A local furniture maker has requested three sheet iron flares similar to the bell of a trombone in dimension.
they will be used for a set of lamps.
My first thought was to develop a pattern like for a cone, but I ca'nt find a formula.
Plan B was to form a cone and try to forge out the flare at the end. That is alot of metal to flow, though.
any ideas?
thanks

Get a paper oil funnel or a snow cone paper holder. Use a razor and cut the funnel. Open the funnel flat. Now you have a start. Experiment with a compass ( on paper ). Continue on until you have a funnel ( no neck ) that you like. Good luck.

Another trick is to use modeling clay until you can work out your setup and volume calculations.
A couple of us spent a few hours trying to make lily style candle holders until we made a finished one out of clay and cut them open to show the shape of the flattened blank.

Ten Hammers approach works for me, but if you want to crunch the numbers try this site:

Sheetmetalworld.com News - TUTORIAL: Learn how to layout a cone
Sheetmetalworld.com - Sheet metal tutorials supplied by The Sheet Metal Shop.

Different means to the same end. Say you want a cone that's 2 inch dia at the top, 8 inch dia at the bottom, and 10 inches tall. Cut discs out of plywood, 2 inch and 8 inch. Screw them both to a stick so the construct is 10 inches tall. Mark a starting point on a disc, roll and trace the path of one revolution. Cut out the pattern. Thats how I make crawdad trap funnels.

thanks for the replies.
I figure ultimately the form wants to be spun on a spinner's lathe, but that's not going to happen. The appearance inside the flare does'nt matter, so welding is ok.
I like the empirical clay method best at the moment.