making patterns

My partner John loves old things!! He is a frustrated quantity surveyor and amateur engineer with a workshop in half of our garage. For years he built steam engines, just for fun and for show, and honed his skills in pattern making, once a common activity in engineering workshops, now less so.

The making of patterns, which are wooden moulds from which metal castings are made, is an essential part of engineering. Basically you make a wooden pattern, take it to the foundry, they press it into sand to make the shape, pour in hot metal, wait till it hardens take it out and you have your casting! Easy peasy! Not!

Without boring you too much, you have to think three dimensionally, make patterns for holes and also build into your pattern an allowance for shrinkage, as the metal shrinks as it solidifies. You also have to allow for machining the casting.

At the moment we are restoring an old wooden yacht and John is making new bronze parts. These are the four parts of the pattern used to make this cylindrical vent 'boss' - a base for a vent. The semi circular parts are to make the hole! The finished boss looks splendid compared to the casting in its raw state.

I hope an unusual entry for the weekly challenge on 'patterns'