ArtMetal

Hi all, I`m making a venturi propane burner forge, and there are two tech details I`m not able to figure out. I want to introduce in a home-made manner, the acelerator concept that ZOELER shows on www.zoellerforge.com/tubeburners.htl
the acelerator with the mig tip screwed at the turned-down-with-a-lathe-end is basic and clear,but the relative positioning of the burner tube over the acelerator I`m not sure how.The latter slides over the acelerator but... any aducated guess? And does the contraption still have the regular reducing T where the tube screws on and the main air stream comes in? What is the meaning (formula) of flare ratio? Thanks for input. nelson.