Wheel Slippage, Coupler Failure, Slack Management and Bad Winter Drivers

Posted by PITHOCRATES - January 8th, 2014

Technology 101

Starting a Train to Move is like Starting a Car to Move on Snow and Ice

Starting and stopping a train takes great skill.  Because one of the greatest advantages of rail transport is also one of its greatest weakness.  Steel wheels and steel rails.  With very little friction between the two.  Allowing trains to travel very efficiently.  Rolling effortless over great distances.  Once they get moving, that is.  Which is where that skill comes in.

Starting a train to move is like starting a car to move on snow and ice.  If you stomp the accelerator the wheels will just spin on the snow and ice.  Just as steel wheels on steel rails will.  Because of the low amount of friction between the two.  The throttle on a North American locomotive has 8 ‘run’ positions.  And one ‘idle’ position.   The engineer starts the train moving by moving the throttle to position one.  As the train begins picking up speed the engineer advances the throttle through all the positions until reaching run eight.

As the engineer moves the throttle he (we will use the pronoun ‘he’ for simplicity in lieu of ‘he or she’) watches the amp meter and wheel slip indicator.  Which is why he advances the throttle through each position.  To slowly start the train moving.  If he ‘stomped the accelerator’ the wheels would slip and spin freely on the steel rail.  Damaging both wheels and rail.  Without moving the train.  In addition to preventing wheel slippage he is also trying to prevent one other thing.  Coupler failure.

Getting a Train Moving is Difficult but Keeping it Safely on the Track can be Harder

Driving a train is a study in slack management.  Each coupler on a train has slack in it.  They are not permanently affixed to the railcar or engine.  They can move forward and backward a little bit.  With a shock absorbing device that deals with the compression and tension forces between cars.  This slack exists at each coupler.  The longer the train the more couplers and the more slack.  When a train starts moving it takes very little effort to pick up the slack in a coupler.  But it takes a lot more effort to get the car moving once you do pick up the slack.  And if you apply that force too quickly you can snap the coupler right off of the car.

An engineer picks up this slack by moving slowly while in run one.  And he moves slowly by having the brakes partially set.  That is, he moves the throttle to run one and slowly releases some air in the train line.  As he does the brakes release.  A little bit.  Just enough to allow the train to move at a crawl.  Slowly picking up the slack without breaking a coupler.  Once he picks up all the slack he releases the brakes completely.   And slowly picks up speed.  Able to pull great weights of freight trailing behind as there is so little friction between steel wheels and steel rail.

Of course, that is also a problem.  For curves.  Where the engineer has to slow the train down so the centrifugal force doesn’t pull the train off the tracks.  Or on gradients.  Where the engineer has to slow the train on downhill portions to prevent a runaway.  Or add sand to the track on uphill runs (through automatic sand feeders in front of the drive wheels).  To prevent wheel slippage by adding friction between the wheel and track.  Getting a train moving is difficult.  But keeping it safely on the track can be harder.  Which requires the ability to slow a train in time for curves and downhill gradients.  Which takes time.  And a mile or so of track.

When it comes to Driving a Car in the Winter you have to approach it like Driving a Train

Driving a train is like driving a car on snow and ice.  There’s a lot of wheel slippage.  It’s difficult to slow down.  And you really have to slow down for curves.  For if you turn the steering wheel at speed your front wheels will just slide across the snow and ice and the car will keep going straight.  If you stomp on the brake pedal and lock the wheels your wheels will just slide across the snow and ice in the general direction you were traveling in.  Today, modern cars have systems to help people drive on snow and ice.  Like anti-lock brake systems.  And traction control systems.

An anti-lock brake system prevents the wheels from locking up during braking.  The system monitors wheel rotation.  If it senses a wheel that is no longer rotating it will begin pulsating the brakes.  Applying and releasing the brakes some 15 times a second.  So the wheel keeps rotating, giving the driver control.  A traction control system also monitors wheel rotation.  If it senses a wheel rotating faster than another (because it’s spinning in ice and snow) it will slow that wheel and/or apply more power to the non-slipping wheel.  Giving today’s drivers more control of their cars in the ice and snow.

