Casting The Keel

The aluminium tear drop pod is designed to accommodate a variable number of similarly shaped lead ingots which locate on the mandrel each side of its centre. Allowing that these would be a handleble 25- 30 kg these were cast in sand so they would be approx 2cm thick. Anything new is bound to be a little worrying and the first casting of these was
no exception. The lead came from my roof as opposed to some local church roof, kept under lock and key since I had the roof replaced.
The former or mold was made from 2cm mdf and all the edges relieved by 7degrees to allow extraction from the sand without damaging the impression. A central handle was vital to ease the mold from the sand.

Important in casting lead, I guess any metal for that matter, is its temperature at the time of pouring. I learned that using strips of sheet lead let in at the time of the pour will give a good idea of the state by way of melting away and at the same time act to cool down the melt - the lead at the edge of the container should just  be beginning to crystalise.

Important, in fact vital, is to wear total face and hand protection and ensure that the sand is not too damp and that tool to be used are not wet and ideally warmed if not heated.

In the picture above we can see the crystallisation of the lead in tail of the casting due to relative rapid cooling where the  blue bloom on the right is a function of the slower cooling mass allowing oxidizing of the surface. It is interesting too to see the shrinkage of the casting from the surrounding sand as the casting cools. Such shrinkage allowed the casting to be carefully removed without shattering the mold such that it allowed ten castings to be made from it after a little tidying up of the mold each time.

The above shows the casting placed into the 'pod' and sitting neatly on the mandrels. The lifting of the casting from to and fro was fascilitated by the T shaped handle that was screwed into the casting after drilling and tapping - (8mm metric).

The little cauldron above was made from a dicarded 'Creuset' found in the street on to which has been attached a bar from its handles. The two cuffs of wood at each end were free to rotate so that when held in pouring the bar on the right can be used to rotate the cauldron to empty its molten contents into the mold. The support underneath was made from a short length of 'I' section onto which two pieced of angle iron have been welded to support the cauldron. A brick was used to close off the back. The curved dish shown conveniently sat around the lip of the cauldron when removing slag from the top of the molten lead.

The space heater in the background, without the heating, provided an indirect draft accross the furnace by hitting the wall, bouncing off and moved fumes toward an open space.