Simple Oscillating Steam Engine - Flywheel

The flywheel was made from an off-cut of cast iron bar.

None of the dimensions were critical but it was important to get it to run true to look right and for smooth running. The diameter would also have to be small enough not to catch the base of the engine.

The flywheel was secured to the main axle with a grub screw.

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The piece of bar was already the right thickness so it was mounted in the 3 jaw chuck and the face was skimmed to run true - this would be he datum face. The centre hole was centre drilled, drilled and reamed to final size in the same setting to ensure it would be perpendicular to the datum.

Next the flywheel was reversed in the chuck and the other face skimmed to run true. Again the datum face was located against to the chuck jaws for this cut to ensure the 2 faces were parallel.









To skim the flywheel diameter an arbor was turned from a scrap piece of steel bar. The arbor was turned to be a snug fit in the flywheel hole and was threaded on the end to take an M6 nut.

A sharp tool was used to ensure there was no radius at the root of the arbor shaft.

Once machined the arbor was left in place until the flywheel was finished as removing it would mean it would never sit exactly central on the lathe axis again.

The finished arbor.









The flywheel was mounted on the arbor with the datum face at the back so that it would sit squarely in place.

A nylon washer was used to provide grip and a nut used to tighten the flywheel to the arbor.

Cuts were taken on the rim until the final diameter was reached. The flywheel was only driven by the friction on the arbor so only light cuts were used.









The grub screw was drilled in through the rim to clamp the flywheel to the shaft.

The rim was marked and punched and a centre drilled to locate the hole.

To ensure the flywheel was orientated so that the hole from the rim would intersect the axle hole, a square was used on the vice jaws as shown. The location of the 2 holes was judged 'by eye' to be in alignment.









The first hole was drilled with a suitable tapping drill for the grub screw.

Before tapping the hole was then counter bored most of the way through so that only the very bottom of the hole, would be threaded. This created clearance for a screw driver and also reduced the need for a long tap.

An alternative to this long hole would be to create a flywheel with a boss, which could then be drilled and tapped for a grub screw. This would be a better solution but my off-cut of material for the flywheel was not thick enough.



The finished flywheel