Single turn continuous track, also known as servo pots, are used in length and angle applications by many crane manufacturers. Commonly J50 types are used with J40 to a lesser degree.
Specially modified J50 pots with a twin wiper arrangement (4 terminals) are used by some manufacturers for slew angle measurement.
Servo pots are also manufactured with custom track angles for some OEM's, so be sure to check the specifics of your original pot.
J50S 2K OHM
J50S 5K OHM
J40S 1K OHM