Nostalgia & History > UP history: Cow + calf pushers on Cajon

I've seen pictures of EMD cow & calf units being used as pushers on Cajon Pass. Apparently this didn't last long and the reason was likely that they were unsuccessful in this endeavor.

Question is why were they unsuccessful? The low speeds required of a pusher and the lugging capability of an EMD switcher would seem to make this a good match. What happened?

Leave it to the fantastic Don Strack to know.

http://utahrails.net/webpubs/up-sw-early.php

Throughout the 1950s, the cow/calf sets were used in helper service on Cajon Pass and on Cima Hill, operating out of San Bernardino and Kelso, California, respectively. At least one TR5 set was also used at Caliente, Nevada for helper service on the two percent grade through Clover Valley Wash, near the Utah/Nevada stateline. These heavy duty switchers were delivered with AAR switcher trucks, equipped with cast iron brake shoes. UP soon discovered the limitations of the braking capacity of these heavy switchers when used to occasionally retard a downbound train, along with the times in which the units were returning light down hill on these steep grades after helping an upbound train. The combination of the stiff suspension of the switcher trucks and soft cast iron brake shoes soon began causing overheated wheels and overly rapid wear of the brake shoes themselves on the TR5s. To minimize some of the costs associated with the use of what were essentially yard switchers in helper service, in late 1952 and early 1953 the TR5 A-units were equipped with dynamic braking. The addition of this EMD-designed feature included a single 36-inch fan, and four resistance grids, one for each of A-units’ four traction motors, installed in an enclosure added to the top of the carbody, just ahead of the cab, blanking out and covering the front cab windows. Because the feature was meant solely to retard the downhill descent of the "light" locomotives, no provision was made for the use of dynamic braking on the cab-less booster units. Due to the limited capacity of the dynamic braking (used only on the cab units to control the speed of their downhill descent), along with the added maintenance for the dynamic braking components themselves, the usefulness of the braking was soon outweighed the associated maintenance costs. Within a short period of time, by 1956, the dynamic braking feature was deactivated, with the components remaining installed on the units, unused.

The use of TR5s on helper service eastward out of San Bernardino was reduced considerably with the delivery of GP7s and GP9s in 1953, 1954 and 1957, but they were still regularly assigned to trains needing helpers heading up Cima Hill. The use of specifically assigned TR5 (and all other) helpers in the desert helper districts was discontinued completely in February 1959, an acknowledgement to the versatility of building block, multiple-unit Diesel operation, which allowed the "locomotive" on the head-end to be matched perfectly to the requirements of both uphill and downhill operations.

Exactly what I wanted to know - thanx

Here is a shot of a set helping the Los Angeles Limited up Cajon in 1952. Photo by JC Weirich.

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The Maine Central also bought SW7s to use as helpers on the 20 miles of 2.5% on the line through Crawford Notch in New Hampshire. They replaced 2-8-0s and 2-8-2s. These switchers also were eventually reassigned to more suited duties.

On the Q we used their 9400 series TR-2's in transfer service (not helper, but the demands of the duty are about the same) on 2.2% grades in St. Paul, and they performed very well for over 15 years (though the B units were rebuilt with cabs to make the fleet more versatile).

Those things would hunker down to about 1 1/2 mph, but they kept on going with trains that would have stalled GP20's, '30's, or SD24's.