Of course none of these systems will help if the driver is irresponsible behind the wheel.  And lazy.  If you don’t shovel your driveway after it snows.  Or if you do but push that snow into the street in your driveway approach.  For a car needs to have the rubber in contact with the pavement for traction.  If not you get wheel slippage.  And we all probably have a neighbor who thinks the best thing to do when this happens is to step down on the accelerator.  To spin those wheels faster.  And does.  Digging a hole in the snow.  And then begins swearing because the stupid car got stuck in the snow.

When it comes to driving a car in the winter you have to approach it like driving a train.  You need to start slowly and monitor your wheel slippage.  Sometimes it’s best to just let the engine idle in gear to slowly get the car moving.  Then once the car is moving on top of the snow and ice you can slowly increase the speed.  But never so much to cause wheel slippage which will just dig a hole in the snow and ice that you may not be able to drive out of.  And you have to start slowing down long before you have to stop.  Always being careful not to lock your wheels.  Simple stuff.  Something every driver can do.  For these are things every engineer does.  And driving a locomotive is a lot more difficult than driving a car.

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Trade, Steam Power, Reciprocating Steam Engine, Railroading, Janney Coupler and Westinghouse Air Brake

Posted by PITHOCRATES - January 25th, 2012

Technology 101

Early Cities emerged on Rivers and Coastal Water Regions because that’s where the Trade Was

The key to wealth and a higher standard of living has been and remains trade.  The division of labor has created a complex and rich economy.  So that today we can have many things in our lives.  Things that we don’t understand how they work.  And could never make ourselves.  But because of a job skill we can trade our talent for a paycheck.  And then trade that money for all those wonderful things in our economy.

Getting to market to trade for those things, though, hasn’t always been easy.  Traders helped here.  By first using animals to carry large amounts of goods.  Such as on the Silk Road from China.  And as the Romans moved on their extensive road network.  But you could carry more goods by water.  Rivers and coastal waterways providing routes for heavy transport carriers.  Using oar and sail power.  With advancements in navigation larger ships traveled the oceans.  Packing large holds full of goods.  Making these shippers very wealthy.  Because they could transport much more than any land-based transportation system.  Not to mention the fact that they could ‘bridge’ the oceans to the New World.

This is why early cities emerged on rivers and coastal water regions.  Because that’s where the trade was.  The Italian city-states and their ports dominated Mediterranean trade until the maritime superpowers of Portugal, Spain, The Netherlands, Great Britain and France put them out of business.  Their competition for trade and colonies brought European technology to the New World.  Including a new technology that allowed civilization to move inland.  The steam engine.

Railroading transformed the Industrial Economy

Boiling water creates steam.  When this steam is contained it can do work.  Because water boiling into steam expands.  Producing pressure.  Which can push a piston.  When steam condenses back into water it contracts.  Producing a vacuum.   Which can pull a piston.  As the first useable steam engine did.  The Newcomen engine.  First used in 1712.  Which filled a cylinder with steam.  Then injected cold water in the cylinder to condense the steam back into water.  Creating a vacuum that pulled a piston down.  Miners used this engine to pump water out of their mines.  But it wasn’t very efficient.  Because the cooled cylinder that had just condensed the steam after the power stroke cooled the steam entering the cylinder for the next power stroke.

James Watt improved on this design in 1775.  By condensing the steam back into water in a condenser.  Not in the steam cylinder.  Greatly improving the efficiency of the engine.  And he made other improvements.  Including a design where a piston could move in both directions.  Under pressure.  Leading to a reciprocating engine.  And one that could be attached to a wheel.  Launching the Industrial Revolution.  By being able to put a factory pretty much anywhere.  Retiring the waterwheel and the windmill from the industrial economy.

