ASVAB Mechanical Review: Springs, Differentials, Linkages, and Couplings

Vocabulary terms and definitions focusing on mechanical components including specialized springs, gear differential parts, linkage elements, and shaft couplings.

Volute springs

Conical springs made from a flat bar, which is so wound that each coil partially overlaps the adjacent one.

Conical spring

A spring that can be pressed flat to require little space and is not likely to buckle sidewise.

Torsion bars

Straight bars, which may be circular, rectangular, or tubular, that are acted on by torsion or twisting force.

Gear differential

A mechanism that adds or subtracts the total revolutions of shafts mechanically and delivers the answer by positioning a third shaft.

End gears

The two bevel gears located on either side of the center in a bevel gear differential.

Spider gears

The two bevel gears located above and below the center in a bevel gear differential.

Spider shaft

The long shaft running through the end gears and the $3$ spur gears.

The spider

The assembly consisting of the short shaft and the spider gears themselves.

Side of a differential

A combination of an input spur gear and an end gear.

Output gear

The third spur gear in a differential, which is the only gear pinned to the spider shaft.

Linkage

A combination of parts such as rods, shafts, levers, rocker arms, or bell cranks used to transmit limited rotary or linear motion.

Bell crank

A linkage part mounted on a fixed pivot used to transmit motion from a link traveling in one direction to another link moved in a different direction.

Clevis or turnbuckle

Hardware used to adjust linkages by lengthening or shortening the rods and shafts.

Sleeve coupling

A metal tube slit at each end that uses clamps to fasten two closely aligned shafts together so they turn as one.

Universal joint

A coupling device used when two shafts that are not in the same plane must be connected.

Hooke joint

An elementary universal joint consisting of two U-shaped yokes and a cross-shaped part that allows operation at angles as great as $25\,\text{degrees}$.

Bendix-Weiss universal joint

A type of joint using $4$ large balls to transmit rotary force with constant angular velocity and less structural strength than Hooke types.