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Sand Casting the Engine Block

I thought some people might get a kick out of seeing how the sand casting process that we used to make our blocks and crankcases works.  It combines a bunch of different manufacturing techniques from rapid prototyping (commonly called “printing”), casting, and machining.  A mold into which the molten metal will be poured to make the engine block must be made.  It has outer walls that define the shape of the outside of the block, and it has “cores” that define the shape of the internal cavities of the part.  These are made out of sand that is held together with a binder material.  The way these are made these days is to use a laser-sintering process.  A computer-controlled laser hardens a thin layer of sand in the shape that is required for the core or mold part.  Then a fresh layer of sand and binder is deposited onto the just-hardened layer and the laser makes another pass, building up the part layer by layer.

Sand cores for the MkII Clarke-Brayton engine

Sand cores for the  engine

Above you can see a variety of the sand cores and molds that were used for our engine block/head.  Basically, you need to have sand filling up all the spaces where you do not want metal.  Building the mold is kinda like building a “negative” of the engine.  All the cores are assembled together.


Special coatings are sprayed on to improve the surface finish of the metal and ensure that sand does not stick to it.


The cores you see assembled here will be passages within the engine block.  Some of these passages will be to allow the air to flow through the engine as needed.  Some will be for coolant to flow through making sure the engs_CIMG4722ine does not get too hot.

There is a last piece that goes on top of the assembly you see above but unfortunately I do not have a picture of the whole mold ready for pouring.  In designing the mold, special care needs to be taken that the molten metal will be able to fill up all the gaps completely, allowing air to escape through vents as more metal is poured in.

After the metal cools and hardens, all the sand gets broken up and cleared away, leaving just the metal part!s_CIMG9663

That part is closely inspected using 3D scanners to ensure dimensional tolerances are maintained and X-ray scanners to make sure there are no internal cracks or other problems that cannot be seen from the outside.

Next, the part is put into computer-controlled machining centers that will cut away excess material and provide all of the tightly controlled dimensions, surface textures, and other features that are required to make an engine work properly!