The Industrial Revolution exploded economic activity.  Making goods at such a rate that the cost per unit plummeted.  Requiring new means of transportation to feed these industries.  And to ship the massive amount of goods they produced to market.  At first the U.S. built some canals to interconnect rivers.  But the steam engine allowed a new type of transportation.  Railroading.  Which transformed the industrial economy.  Where we shipped more and more goods by rail.  On longer and longer trains.  Which made railroading a more and more dangerous occupation.  Especially for those who coupled those trains together.  And for those who stopped them.  Two of the most dangerous jobs in the railroad industry.  And two jobs that fell to the same person.  The brakeman.

The Janney Coupler and the Westinghouse Air Brake made Railroading Safer and more Profitable

The earliest trains had an engine and a car or two.  So there wasn’t much coupling or decoupling.  And speed and weight were such that the engineer could stop the train from the engine.  But that all changed as we coupled more cars together.  In the U.S., we first connected cars together with the link-and-pin coupler.  Where something like an eyebolt slipped into a hollow tube with a hole in it.  As the engineer backed the train up a man stood between the cars being coupled and dropped a pin in the hole in the hollow tube through the eyebolt.  Dangerous work.  As cars smashed into each other a lot of brakemen still had body parts in between.  Losing fingers.  Hands.  Some even lost their life.

Perhaps even more dangerous was stopping a train.  As trains grew longer the locomotive couldn’t stop the train alone.  Brakemen had to apply the brakes evenly on every car in the train.  By moving from car to car.  On the top of a moving train.  Jumping the gap between cars.  With nothing to hold on to but the wheel they turned to apply the brakes.  A lot of men fell to their deaths.  And if one did you couldn’t grieve long.  For someone else had to stop that train.  Before it became a runaway and derailed.  Potentially killing everyone on that train.

As engines became more powerful trains grew even longer.  Resulting in more injuries and deaths.  Two inventions changed that.  The Janney coupler invented in 1873.  And the Westinghouse Air Brake invented in 1872.  Both made mandatory in 1893 by the Railroad Safety Appliance Act.  The Janney coupler is what you see on U.S. trains today.  It’s an automatic coupler that doesn’t require anyone to stand in between two cars they’re coupling together.  You just backed one car into another.  Upon impact, the couplers latch together.  They are released by a lifting a handle accessible from the side of the train.

The Westinghouse Air Brake consisted of an air line running the length of the train.  Metal tubes under cars.  And those thick hoses between cars.  The train line.  A steam-powered air compressor kept this line under pressure.  Which, in turn, maintained pressure in air tanks on each car.  To apply the brakes from the locomotive cab the engineer released pressure from this line.  The lower pressure in the train line opened a valve in the rail car air tanks, allowing air to fill a brake piston cylinder.  The piston moved linkages that engaged the brake shoes on the wheels.  With braking done by lowering air pressure it’s a failsafe system.  For example, if a coupler fails and some cars separate this will break the train line.  The train line will lose all pressure.  And the brakes will automatically engage, powered by the air tanks on each car.

Railroads without Anything to Transport Produce no Revenue

Because of the reciprocating steam engine, the Janney coupler and the Westinghouse Air Brake trains were able to get longer and faster.  Carrying great loads great distances in a shorter time.  This was the era of railroading where fortunes were made.  However, those fortunes came at a staggering cost.  For laying track cost a fortune.  Surveying, land, right-of-ways, grading, road ballast, ties, rail, bridges and tunnels weren’t cheap.  They required immense financing.  But if the line turned out to be profitable with a lot of shippers on that line to keep those rails polished, the investment paid off.  And fortunes were made.  But if the shippers didn’t appear and those rails got rusty because little revenue traveled them, fortunes were lost.  With losses so great they caused banks to fail.

The Panic of 1893 was caused in part by such speculation in railroads.  They borrowed great funds to build railroad lines that could never pay for themselves.  Without the revenue there was no way to repay these loans.  And fortunes were lost.  The fallout reverberated through the U.S. banking system.  Throwing the nation into the worst depression until the Great Depression.  Thanks to great technology.  That some thought was an automatic ticket to great wealth.  Only to learn later that even great technology cannot change the laws of economics.  Specifically, railroads without anything to transport produce no revenue.

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