Could some one smarter than I am tell me why this is not producing any motion .What am I doing wrong .I would greatly welcome  you comments

I think
mc.mcCntlGcodeExecuteWait(inst, "G28.1 A0\nG53 G1 F75.0 A%4.4f\nG53 A-2.0000", (tpos + 12))

should be
formating strings in lua:

local s=string.format( "G28.1 A0\nG53 G1 F75.0 A%4.4f\nG53 A-2.0000", (tpos + 12))
mc.mcCntlGcodeExecuteWait(inst,s)

HTH
RT