‘N7’ overhaul takes a leap forward at EARM
THE return to steam of the sole surviving ‘N7’ 0-6-2T moved a step closer at the East Anglia Railway Museum (EARM) on
July 1, following the dispatch of the boiler to contractor HBSS in Liverpool.
Dismantling of the loco, which last ran at the Churnet Valley Railway in April 2015, commenced at the end of June 2020. The work is primarily being undertaken at the EARM’s Chappel & Wakes Colne site by younger volunteers, with support from those who’ve worked on it previously.
“As with the restoration of any steam loco, the boiler is the key. Unfortunately for the ‘N7’, a lot of work is required on it,” Michael Sanders, EARM locomotive manager told The RM.
“There is some minor building up to do on the front tubeplate and we’re relatively pleased with the condition of the barrel. It’s gone into the HBSS workshop to have the firebox split from the barrel.
Firebox removal
“Unfortunately, the inner firebox will have to be removed from the outer firebox to give us a good look at the copper inner firebox on it. There is hope that the inner ’box could be saved, but if not, that’s another hurdle we’ll have to look at. The quotes are tailored to plan for the worst and hope for the best.
“The outer wrapper is thin on the sides and the backplate is cracked. Other than the throatplate, the majority of it will need to be replaced.
“However, the way I look at it is that in the worst case scenario, we’ll have a new copper firebox and new outer firebox, meaning we can go back to smaller stay sizes.
“Over the 50 to 60 years that the boiler has been in existence, they are getting to a point where they’re at maximum size.
“Our aspiration is for the boiler to not require major surgery in the next 20 to 30 years – apart from new tubes, etc.”
On the chassis, a known issue was the valve timing. After the removal of the spindles, the front bobbin on the forward ring didn’t exist; the remains were found at the front of the cylinder. This was suspected as the cause of the poor timings during the loco’s final few weeks in traffic. All the valve pistons and rings will be replaced.
Discussions are in hand with South Devon Railway Engineering to make a new set of rings.
“The rest of the chassis is very much work in progress,” explained Michael. “We’ve cleaned most of it up and checked the tolerances all over.
“The eccentric straps and big ends have received attention.
“It’s a case of reassembling the motion in a systematic way.”
Livery update
Most of the exterior paintwork has been done, including the frames and tanks. It was felt that a nice touch would be to complete that while things were relatively quiet in the workshop.
“The loco will return into traffic painted postwar unlined LNER black as No. 9621, which it received after the Thompson renumbering scheme in
1946,” Michael said. “This is appropriate as the locomotive was rebuilt into its current guise as an N7/4 with the round topped firebox at that time.
“We have no aspirations for it to run on the main line again. It’s no longer viable to operate another less than a Class 5 as the paths won’t be available. It will go out on short-term hire to heritage lines.”
While timeframes are notoriously challenging to predict, Michael said he is confident a rolling chassis will be ready to receive the boiler by the end of this year, subject to further Covid-19 restrictions.
The project has benefited from ringfenced funding but more is required. It is hoped the loco could return within two years.
■ Donate at www.earm.co.uk/ n7_resto_appeal/