- Econoline fixed center drives utilize the same type of spring-loaded pulley
as an adjustable center drive, only it is normally mounted on the driven
shaft. The driver pulley is of similar size and construction, but it is manually
adjustable. A fixed center drive offers greater driven speed range in a more
compact space. There are two types of controllable pulleys: the M type with
a hand wheel and built-in adjusting device, and the MLA type that uses an
external control. The MLA type pulley can be used with the Lovejoy #76
Control Stand or some other type of linear controller.