In a previous blog we demonstrated the bits and pieces of wood that make up the speeder sweep castings. Once we have the bits and pieces all brad-nailed and glued together, we create fillets (curves) between the ribs and the deck using automotive car body putty. It's a simple matter of squeezing the putty out of the tube and wiping it on the wood, smoothing it out with our finger to create a nice curve. A rubber glove helps to keep the putty off of our fingers. Several coats of body putty, with light sandings in between coats, and soon have nice curved fillets.
The foundryman is not a pattern maker so he needs to know what part of the pattern is the final casting and what part is sand core. In order to help him out, we give the patterns several coats of black and yellow paint - black outlining the final casting and yellow outlining the sand cores. In this way, when he pulls the pattern out of the mold, he knows which sand core goes into which cavity. The yellow outline of the pattern corresponds to a specific sand core.
Here's the top view of our pattern.
Our next step is to make sure that we can make a mold that will accept the sand cores and be ready for the molten aluminum. In effect, this will be a trial run of our mold making to make sure that everything fits together (we hope!).