or How I Built a Gravity Car for Mt. Tamalpais
by Jerry Coe
This article was written for the California Blacksmiths Association Newsletter.
Mt. Tamalpais State Park’s East Summit rises some 3,000 feet above the Golden Gate Bridge and the north shore of San Francisco Bay. In 1896, a tourist railway was built that led to the summit of Mt. “Tam,” rewarding sightseers with top-of-the-world views of the entire San Francisco Bay below, the open Pacific to the west, and (on a clear day) of the Sierra Nevada to the east. To get back down the mountain, sightseers boarded an exciting novelty-a gravity car-that took them on a breathtakingly scenic 15-minute ride that snaked its way through 281 curves before reaching the village of Mill Valley at the bottom of the mountain. The twisting, turning descent of the railway gave it its nickname: “The Crookedest Railway in the World.” Sir Arthur Conan Doyle, author of The Adventures of Sherlock Holmes, once described the railway as “more exciting than anything remotely like it in the world.”
In 1929, some 34 years after the railway’s inception, a road for autos and buses was built to the summit of Mt. Tam and proved to be more economical than a railway. The unique Mt. Tam Railway closed that same year, its rail tracks removed and its special gravity cars destroyed or sold for parts.
May the Force Be With You…
Around 1992, State Park Ranger Randy Hogue, who had worked at Mt. Tamalpais State Park for 20 years, came up with the idea of having a centennial event in 1996 to commemorate the hundredth-year anniversary of the gravity cars and the “crookedest” railway. Hogue’s aim was to bring public awareness to the unusual story of Mt. Tam’s bygone railway and also to celebrate the natural history of Mt. Tam State Park. He wanted to build a museum on the summit dedicated to the history-both natural and man-made-of Mt. Tam, and he began by raising money to build a full-scale, authentic, working gravity car. He asked me to build it.
Even though funding really only covered materials and subcontractors-not the tremendous amount of historical research and labor I expected I would have to put into the project, I couldn’t turn it down. It was a one-of-a-kind project, it benefited an important state park, and Hogue was an excellent salesman for the project (and became a good friend during the following year as we consulted on the progress of the project).
Down By Law
Gravity cars held 25 passengers and were built much like roller coaster cars. They had no engines and got up the eight-mile railway track to the summit of Mt. Tam by being towed by a steam engine. Although hurtling downhill propelled by gravity sounds like a potentially dangerous ride, there were never any accidents in the 33 years of operation of The Crookedest Railway in the World.
The ride down began by passengers boarding the gravity car and sitting on its wooden-bench seats. To get the car started on its rolling motion, passengers were asked to rock forward and back in their seats until gravity began to roll the car forward, and then down it went, rolling curve by curve down the mountain, through redwood groves and past panoramas of San Francisco and the Pacific until it reached the village at the bottom of the mountain about 15 minutes later.
Unlike a roller coaster, however, the gravity cars had the addition of a brakeman (known as a “gravity man”), who sat in the front seat of the car and worked a pair of hand brakes to maintain a safe speed. The brakeman usually kept the gravity cars descending at an average of 12 miles per hour, but one of the still-surviving gravity men, Bill Provines, now age 90, reported to me that he had a speedometer put on a gravity car once and it showed 27 miles an hour. “But I know we went faster than that,” he added.
The Research Begins, or, Reinventing the Wheel
I began my gravity car research by reading everything I could find about railway carriage construction and railway history. Nothing remained of any of the original gravity cars. I had to build one by working only from four or five old photographs taken between 1896 and 1925 of passengers sitting in the gravity cars in their Sunday finery.
My blacksmithing background had included apprenticing to a shipwright and rigger, constructing a reproduction of a two-masted square rigger, and building carriages at Yosemite’s Pioneer History Center, but when the gravity car project came up, I had only distant memories of these skills.
The first gravity car built in 1896 seemed an eclectic assembly, but by 1910, problems were worked out and the cars were standardized. Douglas fir was readily available then and was used for the structural lumber and decking. Oak was used for the seats and everything was painted for weather protection. Originally, the whole gravity car structure and deck were probably made of no-knot, quarter-sawn (also called edge-sawn), 25-grains-per-inch, fully sun-dried (one-year stickered) lumber. Today’s lumber is only stickered 30 to 90 days, and is mostly 5-6 grains per inch.
