A pattern is used in the casting process. To create a sand casting, you put a pattern, or model of the part into the casting jacket (also called cope (top half) and drag (bottom half)) and then cover it with sand and pack it down tightly around the pattern. You then flip the jacket and sand over (the damp sand gets so hard that it won't fall out) , remove the board, and then put the top half of the jacket on. You put parting compound over the pattern and the sand in the lower half of the mold. You then dump sand in to fill the top half of the mold and pack it down. When it is totally packed down, you lift the top half of the jacket with the sand off. You then remove the pattern and cut the sprue through the top half (hole where you pour the molten metal in) and then cut your gating system into the lower half of the mold. You then take a metal wire and make vertical holes out the top of the mold to allow gas to escape as the metal pours in. You then put the two halves back together, remove the upper and lower casting jackets and put a pouring jacket on, pour the metal in, and when it has cooled, break all of the sand away, leaving your part and metal in the shape of the gating system behind. All that work must be redone for each casting. Also any holes or cavities need to be created using pre-made sand cores. The reason I know the process so well is that I did casting last year in school.
There are a couple things that "New Pattern" could mean. Either a pattern broke and they made a new one and made a batch of test parts to ensure the pattern was good, they changed the part's design and made a test run of parts for the new design or did it to distinguish between old parts on hand and new ones to ensure the old stock got used first. Does the casting have a casting date on it along with a part number on the distributor side of the tractor?
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Today's Featured Article - The Cletrac General GG and the BF Avery A - A Bit of History - by Mike Ballash. This article is a summary of what I have gathered up from various sources on the Gletrac General GG and the B. F. Avery model A tractors. I am quite sure that most of it is accurate. The General GG was made by the Cleveland Tractor Company (Cletrac) of Cleveland, Ohio. Originally the company was called the Cleveland Motor Plow Company which began in 1912, then the Cleveland Tractor Company (1917) and finally Cletrac.
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