DCC Locomotive Speed Matching


Prototype railroads operate long trains by adding more diesel locomotives to provide the power needed to move the train at the desired speed over the track profile of the route to be followed. This locomotive lash up is called a consist; several locomotives are being run together as a single locomotive. Prototype locomotives have equipment to synchronize the members of the consist for efficient aggregated tractive effort. While steam locomotives each require a crew the end effect is the same as for diesel locomotives.It is well known that our N Scale model locomotives from different manufacturers and different locomotive models from the same manufacturer do not run at the same speed for the same throttle setting. Thus we cannot consist (MU) locomotives of different types/manufacturers as freely as prototype railroads can. Essentially, without speed matching, we are limited to consisting locomotives which just happen to run at the same speed. This is so because even the same models from a manufacturer, e.g. 2 x Atlas GP9, do not offer much chance of being reasonably speed matched. Most are not.The answer is to speed match the various locomotives. This can be done utilizing the capabilities of DCC decoders in two ways:

  • Use the Vstart, Vmidpoint and Vmaximum settings in the decoder Configuration Variables (CV). This is a quick and easy way to get close, especially with two locomotives of the same type and manufacture. Close is often not good enough.
  • Use the 28-step speed table built into most DCC decoders.
    Using a special Speed Matching Script with JMRI software and a specially constructed layout allows for a relative easy method of setting the28-step speed table to speed match our N Scale locomotives so we have the same freedom as the prototype in consisting locomotives.The individual operator can choose the speeds in which to match his/her locomotives. One suggestion for matching different locomotives is provided in the table below for diesel locomotives: 



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