When this kit first appeared 20 years ago it gained a reputation for being very highly detailed and accurate to prototype, but definitely not an easy build. The world has moved on since then and while the finished kit will still, with patience and care, bear comparison with the best that today’s market can offer, etching technology (and the thinking behind it) has also moved on, and it seems to me that the best of today’s products offer the same high level of detail, but with much easier construction.

With use of the variant parts supplied the etch will make up into either Diag O.33 (various GWR Lots between 1930 and 1945) or Diag O.62 (various BR Lots from 1950 to 1955). Diag O.33 evolved Lot by Lot and there are significant underframe differences, all of which are catered for by the etches. Some of the etches in the box had been sourced from Scorpio Models so perhaps the kit is in their catalogue today.

My example, which I had bought secondhand but unbuilt, was in an incorrect box for an Oakville Monster as the label had been over-written, presumably by the previous owner, ‘Diagram O.62 Syphon G.’ I had bought it and begun construction based on his assumption, but in fact the kit I’d purchased was supplied with 7ft heavy plate bogies, which are only suitable for some early examples of O.33 and not for O.62. I should have checked the bag with the bogie castings sooner, as it would have saved me undoing some work. There are some additional etched and cast parts in the kit to ignore as they are not needed for either O.33 or O.62 – some spindly early Churchward pattern lamp irons, end steps needed only for earlier gas-lit Diagrams which Oakville also produced (eg the O.22), four gas lamp tops and a gas cylinder.

The spice of life There are many bogie variations; five different types were fitted to the two diagrams, and individual vehicles sometimes had a different pattern fitted after general repairs, so work from a photo at your chosen date if at all possible. Despite this sage advice I failed to find a picture from around my 1955 modelling date, so my random choice of running number is based on probable rather than actual condition.

The main difference between the O.33 and the O.62 body is that the latter was fitted with continental style steel ventilator covers which slid up to reveal additional louvres just above floor level. The brake gear also evolved over the years. I eventually settled on building an O.33 to represent a van from the first batch, Lot 1441, the only one which I could see with certainty had 7ft plate bogies and Dean Churchward brakes from new, as opposed to the lever brakes of later Lots of O.33.

It didn’t help with decisionmaking that J H Russell’s GWR coach books are in their usual muddle over detail differences. I wanted mine as running in BR carmine, though as most were never washed it quickly became almost impossible to see what colour they were meant to be. For mine a halfway house between pristine and filthy seemed a reasonable compromise, so it ended up being modelled grubby but not woebegone.

Many of the Siphon Gs ran as parcels vans well after milk-churn traffic dried up; I photographed an O.62 in begrimed BR corporate blue at Newcastle Central as late as 1978. If you are prepared to source six shell-pattern ventilators you could also model an O.33 as returned to use as a Siphon after war service in ambulance trains, and if you plated over most of the louvres you could represent your Siphon as an ambulance coach in military use. There are photographs of both these versions in Jim Russell’s GWR Coach Appendix Vol 2.

Betrayed by his fingerprints There are hundreds of parts and this is absolutely not a shake the box and it builds itself kit. I’d built three other Oakville Siphons to earlier diagrams for clients some years ago, and recall them being difficult to assemble and definitely not for a beginner, despite the extensive drawings and detailed instructions. Poor etching had added to the difficulty in two out of three cases; the brass had been in the acid too long and many of the fold lines on smaller parts were too fragile.

This one seemed better on initial inspection, but as before it had not been cleaned after etching and was covered in black fingerprints from the hands of the etcher; I was tempted to call in the CID to help identify the culprit. It took me an hour with a rotary steel brush in a drill and a glass-fibre pencil to clean it up, an essential task as neither solder nor paint will adhere properly to tarnished areas. The roof was supplied pre-rolled, but sadly to the wrong profile entirely, and a lot of finger manipulation was needed to correct this.

The double rainstrips are half-etched onto the roof, which makes this correction even more difficult. It also had several deep dents along the edges where the webs to the mother etch had been cut carelessly. You can of course ignore the instruction telling you to use the straight brass wire provided for rainstrips. A lot of the white-metal castings were no better than adequate and some were not fit for purpose.

