I would like to know if radius devided by the diameter r/d in a bend increases the presure drop. i.e as r/d increases from 1 to 5 does the losses increases or decreses.
Because he lives in Australia he is probably sound asleep already, but Dennis Kirk is a member of this forum and has generated a useful graph of exactly what you are asking for.
There is similar data given in tabular form in the Crane 410 technical manual. If you do not have access to Crane 410 and you will be doing any significant amount of pipe hydraulics calculations you should consider buying it. See