Pelton parted out

Above Luke is aligning the crankshaft of the governor control with the rod that connects the governor to the deflector. The way this machine regulates its power is by raising and lowering a curved piece of steel into the stream of water that comes out of a 2" (50 millimeter) diameter nozzle aimed at the cups of the Pelton wheel. When the deflector drops, the full stream hits the wheel; when it rises it deflects the water away from hitting the wheel. Some power plants actually reduce the amount of water by constricting its flow with a fast-acting valve. If we did that, our pipes would burst if the water shut off suddenly due to the momentum of several tons of water in the half-mile (0.8 kilometer) penstock. Unless the valve simultaneously directed the unused part of the stream away, which defeats the purpose.

Above is the heart of the regulating mechanism. The part on the right has the flyball governor, which is driven by a rubber belt connected to the shaft of the Pelton wheel. As it spins, the balls fly out by centrifugal force, pushing down on a shaft that has part of the sleeve valve on it. This controls hydraulic pressure on a 5" (14 centimeter) piston that in turn is connected to a crankshaft connected to the stream deflector. (Are you following? There will be a test.)

The two interacting parts of the sleeve valve are shown here. On the left you can see pitting on the steel cylinder, which will probably contribute to a slight tendency for the regulator to “hunt” a teensy bit before settling down to the correct speed. The most critical part is the little brass or bronze piece on the shaft to the right. If I remember correctly, it is machined to one ten thousandth of an inch (metric equivalent—super teensy), the most precise part in the whole regulator. (I was told by a mechanical engineer that nobody did anything that precise in the 1920s, but that was the specification on the blueprint.) The “lands,” which are the edges where they are cut at a 90° angle, are still as sharp as they were when I last tore into the regulator about 25 or 30 years ago. I was very careful not to put a scratch on either of these parts.

Both pieces fit into another cylinder that directs the hydraulic oil to either side of the drive piston. The steel cylinder in my hand provides feedback from the piston. It rides up and down on a steel inclined plane attached to the drive piston. As the piston moves right and left, the sleeve rides up and down, balancing the movement of the little brass spool connected to the rod of the flyballs. The ankle bone is connected to the shin bone, the shin bone’s—you get the idea. It’s intricate; the entire range of vertical motion of this assembly is around 1/16" (1.6mm) which makes the hydraulic cylinder connected to the deflector move about 4" (10 centimeters) total.

Lots of cleaning and careful gasketing with modern anaerobic two-part liquid gasket material will give us another decade of essentially free electric power. Well, not free since we have to pay a license fee to use the water to the United States Government and the State of California and the Fish and Game Department and…

Nothing’s actually free anymore, is it? Even after it’s been paid for.