Month: February 2016

Duclos Gearless Ep. 5

In today’s episode, we’ll look at the crankshaft assembly.

I changed the design of the crankshaft from a one piece to a built up design. I feel a built up crankshaft has the advantage of being easier to build and can produce a strong, true running shaft. Another advantage is, that we can use a needle roller bearing, and the connecting rod doesn’t need a split bearing.

First, the connecting rod:

Completely  machined the first side of the connecting rod. The two bores, and the contour are on finished size.

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Next, I machined a set of soft jaws to hold the connecting rod, to machine the second side. (The jaws have been used before, hence the extra machined areas)

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The second side is being machined and the finished rod, still in the vise.

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Finished rod:

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Here we have all the parts for the assembly:

The needle bearing inner ring is the crank pin. The crank web faces are turned true after they are mounted to the shaft. The whole design relies on the faces to be very accurate, as even a small error would cause a wobbly crankshaft.

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Test fitting of the crankshaft to show the inner ring installed.

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Needle roller bearing is installed in the rod.

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Connecting rod is installed on the crankshaft.

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The piston is made out of cast iron. The rather large groove will be for the O-ring piston ring.

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The entire assembly finished.

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Duclos Gearless Ep. 4

In today’s episode, I’ll start with some finished parts.

The push rod is made out of cold rolled 1018 mild steel.

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The two bearing blocks and the base plate are finished as well. They are made out of 6061 aluminum.

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Up next, we have what Phillip Duclos calls the pillar shelf. It’s main function is as a guide for the push rod.

It has a deep slot, with a depth of about 3/4 of the materials thickness, where the push rod will ride in. Using cold form material as stock, I was worried it would distort the work piece from the internal stresses while cutting the slot. So, to keep it accurate I proceeded as follows:

First, I roughed out the slot: I left about 0.5mm on all surfaces to be cleaned up.

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Checking if it distorted with a beveled straight edge, we can clearly see the “day light” shining through…¬† well, we saw that coming…

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Next, milling the back surface, which will be our new datum.

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Front side again, finished the face and the slot.

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Next, I surfaced the top, and finished one side.

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Repeated on the other side with finishing to thickness and length. The two holes for mounting it to the pillars are drilled. The small slot is for clearance of the cam roller.

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A hole for a set screw is drilled (Tapping will be done afterwards on a hand tapper).

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…and finishing the part with chamfers.

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Finished part.

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Duclos Gearless Ep. 3

The valves are made out of 303 Stainless. The valve stem diameter is 4mm, head diameter 10mm, and over all length is 38mm.

Turning a long, small diameter can be tricky, as the tool pressure will deflect the work piece, causing a taper.

To prevent deflection, while turning the small diameter, I turned it in short sections. It is turned all the way to the final diameter, before starting the next section. The sections are about 8mm (2 times the diameter).


This method turned out a very accurate valve stem over its entire length, without any taper.

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Parting off the valve with allowance for the next machining operation.

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The valve is then turned over and chucked on the valve stem to finish the head.

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Last operation is a 1.5mm hole drilled for a pin and spring retainer. I’m using a sensitive feed drill chuck for this operation.

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Finished valves.

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Valves together with the valve bodies. The valve bodies (or valve chests) will house the valve and are mounted to the cylinder head.

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Duclos Gearless Ep. 2

The work continues with the flywheels.

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It needs a few tapped wholes, and the flywheels are done.

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The cylinder sleeve is made out of cast iron.

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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.

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Next, the relief for the valves is milled

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Back to the lathe to finish the OD and cooling fins

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Next, the cylinder head.

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

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The cylinder and cylinder head together for the first impressions

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Well, it has to start somewhere. I’ve been wanting to create a blog for some time now, to share and document the fascinating hobby of model engineering.

So, the blog is started and the journey can begin…