With Sacramento Northern 1005 nearing completion, preparations have begun to install controllers and brake stands on Oakland, Antioch & Eastern trailer 1020. When completed, this project will allow us to operate an authentic SN passenger train on our restored SN track. The first step has been to restore 3 cast-iron electrical junction boxes needed for the control cables. These boxes were found in our warehouse, and were completely dismantled and painted. Several broken latch pieces were repaired, and our machinists made lots of new special nuts and washers to replace those missing from the terminals inside the boxes. In addition to the junction boxes, restoration has begun on the four 12-pin MU plugs needed to connect the control cables to adjacent cars.
Research in the Archives showed that several types of signs were displayed inside SN 1005, including warnings not to touch the third rail and not to lean out of the car windows or doors while the car is in motion. Also, there was a sign that the toilet will be locked between Moraga and the Oakland Pier to protect Oakland’s water supply. There were 3 signs which could be changed from “SMOKING” to “NO SMOKING” by means of a sliding metal flap, depending on the current smoking status of the car. All of these signs were mounted in glass-covered wooden frames.
The missing overload relay that had been removed from SN 1005 by the Key System was reinstalled and set to the proper amperage. The electrical reset circuit which allows the motorman to reset the overload relay from the cab does not work because the resistor that supplies it has failed. Work continues on restoring it. A jumper has been removed that Key System had added to the main traction power cable when the relay was removed, and the cable has been restored to its 1934 configuration.
The engine rebuild project for the VE 502 continues. The engine rebuild has been completed and the rebuilt generator is now attached to the engine. All worn parts were replaced or reconditioned in our shop, and the generator was rebuilt by a shop in Stockton. The assembly has been cleaned and painted. Last month, the engine and generator set was installed on the deck of the 502. Work continues on cleaning and painting the engine compartment, engine hood, and other parts used to mount the engine. Now, all the various pipes, wires, and hood parts are being reinstalled. Before the hood is put in place, the engine will be run to make all the necessary adjustments and to be sure that everything works OK.
The restoration of SN wooden caboose 1632 is nearly complete, with much detail work being done recently. Two new kerosene caboose lamps were purchased on Ebay and installed. New heat shields were built and mounted on the ceiling above each lamp. New seat and bunk cushions were made by our upholstery contractor in Sacramento. A metal box for storing fusees and torpedoes was painted and installed. New molding was installed around the cupola floor, and it and the floor were painted.
Work continues on the exterior of Shipyard Railway car 563 to prepare it for exterior painting. Much filling and sanding has been done, and new battens have been installed on the siding. Work continues on adjusting one truss rod to correct a sag in the body. The 4 sheet-metal route designator lights mounted on each corner of the roof have been removed together with the conduit supporting them; these lights are extremely weathered and will require extensive repair.
The shop crew has nearly finished rebuilding a Do-All band saw to use in the wood shop. This will replace a very old saw which was originally used in the Market Street Railway’s Elkton Shops. Gary Baker is building a heavy-duty DC power supply for it, which will provide DC power from 0 to 600 volts with over-current protection adjustable from 5 to 55 amperes. This will be very useful for testing traction motors, air compressors, unit switches, and other electrical systems on our cars.Restoration of Power Resistors on SN 1005
by David Johnston, Al Stangenberger, and Joe Magruder
Restoration of the body of SN 1005 is nearly complete. However, 2 systems still need work to insure reliable operation of the car: the control resistors and the power resistors. This article discusses the function and restoration of the power resistors.
Power resistors function only when an electric car is accelerating. These resistors reduce the voltage to the traction motors to allow a reasonable acceleration rate. SN 1005 runs on either 600 or 1200 volts direct current (DC). During most of the electric railway era the most common ways to change the voltage of DC power were either a motor-generator or resistors. The motor-generator uses a DC motor to drive a DC generator to generate the desired voltage. They were heavy and expensive but were fairly efficient. The other way was to use resistors. These are made of metals that do not conduct electricity very well and withstand high temperatures. Resistors are inexpensive to manufacture but very inefficient electrically.
