The thread recently with discussion of 24 vs 26 brake systems and some discussion of earlier brake systems promted me to share email on the subject with "SP5103" who suggested I post this story here. A little back ground to set the stage for those not familiar with Oregon's Sumpter Valley Ry. It was a 36" gauge common carrier line that ran through the mountains in N.E.Oregon. It's principal freight was logs and lumber which was mostly east bound to Baker. In the 19teens there were several mills out in the middle of the 80 mile line with 2 summits with heavy grades of at least 3% east bound between them and Baker. Larch Summit the one further East about 35 miles from Baker had a small yard along with a wye. Tipton Summit also had a small yard, along with a depot, but less storage track. Typical freight train operation for moving loads east was for one of the railroads 3 Mikado's (5 after 1920) to move five loads and caboose to the 1st summit, go back and bring up 5 more or 10 might be brought up with a helper on the rear. This could continue until all loads were brought up to the first summit and then a large consist would descend and be broken up to go up to the second summit in 5-10 cars blocks depending on if a helper was available. This is the general pattern that went on for many years with varitations. I should also point out that the railroad rostered over 400 flat cars at one point in time, besides box cars, stock cars, passenger cars and a good deal of other equipment.
This story was related to me by two sources one being a guy who knew one of the engineers involved and the other that engineers daughter. Did the number of cars grow a little each time the story has been retold? We may never no for sure.
It was the eve of a holdiday weekend and for what ever reason there was a huge back log of loads filling every siding from Austin (about MP60) back to Larch summit. The Mikado's at this time each had one 11" air pump and 6ET brake systems. They crews wanted to clear out the back log so they could take the weekend off. They started making up a train at Larch. As I recall the story the long trains rear helper and a third engine were used to assemble the train. The helper kept bringing cars up and putting them on the rear and the head end soon was out of room and had to keep moving down grade as more and more cars were added to the rear. When they were finally done adding cars they had the longest train ever ran on the SVRy at 150 cars. The helper coupled up to the rear and it took both engines pumping air to charge the train. Once the train was charged and the head end whistled off and engine brakes were released, the rear end continued pumping air for the trip down the mountain to offset the leakage througout such a long tran so they didn't stall. The guy who told me the story was a retired SP engineer I knew quite well and he swore to the truth of the story and povided the details as I have posted to the best of my memory. The daughter of the engineer that was on the head end told me the story only in general details saying it was the longest train ever ran on SVRy but I don't recall she specified the number of cars.
One thing I brought up with "SP5103" was what the triples K1's and H1's would have been doing. Presumably retainers were turned up on the entire consist which was std. procedure to descend from Larch which had a short stretch of grade just over 4%. The cars near the head end were probably seeing cycle braking, the rear of the train released but if one set and release had been made, air in the brake cylinders due to the retainers and then some real sporadic setting and releasing in the middle of the train though again air would have been in the brake cylinders at all times with the retainers turned up. It seems like the slack action could have gotten a bit chaotic out there in the middle?