Primary Movers - Engines - Motors

In technical description an internal combustion engine either diesel, liquid gas, or LPG is called an engine or primary mover because it causes motion in other components of a system.


A system is a compilation of primary mover, to a driven component like a pump of some type or gearbox. The system is all the components working together, the circuit is the conduit either pipes, tubes, hoses, or electrical wiring. The load is the weight being moved by the system.


The fuel to make power in an engine has a rating BTU which is the heat product from burning it efficiently. A motor technically is electric driven, a hydraulic motor is driven by fluid, a pneumatic motor is driven by air but an internal combustion engine is powered by the fuel.


Fuel is a direct source of heat and potential to do work within an engine, hydraulic flow is produced by the engine powering a pump and the motor is actually a driven device by hydraulic flow, electrical current called a generator or alternator produces current powering an electric motor. An air pump produces the flow of air or gas called CFM (cubic feet per minute) and powers a pneumatic motor.



The point here is that the primary mover in all cases is the engine producing power to pumps of some type. These powered pumps produce a flow of the intended element (air, fluid, electricity).


AIR - FLUID - ELECTRICITY and working with them is a necessity for a mechanic to understand for advancement in the trade.


First off is the fundamental property of air or a gas, they both have the ability to be compressed. The more compression the more heat is generated into the pressurized air or gas. Air or gas is compressed into a tank by a piston and compression chamber. The better the compression chamber or tube in sealing and physical properties the more the air or gas can be compressed.


For example compressing one cubic foot of air 10 times would net a 1/10th of a cubic foot compression chamber size resulting volume at a specific pressure. So the quantity of air or gas taken into a piston compression chamber can be moved from one place (atmosphere) into a container (compression chamber). If the compression chamber is a tank (air compressor) then the volume compressed inside is limited by the ability of the physical container to hold pressure. Pressure results when a restriction to flow is observable.


So Air and Gas are compressible and fluid is not. Fluid and air have somewhat the same operating properties whereas heat is generated when air is compressed. In a compression chamber a mechanic can calculate the heat build up by the chamber i.e. every pound of compression raises the air temperature 2 degrees F. It depends what the ambient air temperature is as it is drawn into the compression chamber as to what specific temperature it ends up being after it has been compressed. Fluid flows within a conduit system and builds pressure instantly when it is restricted to flowing. The more pressure built up the more potential heat can be generated when it is released outward the conduit. 



There are variables in compression chambers that can regulate compression temperatures. When you have a sealed chamber that holds one quart of air or gas (approximately 1000cc) and compress it into one pint (approximately 250cc) you have a ratio of compression of 4:1. as an example. Fluid on the other hand becomes solid as soon as all the conduit (hollow area) is filled with fluid, and the result is a pressure buildup instantly after a restriction to flow of the fluid.


Important now is the ratio understanding, air and gas both have compression ratio's. Air and gas are compressible and calculated from the volume of air intake to a volume of compressed air outward. A primary mover rotates a shaft which is rated in RPM, both the primary mover shaft and the driven member shaft rotate at mechanical ratios. A one to one ratio drives directly from the primary mover shaft into the driven member shaft and written as 1:1. The primary mover shaft rotates once and rotating the driven member shaft once. A mechanical pulley system connecting the two together changes the ratio by the diameter of the pulleys. For example a one inch pulley on the primary mover shaft and a two inch pulley on the driven member shaft would equal a 1 to 1/2 ratio or written as a 2:1 meaning the primary mover shaft has to rotate twice around to rotate the driven member once. Everything needs calculated from the primary mover down the component list to the end work resulting from the fuel burned. So ratios in mechanical pulleys and gears are identical to ratios involving air and gas. 10:1 ratio in air or gas is the compressed air occupies 10 times a smaller volume than 1 part of intake air. Air and gas are measured in volume flow, cubic feet per minute and hydraulics or fluid flow is also measured in volume, gallons per minute.


Fluid has no calculable compression factors that are accepted in mechanics, fluid in a mechanics training dictates fluid is not compressible. That would actually be pretty cool if someone developed a compressible fluid, hydraulic flow needs to be generated as the primary mover rotates and when the engine or primary mover stops so does the flow of hydraulic fluid. In the compressible system of air and gas that can be generated and stored in a tank and used for a period in time until the air or gas pressure is used and reduced below the level of work force needed to do the work. Then at that time the engine or primary mover can be started and again compress the air or gas to a level of use and then shut off. Air motors and gas are used at lower pressures than the fluid systems. The air or gas systems react in a springy way and the fluid systems react in a firm or solid way.     

