Scores are relative 0–100 marks within this atlas. Use them to browse, not as an engineering spec.
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Quick answers
Which local authority or corridor rules matter for this type?
Start with the local lens: type approval, operator licences and the hubs named on this page — not a single global checklist.
Is this a buying guide?
No. Tool-Lifes /vehicles is an educational atlas. It explains history, systems and culture without affiliate rankings.
Are the scores official?
No. The six scores are relative editorial 0–100 marks across the 48 types on this site.
Where do the photos come from?
Lead images resolve from Wikimedia Commons via Wikipedia titles on the English masters, with licences recorded on the credits page.
Why metric units?
Metric is the default. Regional notes (US customary, local brand culture) appear in culture and market chapters.
How is this different from a wiki article?
Each type gets seven fixed-depth chapters, comparable scores and cross-type labs — structured for browsing, not a single freeform page.
Every Steam locomotive is a negotiated stack of structure, energy conversion, control and human interfaces under weather and regulation.
The systems, meters and hotspots below are type-level engineering — manufacturers vary; load paths and failure modes do not.
Systems
Boiler & firebox
Firebox tubes transfer heat to water-steam; pressure vessel ratings govern working steam pressure.
Reciprocating steam engine
Piston and crosshead convert steam expansion into crank rotation via Stephenson or Walschaerts valve gear.
Regulator & cutoff
Driver controls steam admission timing and cutoff for efficient expansion versus starting torque.
Cab instruments
Pressure gauge, water glass, and injectors dominate human feedback—no electronic aids.
Safety valves & fusible plugs
Pop valves vent overpressure; fusible plugs melt if water level exposes firebox crown.
Tender coal & water
Fuel and feedwater capacity set range; injectors and pumps maintain boiler level while moving.
Relative meters
Hotspots
Firebox stays
Broken stays leak and weaken shell—requires immediate out-of-service repair.
Tube plate cracking
Thermal cycling at throat sheet leads to costly boiler work.
Valve gear wear
Sloppy linkages cause uneven power and excessive coal use.
Driver tire shells
Hollow wear and thermal shells cause rough riding and flange stress.
Injector clogging
Poor feedwater treatment blocks injectors on grades.
Materials
Firebox copper stays
Conduct heat while tying inner and outer firebox sheets.
Wrought iron/steel boiler plate
Riveted or welded shells per historic construction era.
Graphite lubricants
Cylinder oils tolerate high steam temperature interfaces.
Bituminous coal grades
Heat content and clinker formation affect fireman workload.
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