Exhaust Manifold Drawings

Before I can make the parts of the manifolds I need to know what the parts should look like.  I don't have any Curtiss factory drawings.  I have a WACO drawing for the exhaust on the TEN.  For the TEN they modified the exhaust from the Curtiss parts.  They had to shorten it to clear the landing gear strut so the drawing doesn't have a lot of information.

My first step was to make a sketch of my old manifold.  I set it on a piece of paper and used a square to draw the outline on the paper.  The holes you see in the flange are rusted out spot welds.  The edges were welded about every 1/2".

A form gauge was used to determine the shape at various cross sections and draw them on the sketch.

To measure the thickness of the shells and understand the seam a section of the flange was cut out and scanned.

 I scanned the sketch in sections and carefully pieced it back together.  I brought it up in TurboCAD and then drew my working drawing over it.  The WACO drawing was used for the location of the flanges.  Much of the work doing this is to figure out what dimensions they used for the original Curtiss drawing.  I try to keep in mind they used a scale in fractions of an inch.  Something like this manifold would not have had many dimensions in increments smaller than 1/16", most would have been 1/8" or larger increments.

 Here is the layout of the manifold  shell as I plan to make it.  The second drawing includes the cross section shapes.  The third drawing includes the layout for the cut out in the form block I'll use to shape the shells.