DPU Distributed power units explained

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Active Member
Another advantage is it increases the capacity of the line. From a dispatching point of view a long train consumes the same track capacity as a short train. One of the first applications of DP was a on a mountain territory that was physically constrained because the tonnage precluded long trains due to drawbar forces and the route was limited to about 50 trains a day. Unit trains would have to be split in two to go over the grades or they would have to run two crews on every train, doubling the cost. By using DP they instantly doubled the train size, doubled the capacity and more than doubled the speed of the cars since the cars didn't have to wait for a slot, they could just go over the mountain in the same train.

Another critical thing with DP is a continuity check. Back in start of the technology, a DP train was stopped on a main track on a crossing. Some irate motorists decided to turn the angle cocks and uncouple the cars. At that time there wasn't a continuity check, so when the train started up, both the head end portion and the rear end portion started moving, and when one portion stopped, the other portion stopped too. Since the head end portion had fewer cars and 2 engines and the rear portion had more cars and one engine, the head end portion gradually pulled away from the rear portion until they were separated by about a mile. It was finally caught when somebody noticed that the "second" train didn't have an engine.


Well-Known Member
Just about every train I run on the club layout has helpers on it. If some manufactures would start producing product instead of talking about it I can expand my coal train about 30 cars to get it over 100 and add a couple of mid train helpers or DPU's as they're called now.


Well-Known Member
Staff member
The problem, as I see it, as DPU setups are applied to model trains would be getting the individual engines in such a train to mimic the prototype's ability to match power and speed over all the units, because no doubt they are all communicating in some way to ensure this. Might be a job for Ring Engineering's RailPro, which does have that automatic feedback feature.

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