by Virgil Teague

Created on: April 01, 2009

THE NODDING DONKEY
One of my first impressions when relocating to the north Texas plains was the proliferation of strange mechanical contrivances that dot the landscape. It's impossible to drive more than a mile or two without seeing several of these gizmos, heads going slowly up and down, and it takes no imagination to realize that here is the very source of the fuel which drives our vehicles and a large part of our national economy.

My new home on McFall Road sits over a vast pool of petroleum. Along this two-mile stretch I have counted more than twenty pump jacks in action and another six or eight sitting idle at the moment. These tireless machines run all day and all night, resembling those goofy-looking dipping birds you used to see on the back bar of every roadhouse. It takes a bit of getting used to, the constant chuffing and clanking, and some are noisier than others. The one at the back of my tract is noisy, but it can't compete with the one the next-door neighbor has to contend with. The noise from that one carries to my house perfectly clearly, and I keep thinking that something will finally clank too hard and shut the thing down for a day or so of blissful silence. Apparently these are such simple machines that virtually no maintenance is required and they chuff along like perpetual motion devices.

I've
called them "pump jacks" my whole life, but they're also known as "thirsty birds," "horsehead pumps," "sucker rod pumps," "jack pumps" and my favorite
"nodding donkeys.

Actually, they are
pretty simple. When a well is dug or more accurately, when oil is found, because it doesn't happen every time the hole is enlarged in order to create a cement retainer that contains a steel casing and a polished tube. Inside the tube rides the sucker string that pulls a traveling valve up and down. At the bottom of the tube is a fixed valve submerged in the crude oil pool. On the upstroke, the traveling valve closes and suction is created as it moves up. This causes the fixed valve at the bottom to open, and the crude (a mixture of oil, water and some unavoidable by-products) is drawn up into the pipe. On the down stroke, the fixed valve closes, and the traveling valve opens. Little by little, the crude is drawn up the pipe.

This is all accomplished by what's seen above ground, of course, and it, too, is fairly straightforward. There's a power source usually an electric motor
connected by a drive belt to the gear reducer that turns a crank attached to a Pittman arm. The

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