Simple Oscillating Steam Engine - Cylinder

The cylinder was designed to be made using only the 3 jaw chuck but it also required a simple milling operation which could be done in a milling machine or on the lathe with a little ingenuity.

Click for larger drawing









The cylinder was machined from a 1" diameter piece of brass bar. The bar was cut just over length and then machined to final length (30mm) in the lathe. See this article for details on how to machine to a specific length.









The flat side to the cylinder was machined using a vertical slide on the lathe. However a milling machine could be used if available.

If neither are available then the lathe can still be used by mounting a small vice on an angle plate and then bolting this to the cross slide.

To ensure the cylinder was square to the cross slide it was bought up in contact with the tip of the chuck jaws (see below) before tightening the vertical slide mounting bolts

Cylinder blank on vertical slide


Squaring up the cylinder blank against the chuck jaws.









Progressive cuts were taken across the side of the cylinder until 2.5mm of material had been removed.









To bore the cylinder it was mounted in the 3 jaw chuck with the flat face against one of the jaws. The 2.5mm offset of the cylinder positioned the cylinder bore in the correct place.

The cylinder was then centre drilled, drilled and reamed to the final size of 12mm diameter.









Once the cylinder cap had been made it was used as a template to mark the cylinder for drilling and tapping.

Note that the cap was orientated so that no screw holes lined up with the steam port in the cylinder.









The pivot hole was marked out exactly in the centre of the port face.

It was then drilled and tapped on the pillar drill. To ensure the hole was square, first the drill table was checked for squareness. Then the vice was used to hold the cylinder and an angle plate and small square were used to locate the port face horizontally (see photo on right).










Once located the vice was tightened and the marked hole was drilled and tapped.

To tap the hole the spring was released on the pillar drill quill and the chuck was turned carefully by hand to cut the thread.









To remove the machining marks form the cylinder a wooden dowel was turned to be a sliding fit in the bore. This could be turned from a broom handle or perhaps a chair leg.

The dowel was drilled to take a small screw and was then cut 3/4's of the way down the length. The screw could be used to adjust the diameter of the dowel.









The lathe was used in a slow speed and metal polish was added to the dowel. The cylinder was carefully moved up and down the dowel by hand.

This photo shows the bore with all machining marks polished out.











The finished cylinder











The final operation on the cylinder was done with the engine fully assembled. With the crank rotated to find the extreme oscillations of the cylinder, the cylinder was positioned so that the exhaust port lined up with the centre of the cylinder. Then a drill was used to mark the exact location of the cylinder port through the exhaust port hole.