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A web-site by Rob Speare


A rebuilt Merchant Navy class 35006 in 5" gauge
- as someone wrote, not for the faint hearted.

An article by Kevin Neate - Part 1 


The first 5" loco I made was a King class to the James Perrier drawings, started in 1986 with castings supplied by Norman Spink.  The drawings gave all the information needed, the castings were fine and I first steamed the King in 1989, finishing it a year later.  In between, I joined Stockport model engineering club so had use of their raised 5" track and ran the loco for many years.  Why a King ?  It is a lovely looking loco !

However, near to where I went to school in South Wales was the famous Barry scrapyard, and I went there many times and always liked the huge locos with the unusual wheels.  So the next loco had to be a Bulleid pacific, and in 1996 I decided to build a 5" gauge Merchant Navy.

All the info seemed to be out there in the form of Keith Wilson's articles in Model Engineer, and drawings and castings available from MJ Eng.  I got on with it and made the frames, bogies, boiler, cylinders and an assortment of other parts, but did not assemble much of it as there were too many unknowns.  Then I ventured into 7¼" and built 2 Bagnalls to the MJ Eng design, and abandoned the MN.

After that I restored a couple of old cars, then moved back to Wales and started renovating old houses, before building my own house, then built two more houses, and since have continued doing building renovations.  Hence the MN sat rusting under the bench from 1998 until now, when I seem to have a bit more time !

What did I do originally ?

I made the boiler first.

For me the easy bit having made several copper boilers before, and with the wide firebox it is easy to get at inside.  The Ariel design is fine and a good representation of the original, although the throatplate is incorrect but can easily be disguised by the boiler cladding.

As with most model engineers there is a need to keep the cost down !

I made the boiler for my 5" King from a 1/8" gauge 12" diameter copper tube 6 ft long, bought from a scrapyard in Scotland for £20.  This came from a WW2 ship and had been lying there for many years.  After making the King boiler there was plenty of the copper left to make the MN boiler.

The formers were made from steel cut by DJ Profiles in Stockport, and finished to shape with the good old angle grinder.  The inner and outer wrappers were formed over a piece of 2 ft narrow gauge rail.

I fitted the superheater tubes as per drawing, but modified the flue tubes as I happened across a surplus quantity of new copper tube 11/16" OD x 16 swg going free, so pitched the flue tubes accordingly.

The flue tubes were fitted to the combustion chamber with high melting point silver solder, as was the tubeplate to the inner firebox.  This was blanked off and pressure tested as a separate sub assembly before fitting to the outer shell.

Not a difficult boiler to make, passed the hydraulic test 4/6/96 and stamped N4 100 - 312.  It remains to be seen how well it will fit the loco.

Next I made the front bogie.

All the info appeared to be there and I bought the centre casting from MJ.  I already had the wheels – see later.  Pretty straightforward until on finishing it I found like many others, that the housing for the spring guide was supposed to be horizontal not diagonal and had to be altered.

Then the bissel truck using the cast frame version – it looks better to me than the fabricated type.  I had to cut, bend and re-weld the centre ribs to give side swing.  The axle boxes were severely altered removing the outer flange and fitting a separate bearing cover to look like the full size.



The shape of the frames as shown on the KW drawings is pretty much correct, when compared to the full size frame drawing W11520 that I acquired later.  I made the frames next and all the lower wheel stretchers.  All I can say is watch where you drill the holes !!!!

The frames were cut from 3mm steel the old fashioned way before laser cut frames became readily available.  I drilled all the holes I could identify from the KW drawings, and left out the rest until I was certain what they were for.  Some of the holes turned out later to be incorrect, and were filled in with rivets.


At first glance the various brackets that are fitted to the frames look a frightening prospect.  They are, but when you get on with it they are just plain fiddly.

The detail bits were cut from sheet steel with a bandsaw and tack welded with an automotive MIG welder, before being silver soldered or brazed with SIF bronze using oxy propane.

I thus got on and made the various fabricated brackets as per the KW drawings in ME without too much difficulty.  What I did not realise until much later is that some of them are far from correct.  The spring support brackets worked out OK as did the drag box and front buffer beam, so these were riveted to the frames along with the stay over the rear axle.

The motion and slidebar brackets were more difficult.  I altered the outside motion bracket to the MN shape rather than the West Country/BoB design.  These brackets could not be fitted to the frames at this stage.

I abandoned the reverser bracket when part made, the opposite brake hanger/platform bracket came out OK.  There were also two more stays over the middle axle that seemed to be missing with no detail on the KW drawings.


As previously mentioned, I abandoned the MN for a long time as my interest turned to 7¼" gauge, and I made two 7¼" Bagnalls to the MJ Eng design.  Another story but I had previously made 3 steel boilers for others building Bagnalls at the time.  Two of these gave up and I was left with 2 surplus boilers that sat in my workshop for a long time.

