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Friday, July 25, 2014

Out of Time for Engines.

Timing, timing, timing.  Being in the right place at the right time can bring possibilities to reality, and can assure that things go according to plan.  Timing plays a huge part in all things life oriented, timing also comes into play with engines (electric motors too).  This article will be fairly short, but the info is crucial to the proper function of any engine.

Without proper timing in an engine, all sorts of issues can arise that include  loss of fuel efficiency and power, overheating and thus warping of metal parts, and even total catastrophic destruction of the engine.  

It is imperitive that all the parts in an engine operate in the correct sequence, at exactly the time they are supposed to.  We must assume that the engineers who designed the engine took into account how different engines require differing timing needs.  

A big, slow turning truck engine compared to a small, high revving motorcycle engine will have very different timing needs, but the basics remain the same. Creating an engine that can make alot of power instantly requires that combustion occurs precisely when the maximum energy can be delivered from the chemical form in fuel to mechanical energy out the wheels.  

In some engines, the timing system must keep the valves and pistons separated physically so that damage does not occur- this is referred to as 'interference'- literally the engine parts interfere with each other.  If a timing belt or chain breaks, the parts meet without any ability to move and thus bend and break.  This usually adds up to very expensive repair bills, or recycling a machine back to its constituent components.  

Combustion, or more commonly, ignition timing is a matter of when the fuel in an engine actually burns.  Igniting the fuel under pressure in the cylinders causes a huge pressure pulse or spike that actually makes the power to turn the wheels.  It is the pressure spike that drives the piston down comes after combustion.  

The burn time is remarkably short and must happen just as the piston comes up to 'TDC' or top dead center, so that the pressure pulse pushes the piston back down as it rolls over the top of the combustion stroke and into the power stroke.  

If that combustion happens too early, referred to as advanced timing, the internal parts in the engine are put under tremendous stress from the piston coming up and combustion pushing the piston down at the same time.  This causes 'ping' or 'knock' at best, engine destruction at its worst.  A tiny bit of ping is acceptable in most engines, but too much will drastically reduce engine life.  

The pinging sound is actually the slap of the piston against the cylinder wall as it cocks slightly sideways from added stress of pre-combustion.  This can seriously and quickly  wear out cylinder walls and piston skirts, or even snap the piston skirt completely off the bottom of the piston.  The loss of the piston skirt not only puts broken metal shrapnel into the engine, but will rapidly cause added wear from a piston that now fits loosely in the bore.  

If ignition happens too late in the process, called retarded timing, instead of too early, the combustion is rapidly quenched by the expansion of the gasses instead of accelerating combustion due to compressing the fuel and air together as ignition happens.  Overly retarded  timing results in engine overheating, burnt exhaust valves, and severe loss of power. 

A properly tuned engine will have the combustion happen at the precise moment when the pressure spike can deliver the most power output from that combustion.  Not a millisecond before or after.  Its very precise.  Generally, a slight advancement from stock settings will result in more power, lower temps, and improved fuel efficiency. 

A bit off topic here, but not by much. The tyrannical EPA and its nonsense emissions rules mean that engine builders retard ignition timing back from its optimal point in order to waste fuel and sacrifice engine life and performance just to keep emissions to dictated levels.  The EPA is run by, and these levels of emissions are set by ex-oil company executives and ex-car company CEOs and other execs.  It is in the interest of these corrupt jerks to get you to waste more fuel and throw away engines to increase the profits of the companies whose stocks they own  I say focus on fuel efficiency, the emissions will follow.  Make engines last as long as they can and the coal burning power plants that power our manufacturing base will save fuel as well.  I will go into emissions more later in another article.

I hope you now understand better what it means to the operation of an engine to have the mechanical and combustion timing perfectly set and maintained within a tiny window of acceptability.  Thanks for reading, and remember, if you have an engine with a timing belt, have it changed out before it can break or stretch and compromise engine performance or integrity.  Check back for more helpful info...

MW outta here and onto the next fix-er-up... 
'Til next time, love your machines!


Tuesday, July 22, 2014

More Magnets and Machinery...

In the last tech article on magnets and machines, I described how any piece of iron bearing metal can be made magnetic and can act just the same as any other magnet simply by wrapping that chunk of metal with insulated wire and applying an electric current to it.  Lets explore more of the capabilities of these wonderful devices, electromagnets, and what they can do for us.  

Alternators and generators are machines that transform mechanical energy into electrical energy.  They do this by spinning a magnet inside of multiple coils of wire. 

OK- time to backtrack?  Cool, back to basics. So one of the fundamentals of physics, and more specifically, electromagnetism, is that a moving magnet can induce an electric current in a wire.  When a magnet is passed over even a single strand of wire, the magnetic field knocks electrons loose from the atoms of the metal and pushes them into the next atom.  This bumping of electrons from one atom to the next one near it is the transference of energy from the magnet to the wire.  

Electrons move from one atomic cloud to the next and we call that electric current: the flow of electrons in a conductor.  That electronic flow is what we use to do various types of work in toasters and microwaves, electric tools and computers, cell phones and satellites. Creating that electron flow in a wire is now considered basic physics, but 150 years ago, it was unheard of and unknown to most people.  Experimenters like Maxwell, Faraday, Edison, Tesla and a myriad of others all contributed to our knowledge of how electric current could be created and utilized. 
Most of the electricity that powers our homes and businesses comes from the burning of coal or natural gas, or from nuclear plants, but they all do it the same way- heat water, boil it to steam under high pressure, then release the pressure and allow the steam to expand and cool as it moves through the turbine.  As the superheated steam passes through the turbine unit, it cools and transfers its energy to the turbine blades attached to the shaft, then to a generator/ alternator.  As the steam passes through the turbine,  most of the energy in the compressed superheated steam gets used to spin the turbine at very high speeds.  The turbine is connected via a common shaft to the generator or alternator head usually.

In a car, the alternator is spun at high speeds by a belt on a small pulley driven from the crankshaft pulley.  Usually these days a large, flat belt (serpentine belt) is responsible for turning the alternator in a car along with all the other accessories that need spun (A/C, power steering, water pump...) Regardless of how they are spun, an alternator is an interesting piece of equipment.   Inside an alternator, there is is the inner core (rotor) anchored directly to the spinning shaft.  This rotor is simply a coil of wire that is charged with a small electric current to become a magnet.  That magnetic coil in the rotor has ends and center made of iron, (steel) and thusly as current is applied to the coil in the rotor, the magnetic flux in the rotor core increases proportionally to the current flow.  These steel ends are brought around to the sides of the rotor to create a series of alternating North and South magnetic poles around the circumference of the rotor.  It is the constantly changing magnetic flux, switching rapidly from North to South that induces a current tin the stator coils. 

Controlling an alternator to put out specific voltage or current is simple in some ways.  A separate, or integrated voltage regulator controls output power by varying the small current that flows through the rotor.  Surrounding the rotor are the stator coils that are excited as the magnetic rotor spins inside them.  This creates a tremendous voltage and current in the stator with only a small current flowing through the rotor.  Its the input current that controls the output current.  For this reason, this design of alternator has become the standard for almost all equipment that must produce electrical power.  

So, again, heres to magnets and the ability to create all sorts of machines using them.  Magnets can be used to make speakers that spread sound through the room, or they can be used for detecting the position of something tiny and in need of perfect calibration.  Magnets are everywhere, and where they are not, we can make them using steel and wire to create electromagnets.  These electromagnets can be easily controlled with tiny amounts of power, thus the output of an alternator is also easy to adjust and control.  

Heres to long lived machines and healthy, happy people too,

             Again soon, MW