compound locomotive
Enable an agent to recognise a compound steam locomotive, assess its staged-expansion machinery and operating state, and identify evidence required before recommending operation or intervention.
Bundle → Layer → Finding → Questions Filled
6 bundles · 11 layers · 18 findings · 28 questions
Compound identity Establish what makes the registered kind compound and distinguish that identity from historical labels.
Successive expansion
Identify the working steam path that establishes compounding.
Stage-to-stage working
Record the connection through which higher-pressure exhaust supplies a lower-pressure working stage. A documented example is [Union Pacific 440 at Mid-Continent Railway Museum](https://www.midcontinent.org/equipment-roster/former-collection-items/union-pacific-440/); its particular cylinder arrangement is not a requirement for every compound locomotive.
- Which cylinders receive steam from a preceding working stage, and where does their exhaust go? definition
- Which drawing, technical description, or inspection establishes those connections? provenance
Configuration boundary
Separate the registered kind from class, unit, and configuration history.
Present versus historical compounding
Keep original classification, subsequent rebuilding, and present physical configuration distinct.
- Does compound describe the original design, the current installed machinery, or both? boundary
- What dated evidence establishes any conversion between compound and simple expansion? provenance
Stage and drive architecture Describe how cylinder stages exchange steam and transmit mechanical work.
Cylinder and interstage layout
Resolve cylinder geometry, stage roles, and connecting spaces.
Stage geometry and connections
Record cylinder dimensions and interstage arrangements without inferring a separate receiver or a fixed displacement ratio.
- What are the count, bore, stroke, and stage assignment of the cylinders? measurement
- How are successive stages connected, and which spaces act as interstage steam storage? definition
Mechanical output mapping
Connect stage output to the locomotive's driving mechanism.
Stage-to-wheel coupling
Map cylinders to driven wheel groups and record articulation independently. [Illinois Railway Museum's N&W 2050 description](https://www.irm.org/player/nw2050/) documents one arrangement with rear high-pressure and front low-pressure cylinders.
- Which cranks and driven axles receive work from each expansion stage? definition
- Are the stage-driven wheel groups mechanically coupled, and can their rotational speeds differ? boundary
Admission and mode control Represent supported steam-routing modes and their controls.
Starting steam path
Determine how the installed arrangement develops starting effort.
Starting assistance evidence
Identify any starting, reducing, intercepting, or bypass valves from the applicable documentation; do not assume every design has each device.
- What steam paths and valve positions does the documented starting arrangement provide? definition
- What documented limits and prerequisites apply before using that arrangement? action
Compound working control
Record how the locomotive enters and maintains its supported running modes.
Mode and cutoff coordination
Represent automatic or manual mode changes and the relationship between stage admission settings.
- How is transition into compound working initiated and confirmed on this design? action
- Which controls adjust stage cutoff, and how are their settings linked or constrained? definition
Stage performance evidence Assess staged expansion using operating measurements and comparable duty evidence.
Pressure and work distribution
Connect stage measurements to the conditions under which they were obtained.
Stage loading assessment
Record pressure measurements and available indicator diagrams alongside speed, load, and admission settings.
- What pressures or indicator diagrams are available for each stage and the interstage connection under the same operating conditions? measurement
- What design or test evidence defines acceptable work distribution between the stages? provenance
Comparable economy
Separate measured resource consumption from unsupported efficiency claims.
Duty-qualified consumption
Require stated duty and measurement boundaries before attributing an economy advantage to compounding.
- What steam and fuel consumption were measured, using which power basis, fuel specification, speed, and load? measurement
- Does the comparison control for superheating, boiler condition, route, and other changes that could explain the result? boundary
Compound condition and action Link condition evidence from compound machinery to maintenance and operating decisions.
Interstage and valve condition
Localise defects affecting steam transfer and stage control.
Compound circuit defects
Capture evidence concerning interstage leakage, valve sealing and movement, drainage, and lubrication at the relevant components.
- What inspection or test evidence identifies leakage, sticking admission devices, retained condensate, or inadequate lubrication in the compound circuit? measurement
- Which documented inspection or maintenance procedure applies to each suspected component? action
Operating release evidence
Connect compound-specific limits to the broader locomotive's authority to operate.
Stage protection and authorisation
Record documented lower-pressure circuit limits, installed protective provisions, outstanding defects, and applicable operator requirements without treating this model as an operating certificate.
- What pressure limits and protective provisions apply to the lower-pressure circuit in each supported admission mode? provenance
- Which inspections, defect clearances, and approvals are required by the applicable railway authority or operator before the proposed action? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these check these first hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these kinds and varieties hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these identifiers and schemes hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these real-world use hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these typical measurements hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these failure modes and hazards hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these regional variation hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of compound locomotive this model covers, and on what evidence? provenance
Classifiers Filled
- Family
- Thing Registry
- Category
- Physical world and living systems
- Entry kind
- thing
- Plane
- PHY
- Domain
- PHY.OBJ
- Other names and narrower kinds
- LNER Class W1, Saxon I M, RA class 500, BHStB IIIa5, CP 261 to 272, CP 351 to 370, Norte 4601 to 4656, SJ Tb, PO 4001 to 4085, PLM 231.G, SCB A 2/4, PLM C.61 to C.180 → PLM 220.A.1 to 120 → SNCF 5-220.A.1 to 120
What it is Filled
A compound locomotive is a steam locomotive in which steam performs work by expanding successively in high-pressure and lower-pressure cylinders before being exhausted.
