Feed Valve Work

Frank writes...
On Saturday I headed out to the museum where I met up with my father, who was doing some paint stripping and sanding on the 36. We got to work on further testing of the air systems on the 308, 309 and 319. My father reinstalled the triple valves on all three cars, allowing for the air systems to be fully charged and tested for leaks. We found a few more leaks that hadn't been discovered last weekend, notably two cut-out valves located in the 308's cabs. We also noticed some arcing in the 319's air compressor but the commutator and brushes looked fine so we left a lit drop light in the compressor's motor to try and dry it out, just in case the damp air was causing the problem.
The biggest issue we discovered was that the feed valve on the 308 was stuck, so we disassembled it for cleaning, as shown above. For something that is basically a pneumatic on/off switch, it's pretty complicated! The feed valve regulates the air being fed from the main reservoir (which itself is fed from the air compressor, regulated by the governor) into the brake pipe. Reductions in pressure in the brake pipe set the car's brakes. Pressure in the main reservoir can vary from about 85 psi to 100 psi or so, but brake pipe pressure needs to be kept at 72 psi (except when the brakes are set) by the feed valve. The 308's feed valve was rebuilt in 2007 but disassembling it revealed a good deal of built-up rust and dirt which had jammed it. Once the feed valve is cleaned up and reinstalled it ought to work fine.

We also headed out to Yard 14 to inspect the tarp on the 321, which is fine. As always the Car Shop was abuzz with activity, including progress on window parts for the Cleveland PCC car, inspection work on CA&E 409, window work on CRT 1797 and interior restoration on KCPS 755 along with an operating rules review being conducted for new volunteers.

Randy adds:
This is the slide-valve type of feed valve, which consists of two parts: the regulating valve, disassembled towards the front of the picture above, and the slide valve, which looks like a small triple valve. These valves tend to accumulate a mixture of water, emulsified oil, and miscellaneous crud, and the usual failure mode is that the feed valve sticks open, so that the control pipe is supplied with the main reservoir pressure, and therefore goes up and down. It's still possible to apply the brakes when this happens, but you also get unwanted brake applications. Motormen should make a habit of noticing on the clock whether the brake pipe pressure is exceeding 70 psi when in release. If so, the feed valve needs attention.

The most obvious effect of a stuck feed valve is that when you blow the whistle the brakes come on. That's always good for a few laughs. (The reason for this is that usually the motorman's valve will be in the release position, so there's a direct connection between the brake pipe and the control pipe. And if the feed valve is stuck open, there's a direct connection between the control pipe and the main reservoir. So a sudden drop in main reservoir pressure due to blowing the whistle causes a drop in brake pipe pressure, and the brakes set up. Ha ha ha.) And I should admit that the main reason for taking the above picture was to help us put all the parts back together correctly!