What is a "motor carriage"

It's a good thing you didn't ask this of Interfacing -- he would have described them near-pornographically with zero substance.

A motor carriage (abbreviated as both 'MC' and 'car') is a type of passenger vehicle which is self-propelled, primarily transports one or more people rather than cargo, and may run mostly on roads created specifically for the thoroughfare of vehicular traffic. Popular brands that mass-manufacture MCs include the Coupris MotorCorp, Linnea and LUM, though there are a wide range which may range widely in price, power and style.

Motor carriages generate power using an internal combustion engine (ICE). These engines work by converting chemical energy into mechanical energy, or torque. The reaction of oxidizers mixing with a fuel and being ignited causes pistons to move up and down within a cylinder; the pistons are connected to and spin a crankshaft, which in turn rotates the wheels of the car and causes it to move. Most engines will contain anywhere between one to twelve cylinders and be four-stroke; this means they work by first drawing in the air-fuel mixture as the piston moves down (intake, induction or suction stroke), compresses the mixture as the piston moves up (compression stroke), the mixture is ignited forcing the piston down (combustion, power or ignition stroke), and then the spent mixture is pushed out through the exhaust port (exhaust or outlet stroke). Multicylinder engines will offset each individual cylinder's cycles to ensure the engine runs smoothly, and the cylinders will be arranged in either a line (such as in the KR18GU engine of the Coupris 40) or a V-shape (such as in the V12 engine of the Coupris Kineema).

MCs have several forward 'gears' which dictate how much power you would like to use from the engine. These range from 1 to 5, with 1 being low gear (generally used when you first start your MC to move it) and 5 being your highest gear. There is also neutral, which means you are in no gear, and reverse. The car is controlled using the brake, accelerator and clutch; brake slows the car, accelerate speeds it up, and clutch disconnects the wheels from the engine.

Modern motor-carriages are operated using two clutch levers, two brake levers attached to the aforementioned clutch, a gearshift pedal operated with the left foot, and an accelerator and differential lock operated with the right foot.

MCs are steered using a hybrid of clutch-brake steering and braked differential steering systems. Early MCs only used the clutch and brake to steer the car; rather than turning the wheels to change the direction it is moving in, power is disconnected from either one side or the other with a clutch. Some would also apply slipping of the brake in order to tighten the turn. One issue with this braking system was that, since the wheel is disconnected entirely, the average forward momentum is not maintained, and so the car would slow significantly; as well as this, on downslopes, sometimes declutching one side to turn would result in a turn in the opposite direction. An alternative, coming later, was braked differential steering; using a differential (a gear train which has the property of one shaft's rotational speed being the average of the others), braking power is applied to one side to turn the vehicle. This had an advantage over clutch-brake systems in that it would maintain the average speed, as the opposite wheel would speed up accordingly due to the differential. However, this system had a problem that, in the case of one wheel meeting a higher rolling resistance than another, the differential action would engage. In some models, particularly ones made for off-roading in rough terrain, this had to be solved by creating a differential lock to prevent unwanted differential action. Modern MCs use a clutch, brake and differential system with a differential lock.