Duclos Gearless Ep. 1

In this build log, I will document building a Hit n’ Miss engine designed by Philip Duclos. The drawings and description are published in the book “Two Shop Masters” by Frank McLean and Philip Duclos. The book is published by Village Press.

As always, I can’t just build an engine to plans. I have to modify it.

The biggest difference from my engine to the one Philip Duclos built, is an increase of the size of the engine by about 25%.

Some of the key dimensions:

  • Bore: 25mm
  • Stroke: 36mm
  • Flywheel diameter: 160mm

To illustrate how the finished engine should look like, I’m including a CAD rendering.

The whole engine was first modeled in 3D CAD, to prove the design, and modify it.


The section view reveals the inner workings.



Let’s jump right in with making parts. First up, the cylinder:

The cylinder is first rough turned on the outside, and the bore finished to size. The next operation, on the milling machine, to mill the square part to have a reference for the next operation.

2015-03-04 12.46.25 (576x1024)

Next, the relief for the valves is milled

2015-03-04 17.23.05 (1024x576)

Back to the lathe to finish the OD and cooling fins

2015-10-09 19.38.29 (1024x576)2015-10-09 19.38.37 (1024x576)

Next, the cylinder head.

I took the pictures before I deburred the part. Lot’s of edges to deburr…

2015-10-17 14.24.49 (576x1024)

2015-10-17 18.54.31 (1024x576)2015-10-17 18.55.00 (1024x576)

The cylinder and cylinder head together for the first impressions

2015-10-17 18.57.31 (576x1024)



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