Rivet, rivet The first job is to identify which of the variant half-etched dimples need embossing or drilling for your chosen example, (yes I know they are bolt-heads really, but we are talking ‘rivet-counting’ here). I don’t have a riveting machine, just a 2 inch nail and a tack-hammer. Some dimples near the body ends are to be drilled for commode handles, not pushed out as rivets, and the O.33 has them further inboard than the O.62 so make sure you only drill two of the four witness marks at each end. Even if you have a posh riveting machine, expect punching out all the dimples to take a long while.

It’s a good idea to tag the witness marks you don’t need with a felt-tip pen to avoid mistakes. Amongst these redundant marks are dimples for a bolt-head below the bottom hinge on each door, which I duly punched, and it was only much later that I discovered that this is a drawing error, and the raised bumps I had lovingly created in fact prevented the L-shaped bracing brackets from fitting flush. Two of the four holes for the handles in the battery boxes are also in the wrong place and a drawing (but not a note in the written instructions) tells you how to correct this. Of course I only noticed the drawing after I had drilled a set of incorrect holes. Additional stretchers from scrap brass beneath the roof to prevent the louvres from bowing in.

There should be holes etched into the ends for commode handles and jumper-cables, but these are missing and there are no witness marks, so you have to locate them using measurements provided on another drawing. It’s simplest to mark only one end like this, drill it, then use this end as a template for the second end, drilling through both layers. No castings were provided for the jumper cables and I judged by eye where holes should be drilled, and then scratch-built the cables and plugs from wire, washers and plastic. Two holes also need drilling 1.3mm in one of the two solebars for the vacuum pipe, which ran almost the full length of the vehicle in plain sight. Replacement T-handles from brass castings, 0.7mm brass wire commodes, 1.0mm brass wire for vacuum pipe, and note that the running boards this side have to be mounted so as to clear the vacuum pipe.

Bend it like Beckham On to forming the solebars next. You really will need access to folding bars, or at the very least use G-cramps and two lengths of planed timber slightly narrower than the height of the body, as the solebars are etched integrally with the body sides and three full length folds are needed to create a channel cross-section. The slots in the solebar ends to allow clearance for the headstocks needed widening; it would have been easier if I had spotted this before I made the long folds.

Folding the solebars is a nightmare of a job, even if the fold lines are deeply scored first. I reinforced the final solebar fold, which is inside the body, with a good fillet of solder. There’s a fourth fold along the top of the side, and this is even more tricky, as there’s only 2.5mm of metal above the fold line and 1.5mm between the top of the side and the louvres. If you manage the job without putting a kink into one or more of the louvres you’ll be very lucky. I wasn’t lucky, or maybe I simply ran out of talent.

If I were making another I would use a slitting disc to make vertical cuts every few centimetres along the metal above the fold-line and make small folds, one section at a time, in a small vice instead of trying to do the whole length in one movement. A length of scrap metal could then be soldered behind the fold to restore rigidity.

There’s a recess in the end boards to take a half-etched plank with an embossed tonnage numeral, 26, 27 and 29 tons being the alternatives available. For the O.62 with 9ft ‘modern’ bogies you need No 26, judging by the photo in volume 2 of Russell’s coaches book (fig 458). For the O.33 with 7ft plate bogies the No 27 is appropriate according to the instructions. Commode handles and jumper cables fitted to end, holes drilled ready to fit a jumper socket. Note the overlay plank with the 27 tons embossed numerals, and rivet detail punched into headstock

The instructions work on the assumption that you will add most of the body detail (hinges, commode handles and the like) before you construct the basic box of sides/ends/floor. But I prefer to add small detail parts, which might be vulnerable to handling damage and/or loss, after the body has been made up. I removed small parts from the motheretch prior to assembling said box. Take care, as the area around the small parts is not scrap etch, it’s part of the floor, and I chopped up one section in error - gah!

Ensure the side/end corners are exactly 90 degrees or the floor will not sit true.

Up on the roof I dislike having to solder a roof permanently to the sides and ends, as it makes masking and painting so much more difficult, but in this case there was no option. Given the thinness and irregularities of the roof; it was the only way I could ensure the roof stayed put and was without ripples. I also soldered three longitudinal strips of scrap brass about 2cm wide inside the roof at a quarter, half and three quarter distance for extra rigidity.

Having a fixed roof also means putting in some backing material behind the upper louvres before the floor and underframe details are attached, whereas I normally prefer to spray some card in body-colour and add it at the very end, just before fixing the roof, as airbrushed paint tends to shrug away from the slots if you add the backing before painting. This backing material is absolutely essential, as on the real thing the louvres are angled so it is impossible to see daylight through the vehicle. Black cartridge paper was my choice, added after the body had been washed for the last time.

