METRIC MINNIE

By Arthur Groves, Julius de Waal and Darius Zimmermann

Large scale traction engines are attractive to operate, but they are not everyone’s favourite size to build. Storage and transport are also not practical for everyone.

The Minnie scale is so much more convenient to handle and is a 'single-handed' engine. And it can be proudly displayed on the sideboard which you can’t do with a half-size Burrell. If there is a balance between building and operating a model traction engine then the Minnie is definitely biased towards building satisfaction.

This version of the Minnie is geared to the newer workshop with metric tooling, tho most have little difficulty in moving between measures.

Some time ago Arthur Groves set about producing a metric version of Len Mason's classic small traction engine design. There were a few dimensions missing, and the grouping of components was not easy to follow. We asked Julius de Waal if he would like to have go at re-presenting Arthur's design in a way more suited to publication. He agreed, and with astonishing speed re-worked things in Solid Works.

Castings have been available for many years from several suppliers for the original imperial version and they should also be alright for Metric Minnie. However, as Len Mason pointed out when introducing the original design, there is no reason why most of the parts should not be fabricated.

The prospective builder confronted with a new traction engine design looks first at the flywheel and rear wheel diameters, assessing his lathe’s capacity for turning them. Even in 1:8 scale rear wheels can pose problems for a 3.5” lathe, even a Myford with its gap bed. Not so with this 1:12 scale engine. That makes everything possible for those with a small workshop. What is more the boiler comes within the ambit of the home amateur with easier silver soldering compared with larger models. And, of course, everything costs so much less. Especially if the builder makes extensive use of fabrication.

The design is practical so that, for example, the need for ‘watchmaking’ to make a tiny governor that won’t work anyway is designed out. However, Metric Minnie is reasonably correct full-size practice, and definitely not in the ‘toy’ class. It is still a complex thing to make and definitely not a quickie, even with simplification to fit the scale.

Minnie is also be commended to those who do not wish to slavishly copy the design for authenticity. As a freelance design the builder can play whatever tunes he likes and fear nothing from the rivet counters and nose tappers.

Here, then, is the first part to inspire you to take up the project.

This is not a blow by blow account of how to build it. That has already been superbly covered by Len Mason first in a series of articles in Model Engineer in 1969/70 and in a book entitled Scale Model Traction Engine Building Featuring Minnie, now out of print. Back copies of ME are usually available from TEE Publishing with the bonus of all the other material published in the magazine’s heyday.

CLICK ON DRAWINGS TO DOWNLOAD - FOR PERSONAL USE ONLY. SEE ALSO PART 1   PART 2    PART 3   PART 4  PART 5  PART 6    PART 7    PART 8    PART 9