Digital Command Control

Installing Wired DCC Decoders in N SCale Locomotives

The two manufacturers are Aztec Manufacturing Company and Southern Digital. Aztec modifies the original frame from the locomotive so it has space for a decoder and channels for the wires. Southern Digital provides replacement frames (retroframes) for diesel locomotive frames and/or weights that have been cut away to provide space for DCC decoders, and channels to route the various wires from the decoder.

Locomotive frames must be precisely manufactured to give the correct orientation and tolerances for drive train components, and alignment of the motor and electrical pickups, etc. to produce a smooth-running and quiet locomotive. Aztec and Southern Digital follow different approaches in the way they produce their retroframes.

Aztec uses OEM frames from the locomotive manufacturer or the customer and mills them on precise computer-controlled milling machines to create wiring channels and space for the decoder. These frames do not void the manufacturer's warranty, and most manufacturers will accept locomotives with Aztec frames for repair.

Southern Digital creates a copy of the die cast original frame modified with the wiring channels and space for the decoder. These are then copy cast in rubber molds in lower temperature, but more dense, alloys than the original.

Each approach achieves its purpose of converting an analog locomotive into a digital locomotive. The following table indicates some of the differences between the approaches and the companies:

Currently, frames are, or have been, available for the following diesel locomotives:

Notes:
Due to short supply of some OEM frames, Aztec may require your existing frame as a trade-in. Check at their web site: http://www.aztectrains.com. Aztec also posts the instructions sheets for installing decoders in the frames they produce. Check their web site.

Southern Digital Digi-Frames are fairly brittle, and have been known to break from incorrect handling or dropping of either the frame alone or the frame in a locomotive. Southern Digital also had, at one time, some problems with frame dimensions; watch out for these if purchasing on the used market or over the Internet.

New frames are added by the manufacturers from time to time, and some are discontinued, so check with the manufacturer or dealer for availability.

You can also modify your own existing frame to accept a DCC decoder. If you have the tools, time and inclination, you can avoid purchasing another frame.

Be extremely careful when modifying/grinding Kato or Atlas/Kato frames that you do not damage or destroy them. Most are no longer available from Kato or Atlas.

Details are provided in the individual publications for locomotives where this is an option.

If you are going to use a commercially available retroframe and/or modify your existing frame you will need the following tools:

The various conversions listed below provide detailed descriptions covering installations actually performed by model railroaders throughout the world, and reflect the experiences encountered during those installations.

After selecting the locomotive manufacturer below, from the listing click on the author's name(s) corresponding to the desired locomotive to go to the detailed installation description.

Note that some descriptions are located in the files area of various Yahoogroups DCC-related lists, and may require membership in the list for access. Alos note that articles published in the model railroad press are not generally available online. Contact the publisher to order a desired issue.

Aztec Manufacturing also provides detailed installation instructions for the locomotives for which they manufacture TrackMaster frames. Click on the links above or check their web site: http://www.aztectrains.com

The manufacturers of retroframes for N Scale diesel locomotives can be contacted as follows:

• Instruction sheets for various locomotive conversions from Aztec Manufacturing Company, N Scale of Nevada and Southern Digital.

• "N Scale Digital Decoder Installation," by Paul Lator, Clinic Presented at NMRA National Convention, Atlanta, GA, July 20, 1995. (Paul Lator is owner of Southern Digital).

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Last updated: Friday, June 19, 2009

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