Once the body has been completed you will also want to glue in some thin card to form a floor, as from some angles the track can otherwise be seen through the hand holes in the doors. Several small pieces of card are easier than one big one.

Stop adding body details before insanity sets in. The steps beneath each door on the solebars are to be folded double to achieve scale thickness, and are of two sizes, the four narrower ones being for the side with the vacuum pipe, these being quite difficult to fit as they have a space behind them to allow clearance for the pipe. The mounting brackets for the steps have an etching error, which is admitted to in the instructions, and a sketch shows you how to remedy the fault.

The door commodes went on next, then the T-handles. The kit provides tiny half-etched backing plates for the handles, but these are so flimsy it’s impossible to cut them from the mother-etch without distorting them so I simply left them off. The etched T-handles are useless too, so I substituted some lost wax alternatives (DJB I think, no longer available, but Slaters do an alternative).

There are twin holes each side of the doors to insert wire for bump-stops, but I reasoned that spigots of wire intruding into the interior would prevent me from adding a backing sheet for the louvres without a great deal of re-drilling, so from sheer laziness I sacrificed this small detail, and simply filled the holes with dabs of solder applied from inside. The tiny hole above the commode handle in each door was also filled and the miniscule fragments of etch (hooks or locks?) which are meant to sit in these holes were discarded. I also decided to omit the corner bracing strips above the louvres at each end, as there was really not sufficient space for them between the louvres and the edge of the roof.

Very cleanly cast steam hoses and vacuum hoses are supplied, but these are white-metal, which is too fragile for hard use on a layout, and as they make the coupling hooks even more inaccessible I simply left them off. You hardly see the lack under the gangway bellows.

Each pair of doors has six hinges and each hinge is meant to have four bolts, that’s 192 dimples to punch, which is quite ridiculous as each piece of brass is only about 2mm by 3mm, and the design betrays a lack of joined-up thinking. Forming the rivets on such tiny pieces creates unacceptable levels of distortion, then you are meant to turn the hinges over and sweat a tiny piece of 0.45mm wire into the half etched groove on each one, and finally solder the hinge into place on a half-etched recess on the body, at which point the carefully placed piece of wire unsolders itself and falls off.

The hinges on the etch were not even properly lined up so that one piece of wire could do multiple hinges and then be cut to length. I spent a completely wasted hour, ending up with a little pile of mis-shapen and solder-saturated scrap. I then tried again with some hinges supplied in another maker’s kit, I don’t remember whose, and achieved a more useable set of hinges, albeit with no rivet detail. A much simpler design solution would have been to etch a tiny witness mark on the body for each hinge instead of a recessed rectangle, and then draw the hinges as a half thickness etch with raised bolt-head detail so that each could be soldered onto the flat surface.

Once I had cleaned off the flux I cut my 48 hinges off the etch, and super-glued them to the body so as not to disturb the bits of wire with a hot iron. Only one fell off in subsequent handling. The bracing plates at the lower corners of the doors also need riveting and then flattening to correct the distortion the process induces, and again I superglued them rather than sweating them on with solder. (Note my earlier note about the redundant rivet below the bottom hinge on each door frame.)Soldering 0.7mm brass rod to a set of replacement hinges.Replacement hinges glued in place.

Bellows Gangway suspension brackets can now be folded and soldered into the recessed patches in the ends, and the inner framing of the gangways folded in a vice and then sweated on. Two tiny circles of etch are provided for the light switch, mounted to the right of the gangway about two-thirds of the way up. Note that on the real thing there’s an L-shaped lamp iron on the left hand side of the outer frame of the bellows, and a scimitar-shaped handle on the right hand side. I simplified the suggested bellows system which is wonderfully detailed, but really only practical for a static model. I made up a concertina out of folded black paper and cotton, similar to ones which are available commercially, and omitted the etched parts, as a smooth rubbing surface between vehicles is essential for snag free running. Gangway suspension brackets and inner framing for gangway sweated on.End detail showing working paper bellows. Buffers are unsprung and fragile, due for replacement sharpish.

Non-sprung whitemetal buffers are supplied; there were two spares in my kit, one already broken, and I snapped the head off a second one cleaning up the huge amount of flash. They are really too flimsy for anything but cosmetic use on a glass-case model. I’ve temporarily fitted them with just a touch of solder solely for the photographs as I’m currently out of stock of the sprung variety. I think Haywood do a nice pre-assembled set, which I need to buy. The CPL lost-wax variety are handsome once fettled, but getting the rectangular shank to be a sliding fit inside the buffer body takes a lot of filing.

