JOHNtheREDNECK wrote:...
The only major difference between the 2 is the PRR removed that giant block thing on the roof that the GN called a stinger. That big box apparently was an early MU connector device.
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That's what's known as a power buss, but may also be known by the more generic term, buss bar. This was intended to ensure that all locomotives in a given consist had power at all times, which is particularly important in helper service. Were one locomotive to lose power through a failed pantograph or some other reason, the other(s) would slip from the sudden overload and stall the train. At best, this would tie up the railroad, but at worst, such has hauling a live steam locomotive through a long tunnel, it had the potential to be fatal.
The Reading had similar hardware on at least one class of MU cars in the Philadelphia area. Of the other electric railroads that did this sort of thing, a less expensive heavy cable would have been used. Many electric railroads, such as the Pennsy, didn't have the operational need or the willingness to incur the expense. The last such operation I'm aware of involved the New Haven's EF-4s, the very last of these being a dedicated pair sharing one pantograph.