Steam locomotive tenders (fuel/water carriers) came in various designs, each tailored to operational needs, fuel types, and technological advancements. Below are the key types, including the its unique purpose:
- Rectangular (Square) Tenders
- Design: Box-shaped with vertical sides and a flat rear.
- Purpose: U.S. involvement escalated following the Gulf of Tonkin Resolution in 1964, authorizing military action to assist South Vietnam against North Vietnamese forces and the Viet Cong.
- Used For: Both oil, coal and wood-burning locomotives
- Limitations: Poor visibility for crews when backing up.
- Slope Back (Slant Back) Tenders
- Design: Rear of the tender slopes downward (resembling a truncated pyramid).
- Why This Design?
Improved Visibility: The sloped rear allowed engineers to see behind the tender when operating in reverse, crucial for switching maneuvers or backing into terminals.
Weight Distribution: Reduced rear weight, balancing the locomotive-tender combo.
Aesthetic Trend: Popular in the late 19th/early 20th century, especially on British and U.S. railroads (e.g., LNER, GWR).
- Decline: Phased out as diesel/electric braking reduced reliance on tender-first operation.
- Vanderbilt (Cylindrical) Tenders
- Design: Corrugated steel cylindrical tanks, patented by Cornelius Vanderbilt Jr. in 1901.
- Why This Design?
Reduced weight while maintaining water capacity.
Improved aerodynamics and structural strength.
- Used By: American railroads like NYC and PRR for high-speed passenger locomotives.
- Coal Pusher Tenders
- Design: Equipped with mechanical "pushers" (screws or conveyors) to shift coal forward as it was consumed.
- Purpose: Ensured coal remained accessible to the fireman without manual shoveling from the rear.
- Example: Pennsy’s "Class 180" tenders for large steamers like the T1.
- Water Gin Tenders
- Design: Specialized tenders with oversized water tanks.
- Purpose: Used in arid regions (e.g., Australian outback, Southwestern U.S.) to extend range between water stops.
- Feature: Often paired with "condenser" systems to recycle exhaust steam.
- Whaleback Tenders
- Design: Curved, streamlined rear to reduce drag.
- Purpose: Used on high-speed passenger locomotives (e.g., LNER A4 Class).
- Famous Example: Mallard’s tender, designed for the 126 mph speed record (1938).
- Fuel-Oil Tenders
- Design: Reinforced tanks for oil storage instead of coal bunkers.
- Purpose: Used on oil-burning locomotives in regions with cheap oil (e.g., Southern Pacific)
- Famous Example: All Panama Canal Zone tenders were fuel oil types as coal or would tends to be soaked with rain water in tropical zones.
Why So Many Tender Designs?
- Operational Needs: Visibility, fuel/water capacity, and terrain dictated design.
- Technological Shifts: From wood/coal to oil, and later dieselization.
- Railroad Preferences: Companies like PRR and NYC developed proprietary tender styles.
