Re: BLW Sequence # & Construction #

8-18C is a class of Locomotive. A 4-4-0 with 12" Bore.
Reguardless of Guage, or Drawing #, all 8-18C locomotives are sequenced in order 1,2,3,4,etc. This number is assigned at time of Purchase. Engines ordered in batches will recieve sequencial Class Numbers. Engines added to an existing or previous order will recieve the next unassigned Class Number.
Construction numbers, as found on builders plates, were assigned at time of completion (as in just before shipping them out the door). Locomotives built in batches were given sequential construction numbers. Engines built to the same Specs, or Order, but built at different times will have non-sequential construction numbers.
Clear as mud eh? " />
"I am also told that the Baldwin class system started with an early identification system and then had to modified to allow for different lead and trailing trucks, etc. " - Brian
That would appear to be the case. In looking at work orders from the 1870s through the 1920s you can see the degredation of the Class Syetem over time and how they had to modify it. Such as you mention in the case of Trailing Trucks.
Originally the Class Number was the number of Wheels, and the number of Drivers, what was left over was for the Engine (Lead) Truck. Trailing Trucks required the addition of the 1/3 (No Lead Truck) and the 1/4 (Lead Truck and Trailing Truck).
The 1/2 indicated a Special Order: Bigger boiler and/or Longer Stroke and/or Over Sized Cylinder Bore than standard for a particular class. There were 8-18 1/2-C class engines built with extra long strokes, but have sequential Class Numbers with the other 8-18Cs.
The Pacific Coast RR 2-8-0s all had "1/2" added to there specs for a special order in that their cylinders were over-bored for their class.
And espically when the compound artuculated engines showed up things got really confusing!
It's one of those thing you just have to accept and move on. " />
Cheers,
Curtis