PATTERNS
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These photos show an arrg’t I use for small casting runs if I have an original to work with. In this case the original is built up with spray putty (spray putty is purchased in a pressure pack from any automotive specialist store) to allow for the shrinkage. All faces, which are to be finish machined, are built up with 3mm MDF. The round extensions on the ends of the built up patterns are core prints, these are used to align the cores in the rammed up sand mould. The whole thing is then sprayed with an enamel paint to harden the surface up.
I find it hard to set a parting line in the sand with a solid pattern so I make up a “follower” plate. This sets the parting line making it easier to ram up. The follower plate has the rough shape of the pattern jig sawed out. Blocks of wood are glued underneath to support the pattern at the split line. The pattern is then coated with grease and placed in the hole. Body filler in then applied around the gap then sanded. The patters can be rammed up, and then rotated upside down, the “follower” can be removed, and bottom half of the flask added followed again by ramming.
These patterns where used for a run of 20 castings. Split patterns were made up latter in fiberglass from moulds made from these originals. (The castings were needed in a hurry so no time to make split patterns up front.)
These are split patterns made up in fiberglass from plaster moulds taken from the originals. They are currently in the final stages of being touched up. Note the red blobs on the core prints where the dowel pins have been drilled through.
The spigot on the end is used to locate the fuel filter via a banjo fitting and needs to be concentric to the inner bowl. Final machining of the pattern ensures this remains the case.
The above photo's show the completed Carburetor body pattern's that were made in fiberglass from the originals. These are now the permanent patterns, the originals were broken down and sand blasted before being returned to their owner.
These photos show half patterns mounted to a match plate. They are doweled through the plate to align each other. This method is ideal for small fiddly parts where big hands and sand moulds don’t mix.
These photos show how odd parting lines can be set on a match plate. Makes molding these odd parting line patterns so much easier.
These photos show some of the core boxes used to make cores for the Zenith Carby sets. These were cast in plaster from males that were manufactured from impressions I made from the originals (sounds easy when you say it). Note the left hand photo and the slide in/out pocket to form the jet nozzle in the core sand. The molds are doweled together and the sand rammed in, the sand is pre-mixed with sodium silicate. Once rammed, Co2 gas is injected in, the resultant chemical reaction instantly hardens the sand. The core boxes can then be split and the sand core removed.
The photo beside the core boxes shows some of the finished sand cores which form the cavity in the sand mold when the molten metal is poured. These are broken out when the metal has cooled.
These photos show a flywheel pattern and a blocking plate. The blocking plate has the blank shape of the spokes glued down. The flywheel is placed into position; the blocking plate sets the parting line for the spokes. Makes life very easy on jobs like this.
These photo's shows how easy it can be to mould up small parts on a blocking plate. The flasks are positioned on the pattern's ready to mould. Note the dowel holes in the flasks that ensure the moulds are aligned when the flasks are put back together when ready to pour.
Large pattern for an 'R' Class loco number plate.