The restored Murphy's Winmill, Golden Gate Park
If you haven’t been out to Golden Gate park recently, there is a grand new attraction. The 106 year old Murphy’s windmill at the Southwest corner of the park has been restored to operation. The sweep of the sails, the largest in the world of traditional Dutch design, takes one breath away. It’s a wonderful work of mobile art, craft and technology; history and the future wrapped in a slate and copper skin. Modern wind turbines may be more efficient, but this clipper ship of the windmill world is far more beautiful.
I was fortunate to get a personal tour last October from Lucas Verbij, of Verbij Windmill Design and Construction BV, the Dutch consultant who restored the cap, sails and mechanical workings of the windmill while the base (the ‘smock’) of the structure was being re-built by local contractors. He and his rigger – who climbs onto the wood ‘stock’ frames to set the cloth sails – were here to test the operation before handing the project off to the city.
The 64 ton cap (the top of the tower which holds the axis of the sails and which spins to face the wind) was reinstalled last September, after an almost ten year restoration process in Lucas’ workshop in Holland. The cap supports the sails, holds the main shaft and brake and gearing mechanisms. One of its more intricate parts is the fantail, a small windmill at the back, whose purpose is to drive the cap around so that the main windmill faces the wind. Any shift of the wind direction, left or right, and the small fantail mill turns and rotates the cap in the right direction. It’s an intricate dance. The main sails – the propeller blades – rotate at around 15 revolutions per minute under a strong wind. The blades are a work of art in themselves - heavy wood beams tapering to a narrow end, pierced with angled wood framing to creating a delicate winglike structure.
I was surprised to hear that, so far at least, there is nothing for the windmill to do. The original purpose, when it was built in 1905, was pumping irrigation water for the park. Murphy’s windmill and its slightly older cousin at the northwest end of the park could together pump 1,500,000 gallons of water per day from the freshwater aquifer that underlies the west end of the park. Lucas described the original pump and gearing as having a perfect design, with a kind of pre-Detroit syncromesh transmission. All of that was lost in the decades following its installation, as electrical pumps replaced the fickle wind and the structure was left to rust and decay. So at the moment, the system is running with the brakes on. Lucas said there was enough potential power to move 10 cubit meters of water a minute, 75 kilowatts of electrical generating capacity. That's about enough power to electrify about thirty homes. Hopefully this will be put to use. Why not power the park’s waterfalls or lighting with this sustainable resource?
Phil Ginsberg, the Rec and Park General Manager, says there is a plan afoot to have the windmill pump a small amount of water to irrigate a produce garden which will be used in connection with a food concessionaire in Millwright's Cottage. We can only hope this plan is brought to fruition and is able to keep the sails spinning.
See http://www.sfmuseum.org/hist/wmill.html for more history of the windmill