Early garage door openers only offered the most basic of functions – lifting and closing the door. Over the years many variations have been developed. Today there are several types of opener systems commonly available. These include chain drive, belt drive, screw drive and jackshaft units. The type of unit most of us might be familiar with is the drawbar or trolley type. This is the most popular for use in residential applications and features a power unit housing the motor and control devices.
This power unit is attached to a track, or boom, that includes a chain, belt, or screw that moves a trolley which connects to the top of the door with an arm or a bar most often referred to as a drawbar. The jackshaft unit might be a bit more obscure to most customers.
This unit is appropriate for use only on door systems that use a torsion spring counterbalance (more on springs in an upcoming post). These side mounted jackshaft units attach to the torsion spring counterbalance shaft and move the door by turning this shaft rather than pulling or drawing the door up a boom as described earlier.