber decays over time. Due to chemical deterioration, the bulb became hard to squeeze and the miniature did not operate for many years.

However, we never stopped thinking about possible solutions for putting the Museum’s smallest engine back in action! Besides, every working model has to run a few turns once in a while in order to stay operable. Our objective is to preserve the model engine in a good condition, running it periodically and also to give you the opportunity to witness its conservation through a series of posts in this blog. As the conservation treatment manages to make the model work again, we will prepare a video which will be available for streaming through this blog.

So what can you do?

You can join in by posting comments and questions. We would like to know if there are other miniature engines around! Feel free to ask questions about the conservation treatments or general information about the miniature model.
The project is challenging but promising. In the next post, we are going to do the pre-treatment documentation, using digital photography and stereomicroscopy.

Griffiths, Denis, (1997), Steam at sea: two centuries of steam-powered ships, Conway Maritime, p. 116
Rowland, K., T., (1970), Steam at sea: a history of steam navigation, David & Charles, Newton Abbot, p. 201