Tuesday, April 16, 2013

The Mules of Panama: how rail built, and runs, the Canal.

Recently I was on a cruise through the Panama Canal.  I accompanied it by reading David McCullough's excellent history, The Path Between the Seas, from which I learned that the Canal was started by the French, before being sold to the Americans.  In an era of "anti-government", it is nice to read an example of what American government can really do--it couldn't have been done without marshalling the resources and know-how of a nation.

The tracks along the Miraflores lock
The first problem in building the Canal was logistical, and the utilization of the small Panama railway that crossed the isthmus became essential.  It was rail that allowed them to move in the big steam shovels to cut through the Continental Divide in the infamous Culebra Cut.  It was rail that allowed them to move men and machines from Atlantic to Pacific.  Only after they managed the rail, were they able to build the canal.

And it is rail that works now!  Unlike many river locks, when big ships enter the canal, they don't tie up to the side.  They are attached to funny little locomotives, called mules, which run along a track at each side of the lock.  You can see the tracks them in the image at right--and note how they run up an incline as they go to the higher locks.  (This is Miraflores, on the Pacific side, which has two locks.)

Each mule has two lines to the ship, which are brought out by rowboat (!) and thrown to a crew of Canal linesmen who are on the ship.  Our ship had three mules on each side. We picked up the mules on one side first, and then on the other.

You can see the two pulleys on the side of the mule in the picture at left, although it's not under tension yet.

Once the mules are attached, they maintain the position of the ship within the lock.  The ships go through under their own power--the mules do not pull them. The mules adjust its lateral position.  The lights on the top of the cab, along with bells, allow the mules to communicate with the Canal pilot who is in charge of the ship in the locks.  So the pulleys are constantly adjusting tension so that the ship is positioned accurately.

The ship we were on was well under the maximum size (Panamax) so there was plenty of space between the ship and the walls of the locks.

Incidentally, the locks function by gravity feed, with the water from the lake in the middle running down into the locks on the Atlantic or Pacific. The water feeds through concrete channels into the bottom of the locks.  They still work elegantly, 100 years after they were built.  New locks that will admit bigger ships are being constructed.  They will save some of the water, but as a result, they will need power to run them.

The mules are made by Mitsubishi, in Japan.

Hope you enjoy!

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