Devised, researched
 and written
  Peter King Smith BSc

                                                         The mid-1960s, German-built multi-track tape recorder with FM/AM/SW radio

Long play v. Default play

Tricky replacement work
The only problem with this dual-pulley arrangement, Jim adds, is that "you have to remove the back cover of the cabinet to access the pulley, when you need to change the spindle around. This is a bit cumbersome".

Incompatibility issue
It should also be pointed out that recordings made using the original pulley (22 mins) cannot be played back properly using the slower, 30-minute pulley and vice-versa, as the playback speeds will be incompatible with their original recording speeds.
Consequently, if you wish to preserve old recordings that were made using the default mode, and you also want to record 30-minute (long-play mode) radio programmes, you will need one of Jim's pulleys.

High degree of craftsmanship
It would be extremely difficult to make such a pulley oneself, as it requires a high degree of skill and a lathe, amongst other things. Another job best left to the real craftsman.