'Peninsular & Oriental S. N. Co.'   -     A Southern 'Spam Can'.

An Original Merchant Navy class built by John Cottam.

My working life started in a textile engineering factory aged 15, working on industrial size knitting machines up to 80 feet in length for S. A. Monk Ltd. of Sutton-in-Ashfield.

I learnt to assemble, repair and install them around the world, and now that the original manufacturer has gone, I have spent the last 10 years self employed, maintaining these 'fully-fashioned' knitting machines.

As a result of needing to make parts, my workshop contains a Bridgeport milling machine, Colchester Student lathe, Myford M lathe, Centec 2B miller and a small surface grinder.

My interest in model engineering came from my father, the village plumber, who built a 1.25" scale traction engine, and also the Great Central Railway line ran through the village.  Plus, Sam Monk (my ex boss) had a 10.5" track around his garden and 3 or 4 locos, one a Duchess.

For many years I was away from home too much to get involved, but then I did build a 3 1/2" gauge Britannia, which gained a silver award at London, and a 1st award at the Midlands and Harrogate exhibitions.

I always wanted to build a Gresley 'P2' but felt I did not have enough time; then in 1997 I was offered a part-built Merchant Navy which I thought it would be a time saver.

In hindsight that was probably the worst thing I ever did, as I have ended up stripping it right back !  The assembled chassis had been constructed with Marshall valve gear, a steel boiler with boiler casing and a cab.

As I had no drawings to work from I bought a number of MN books to study.  I constructed a new boiler to the correct outline based on the design of a Britannia boiler, but modified for three central safety valves and twin top feeds; it has 3 superheaters which are radiant, 32 tubes and a small combustion chamber.  The firehole door was made 1/4" wider and 1/8" taller to allow easy firing with a large shovel of coal, so I can easily feed all areas of the fire.

The cab was completely re-made to fit the new boiler, as were the casing sides and top.

As I work in an industry where accessibility is critical, I used the same idea on the loco.  So the casing top is secured by two thumb screws under the smokebox front cowling, and at the back this clips under a lip on the cab front.  Similarly the side panels include 2 pegs on the rear which locate into the cab front, and the front of each side panel slots in and is secured by a single screw.  The 3 three panels can be removed and refitted in a couple of minutes, allowing easy access for oiling up and inspection of the valve gear.

The tender body is steel plate with brass inside, and has an inner coal tray made from acrylic sheet which can be lifted out; there is also a generous cut out at the front to allow good access to the cab for driving.  The vacuum tanks on the tender are dummies.

On first steaming the loco it was obvious that the valve gear was hopeless, so I stripped the whole lot off and threw it in the dustbin.

I have a friend who used to work in the B.R. drawing office at Derby, and together we worked out a new version of the Marshall type valve gear, chain driven of course.  This allows the loco to be notched up to 30%, and on the track this performed must better.

A drip feed under the casing keeps the chain and other valve gear components lubricated, but although mine does not have a sealed oil bath, there is a large sump tray which catches oil drips - otherwise I would be in trouble for dumping oil on the track.

Lubrication of the cylinders is by a home-made hydrostatic system with triple sight feeds and individual valves, with distribution pipes running behind the right hand side of the casing.  The sight feeds were originally fitted with plastic tubes but after a blow back the temperature of the flames melted one of them, so now they're all been replaced with glass !

The steam operated brake has a limiting valve to stop the driving wheels from locking up.  The reverser is a screw type gearbox in the cab operating a reach rod, with a lock to stop it creeping while in motion.

As I have an artificial hip I have fitted this and the regulator with extension handles, and can drive most comfortably.

Being from the North, I don't really like Malachite green, but during my research I found that the MN was painted in two experimental shades of blue.  I rather liked one and took it to a local automotive paint supplier, who matched my preferred choice to a BMW sports car colour in synthetic enamel, in which the loco is sprayed.  The name plates were made for me by Diane Carney.

Well, the loco was sort of finished in 2004, but it has taken a further 3 years to get it all working satisfactorily . . .

Specification of '21C6'
Cylinders :	3 cylinders, each 1.5" bore x 2.125" stroke. Cast iron pistons - 2 C.I. rings in each.
Piston Valves :	Phosphor bronze liners / stainless bobbins. Inside admission - Outside exhaust 0.860" o.d.
Valve Gear :	Modified Marshall valve motion, chain driven.
Steam Brakes :	From 2 cylinders with limiting relief valve to stop the wheels locking up.
Boiler Water Feed :	2 x injectors 22oz; plus axle pump with bypass valve.
Reverser :	Geared screw reverser in cab with a lock.
Lubrication :	Own design hydrostatic lubricating system, with 3 sight feeds (one for each cylinder)
Boiler :	All copper, silver soldered with combustion chamber. 32 fire tubes & 3 radiant superheat tubes.
Whistle :	2 note chime at side of boiler over wheels
Regulator :	Sliding type fitted under dome

 

The next problem was that of adhesion, or rather lack of it, and I worked out there was a problem with way the leaf springs were hung on angled brackets.  In certain situations the axles boxes would lock up, stopping the even distribution of weight.  So back to the dustbin and I fitted 2 vertical coil springs to each axlebox, this has been very effective and now the wheels all sit down and the loco pulls well.  In balancing the loco I found it to be tail heavy, so there are additional ballast weights located in the bottom of the smokebox.

Running on the steep gradients of my local club track at Chesterfield can knock the pressure back quite dramatically whilst pulling a few heavy trucks, so I need to keep a good fire and under 50 psi the injectors won't pick up.  So last year I installed a double acting pump driven from an eccentric fitted around the rear axle.

The latest modification is a reduced size drop-in chimney, retaining a spark arrester mesh cage.  This is working together with a modified blast arrangement that allows me to try different size nozzles.  I have gradually been reducing the size, and found that the five 5/32" nozzles seem to give the best results for consistent hauling.

With the loco all sorted, a most pleasing loco it is to drive, though like it's full size counterpart, the MN is quite heavy on coal.

So now it is time to start on that 'P2' !

Editor's note: John's beautiful P2 is also finished and was IMLEC winner in 2014 and 2015...