Sorry, not right now. If folks are interested I guess I could take some pictures.

Let me try again. Take a piece of aluminum tubing the size of the velocity stack body you want, say 6". Put a little soot on one end by choking off the air on the torch. Heat the tubing, holding it with something other than your bare hand, by playing you torch flame on the metal end you intend to spin. Twirl it around to do it evenly. Plunge in water. The material will now be very soft. Chuck it in the 3-jaw with about an inch sticking out. Face it off and touch it up with some sandpaper to round the edges, please don't cookie cutter a piece out of your hand! Set up a tool holder, I use my boring bar holder, to give you good leverage to pull athe the tubing from the inside. Use a long polished round rod with a rounded end to do the pulling by leverage. Put some grease inside the tubing so it does not gall. turn the work as fast as you lathe goes. You will find as you push the inside of the tubing out it stays that way. Work the tubing to larger and larger diameters untim it is time to bring it back against the chuck to make your flange.

It is like throwing a clay pot on a potter's wheel. I found some articals on the net on "metal spinning". Check it out. It is fun. At one time I had plans to spin a metal cowl. For that kind of thing you need to make forms to spin against. Your local aircraft shop should have buckets of fancy aluminum sheet the recycle bin. Some of it is hard some very soft. You want soft. It will work harden.