In scope
- Successive expansion of steam through higher- and lower-pressure cylinder stages
- Cylinder grouping, interstage passages or receivers, and connections to driven axles
- Starting assistance and transitions between supported steam-admission modes
- Stage-specific performance, condition, maintenance needs, and operating restrictions
- Evidence distinguishing original compound construction, conversions, and present configuration
Out of scope
- General steam-locomotive construction, braking, running gear, and route compatibility except where compounding changes their assessment
- Boiler design, firing, fuel supply, and pressure-vessel certification as independent subjects
- Stationary and marine compound steam engines
- Simple-expansion locomotives without successive cylinder expansion
- Manufacturer histories, locomotive-class catalogues, and individual vehicle biographies
- Railway timetables, train operations, and infrastructure management
Why it exists Filled
Enable an agent to recognise a compound steam locomotive, assess its staged-expansion machinery and operating state, and identify evidence required before recommending operation or intervention.
Distinguishing features Filled
- Confirm a designed working path in which steam exhausted from a higher-pressure cylinder stage performs further work in a lower-pressure cylinder stage; multiple cylinders alone do not establish compounding.
- Identify cylinder stage roles from steam connections and design evidence rather than cylinder count, external appearance, or the word compound in a name.
- Record articulation separately: an articulated frame does not by itself demonstrate successive steam expansion.
- Distinguish steam superheating from compounding by checking whether steam passes through successive working cylinder stages.
- Separate permanent conversion to simple expansion from temporary starting or other supported modes that alter steam admission while retaining compound machinery.
What robots and AI may and may not do Filled
Must not
- Operate or fire a steam locomotive without a qualified crew and a valid boiler certificate.
- Advise running a boiler whose safety valves, gauges or water level controls are faulty.
- Confuse compound working with simple expansion when describing a locomotive's design.
- Present a restored or rebuilt locomotive as wholly original without saying so.
Only with a human decision
- Returning a preserved locomotive to steam after inspection.
- Disposing of or scrapping a historic locomotive.
May
- Describe a compound locomotive's cylinder arrangement and history from railway records.
- Record condition and inspection findings for a preserved locomotive on its keeper's instruction.
Moral aspects Filled
- Steam boilers store large energy, and a failure can kill crew and bystanders.
- Surviving locomotives are railway heritage that cannot be replaced once lost.
Who is affected
- Locomotive crews
- Passengers and visitors at heritage lines
- Heritage railway volunteers
Owners Filled
Steward
The owner or heritage operator who keeps it; the railway safety authority regulates its running.
Master systems
- National railway vehicle registers
Links to other meta-models Filled
parent
- Q171043 - registry parent class
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.compound-locomotive
- Wikidata: Q617792 (https://www.wikidata.org/wiki/Q617792)
Direct properties required Filled
- Expansion-stage topology: Directed connections from steam supply through identified cylinder stages to final exhaust
- Cylinder allocation and geometry: Cylinder count per stage; bore and stroke in mm
- Interstage connection: Receiver, direct connecting passages, other documented arrangement, or unknown
- Cylinder-to-drive mapping: Each cylinder group linked to its crank, axle, and mechanically coupled wheel group
- Steam-admission mode: Compound working, documented starting assistance, documented simple working, isolated, or unknown
- Stage pressure evidence: kPa with gauge or absolute reference, measurement location, operating condition, and timestamp
- Valve timing and cutoff relationship: Common, linked, independently adjustable, other documented arrangement, or unknown; cutoff values as percentage of piston stroke
- Duty-normalised consumption: Steam in kg/kWh; fuel in kg/kWh with fuel specification and indicated or drawbar power basis
- Compound-machinery condition: Inspected serviceable, restricted, defective, isolated, unassessed; component-level evidence required
- Configuration lineage: Dated links to original design, rebuilding records, conversion records, and present inspection
Recognition required Filled
- Cylinders of visibly different sizes, the larger ones for low-pressure steam.
- Extra steam pipes linking the high-pressure exhaust to the low-pressure cylinders.
- Often four cylinders, with some inside the frames and some outside.
Capabilities and actions required Filled
- Classify a documented locomotive by tracing its staged steam path and identifying contrary evidence.
- Map expansion stages to cylinders, controls, interstage components, and driven wheel groups.
- Check whether recorded pressures, valve settings, and operating mode agree with the applicable design documentation.
- Compare consumption or stage output only after aligning duty, measurement basis, and configuration.
- Identify inspections needed to investigate interstage leakage, admission faults, or unequal stage performance.
- Determine whether evidence supports a proposed operating or maintenance action and refer unresolved authorisation to the responsible operator.
Hazards and failure modes required Filled
- Boiler failure releasing steam and scalding water.
- Scalding and burns to crew from steam leaks.
- Lineside fires from sparks and hot ash.
Standards and interfaces required Filled
- The United States Federal Railroad Administration issues 49 CFR Part 230, Steam Locomotive Inspection and Maintenance Standards, which applies to compound steam locomotives operating within its scope.
Context of use required Filled
- Compound locomotives are encountered in railway history, museum collections and heritage railway operations.
- Their successive steam-expansion stages were intended to improve steam economy during railway haulage.
Sources Filled
- Wikidata item Q617792: compound locomotive - identity and sense of the item
- Wikipedia: Compound locomotive - general description of the item
Open questions
- Does the registry intend compound locomotive to include experimental expansion arrangements beyond conventional high- and low-pressure cylinder stages?
- Does an existing Vercy world model already own this concept or its steam-locomotive parent, requiring a link rather than a second publication?
- Which primary manuals and drawings establish the cylinder arrangements, starting systems, and mode restrictions across the principal compound design families?
- What defensible ranges of stage displacement ratio, pressure, and consumption can be stated by design family and duty without implying universal values?
- Which jurisdictional rules and operator procedures govern present-day operation of surviving examples, and what compound-specific inspection requirements do they impose?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q617792/spec.json