Anthony Mount

STEEPLE STEAM ENGINE

This model seen at a Bristol show is of a Steeple engine, so called because of the resemblance of the piston rod extension to a church steeple. It is sometimes confused with a table engine, but the difference is quite easy to see. This model is by Anthony Mount to his own design, and drawings and castings are available.

The cylinder in a table engine literally sits on a table, with the crankshaft below the table. With a steeple engine the cylinder sits at floor level and the crankshaft passes over the cylinder. There are also marked differences between the piston and connecting rod arrangements.

Steeple engines were an early attempt to get away from the beam engine arrangement. The first were designed by Napier in the 1830s for use in paddle boats. The cylinder went in the bottom of the boat, the crankshaft was at deck level, and the upper section was housed in a deck house.

This model is based on a land engine of the 1860s. The flywheel construction is quite interesting. Full size the boss and rim were cast around wrought iron spokes laid in the foundry mould. This is not possible in a model, so the boss is built up and the rim is a gunmetal casting that can be machined all round. The spokes are rods Loctited in position. The lathe is used as a jig to hold them in position while the Loctite cures.

The model has a 9” (229mm) diameter flywheel. The base, flywheel rim, main frame, cylinder, steam chest and eccentric strap are gunmetal castings. The drawings have both imperial and metric dimensions.

The engine is a delight to watch in motion and an interesting project to build. Construction is possible on a 3½” (90mm) gap bed lathe. The gap being needed for the flywheel.

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