The only solution was to make the engines to take the boilers.  Thus I made the two 7¼" Bagnalls.  One I kept and have run it hard for 18 years, the other I sold.

The castings for the Bagnall are very expensive, so I bought very few and fabricated everything else from steel, with parts cut by DJ in Stockport.  All except for the cylinders !

For these I bought a piece of top quality cast iron about the size of a 4" concrete building block, from a stockholder in Bolton for £70.  From this I made the four Bagnall cylinders, machined from the solid.

There was just enough left to make the MN cylinders.  Only just, as I had to carefully cut the metal to get the best from it.  Even then there were a few areas of surface porosity but they machined up OK, and the rough bits are hidden !

These were machined on an Elliiot Omnimill combined horizontal and vertical mill, a great machine as much can be done at one setting.  When you consider the amount of machining on a cast cylinder there isn't much difference in time if machined from solid.  I made an error on the outside cylinders with the inlet steam ports but there is a way out.  I then made all the pistons, valves, covers etc. as per the KW drawings with no apparent problems.

Wheels, axles and coupling rods

A club member at Stockport ME is a lecturer in foundry technology.  He had acquired one of each type of MN wheel casting.  From these he had made several sets of very high quality MN wheel castings at £100 per set, a great saving on the full price !

These machined up beautifully but did not have the undercut, very prominent on the full size wheels.  I modified two angled milling cutters by grinding off part of the flutes so as to form a guide similar to a router cutter; a small cutter for the bogie wheels, and a larger one for the driving wheels.  I didn't undercut the bissel or tender wheels as the undercut cannot be easily seen.

KW showed 2 types of crank axle, one with webs and one without.  I mistakenly made the one without the webs.

The crank axle was welded together and ran true afterwards, so rather than scrap it I made webs to suit from cast iron and attached them to the plain webs using hidden screws; and a bit of car body filler to hide the joint.

The driving wheels were quartered using a rotary table, and loctited in position.  These were then pinned from behind, as other driving wheels I had loctited previously on other locos eventually came apart.

The coupling and connecting rods were machined from black mild steel as per the KW drawings, omitting the flutes on the coupling rods.

I also made the main leaf springs, easy to make but a fiddle to fit and to make them work; I had to slot the holes in the stays and make spherical washers to fit under the retaining bolts.  Loaded with 5 concrete blocks (about 200 lbs) on the chassis, there seems to be just about the right amount of bounce !

That was about the sum total of the build up to sometime in 1998 when I put it to bed.

Restarting the Build

A while after I stopped work on the MN, a club member at Stockport MES lent me some drawings he had rescued from Brighton Works in the sixties - genuine BR works drawings of the MN rebuilds.  Some of these are huge and I had them photocopied at the full size. 

Last year I was talking to someone about model locos and the subject of my part built MN came up, so I got it out from under the bench for a look.  Considering how long it had been there it wasn't in too bad a state, a bit grubby and a bit of surface rust here and there.  Hence I decided to take it all apart, clean it up and get on and finish it !

But where to begin again ?

From here on I hope to give an update on progress, provide a few details of what I have done and add to the site as I proceed, and hopefully this will assist others with their build.

The first thing I did was to dismantle the chassis as it stood, and clean it all up together with all the other bits I had made.  Obviously it was essential to complete the frames with all the stretchers, brackets and other bits that support the boiler and cab etc.  This has turned out to be quite a long and tricky process and has shown up many problems !  As far as I can tell, the KW drawing set does not include a frame assembly drawing, so I turned to the full size drawing W11520 for the frame assembly and several things became apparent.

Firstly it is important to get all the brackets and fabrications that support the platform plates at the same height.  Secondly this drawing gives very few dimensions apart from the positions of the holes in the brackets that carry the expansion links, weigh shaft and the swinging link on the slide bar bracket.  The full size drawing is dimensioned to 3 decimal places in some cases, so I conclude the designers considered these sizes important.  Thirdly the drawing shows various other stretchers and brackets not given on the KW drawings.  These are a stretcher over the centre driving wheels, a cover plate, a series of platform support brackets, and 4 brackets between the driving wheels that must be some sort of side guides for the brake levers (I think).  As well as these there are some angles at the front that support the plates below and in front of the smokebox.  As we all know now, the KW fabrication drawings are part MN and part BoB/WC, and part wrong !

Then I measured the widths of the stretchers I had made but not so far fitted.  Not exactly 3½" wide to go between the frames and a bit distorted as well, due to heat from fabricating.

