spacer BSM Track Updates . . .
by
John LaCosta


Track Updates for April 26, 1998


    T he PCC, 7407, has continued to run with no problems after it recent repair. The 60 feet of new track has had its final tamping and only needs a load of stone to fill the space between the ties.

     The Witt, 6619, is back in service after a 3 week absence. While we thought that the problem was due to "crud" in the controller, it turned out that the real problem was a set of replacement parts we had installed on the controller. We had to make these replacement parts to repair some parts that had failed over the past two years.

     These parts are somewhat completed, and were originally cast to reduce the amount of machining. When this controller was designed (around 1930) a new form of casting was popular and used what was to be called die cast white metal. This process had a lot of advantages over casting in brass or copper; the most significant was that the item did not shrink when it cooled. If the die was made carefully, each part that was cast was ready to use with out any further work.

     But as is true for most things in life, there is always a down side to everything. At the time it was the high cost of making the die for the parts. If a large number of parts were made, the lower machining cost offset the large up front cost. What later turned out to be an even bigger down side was that after many years the metal would start to develop cracks, and fall apart.

     Three guesses what metal was used for some of the parts in the controller? One of our members, Paul, made new patterns for the pieces and we had them cast in aluminum. Since they tended to shrink when they cooled they were made a little over size and machined to the proper dimensions... well almost.

     It turns out we left one dimension just a little bit too big. When we replaced the first one the interference was small enough that the motor could overcome it. But as we continued to add pieces over the last two years the controller started to slow down until it stopped. We now know how to prevent the interference and with the "crud" out the leather piston cups should last longer.

     The test run after the controller did not start well, the car would not move in the first point, but boy did it move in the second. This was quickly isolated to two wires that had been reversed. Once they were put in the proper place the car started to perform as it use to. We did have to clean the air control valve, but that only to an hour and by Lunchtime on Saturday the Witt was back in service.

     While waiting for lunch to arrive our attention turned to The Crane. Over the past two weeks the air compressor governor was removed, rebuilt and reinstalled on the car. The governor is a very old style unit that needed a new leather piston cup, and two new contacts. The local supply house had the piston cup and Rick machined the new contacts. With the governor installed a jumper was connected from the trolley wire to the trolley base and the air compressor started to run. The governor worked as expected and for the first time we got to hear the whistle blow. With power on the crane the boom which had been shipped resting on the car body was raised up and the hook line was pulled out and rewrapped on the drum. Lunch arrived and since we were hungry work on the crane stopped.

     The afternoon saw the line crew repairing one broken insulator at 28th Street and installing a trolley contactor just south of the 28th loop switch. This contactor will be use to signal the shop and dispatcher when a car enters and exits the loop. This still is a number of months away before all of the system is together.

     A training class has started and I gave them the "pit" tour so that they would see what's under the car and how turning the hand brake stops the car.

     1164's traction motor is on the East Coast and we will pick it up in the next couple of weeks. Hopefully we can get 1164 back in service this summer.

     Take care,

     John

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