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.

Tuesday, December 22, 2009

Buffers and Pipes

The buffers on 1005 were very badly rusted. It was all surface rust, but there was an awful lot of it. It's a job for a sandblaster.

Our beadblast cabinet is wonderful, but its glass beads are intended for lighter work, and the cabinet is intended for lighter (and smaller) pieces. So one of the volunteers funded sending it out to a commercial sandblaster and powder-coater.

Powder coating was not used in the "good old days". They would have if they could, because it is so much more efficient. It is applied as a powder and then heated to melt it onto the part. Click here to see how powder coating is applied. The gun "fluffs" the powder into the air, while imparting an electrostatic charge which draws it to the part. It's pretty easy to get a uniform coating, because a thick enough coating insulates the electrostatic charge, meaning new powder won't stick as well. But you have to get it right, a coating already baked on cannot be re-baked.

Once the part is coated, it is gently carried to an oven. Jarring the part would knock off the powder. It's typically baked at 400 degrees for 15-30 minutes depending on the part. The coating melts onto the part, giving a uniform, spray-like finish. No runs, drips or errors. One coat. And no toxins either - powder is relatively non-toxic compared to paint. Cleanup is easy, and if the shop is clean enough, spilled powder can even be reused. It is not a historic method though, so we don't tend to use it much.

Lastly, here is a bunch of the air piping under 1005, going to scrap. This gives you an idea how much piping was replaced during the restoration.

Friday, December 11, 2009

Let there be heat!

Last Saturday was cold, but the SN 1005 crew was toasty warm. It was time to test the 1005's heaters. They worked without a hitch! Although... when a heater is started up after 10 years... it does make some funny smells.

The thermostat hadn't quite been worked out yet. The circuit for the thermostat is just the type of ingenuity you saw in those early electrical systems. SN 1005 does not have batteries. How do you make a 600 volt thermostat without exposing the public to hazardous voltages? The 600 volt current path is a ladder, going through two large power resistors, through the heater contactor coil, to ground. That circuit, alone, would have the heat run all the time. The thermostat is wired "across" the heater contactor coil. When the heat should turn of, the thermostat closes contact, shunting the coil. This causes the contactor to drop out. There is an additional resistor through the thermostat circuit, so some current continues through the contactor coil. They also included a snubbing capacitor to reduce arcing in the thermostat.

The crew also beeped out the #1 and #2 traction motor leads on the carbody, comparing the leads and their markings to the drawing. These were checked against the two traction motors on the truck being serviced. Those traction motor leads are being repaired, given new sleeves and new cleat blocks (made of wood - seen here in the poorly lit paint shop), which guide the traction motor cables.

The conductor's bell was also tested. You can hear it after the whistle and horn.

(the embed caused problems on some computers. Go here to hear the sound.)

At this point, if the Westinghouse HL controls are operated, the reverser will throw and the switch groups will click and clack, transitioning through resistor grids and series/parallel. Here is the switch sequence. Notice that several contactors have exactly the same sequence, i.e. S1 is always thrown at the same time as S2. In some cases, two contactors were wired in parallel for increased current capacity.

Sunday, December 6, 2009

The No. 14 Double Check Valve

Here is a drawing of a "No. 14 double check valve", one of many air-brake parts on the SN 1005. Many of these parts have come off 1005 for servicing. When this is done, the opportunity is also seized to paint both the parts and the piping.

In most cases, the parts are "hard plumbed" into the 1005's plumbing, which means a part comes off by following each pipe back to a union. The part comes off with an octopus of pipes attached. Here is an example of a double cutout cock, in which one handle closes two pipe circuits at once. The proximity of the ports makes piping a real challenge.

Before we are done, that part will be thoroughly cleaned externally, and overhauled internally - for this cutout cock, that means lapping the valve. And then, it will be painted - the valve will receive two coats of Awlgrip 545 primer then up to two coats of Awlgrip topcoat, "super jet black". The pipes will receive cold galvanizing compound, which will weather to the appearance of galvanized pipe.

Let's return to the No. 14 double check valve. Here you see a picture of WRM's spare unit. It is an interesting exception to the rule when it comes to "hard plumbing". As you may know, there was a major "shift in consciousness" about railcar plumbing. Now all the pipes go to a pipe bracket which is nothing but a manifold for attaching pipes. The device attaches with a gasket and a few bolts. It can easily be swapped, or carried as a unit to repair.

If you look above at the drawing, where you can see a clear separation line - above gasket #11. Is the upper piece really intended as a pipe bracket? A quick consultation of the parts list (below, off page) reveals that part #10 is indeed called a "pipe bracket". But you also see where the repairman had better know what he is doing if he means to unbolt the lower assembly from the pipe bracket - he's liable to have parts going everywhere. Clearly, pipe brackets have come a long way since.

Saturday, December 5, 2009

Truckin' Along

The truck is coming along. Here, you see one motor tipped up and out of the way, to allow painting of both motor and truck. Since the traction motor is nose-hung (half hung on the axle and half tied to the truck), this is very easy to do. Both motors have been painted, and the truck is being painted too. This is slower than you'd think. Scraping is the hard part. Media (i.e. sand) blasting cannot be used, because sand and blasted bits go absolutely everywhere and into everything. (Dry ice blasting is often touted as a solution to this, as the dry ice evaporates. However those blasted bits are just as bad as sand. The beauty of dry-ice is when when sending shop sweepings to hazmat disposal at $500/barrel.)

Applying paint on the intricate surfaces is also slow. A truck has a lot of surface area. But it's not just about paint. A lot of electrical work has been done on one of the motors, and the other will get the same. The commutator was cleaned, and the micas were re-grooved. Then the commutator and other areas were masked for painting. The area on either side of the commutator needs painting. The paint must have a high insulating value.

Twin-Pack is a two-part silicone epoxy coating. It comes in a box with two packs. That may be why they call it Twin-Pack. Or maybe because each pack is a very heavy plastic bag, with a clip in the middle. The clip separates the two parts of the epoxy. Remove it and knead the two parts together, then clip a corner and pour.

Trouble is, our stock was old. When mixed, it resulted in a heavy paste. The company only sells it in a minimum quantity of ten, um, Twin-Packs, and we use about one box per motor. So we sacrificed a Twin-Pack to the altar of science. What might be a compatible thinner, a solvent/diluent to reduce Twin-Pack to paintable consistency? Paint thinner resulted in only an angry emulsion. The same for mineral spirits, toluene, Awlgrip T0031 epoxy reducer, nor Imron reducer. Until - YES! Denatured ethanol did the job. A test paint yielded a very durable dry coat. So one of us played bartender, mixing up packs of epoxy as the painter needed it. The truck had to be moved several times to expose the relevant parts of the commutator.