Friday, December 25, 2009

Green Truck

The SN 1005's second power truck is now fully painted. While the truck was primed in Awlgrip, this is an oil-based alkyd paint. In the cold shop, it is taking literally days to dry. The motor is tilted up merely to paint motor and truck. Wheels and axles are not painted because practice in the United States is not to paint them, to make the wheels easier to inspect for defects.

Look close at the roller bearings, and you notice two things. First, these are roller bearing axles. Second, the two casting ends are different and even bear different names. These facts are related.

One can guess that in 1912, this car was not built this way. Roller bearings were introduced in the 1930s as part of the plan to use the San Francisco Bay Bridge. The railway across the Bridge did not require roller bearings, but it did require cab signals. And those required speed control - which required speed detection. That was accomplished with a sensor inside the end cap of a roller bearing. The cap on the left is the stock Timken cover. The cap on the right is a special casting made by General Railway Signal company to serve the same purpose as the stock cover, and also house the speed sensor.

And so, all Sacramento Northern cab cars which meant to use the Bay Bridge had to be retrofitted with one roller bearing axle per car. If one is needed, why do we see two? Because near the end of the the life of these cars, the owner (at this point the Key System) swapped parts between cars on a regular basis. The newer retrofit axles had the best wheels on them, so they tended to be swapped onto surviving cars. Three out of the four axles on SN 1005 are roller bearing.

A thousand details are required to wrap up a restoration. One of them is securing loose air piping. Long pipe runs tend to rattle, and they need to be clamped to the car. A number of pipe clamps, blocks and spacers have been fabricated and are being fit to the car. The museum has special dies which can be placed in the hydraulic press, to bend hot-rolled steel bar to the shape of a pipe clamp.

Here are photos of the evolution of the truck.

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