Beam Pumpjack

The nodding machine of every oil lease, drawn at full size in real millimetres and then reduced by a single number, 1:40.

The horsehead

Its face is an arc struck from the beam’s pivot. However far the beam tips, the bridle hanging off that arc stays plumb over the well.

Walking beam and samson post

The beam is a lever, and the samson post holds its fulcrum high over the skid. A ladder and a railed platform climb to the saddle bearing, as they do on a working unit.

Cranks and counterweights

Pitman arms hang from the tail of the beam down to the cranks. The heavy weights on those cranks balance the rod string, so on a real lease the motor only has to lift the oil.

Gear reducer and prime mover

At the back of the skid sit the motor deck and the reducer, which trades a fast motor shaft for a few slow, heavy strokes a minute.

Polished rod and wellhead

At the far end the polished rod drops through the stuffing box into the casing. It stands clear of the skid, the way the well stands apart from the machine that works it.

Side elevation of the pumpjack in solid silhouette: skid, gear reducer, samson post, walking beam and horsehead, with the polished rod at the right.
The model’s side elevation: 6.4 in tall and 7.4 in long. The same outline at full size stands 21.4 ft and runs 24.6 ft.

One number between this and the lease

Every dimension in the CAD was set at the size of the real machine, in real millimetres, the way a manufacturer draws a pumping unit. Then one scale factor, 1:40, brought the whole drawing down to a desk.

That is why it looks right from any side. The reach of the horsehead, the height of the samson post and the throw of the cranks all shrank together, so nothing was fudged to fit.

In the hand

The printed pumpjack seen from the wellhead side: horsehead and polished rod in front, the ladder up the samson post, the gear reducer behind.
From the well side, the whole run of the machine reads at once: rod, horsehead, beam, ladder, reducer.
The pumpjack from low down near the wellhead, the horsehead looming over the polished rod.
From ground level the horsehead looms, the way it does when you stand at the well.
The pumpjack from behind the motor deck, with the reducer and cranks in the foreground and the beam above.
From behind the motor deck: reducer, cranks and pitman arms, with the beam overhead.

Beam Pumpjack, 1:40

Overall size
7.4 × 2.5 × 6.4 in length, width, height
Weight
4.7 oz
Scale
1:40 21.4 ft tall at full size
Material
PLA
Print time
15.6 hours