Miniature Traction Engine

miniature traction engine drawing

This is a work in progress around the research, design and building of a miniature Burrell 6NHP traction engine.

Cherry Hill's model engines a book by David Carpenter

My son bought me this book for my birthday as I’ve seen a number of Cherry Hill’s models and they are inspirational.

This book has made me think about my approach, my research and as I’ve got older how I can more calmly make parts and remake parts.

The main image shows the elevation view of this traction engine printed on a sheet of A4 paper. This is meant to be a small traction engine that works and make to enchant.

Basic dimensions:

  • Length: 263mm
  • Width: 122mm
  • Height: 176mm
  • Bore / Stroke: 12/17mm
  • Rear wheels:
    • diameter: 97mm
    • width: 22mm
  • Front wheels:
    • diameter: 70mm
    • width: 12.5mm

Boiler

boiler endplates

The boiler design is to heat from underneath and with through tubes with the firebox being separate. This means I can make a simple copper boiler and fix this into a steel firebox. Firstly I need to learn how to make the boiler endplates.

What is the right angle for the boiler to sit relative to the road surface?

Crankshaft

One of the initial design questions was around the clearance between the crankshaft and the top of the firebox, in particular the clearance to the conrod bigend.

Smokebox

smokebox and lower chimney assembled

The smokebox is gradually taking shape with some basic dimensions being sketched out and then I’ve machined the main ring out of mild steel.

Wheels

rear wheel treads machined

The rear wheels are only 97mm OD, hence my initial thought was to buy some thick walled 4 inch diameter pipe, but I just could not find any. I bought 100mm mild steel round bar, 2 off pieces at 1 inch long, I then had to machine the rims roughly to size.

Machining the treads at 10° to the wheel was tricky but rewarding.

About Nigel 255 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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