What type and thickness sheet metal to use? THICKNESS: .7mm is a good thickness for a cheap build because you can roll the cones by hand. Or buy 1mm thick and use a rubber mallet with the sheet resting on a tube of some sort so you can hammer it to bend little by little. 22 gauge is .76mm thick. 20 gauge is 1mm thick. 18 gauge is 1.25mm thick. 16 gauge is 1.5mm thick. Home Depot sells 2 ft x 2 ft sheets of 22 gauge plain metal for $20, and the same size of 16 gauge for $36. Metals Depot online has a wider variety of sheet metal to choose from. TYPE: Plain sheet metal (steel) is preferrable. Just paint it with high heat paint when finished or else it will rust a lot. The inside doesn't rust because of the engine oil that will coat it. Sharpe Products can sell you header tubing bent at various degrees and inner radius.  This site allows you to print your cone template but it is usually printed with slightly changed dimensions. It's best to just draw it out yourself with the help of my free spreadsheet. 
Here's stinger tubing that has 1.65mm wall thickness you can order in whatever length you want. They are available from Metals Depot online. (The second one actually has .9mm thickness.)
Here's two short videos I made about manually rolling a pipe section: video #1 video #2 And a video showing how to make a curved belly in 3 sections: Video Here's my pages about how expansion chambers work and how to obtain my Excel spreadsheet for designing and analyzing pipes: click here 19jaguar75@gmail.com |