Wednesday, September 9, 2009

Draft gear, redux

The draft gear and couplers are a big job, and the work continues. Here, you see the coupler mated with its draft gear housing. The entire draft housing has been freshly painted with Awlgrip. You can see the hole on the right where it ties to the carbody and pivots. What you can't see is the draft gear including its essential spring, but it's a fairly conventional Janney arrangement. More on that later.

Here is the other, less freshly painted, draft gear mounted on the car - my apologies for the picture quality but it was very low-light. You can get a peek, through the side hole, of the outer draft gear spring - there's a second spring nested inside the first.

There are several interesting features in this shot. First, to the lower right, is a 3-way pivot arm directly on the coupler pivot point. It has three arms, which connect the cut levers on each side to the coupler itself. One of the cut levers was forged at a blacksmith (see previous post).

And on the upper left, you see a bracket. This is one of several brackets along the coupler. They carry three air pipes, and one heavy 600V jumper cable. Normally, connections like this come from the carbody. But on 1005, the connections are hung from the coupler shank itself, so they pivot as the car pivots. That means it won't part an air hose going around a sharp curve.

Here you see the brackets which ride closer to the coupler. This is where three air pipes connect to the air hoses and "glad hands". An electrical connection is made here as well; this carries third rail current down the train. Another connection, up high, trainlines trolley power.

The three air hoses are not the same as a locomotive. The first connection is, as you would expect, brake pipe. The second connection is a signal whistle, which allows the conductor to signal the motorman. The third connection is not main reservoir. It is called "control pipe", and it provides the air supply to the brake stand on a control trailer. In this configuration, the brake stand does not have a feed (reducing) valve - "control pipe" contains reduced pressure at the nominal brake pipe pressure.

Now, let's revisit the draft gear itself. Earlier this year, there was an RyPN discussion about couplers and draft gear on a narrow gauge car at the SPCRR, Society for Preservation of Carter Railroad, in Ardenwood, Fremont, CA.

Here's one of the narrow gauge couplers Randy was referring to. It's now the Sunday before Labor Day, and the coupler and draft gear is ready to reinstall in the NWP caboose. Here you see draft gear that is very similar to SN 1005's. In draft (pulling), the forces pull around the C-strap, compress the spring, which pushes against the left "ears" which press against the car. In buff (pushing), the forces push directly down the coupler and compress the spring, which pushes the right "ears". This entire assembly can be lifted by two men, rather unlike SN 1005's. The wooden blocks, I'm told, compensate for the draft gear having been converted from link-and-pin to knuckle many years ago.

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