On SN 1005 the power resistors are connected electrically between the trolley and the traction motors. Large pneumatic switches bypass portions of the resistors in 6 steps to increase the voltage on the traction motors until the motors are getting full voltage. The resistors are iron 8-inch by 8-inch grids with thin iron bars going back and forth in a serpentine pattern. They are designed to radiate the heat generated. If the operator does not accelerate the car rapidly enough, the resistors overheat causing the iron to oxidize and in extreme cases, to melt. Due to overheating, the resistor grids on SN 1005 have lost a lot of metal due to oxidization and have warped because they were so close to melting that they had softened and lost their shape. Where the oxidation has reduced the cross section of the resistor elements many of them have cracked and no longer make connection.
The power resistor grids on SN 1005 are Westinghouse Electric 3-point 8-inch resistors of 2 different resistance values. There are 76 of the 0.04 ohm grids and 76 of the 0.126 ohm grids. Since the mid-1970s these resistors have not been manufactured in the USA. When looking for replacement grids, we approached many iron foundries concerning the possibility of having the grids cast using our patterns. None wanted to take on the project due to the difficulty of shaking the freshly cast grids out of the sand without breaking them. This will have to be resolved for future restorations.
Fortunately, grids for SN 1005 were located. The Shore Line Trolley Museum sold the Western Railway Museum 80 new grids that they salvaged from the Connecticut Company when it went out business. The others were found at WRM. Some appear to be substation or industrial grids, but are the correct value for SN 1005 and appear to be nearly new. Don McKinsey used the surface grinder to remove an eighth-inch off of the wide boss industrial grids. Several other sources of smaller quantities of grids were also found. The used grids were reworked for use, but their resistance was found to be 10 – 15% higher than that of the new grids.
On the SN 1005 the resistor grids are electrically organized into 4 sets. As the car accelerates a decreasing number of theses sets are placed in line between the trolley and the motors, thus increasing the voltage at the motors. Each of the 4 sets has 2 sub-sets that operate in series in 600 volt mode and in parallel in 1200 volt mode. This is controlled by the voltage change-over switch.
Because there is considerable variation in resistance among the grids, each grid had its resistance measured to allow the best possible match of the grids. The resistance of each grid is too low to be measured with a standard ohmmeter. To measure the resistance of the grids, a test bench was built allowing 7 grids to be connected in series. Test power was provided by the WRM’s motor generator welder. To use the welder, an additional box of resistors was included in the series circuit. With all these resistor grids in series and the welder set at about 80 volts, the current through the series circuit was about 30 amps. The resistance of each grid was calculated based on the voltage and current recorded. Several hundred grids were tested this way. Mike Dreiling wrote software to sort the grids into sets with nearly identical resistance.
In addition to the grids, several other items were needed to build the resistor assembly. The end frames are being salvaged and are being reconditioned, including new galvanizing. New spacers were turned in WRM’s shop. Many custom size washers are required to replace washers corroded beyond usefulness. These washers were designed and custom stamped. New mica tubes and washers were ordered. Some of these are being produced in the USA and some in India.
The grid boxes are made up of grids, spacers, mica washers, and steel washers all sliding onto the mica tubes, which fit over steel tie rods. All these parts have to be slid onto the 3 tubes in the proper combination to keep the grids parallel and flat so they will not crack when the tie rod nuts are tightened. To get the proper combination of the proper thickness parts, detailed drawings were made of each tie rod to get the correct combination.
In addition to the resistors, the copper wiring that connects them to the changeover switch and the switch groups is badly deteriorated and must be replaced. This wire is supported in wood cleat blocks, many of which are charred and burned. The blocks will be removed and the steel framing scraped down, primed and painted. New cleat blocks will be made and several hundred feet of new wire will be installed. Then the rebuilt grid boxes can be reinstalled on the car and connected. This should provide the car with many years of useful service from the power resistors.
|Copyright © 2013, Bay Area Electric Railroad Association.
All Rights Reserved.
The Western Railway Museum is a project of the Bay Area Electric Railroad Association, a 501 (c) (3) non-profit, tax-exempt, educational institution. Powered by ShowTel