Slotting the Comm

Frank writes...

Sunday was one of those days that consisted of one task that took the entire time.

The task at hand was "slotting the commutator" on the 18's National BB2 air compressor. The comm is made up of copper segments with mica insulation between them. The mica insulators are supposed to be lower than the segments, so to speak, but depending on wear and maintenance, you can get to a situation where the comm surface is basically smooth, with the mica at the same level as the segments. That's not good, as it can cause excessive wear and sparking, but that's what the 18's air compressor has had. So, my job was to go around the comm and use a cut-off hacksaw blade to "slot" it - i.e., cut down the mica insulating pieces and create shallow slots between the segments. In the above photo, the segments right of center have been done, while the ones left of center haven't. Unlike with a traction motor that's attached to a car, this comm can easily be turned by hand to advance to the next segment.

I spent the whole afternoon working on this, which was tedious, but not especially unpleasant. The weather for the museum's last regular-season open day of the year was gorgeous, so for a while I had the garage door at the west end of the lean-three open for some fresh air and light. This commutator work is (we hope!) the most laborious of the improvement tasks we have planned for the 18's air compressor, but I got through maybe 70% of the work, so I hope to finish it the next time I'm out. Thanks go to Richard, for guidance with this, and to Steven, who drained the last of the old oil out of the pump and also worked on sourcing new wire terminals that will be needed.

Further east in the shop, we were invaded by several Steam Department volunteers, who were cutting boards for a new deck for the tender on Commonwealth Edison 5. Here, Matthew and a volunteer I don't know retrieve boards from the pile.

And our team of Brian Sawyers - Brian D on the left and Brian L on the right - work at the radial arm saw to cut the boards to length. When they were done, the wood was picked back up by the forklift and returned to the Steam Shop for painting.

Speaking of ComEd locomotives, ComEd 4 was on the inspection pit, as shown here. Unfortunately, it's temporarily out of service.

Here's the reason: a brake beam was found to be cracked at the end, just outboard of the bushing. This will be replaced.

When Brian L wasn't working with the steam guys to cut boards, he was working on air valves. Here's a nice, newly overhauled M15B motorman's valve body. When he finishes fixing up its innards, he'll give it to us for blue paint, and then it can go onto the 309 to replace a valve that's been causing some issues. Thanks, Brian!

Finally, not necessarily big news, but when I was driving onto the property, our Muni trolley bus was sitting outside the Andersen Garage in good sunlight, so I snapped a photo. This Fageol-Twin Coach trolley bus was built in 1949 and I believe it's the last of its type.