(jeb@oscalemag.com). - O Scale Trains Magazine Online

Distributed PowerLooking at the photograph of Train C-BAMPAM3-13, withBNSF 8981 and a trailing SD70-MAC, your first thought mightbe, ”There’s only two engines assigned to this unit coal train.”That’s not the case. On the rear, 7,300 feet back, is a remotegroup of three more SD70-MACs, all engines being one consist.In the early 1990s, on the Burlington Northern, we startedseeing locomotives equipped with “distributed power” or “integrateddistributed power” systems which consisted of an externalcontrol box mounted on the control stand with additionalradio telemetry equipment. When the “ICE” monitor displayscreens became the standard, with the EMD 70 series and GEDash 9s, the DP control system became a standard option availablefrom the builders, with operational control shown on theICE displays and program functions standardized for the railwayindustry.Over the years, with the advancement of locomotive technologyand horsepower ratings, train size (both tonnage and trainlength) has increased. The 15,000-ton unit trains (with 15,000-plus horsepower located on the head end) that were commonup to the 1980s were at the upper limit of tensile strength of railcarknuckles and drawbar assemblies. When things went wellyou scratched over the hills; when they did not, you createdscrap iron.The trains of today are often over 19,000 tons, with locomotiveconsists producing more than 20,000 horsepower. Theywould be rolling scrap iron producers without the ability todistribute the available horsepower to reduce in train forces.“Distributed power” gives the locomotive engineer the abilityto operate more than one locomotive consist within a train,either all in unison or in independent groups of units, accordingto what is necessary to navigate the territory they are operatingover. Even with this technology, things can and do occasionallygo wrong.With the principles of distributed power in mind, let’s lookat applying this prototype practice to our model trains and layouts.We will take a look at each of today’s control standards forboth two- and three-rail layouts. Let’s first consider a few basics,trackwork and car weight.If you are currently operating trains over your layout in anefficient manner, then there should be no problem with operating“DP” trains. On any layout, sub-standard track will causeproblems regardless of the type of operation. Car weight is critical;freight cars need to be weighted to NMRA standards for thecar length. The forces of an engine pulling from the front andan engine pushing from the rear can result in derailments if theyare handling lightweight freight cars. On the prototype, you maysee an empty train with a “DP” engine located at the rear of thetrain. Usually this engine is being used instead of a FRED (FlashingRear End Device), and its use is restricted.Using conventional two-rail DC or three-rail AC cab control,multiple engines should operate well together in a multiple unit (MU)consist. You would be limited to a single operating consist, unlessyou could manage multiple consists in separate power blocks controlledby independent throttles (which would be very complicated).The Lionel TMCC system, used both in two- and threerailoperations, simplifies this matter. You have the ability toassemble either one consist with engines in multiple locations,or multiple consists in the train controlled by separate throttles.A multiple consist allows the operator to perform station workwith the lead consist while the rear consist remains in idle.With the DCC equipment available in the O Scale market,operators have the option of combining or “nesting” multipleconsists into one operated by a single controller. DCC also givesthe operator the ability to split these consists to perform stationwork, re-combine, and continue on after the work is completed.As with TMCC, you can operate each consist independently fromthe other by using a controller for each consist. Like the prototypeengineer, you have to be focused to the operation of your train tonavigate an undulating track profile with split consists.Another possibility to consider would be using non-poweredlocomotives in your consists to represent operating engines,without putting your power supply in a strain. I have experimentedwith conventional DC and TMCC operating systemson my layout concerning “DP” train operation with satisfyingresults over the last couple of months. As with any mode of trainoperation, a little practice builds experience.Researching DCC has convinced me to make the move. Iwould expect operating results and opinions to be in by the timeyou read this column. Check the OST Blog at [www.oscalemag.com/wordpress/] for posts concerning this and other projects,and feel free to post your comments and questions concerningthe "Modern Image".To Jim Scorse of NCE Corporation, a special thanks foranswering my questions concerning the operational possibilitiesof DCC.Until next time, “Roll-em”.uMar/Apr ’07 - O Scale Trains • 17