Definition - What does Jackshaft mean?
A Jackshaft is a mechanical design component that synchronizes or transfers the rotational force in machines. It is generally a short stub with supporting bearings on its ends. It also has gears, cranks and two pulleys attached to it. Any shaft that is used as intermediary to transmit power to a drive shaft from driving the shaft is also considered as a Jackshaft. It is located away from the motor generally on its frame and it is used as sprocket on the engines which cannot lineup on sprocket of the axle or the drive shaft.
Petropedia explains Jackshaft
The Jackshaft can increase or decrease the ratio of a gear in an engine. The chain connected to Jackshaft from the clutch is the primary drive and the chain connected to the rear wheel from the clutch is the secondary drive. It is hidden inside the large machinery as the component of an overall large device. It is the short shaft that is connected by gears, belting, etc., to transfer the motion from an engine or motor to a single or multiple machines that are being driven. The shaft receives power through the gearing or belts from a main mover and then it transfers it with the help of the same means to the line shaft or other intermediate shafts.