Classification
Classification is complex. The NER initially classified these locomotives "M1" while a variant (with compound expansion) was classified "M". The compound was later re-classified "3CC" and the "M1" was re-classified "M".
Under LNER ownership the "M" (formerly "M1") became LNER Class D17/1 and the "3CC" (formerly "M") became LNER Class D19.
This table summarises LNER classes D17, D18 and D19, which were all very similar:
| Original NER class | New NER class | LNER Class | Cylinders | Driving wheels |
|---|---|---|---|---|
| M1 | M | D17/1 | (2) 19″ × 26″ | 7′ 1¼″ |
| Q | - | D17/2 | (2) 19½″ × 26″ | 7′ 1¼″ |
| Q1 | - | D18 | (2) 19½″ × 26″ | 7′ 7¼″ |
| M | 3CC | D19 | HP (1) 19″ × 26″ LP (2) 20″ × 24″ |
7′ 1¼″ |
- HP = high pressure cylinder, LP = low pressure cylinders
Read more about this topic: NER Class M1