Last Updated: 16 June 2025

This guide covers the following models:

  • Union Mills Class 3F 43766 in BR Black

All Union Mills models follow a similar tender drive arrangement. It is usually possible to fit a small decoder inside the tender, however this is not always the case. A decoder may be hidden in the cab, or some material can be milled out from the tender to create space.

Union Mills Tender Drive Conversion

Refer to the Union Mills J39 (old chassis) guide for the detailed step-by-step guide on installing a decoder in the cab, there isn't enough room inside the tender on this model.

Convert Union Mills Class 3F loco to DCC