Electricity ; appears as a flow of electrons, the accumulation of electrons in a battery occupies volume. As a generator (DC) shaft is rotated via. the primary mover output shaft the magnets pass coils at a specific surface speed. As the approach to the coil from the magnetic prospective a raise in electrical amplitude is observed, the approaching magnet effects to the peak when the magnet is at it's most closest point or highest gauss attraction to the metal core of the coils (voltage or EMF electromagnetic force), and as it continues the slope of the peaks are directly related to the surface speed that each magnet is passing the coil core. The differences in magnetic potential are directly proportional to voltages generated. A permanent magnet and coils of copper wire along with iron or steel are the components needed to generate electricity.

The flow of electrons in a DC (direct current) system can be directly compared to the air and gas compression system of physical properties. The generator can be used to store electrons in a DC system (batteries) just as the air tank is used in air compression scenarios (conventional air compressor). The more electrons passing into a battery the higher the voltage (EMF) present at the terminals. DC systems have properties of the compression system of flow.

The flow of electrons in a AC (alternating current) system can be directly compared to the fluid flow system but with the additional property of compression capabilities through the use of capacitance accumulators like a sponge to a flow of water. Moreover a dampening system for AC but important to compare to the hydraulic system and fluid flow dynamics for better understanding.



AC is like fluid power in the way of needing a primary mover running using fuel to rotate a shaft, when that shaft stops so does the AC. AC electricity cannot be stored in a battery system or DC. So the big difference is that ability to store and use DC at an appropriate time when needed over the AC power which has to be used as it is collected in the alternator. AC runs at higher voltages than DC, normally an AC circuit will operate at 120Vac to 240Vac (Volts alternating current). A DC circuit normally operates at 12Vdc (Volts direct current) to 24Vdc and 48Vdc.



When DC voltage is collected and stored in a battery system it is called generated and the DC device is called a generator. The generator has permanent block magnets in the housing and coils with steel in the middle of them. As the generator shaft is rotated the permanent block magnets are rotated and pass the steel part of the center of the coil of copper wire which collects a bit of electrical energy which has an electrical polarity directly proportional to the polarity of the magnet face passing by the coil core (steel part). The faster that magnet is passed by the coil the more voltage is present at the release of the magnetic field as the magnet passes the coil.



So the point here is that as the generator shaft is rotated and the output is polarized voltage that will flow into a battery to fill it up. The voltage will be low as the shaft begins to rotate and rise as the shaft speed is increased. The voltage rate is directly proportional to the gauss rating on the magnet, the strength or magnetic pressure of the magnetic field and the speed at which the magnet passes a coil. For example when you use a compass and the needle on it moves it is indicating around 3.5 magnetic gauss of the earth. That compass can be destroyed easily by passing a strong magnet past it. So the problem with a generator in a mobile DC scenario is the fact that the higher the shaft speed the higher the output voltage and current so a regulator is needed when the speed increases and an undercharge situation will become evident when the generator shaft speed is below that specific speed that allows charge to go into a battery storage system.



A permanent block magnet is polarized, it has many variable gauss field strengths but the practical understanding is that the conventional permanent block magnet contains two useable faces, a North polarized face, and a South polarized face. Anyway in the conventional generating of electrical current or accumulating electrons only the two polarities are used. When the permanent block magnet North Face passes the iron core of the charge coil at a fast rate of speed a spark is developed at each end of the coil wire and the South Face of the magnet will produce a spark also. It takes both polarities to make one full wave of AC. Alternating the magnetic field polarity (N face + S face) will end up producing a full wave or sine wave of Alternating Current.



After the mechanic has experienced the flow of fluids (hydraulic) in a shop situation and has observed flow as it is restricted and results in a pressure drop developing heat. The concept of non compressibility of the fluid has to be compared against the compressible pneumatic flow characteristics that are compressible in the air or gas (pneumatic) systems.



When an understanding develops the conclusion will be that electrons are compressible within a DC system of understanding. DC electronics are in all mobile equipment using a battery or batteries.    

A complete understanding of Fluid Dynamics (hydraulic) Air or Gas Dynamics (pneumatic) Electrical Dynamics (electronic) needs to be achieved by a mechanic wanting to develop into an advanced mechanic who is in great demand.



A Primary Mover, A Driven Component, The Final Drive in that order needs to also be understood. The Primary mover of an energy system is always the driving factor of all other components in a system. The primary mover translates fuel into heat which can develop power to drive the first driven component and resulting in driving the final component producing useable work.