Pump Jack

Another jack fact, if the counterweights had been located farther out this would have been a dead give away that this was a very deep oil well. The rods attached to the pump deep down are called sucker rods the deeper the well more rods are used. This adds weight to the lift, by adding a counter weight that travels in a downward travel as the rods are being lifted this allows the use of an engine having less horse power.

On deep wells even with the counter weights set out as far as they will go you can hear the engine struggle on that upward stroke. Was not expecting a modern engine, below is a video I found with the sound I was hoping for.