combustor includes an outer annular ring an inner annular hub and a plurality of struts extending radially between said outer annular ring and the inner hub the inner hub is provided with a piston ring groove and a piston ring adapted to receive and seal an inner end of the burner tube application_number US 201213566286 A description fig1 illustrates a known combustor cap assembly 10 for supporting a plurality of fuel nozzles not shown in an arrangement where five outer nozzles surround a center nozzle in this particular example all of the nozzles are provided with surrounding or outer burner tubes that are supported on an aft end of the combustor cap assembly in fig1 two outer nozzle burner tubes 12 and 14 are shown along with a center burner tube 16 the invention here relates particularly to the support for the center burner tube 16 at the inner or aft end 18 of the cap assembly 10 accordingly in describing the known arrangement shown in fig1 the focus will be on the center burner tube 16 and its interaction with the inner or aft end 18 of the combustor cap assembly at their inner or forward ends the ends facing or adjacent the combustion chamber the various burner tubes are supported by sleeves 20 welded to an effusion plate 22 the center sleeve also referred to herein as a u201c piston sleeve u201d 20 is also laterally supported by a u201c wagon wheel u201d structure 24 best seen in fig2 and 3 formed by an outer ring 26 and an inner ring or hub 28 connected by a.