5 inch gauge LNER L1 2-6-4T

An exceptionally well made LNER L1 2-6-4T, Thompson's wartime design intended to augment the V1 and V3 tanks designed by his predecessor Gresley. New and unsteamed, it's come to us direct from the builder.

Constructed to the highly-regarded Clarkson design, standard of workmanship is excellent throughout. Machining is crisply done, "fit and finish superb" according to the workshop notes. The British Railways lined gloss black livery has been applied to an exhibition finish.

The silver soldered copper boiler is a beautifully made thing, we've hydraulic tested it and issued certification for same. Fitted with four radiant superheaters, it's a mark of the builder's attention to detail that the elements are individually removable if required.

The engine ran very quietly on air in either direction with some leakage past the PEEK piston rings when cold - when hot, it was a different matter...

Given the new and unsteamed condition, rather than put a fire in it and risk damaging the paintwork, we ran the engine from a remote test boiler. All was well for the first few turns of the wheels, whereupon everything came to a juddering halt as the piston rings expanded in the presence of steam, locking up the piston on one side and, in the process, shearing a small pin in the valve gear.

Whilst PEEK is a material we know - it's a tough engineering plastic - it's not one we've seen used in this application before. PTFE is the preferred choice for rings if you want to go all high-tech, although we still prefer cast iron rings on grounds of dimensional stability, longevity and reliability.

The engine now needs stripping, new rings making and fitting, then reassembling. Inexpensive in material, but a time-consuming, fiddly job, particularly given the immaculate state of the paintwork.

Complete with drawings and a purpose built storage crate.