Making an expansion chamber cone First you need to reproduce the patterns from the construction plans onto stiff paper. To make the curves without a large protractor you can use a ruler with millimeters to make dashes, each being the correct length. Connect the dashes to make the curves. Cut out the pattern. Copy the pattern onto sheet metal. Cut out the pattern using tin snips. Here is one of the patterns cut out. Bend the side edges of the metal more than the amount you could by hitting it with a mallet. Create a gentle curvature in the metal by hitting it with a rubber mallet off-center while it rests on any small metal cylinder. (bicycle steering stem used here). Strong hands can be used to complete the curvature. Channel lock pliers can also be used. Needle nose pliers can also be used. Check for roundness at both ends. The final cone ready for welding.

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