In 1896, when these gravity cars were being built, Bessemer-process mild steel was readily available from the East by rail. Chances are high that very little of any pre-Bessemer wrought iron was used. Probably all non-cast parts, except brake handles and brake bars in the pillar blocks, were hot-dip galvanized, and that was probably done in 50-gallon pots right in the gravity car workshop that existed at that time in Mill Valley. Small-scale, hot-dip galvanizing was a common practice dockside at the shipping wharves in those days.
Blacksmiths of those days did not seek the hardest way to build something to satisfy a purist’s heart. Smiths incorporated each new tool and device that was invented into their shops to save time, money, and effort. Their proficiency was very high, partly a result of the long apprenticeships they served in those days. One of my early teachers, Earl Burnside of Modesto, California, apprenticed in the Studebaker Wagon shop in Chicago from 1904 to 1908 and told me that they produced one wagon every five minutes on the assembly line, verifying the high level of expertise available at that time.
By using ergonomic principals, I easily estimated the sizes of the gravity car’s lumber, exposed nuts and bolts, benches, and brake handles. I determined the sizes of bearings, journal boxes, wood joinery, and the brake assembly by studying existing period-pieces in railway museums in California and Nevada, as well as at the Cable Car Museum in San Francisco. When I had completed my drawings, it was time to start building a gravity car, section by section, from the rails up: casting the wheels, machining the axles, making the crossbars, designing the brakes, building the wooden benches and decking, and finally, getting it painted with historically accurate colors.
Casting the Wheels: Pour Me One for the Road
The original diameter of a gravity car’s cast-iron wheel was 22 to 24 inches, but no railroad operating in California used such small wheels except San Francisco’s cable cars and streetcars. Cable cars and streetcars use a smaller-flanged wheel than regular railway cars because the top of the rail is at street level and derailment does not risk tipping the car over, as can happen on a raised track. It was for this reason that I cast an early cable-car-style wheel, a wooden pattern of which was loaned to me by the City of San Francisco for casting. The wheels were cast at the historic Knight Foundry in Sutter Creek, California, using the wooden wheel pattern. The new wheels were made in white cast iron, a product of melting engine blocks and brake drums. My apprentice at the time, Amy Westphal, went to the foundry to assist in the 600-pound pour. Knight Foundry manager Ed Arata coordinated the operation. Knight Foundry is a story in itself, having been in operation since 1872 with a completely water-powered machine shop. Unfortunately, this old foundry ceased operation in December, 1995, due to a shortage of work (they pour a cast iron no longer in use).
Turning the Axles: One Good Turn Deserves Another
John Morton, foreman of the University of California Machine Shop in Berkeley, started me on the axle process by turning one axle to rough dimensions and enlightening me on use of the lathe. Morton also turned four bronze bearings for the journal boxes. At the Nevada State Railway Museum in Carson City, using a long-bed lathe, I turned all four axles from 4140 tool steel, 4-1/2 inches in diameter, for a press-fit of .003 interference. The work was done under the supervision of Chris Dewitt, Chief Restorer, who works with a three-man crew. The Nevada State Railway Museum is a very efficient shop. They are currently restoring three steam locomotives simultaneously while maintaining and operating a fleet of five previously restored engines.
Pressed for Time
At the California Railroad Museum in Sacramento, California, the wheels were pressed onto the axles by Dennis Dougherty and his crew. Dougherty used a 600-ton hydraulic press and estimated 16,000 to 18,000 p.s.i. for each pressed wheel. That’s the same pressure used on the cable car wheels in San Francisco. Dougherty’s crew for my project was partly made up of highly skilled, railway-buff volunteers.
Making The Crossbars: The “Failsafe” Mechanism
The frame of the gravity car had two, large, wooden timbers bolted under the frame parallel to the axles. I could find no documentary record of the rods and crossbars but they are clearly visible in photos. I placed one crossbar of Douglas fir measuring 4″ x 12″ x 96″ in front of the front wheels of the gravity car and another behind the rear wheels. Both were set on edge so they would clear the rail by only eight or nine inches. The crossbars went the full width of the car, perpendicular to the track. Crossbars held one-inch-round rods vertically mounted in pairs at each wheel. These rods, like fingers of steel, extended downward on either side of the rail. Thus, should a derailment occur, the rods would fall to each side of the rail, confining the car to the track and eliminating a runaway situation.
