By Julius de Waal

Some weeks ago while I was browsing through the pages of Model Engineering Website, to which I have contributed some projects/drawings, I came across an article written by Mr. D. Zimmermann, with regards to traction engines designed by Patrick Stirling.

In his article Mr Zimmermann challenged somebody to take on this traction engine as a project to build.

It has to be noted that the picture shown is very basic due to the fact that it was only a concept drawing to obtain patent rights.

I was very intrigued by the design of this engine and thought that it may be just the project for me.

Although I do not build the engines my self I do design them on paper so that others, who do posses the skill(s) and the machinery, to build model engines to their liking.

Since the drawing, shown in the article of Mr Zimmerman, does not have any dimensions shown it was difficult to put a scale to it. Also as said in the article you must have a good imagination to construct this engine.

After a few quick calculations and interpolations I settled for a scale of approximately 1:35, taken the wheelbase as guideline. So I estimated that the outer dimension of the wheel base may be around the 2500mm (8ft/2.5inches) mark.

To make a reasonable good design I had to alter/change some parts as was shown on the picture.

I have tried the make this engine a working model as much as I could design, however if somebody is going to take up the challenge to actually build it, some parts may have to modified to suit the builders requirements.

It has to be kept in mind that this engine is not for fainthearted builder. It requires some skills of a person whom has build model steam engines before. There is some precision machinery required.

Now let us have a look at the drawings. In the olden days some of the machines were made from wood. So I have designed the frame(s) and the wheels having a wooden core.

Deliberately I have not specified the materials, I leave it up to the builder to choose his or hers available and preferred materials. However as basic materials the following could be used: Aluminium, brass, bronze, steel/iron, silver steel/stainless steel.

The design I made is for a coal fired boiler however with some changes it can easily be converted to a gas fired boiler.

It can be seen that the boiler is not fully drawn with the equipment which forms a part of the total operation of the boiler. The following boiler parts are either propriety items or could be made by the builder if so desired:  Water level indicator, steam pressure indicator, safety valve, non return valve and/or blower. I have allowed for these items on my drawings.

If the water bunker (above the front wheels) is being for its purpose than a filling point has to be made.

If a water feed pump is to be employed than this can be either be bought or made. Also you may notice that I have not incorporated a supply steam on/off valve. Since there are several types of designs of these valves available it is left to the builder to make has own choice and place it in the steam supply line at a convenient place.

If somebody would like to build this engine but find it too small to operate with real steam, but still would like to see it running around than there is always a possibility to install somehow an electric motor and let it operate on a battery and may be use remote control. The possibilities are endless.

I hope who ever takes on this challenge that he or she has a lot of pleasure while building it and if it all works have a lot of pleasure running it.

Happy Modelling