Hold on! Didn’t we just cover this? Well, yes, and no. In our last post, we looked at the motor, particularly as it relates to robotics. Back in January, we covered motor oil, and even revisited it with an examination of synthetic motor oil in February – both are used in the engines of the vast majority of vehicles on US roads. Our recent post on computers, referred to two particular designs: the Difference Engine and the Analytical Engine. The bare bones Wikipedia entry for motor immediately provides a link to the Wikipedia entry for engine. As we did with motor, we’ll first look to the Online Etymology Dictionary regarding the origins of the word engine:

c.1300, “mechanical device,” especially one used in war;  “manner of construction,” also “skill, craft, innate ability; deceitfulness, trickery,” from Old French engin “skill, wit, cleverness,” also “trick, deceit, stratagem; war machine” (12c.), from Latin ingenium “inborn qualities, talent” (see ingenious), in Late Latin “a war engine, battering ram” (Tertullian, Isidore of Seville). Sense of “device that converts energy to mechanical power” is 18c.; in 19c. especially of steam engines.

We find that the word engine seems to come up in the century preceding the use of the word motor. Engine seems to be more generic, simply describing a “mechanical device,” while motor is used to describe a device that creates motion. Certainly, Charles Babbage’s computer designs were plans for mechanical devices. According to William Harris’ article on Babbage’s designs, the functional examples of the Difference Engine that were produced in 1991 had no less than 8,000 moving parts and weighed in at 15 tons each. While the device was designed with the ability to calculate artillery tables, it was not meant to be used directly in war, though it might make decent cover with its impressive weight and its height and length of 7 feet and 11 feet, respectively.

Referring back to the Online Etymology Dictionary entry for the word engine, more recent usage refers more specifically to a device which converts energy into mechanical power. Most commonly today, we think about the internal combustion engines in our automobiles, which convert the energy stored in fuel into movement. As used in robots, and increasingly in consumer automobiles, the electric motor converts electrical energy into movement.

It would seem that a motor is an engine, but an engine isn’t necessarily a motor. The two are often used interchangeably when referring to internal combustion engines in automobiles.