Engine Block Heaters and Battery Heaters

Posted by PITHOCRATES - February 19th, 2014

Technology 101

As Matter loses Heat it shrinks from a Gas to a Liquid to a Solid

There is no such thing as cold.  Cold is simply the absence of heat.  Which is a real thing.  Heat.  It’s a form of energy.  Warm things have a lot of energy.  Cold things have less energy.  The Kelvin scale is a measurement of temperature.  Like degrees used when measuring temperature in Celsius or Fahrenheit.  Where 32 degrees Fahrenheit equals 0 degrees Celsius.  And 0 degrees Celsius equals 273.15 kelvin.  Not ‘degrees’ kelvin.  Just kelvin.

When something cools it loses heat energy.  The molecular activity slows down.  Steam has a lot of molecular activity.  At 212 degrees Fahrenheit (100 degrees Celsius or 373.15 kelvin) the molecular activity decreases enough (i.e., loses energy) that steam changes to water.  At 32 degrees Fahrenheit (0 degrees Celsius or 273.15 kelvin) the molecular activity decreases enough (i.e., loses energy) that water turns into ice.

The more heat matter loses the less molecules move around.  At absolute zero (0 kelvin) there is no heat at all.  And no molecular movement.  Making 0 kelvin the ‘coldest’ anything can be.  For 0 kelvin represents the absence of all heat.  As matter loses heat it shrinks.  Gases become liquid.  And liquids becomes solid.  (Water, however, is an exception to that rule.  When water turns into ice it expands.  And cracks our roadways.)  They become less fluid.  Or more viscous.  Cold butter is harder to spread on a roll than warm butter.  Because warm butter has more heat energy than cold butter.  So warm butter is less viscous than cold butter.

Vehicles in Sub-Freezing Temperatures can Start Easily if Equipped with an Engine Block Heater

In a car’s internal combustion engine an air-fuel mixture enters the cylinder.  As the piston comes up it compresses this mixture.  And raises its temperature.  When the piston reaches the top the air-fuel mixture is at its maximum pressure and temperature.  The spark plug then provides an ignition source to cause combustion.  (A diesel engine operates at such a high compression that the temperature rise is so great the air-fuel mixture will combust without an ignition source).  Driving the piston down and creating rotational energy via the crank shaft.

For this to happen a lot of things have to work together.  You need energy to spin the engine before the combustion process.  You need lubrication to allow the engine components to move without causing wear and tear.  And you need the air-fuel mixture to reach a temperature to burn cleanly and to extract as much energy from combustion as possible.  None of which works well in very cold temperatures.

Vehicles operating in sub-freezing temperatures need a little help.  Manufacturers equip many vehicles sold for these regions with engine block heaters.  These are heating elements in the engine core.  You’ll know a vehicle has one when you see an electrical cord coming out of the engine compartment.  When these engines aren’t running they ‘plug in’ to an electrical outlet.  A timer will cycle these heaters on and off.  Keeping the engine block warmer than the subfreezing temperatures.

The Internal Combustion Engine is Ideal for use in Cold Temperatures

At subfreezing temperatures engine oil because more viscous.  And more like tar.  This does not flow well through the engine.  So until it warms up the engine operates basically without any lubrication.  In ‘normal’ temperatures the oil heats up quickly and flows through the engine before there’s any damage.  At subfreezing temperatures oil needs a little help when starting.  So the oil sump is heated.  Like an engine block heater.  So when someone tries to start the engine the oil is more like oil and less like tar.

Of course, for any of this to help start an engine you have to be able to turn the engine over first.  And to do that you need a charged battery.  But even a charged battery needs help in sub-freezing temperatures.  For in these temperatures there is little molecular action in the battery.  And without molecular activity there will be little current available to power the engine’s starter.  So there are heaters for batteries, too.  Electric blankets or pads that sit under or wrap around a battery.  To warm the battery to let the chemicals inside move around more freely.  So they can produce the electric power it needs to turn an engine over on a cold day.

Once an engine block, the engine oil and battery are sufficiently warmed by external electric power the engine can start.  Once it warms up it can operate like it can at less frigid temperatures.  The engine alternator powers the electrical systems on the vehicle.  And recharges the battery.  The engine coolant heats up and provides heat for the passenger compartment.  And defrosts the windows.  Once the engine is warm it can shut down and start again an hour or so later with ease.  Making it ideal for use in cold temperatures.  Unlike an electric car.  For the colder it gets the less energy its batteries will have.  Making it a risky endeavor to drive to the store in the Midwest or the Northeast during a winter such as this.  Something people should think about before buying an all-electric car.

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Snow Blowers

Posted by PITHOCRATES - January 29th, 2014

Technology 101

If you try to Push or Lift too much Snow you can Wrench your Back, Give yourself a Hernia or Have a Heart Attack

It’s funny, isn’t it?  How much we love to see a white Christmas.  Nothing brings a bigger smile on our face than to see a white blanket out of our windows during the Christmas holiday.  It’s so pretty.  Pristine.  And pure.  Just like the true meaning of Christmas.  But once Christmas comes and goes and that white stuff is still out there our feelings change.  It’s no longer pretty, pristine and pure.  It’s just more of that white [deleted expletive] that we have to shovel.

If you have a detached garage you’re probably no fan of the snow.  Because with every snow fall you have hours of work ahead of you.  To shovel the front sidewalk so the city doesn’t fine you.  The sidewalk up to your mailbox for the mail carrier.  So he or she doesn’t slip and die on your property.  And then that long driveway.  From the approach in the street (so you don’t get stuck in the loose snow there) all of the way into your backyard and to that detached garage.  Over an hour by hand if the snow isn’t too deep.  Or you can let the snow stay there.  Melt a little during the day.  Freeze a little at night.  So you can slip on it and fall.  Breaking your hip.