I had made the frames as per the KW drawings and drilled most of the holes shown.  I drilled the holes in the fabricated bits as per the KW details.  They don't exactly line up !  The other point not clear is which of the brackets etc. are riveted to the frames and which are bolted.  I couldn't find an answer so riveted the lower frame stretchers as hopefully they don't need to be taken off again.  The others are nuts and bolts so can be removed for other work.

I started on this phase of the build by making a gauge with a 17/64" step over the frame top to set up any of the bits that the platform plates sit on.  Using the gauge the brake hanger/platform bracket opposite the reverser was spot on.  As for the rest don't ask !

Ian Tiplady has detailed the platform brackets in his articles.  I made all the bits as he described but alas melted the whole lot when trying to braze it together, so gave up and made the outriggers from solid and brazed these to the back plates.  Using the gauge I set these to the correct height and drilled the fitting holes.  The rear ones fit over the centre driving wheels using the four holes beneath the semicircular cut out.  The front ones fit in front of the smoke box, and line up with the saddle mounting holes.  At the same time I made the cab supports as per Ian's drawings.

The inside motion bracket caused me a lot of grief !  The fabrication was made 20 years ago and never fitted but the mounting holes were already drilled as per the KW drawings.  I checked the width and found it to vary, and be out of parallel.  Fortunately the long (LH) side was quite flat, so I clamped it on the miller and skimmed the small side flat and made a 20 thou shim to compensate.  On fitting to the frames the top of the bracket was well above the 17/64 height, so I dropped it down to 5/32 above the frames as the platform does not fit to it, and drilled and tapped new 7 BA holes.  Then I checked the position of the holes for the expansion link, too low and too far back from the centre line.  Also out of square.  The solution was to cut off the rear extensions.  The body was then fitted to a plate and a 7/16" hole drilled in the plate in the right place for the expansion link.  The extensions had to be shortened and were then fitted to the plate using spacers between the extensions all held in place with a 7/16" bolt.  I Mig welded them back on.  How this affects the position and angle of the inner cylinder slide bar will only be found out later – and it is not good news !

The outside motion brackets caused even more grief than the inside one.  When I made these I had already altered the expansion link mount to the MN shape, but alas not correctly and having set the pair of brackets up on the frames I found the weigh shaft bearing holes were out of line, out of square and out of position.  Believe it or not the expansion link bearings were in the same state.

Using the dimensions on the frame drawing and giving myself an allowance of 1/16" on the hole positions, I set up both brackets on my miller with a plate sandwiched between to try to get the weigh shaft bearing holes correct.  The outer bearing hole on the LH side was best so I had to get the inner hole and the RH ones in the same position.  The weigh shaft is 1/2" diameter and must go through all the bearing holes in a straight and square line.

Sometime in the past I had acquired a collection of 3 flute drills so put a 1/2" one through from the good hole that just touched the inner hole, and ended up using a 17/32" one to get the LH side in line.  As for the RH side this was too far out so I used a boring head to scrape out the bearing to eventually 3/4" and made two inserts soft soldered in and new bearing caps.  The weigh shaft on the LH side has 2 sleeves 17/32" OD and 1/2" bore to compensate for my mistakes !  As for the expansion link bearings they were way out as well.

Using the same process I cut off the offending bearing housings, and used the boring head to make new cut outs in the mountings to receive new bearing housings.  These I made like a bobbin with a centre section semi parted off that could be removed with a hacksaw once brazed into position, and hence keep the bearing housings in line.  Of course the tops of the brackets were too high above the platform plate line, so I sliced through them using slitting saws and bent the top plates down to the right place and then re soldered.


Cover plate.

This is a missing item on the KW drawing and fits to the long row of holes on top of the frames between the front and centre wheels.  I made this from a piece of 1/16 sheet steel folded at the edges and with various holes cut in it.  Dimensions were taken from the frame drawing.  The other missing stretcher is basically a box section with various cut outs fabricated from bits of 1/16 and 3/32 sheet, and fits to the holes behind the cover plate.

The outside slide bar brackets were again made long ago as per KW and the ring of holes on the mounting plates drilled.  Fortunately I didn't drill the holes in the frames.  I set these on the frames to get the 17/64 height and the holes for the swing bar in the correct place then drilled as many holes as possible through the frames.  The faces for the slide bars needed a light skim to get flat and square.  After setting up the slide bars I found the holes in the front edge of the mounting plate were impossible to get screws into and lay over the inner cylinder mounting holes, therefore some of the inner cylinder holes have to have countersunk screws that cannot be seen as they are hidden by this bracket.  From inside the frames I picked up two of the inner cylinder mounting holes and spotted into the back of the brackets so now the brackets are screwed through into the inside cylinder and the front row of holes ignored.

There were no real problems making the reverser bracket.  However I could not see how the die for the reverser screw could be fitted to the slides, so made the top piece removable and as before it was necessary to machine the bearing holders square and parallel to the mounting plate.