Applying The Brakes
No photos exist of the gravity car’s wheels or brake systems. Using wooden brake bars and cast-iron shoes, I decided to blend the present San Francisco cable-car brake system with that of wooden freight cars circa 1896. The brake bars are two 4″ by 10″ Douglas fir timbers that hang from chains behind each axle and pair of wheels. I mortised cast-iron brake shoes into the brake bars and lined them up with the wheel. A 3/4-inch round bar pierces each brake bar and reaches to a brake shaft at the front of the gravity car. The bars are adjustable with a nut and can bring the brake shoes up close to the wheels. Springs keep the brake bars under tension, pressing the shoes back from the wheels. The springs were forged from truck leaf springs-thank God they air-harden, as it takes several reforgings to get the right spring action. The two brake shafts, one for each axle, are mounted in pillar blocks in front of the gravity car and transfer the movement of the gravity man’s hand on the brake handles to the brake rods and so on. The gravity man’s left hand controls the front brake, which is “set” by a ratchet-and-pawl mechanism to drag constantly on the descent, slowing the car. The gravity man’s right hand is on the rear or “free” brake. Apparently, slowing the gravity car required both hands at times.
Building the Wood Joinery: The Jewel in the Crown
The gravity car’s wooden structure is a rectangular frame made of 4′ by 6′ Douglas fir timbers, set on edge, crown up and out. Running lengthwise through the frame are two 3/4-inch throughbolts that connect the front and rear coupling plates. The decking, made of 3/4-inch poplar, is ship-lapped and nailed over the frame parallel to the axles. Bench frames throughbolt to the frame. I had oak lumber milled for the seats, backs, and sides of the five benches, and stabilized them with turnbuckles that reached the length of the benches to provide support against racking side to side. My last addition to the gravity car was to install a 30-gallon water reservoir underneath the front seat and plumb it to provide water to the front-wheel flanges to make the wheels slip on curves rather than climb out of the rails. The water tank was refilled after each descent. In the old days, just as the gravity man would reach down to open up the water valve before departure, the superintendent was known to shout “turn on the gravity!”
A Gravity Man Never Forgets
Special-effects painter Ken Gwinn of Art Effects in San Francisco brought the gravity car to his studio for painting. In his research effort, Gwinn visited ex-gravity man Bill Provines, who lives in Mill Valley. Provine’s memory of his gravity car days is very remarkable, even to the point of remembering the paint colors in detail, with help from Gwinn’s Panatone color index. With a crew of painters and only a week remaining before the official Mt. Tamalpais Gravity Car Centennial Celebration, set for August 18, 1996, Gwinn and crew painted day and night to transform the wood and metal car into a thing of beauty. Graphic designer Steve Kowalski scanned the lettering for the car from an early photo, then digitized it and reprinted it in full-sized letters. Gwinn used that as a guide for hand-painting the delicate lettering on the front panel of the car.
Any Which Way But Loose
Finally, after many months of research and nine months of construction, the first gravity car built in the last 70 years was completed. It was beautiful, authentic, and ready to be taken to the summit of Mt. Tam. The gravity car was carried to the summit of Mt. Tam by a vehicle with a hydraulically articulated flatbed that allowed for safe loading of the 3,000-pound gravity car without a forklift in under ten minutes time.
When more funds are available, Mt. Tamalpais State Park will build a small museum on the summit to house the gravity car, and Tam visitors will be able to sit in the gravity car and watch video footage of The Crookedest Railway In The World in its heyday. Unfortunately, they won’t be able to “turn on the gravity” because the car will rest on 83 feet of level track.
A Special Plaque
A sad footnote to this story is that Randy Hogue, the Mt. Tam Park Ranger who initiated this project, passed away from a long illness just a few months before the centennial event. Although he didn’t live to see the finished gravity car, the gravity car project was a manifestation of Hogue’s spirit. I bolted a plaque to the gravity car that read: “This gravity car is dedicated to the memory of Ranger Randy Hogue.” Thank you, Randy.