Of course that snow shoveling would be quicker if you had a shovel as wide as the driveway.  But if we did we would never be able to lift the snow in it.  Because snow is heavy.  And if you try to push or lift too much of it you can wrench your back, give yourself a hernia or have a heart attack.  Which is why we use snow shovels much smaller than the width of the driveway.  It’ll take a lot more time to shovel the snow off it.  But our odds are greatly reduced for getting a wrenched back, hernia or heart attack.

The Two-Stage Snow Blower is not very Maneuverable but it can move through Deep Snow and throw it a Long Way

Snow is heavy.  And the wetter it is the heavier it is.  And the greater risks there are shoveling it.  Which is why God gave us the snow blower.  Or, rather, gave us Robert Carr Harris who gave us the snow blower in 1870.  Which has evolved into two basic machines today.  The single-stage snow blower.  And the 2-stage snow blower.  One of which is ideal for around the house.  The single-stage snow blower.  While the other is ideal for bigger jobs.  Where we have to move a lot more snow than what just falls around our house.  Though there are homeowners who use a 2-stage snow blower.  Even though a single-stage would be more appropriate.

A 2-stage snow blower can be a beast.  Taking up the footprint of a riding lawnmower.  It’s big.  And heavy.  Too heavy for most people to push through the snow.  Which is why these are typically self-propelled.  Requiring a bigger engine.  And a complicated gear box.  To divide the power between the ‘throwing’ function and the ‘propelling’ function.  The throwing function has two stages.  An auger in the front that turns slowly (requiring more gearing) to eat into the snow and pull it towards the center.  At the center is an impeller that turns much faster than the auger .  As the snow is slowly pushed into the fast-spinning impeller it throws the snow into and out of a directional discharge chute at a fast speed.  Throwing it a great distance.

It takes a fairly large engine to spin the auger, the impeller and the drive wheels.  And it takes a pretty complicated (and large and heavy) gear box to provide various rotational speeds for the various components.  As well as a large frame to hold these components, the drive wheels, controls, safety interlocks, oil and fuel.  Making the two-stage snow blower not that nimble or maneuverable.  Which isn’t a problem if you’re walking back and forth over a long driveway.  But it can be a big problem on a sidewalk with a turn or a curve in it.  For turning these beasts can take some muscle.  Muscle that we apply with our feet on a slippery surface.  Even after we’ve already cleared the deep snow off with the snow blower.  For the auger does not come into contract with the pavement.  Meaning it doesn’t clear away the snow down to the pavement.  But it can move through deep snow and throw it a long way.  Making it ideal for big jobs.

The Advantage of a 2-Cycle Engine is a High Power-to-Weight Ratio making it Ideal for a Single-Stage Snow Thrower

The single-stage snow blower is much lighter.  For it has only a fast-spinning auger.  It eats into the snow, pulls it towards the center and throws it out the discharge chute.   Without an impeller.  Throwing it a pretty fair distance.  And the auger actually comes into contract with the ground.  Which helps pull it forward.  And cleans down to the pavement.  With the only one spinning component there are no heavy gear boxes providing multiple speeds to different components.  Making the single-stage snow blower much lighter.  And easier to maneuver.  And it typically has a 2-cycle (or 2-stroke) engine.  Making it lighter still.

The typical engine on a 2-stage snow blower is a 4-cycle (or 4-stroke) engine.  Where the piston moves up or down 4 times to create power.  It moves down and draws in an air-fuel mixture through an intake valve.  It moves up and compresses the air-fuel mixture.  A spark plug ignites this and the hot expanding gases push the piston down on its power stroke.  And then the piston comes up and pushes the exhaust gases out of the cylinder through an exhaust valve.  Then repeats.  A 2-cycle engine has fewer moving parts.  And half the strokes.  As the air-fuel-oil mixture ignites the hot gases push the piston down.  As the top of the piston moves past exhaust ports the exhaust gases can exit the cylinder.  At the same time an air-fuel-oil mixture enters the cylinder through intake ports on the other side of the cylinder.  The piston moves up and compresses this, ignites and pushes the piston down.  Then repeats.

The advantage of a 2-cycle engine is a high power-to-weight ratio.  Allowing a smaller 2-cycle engine to do the work of a comparable 4-cycle engine.  Making them ideal for a single-stage snow blower.  The disadvantage of a 2-cycle engine is that the crank case is used to draw in the air-fuel mixture on the up-stroke of the piston.  And then the piston pushed the air-fuel mixture out of the crankcase and into the cylinder on the down-stroke of the piston.  Because the crankcase is used as part of the pathway for the air-fuel mixture it cannot hold oil.  Which is why we mix oil in the fuel.  Giving us an air-fuel-oil mixture that combusts in the cylinder.  The moving components get lubricated as this mixture travels through the engine.  Which is perhaps the biggest drawback of the single-stage snow blower.  Having to mix oil with gas.  It’s not difficult.  You just have to make sure you add the right amount of oil.  And not to use this gas-oil mixture in your 4-cycle lawnmower.  And even though we were never big fans of cutting the grass even that begins to look pretty sweet as the snow blows back in our face as we walk behind our snow blowers.  Thinking of but one thing.  Spring.  And thanks to these wonderful machines we may actually make it to spring healthy.  Without having suffered a wrenched back, hernia or a heart attack.

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