All done, took ages.  Take KW's drawings for all the fabricated brackets as a guide only.  The moral to all this is to make all the motion brackets in sections on a jig with the important holes in the correct places to line everything up, and leave a bit of surplus metal on where necessary to machine up after fabricating.  We live and learn.

At this stage I am satisfied that the frames are as correct as they are ever going to be.  The other thing to note is that on a finished loco with the platforms and boiler with its cladding in place very little of what is between the frames can be seen so don't worry about any errors or imperfections!!!!!  The platform plates cover a lot of the motion brackets as well.  One day I will make up a frame assembly drawing based on what I have done.

I have now painted the wheels, frames and brackets – 2 coats of grey car paint primer all over, 2 coats of semi gloss black car paint on the outside and 2 coats of red hammerite on the inside brush painted that looks a bit rough – just like full size !

So having done all of this I put the cylinders, saddle and other bits I had back on, then the smokebox and boiler, and presented it in the part built state for the Bulleid display at the 2017 Bristol show.

Since the Bristol show I have continued with the cylinders, slide bars, rods and crossheads.

As mentioned before I had made the cylinders from solid blocks of cast iron as the castings were a bit too expensive for me.  This requires a lot of machining but probably not much more than machining castings.  I left the outside cylinders in a part finished state as I had made a serious error on the steam inlets.  The inside cylinder is OK.

The cylinders were temporarily mounted on the frames for the Bristol show with the pistons and end covers in place.  Next is to align the outside slide bars on their brackets and so we need the crossheads and slidebars.  Again these were part made long ago and once again I made an error.  I had made all the crossheads as a stick and then cut it apart to give the three of them.  Alas I misread the drawing and cut off the "wings" on the outsides by mistake.  The hook on the inside one has to be welded or brazed on unless one wants to carve it out from solid.  Not to worry I have now grafted new wings on with a Mig welder, and machined the correct profile with judicious use of the rotary table.

Having seen the crossheads on a full size they are pretty crude castings or forgings and are painted black.  As for the little bracket that fits to the crosshead, just a hell of a lot of fiddly work on the miller that took ages; I made them on 2 ends of a piece of rectangular bar before cutting off.  The oil box fitted to the crosshead is quite a visible item but as I need some more details it will be made later.

I had made the pistons fitted to stainless rods previously, and left the rods over length for adjustment to get an equal forward and backward stroke on the pistons.  I put an M5 grubscrew at the back where it can't be seen to lock the piston shaft until all is done.  I also put a 3/32 slot in the crosshead to fit some sort of tapered glut to finally lock the piston rod later on.

I made the outside slide bars as per KW with no problems.  Aligning them wasn't as difficult as expected.  The outside cylinders are supposed to be at a 1 in 40 angle that approximates to 1 degree and 25 minutes.  So to try to set it all up I swung the cylinders on the top rear screw and similarly the slide bar brackets so that they can hinge together.  Somehow the whole lot aligns OK and it all runs very smoothly.  Don't ask me how !  I have checked the cylinder angle using a vernier protractor.  The LH is absolutely spot on; the RH is a little bit off at just over 2 degrees but I am leaving as is.

The next stage is to repeat the process for the inside cylinder.  If you think the outside crossheads are a pain to make, wait till you do the inside one !  Not difficult, but slow and fiddly with many set ups on the miller.  To make the hook I brazed a small steel block to the embryo crosshead, and then spent an age machining it to shape.  Looks good, but you will never see it ! 

Then I fitted the inner rod to get the piston equalised in the cylinder.  The rod fouled the frame stretcher and I had to cut a piece out of the stretcher and then found the mounting for the slide bars on the inside motion bracket was too low so I machined it out to the correct depth and MIG welded a new thicker mounting plate in place.  To get it all set up a shim was needed between the slide bar and mounting plate and it was necessary to thin down the end of the lower slide bar.  At the end of the day it all runs smoothly and the chassis can be pushed along with one finger and with no sticking or tight spots.  All this was done to the KW drawings and all I can say is that they are quite correct for the crossheads, rods and slide bars !

As an aside the last time I saw a full size Merchant Navy loco was in the late sixties at the wonderful Barry scrapyard where I went to play many times when I was a little boy.  I have visited a few preserved railways to try to see and have a ride behind one of the restored ones and get a few detail photos.  As of now I have failed as the locos have been taken elsewhere or have been out for repair, though I have seen several of the restored light pacifics.  Recently I have been in contact with a member of the Gloucester Warwickshire railway, who is involved with the restoration and operation of 35006 'P&O Lines' and has been very helpful and informative.  Thus I have now decided that my loco will be 35006, especially as my brother worked for P&O for many years as a tanker driver.