The new Kalmbach publication “In Search of Steam” mentions locomotives that have recently undergone “class 5 repairs.” What did this involve? I assume that there were class 1-4 repairs as well and am wondering what those consisted of too.
The following list is based on AAR descriptions from 1924. There are slight variations depending on the individual railroad
Class 1
New boiler or back end
Flues new or reset
Tires turned or new
General repairs to machinery and tender
Class 2
New firebox or one or more boiler shell courses new, or wrapper sheet new
Flues new or reset
Tires turned or new
General repairs to machinery and tender
Class 3
Flues new or reset (superheater flues may be excepted)
Necessary repairs to firebox and boiler
Tires turned or new
General repairs to machinery and tender
Class 4
Flues part or full set
Light repairs to boiler and firebox
Tires turned or new
Necessary repairs to machinery and tender
Class 5
Tires turned or new
Necessary repairs to boiler, machinery and tender including one or more pairs of refitted driver bearings
General Repairs to Machinery
Drivers removed
Tires turned or changed
Axle journals turned if necessary
All driving wheel boxes and rods overhauled and bearings refitted
Other repairs needed for the locomotive to perform a full term of service
Thank you for the excellent answer. No wonder railroads had such extensive shop facilities during the steam era!