Dual Tender System

The Dallas and Northern Railroad's Dual Tender System (DTS) was designed to allow locomotives to run longer without refueling by increasing their fuel capacity.

Overview
The Dual Tender System is exactly as it sounds: two tenders behind the locomotive as opposed to a single tender. The main difference between this system and the auxiliary water tenders pulled by steam engines on excursions is that each tender was dedicated to either fuel or water. The fuel tender would be directly behind the locomotive, with a long pipe running underneath to connect the water tender to the boiler. The design was meant to save time between destinations by not having the locomotives refuel as often.

Problems
The DTS was somewhat successful, but the issues were painfully obvious. The first arose in the fact that there was an entire tender dedicated to fuel. Early models used steam-driven coal pushers to ease the burden on the fireman. Later designs were made to be compatible with steam-driven mechanical stokers. However, any engine using this tender required rebuilding to accommodate and drive a mechanical stoker or coal pusher. By the 1930s, a new oil-compatible design was introduced. However, rebuilding was still necessary, as few Dallas and Northern Railroad locomotives at the time were oil-fired.

The second problem was the extended time that refilling the tenders took, as the two tenders were essentially the same, with only the mechanisms differing.

Usage
The DTS was only used on a few express passenger and freight locomotives, all specially rebuilt to be compatible with the mechanisms.

For a brief period after his conversion to oil-firing, No. 1 Terrence was equipped with the DTS. He returned to using a single tender by 1960.

Though he never used the DTS in active service, No. ... Black Widower is displayed with the DTS outside Dallas Terminus.