My method (avoids hard caculations).... set the ADF card as you've described. Pretend it's the face of a clock (analogue !) . When you have a second hand on a clock it sweeps past each 'major' division every 5 seconds. So, read round ADF card to from 'north' to your required heading and count seconds for each major division, 5 seconds, ten seconds, 15 seconds, etc. [Easier done than described]. Then double it. That's the time required to turn at rate1.
That's exactly mine as well...great minds and all that
.