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Mobility Basics
ACF Mobility provides you with a standardized system of entities to move your creations. You have engines which create the power, gearboxes which transmit that power to wheels, and fuel which is an optional component that boosts engine power.
Engines have a number of statistics which are listed in the tool menu.
Displacement, measured in cubic centimeters (cc), liters (l), or cubic inches (cid), is the swept volume of all the pistons (how much space the pistons travel through as they move from top to bottom inside the engine). Generally this is related to how powerful an engine is, but don't assume an engine of higher displacement is always more powerful.
RPM, or revolutions per minute, is how fast the output of the engine rotates.
Torque is a measure of the raw rotation force the engine can output. Torque is measured in newton meters (nm) or pound feet (lb ft) (also commonly phrased as foot pounds).
Power relates the torque and RPM of an engine, which allows you to measure how an engine performs compared to other engines. Power is expressed in kilowatts (kw) or horsepower (hp). A higher powered engine will always be capable of going faster or doing more than an engine of less power. Don't get caught on thinking that high rpm engines will always be faster than low rpm engines, or that low torque engines can't move as much mass as a high torque engine. A high torque, low rpm engine might have the same power as a low torque, high rpm engine. For more information, see the Intermediate Mobility article where this is discussed in further detail.
The RPM an engine naturally rests at.
Powerband, or Ideal RPM Range on the ACF tool, describes the range of RPM where an engine performs optimally. In ACF, an engine produces its maximum torque while the RPM is inside the powerband. So, a wider powerband is better because you have a wider range of RPM where your engine will produce maximum torque.
The maximum RPM the engine can run at.
Engines can be fairly hefty. You may need to take engine weight into account when designing your vehicle.
Specifies the type of fuel the engine can accept. When an engine is drawing fuel from a fuel tank, it produces 25% more torque, which increases power by 25% too. For most engines fuel is optional; "special" category engines always require fuel. See the Intermediate Mobility article for more detail on fuel.
The displacement of an engine in ACF affects its behaviour. Smaller engines have higher rpm, but are severely lacking in torque. As an engine grows in size, the maximum rpm drops but they gain significantly more torque. Most engines are available in 3 sizes, trading high rpms for torque and an increase in power as they grow larger.
Diesel, petrol, and electric engines have different characteristics.
Petrol engines are high rpm and low torque, and have the best power to weight ratio. They usually have the powerband near the top of the rpm range, and a bit of dead space between idle and the powerband where they perform sub-optimally. They are great for racing and general driving. In combat, they are the easiest engine type to destroy.
Diesel engines have low rpm, but high torque, and are considerably heavier than a petrol engine of similar power. The powerband is very close to the idle rpm, allowing you to get full power very quickly and easily get started from a stop. They are good if you need to do some heavy moving, or need torque at low rpms. In combat, they can take quite a bit more punishment.
Electrics are the kings of low rpm torque, but suffer badly in weight and high rpm power. Electrics are the most durable engines in combat.
Check out the Engine Library for a rundown of the different engine types.
Most cars steer by turning their front wheels. Some vehicles can also slightly steer with rear wheels, greatly improving turn radius. Tanks steer by slowing one track, and sometimes speeding up the other, known as "skid steering". Some tanks can turn in place, a process known as "neutral steer" or "zero-point turning", where one track moves forwards and the other moves in reverse.