Left to right: Tony Grzyb, Tom Kimmel, and Terry Stout, Tom's mechanic. The coil that we are making is for Tony Grzyb and it replaces a Locomobile fire tube boiler of about 14” diameter and 14” tall.  The central drum is 5 ½” O.D.  As one can see half of the coils are wound right hand and half left hand.  Because the coils fit together at a slight angle to each other the spacing between the turns is about 1 ¼ the O.D. of the tubing.  The winding procedure used a hydraulically powered rotating table and a mandrel with an acme thread lead screw hand turned at the rate of 8 turns for each rotation of the larger table.  It is important to have drag on the tubing as it is wound.  This is done with a nylon split block squeezed tight with bolts.  The boiler steams very well and it never scorches.

Out of focus. The only top view of all one sided coils applied to central drum.

Both right hand and left hand coiles applied to central drum.

And the finsihed product.