Updated: Jun 18, 2019
This question is often asked by interested members of public, therefore it is no doubt that this may also be a question that some newcomers to the hobby would like to understand a little better.
Equally as confusing, is the number of different ways that the scale of a miniature steam engine can be referred to.
When referring to an engine as “half size” the terminology is quite self-explanatory but often the term 6” (inch) will be used instead. This is a reference to the scale factor of 6” to the Foot. So, any part on the full size which is a foot (12”) long would be 6” long on the miniature.
Common references and their inch scale:
The picture below, taken from http://www.littlesamson.co.uk/ shows a line up of Little Samson Steam Tractors all built to the same design but of different scales 3”, 4” and 6”.