Recently I admitted to being no fan of diesels - I now am hoping to get a little more edumuckated about them and am hoping some kind soul could explain the CO CO and BO BO terminology when referring to same.
I can just see some chaps giggling behind their hands at my ignorance! But no matter - if I dunno sumpin' I akss.
Just to expand on that a bit further, the "o" means that each axle is individually powered, so a class 47 with each axle driven by a separate motor is a Co-Co, whereas a Western, with the same number of wheels driven, is a C-C because the axles are linked together within each bogie.
It's an alphamumeric code for how the wheels are laid out, and it'll work for anything, not just diesels: an example would be a Gresley A4 or Stanier Duchess, either of which would be a 2C1. A Riddles 9F would be a 1E.
Carrying axles get numbers: 1 carrying axle gets a 1, 2 get a 2 and so on. Driving axles get letters. One driving axle is A, two together B. three C. If they have individual drives (electric motors, individual single-action steam engines, hamsters in cages..) they get an o suffix, e.g. Bo If two groups of drivers (each in a single frame, such as a bogie) have a direct coupling between the bogie frames (ie. not through the bodyshell or underframe then there's a "-" between the groups. There's also a "+" linker, but I can't remember off-hand what it represents.
So... A Stirling 8' single would be 2A1 A Midland 4F would be C (like an 08 diesel shunter) An LM&S Beyer-Garrett would be 1C C1 (and a Peak-type diesel 1Do Do1 And the MR Paget locomotive (with steam motors on all axles) would be 1Co1 :)
On reflection, "+" denotes a separate driving group in an entirely separate frame, linked through a coupling? So a steam example might be that mobile parade of steam machinery. Harrison's 'Hurricane' on the GW in the early days: 1A1+3, while a more modern and electric example could be the Swedish Dm3s: