Re: Air set with retainers

I don't know anything about the rr you mention, but I can see where the procedures would be a bit different with extreme grade and unusually heavy cars that might be non interchange ore cars on a mining rr. The reason I say this is that several years ago I was able to buy some assorted air brake parts for the Sumpter Valley from the Nevada Northern. On a whim I got a few retainers to use on some of our cars that do not have them, strictly for prototypical looks as we don't have enough grade to warrant their actual use. Common retainers are 10, 15 or 25lb and some have multiple settings, but these from the NN which had probably come from cars used in the pit are 50lb. Basically with 70lb brake pipe which was the std. for k brakes on frt. at one time, it would take a full service (20lb) reduction to initially put 50lbs in the brake cylinders. Probably they ran with higher train line pressure which raises the equalization pressure. For example at 90 psi. train line equalization would occur with a set between 25 and 26 lbs, with 65lbs. in the brake cylinders depending on piston travel. Perhaps they ran with even higher train line pressure allowing for additional set and release above the pressure retained.