Underwear The brass cross pieces for the cast bolsters each have two small holes pre-etched; one is for a 9ft bogie, the other for the 7ft bogie appropriate for my model and they are clearly identified on the etch. They need opening out to take a 6BA screw. I soldered the screw in from above, rather than the 6BA nut suggested in the instructions (purely my personal preference). The instructions suggest you use only one of the two cast bolsters provided, and at the other end adapt and use a spare bogie centre stretcher as a bolster, which is meant to reduce any tendency for the body to rock. I used two identical bolsters and modified the bogies slightly (see below) after which I found the coach was perfectly stable.

With body detailing complete the whole thing was cleaned in a Viakal lookalike I buy here in France then rinsed and dried. The backing sheets to blank out daylight behind the louvres were then glued in. Use waterproof black plastic card instead of paper to blank the louvres if you want to follow the instructions and add the floor to the body before assembling the underframe components. The floor and underframe detail can however be assembled as a separate module to avoid any further washing of the body, which would destroy a paper backing sheet. I went down this route. Black paper has been used to obscure the unwanted daylight through the louvres.

If you use this method you will need to trim 2mm of brass from each side of the floor so the assembled unit can be joggled into place above the solebars and subsequently soldered. These soldered joints between floor and solebar rear will need to be cleaned up with a damp cloth. This modular method also has the virtue that many of the soldered joints for battery boxes and queen posts can be made from the side of the floor which would otherwise be inaccessible inside the body, making for a neater finish. However, leave off the brake levers until after chassis and body have been united or the completed module will not slide into place.

There are two pairs of queen posts on the etch. Use the longer ones (the shorter ones are incorrectly drawn). You can ignore the garbled instruction and sketch about using the duff ones for transverse trusses as transverse pieces are also on the etch, though they need shortening by 2mm, best done before you fold them up. The instructions also mention removing a little meat from the base of each queen post to enable the trussing to fit snugly, but I did not find it necessary. The trusses have to be slotted at their witness marks, then folded up and finally bent to the correct angle, which is fiddly, and another time I would be tempted to replace them with 2mm milled brass angle. Another modification: the whole of the floor, trussing and brake assembly was constructed as a separate module and subsequently fitted between the solebars, rather than fitting the floor section first and then adding details. Note the backing plates for the battery boxes and the replacement Slater’s cranks. The empty etched slots are not needed for this Lot number. They are for later Diag O33 Lots and the Diag O62 for which the kit provides variant parts.

The etched battery boxes are supplied with hollow backs, and it’s well worthwhile sourcing a rectangle of scrap brass to fill the void on each one, as the omission is very evident from eye-level. But fit the handles first so you can solder them from behind.

The floor pan has multiple slots and tiny etched letters indicating where items should go; it’s designed to be used on any variant of O.33 or O.62 so it’s easy to get confused, as there are considerable differences between Lots. After I’d made several errors and puzzled over the drawing and sketches I think I’ve got everything where it’s meant to be, but it was a struggle and a whole morning’s work. I rejected several of the small cranks for the brake rigging as being too skimpy and substituted equivalents from my spares box (mostly Slater’s bits).

There’s a helpful brake-gear sketch in the instructions, but you need to get your head around the perspective; it’s drawn as if you were looking down on the underframe from inside the body and the floor were missing.

No mention is made of a steam heating through-pipe: I’ve assumed standard GWR practice with the pipe running along the centre-line, just visible between the trusses when viewed from eye level, with the centre of the pipe in a very shallow V and a tiny release valve at its lowest point (a dab of solder suffices for the latter). The dynamo goes (I think) at the far end from the brake levers (see photo). Finally the 2 vacuum cylinders can be added, both at the same end. The casting provides neither cranks nor trunnions so these need making up from spares or scrap brass. The completed underframe. The floor voids need filling with card.

Coupling hooks are supplied on the etched brass sheet, and there’s an additional and better set in nickel-silver with coupling links, but not the tommy-bar and adjustment screw, so I scratch-built these from brass wire. The slot for the links in the hook needs widening slightly. I am however still toying with the idea of fitting Kadees, as using screw couplings beneath gangway bellows is such a tiresome operation.

Beyond a yoke One bogie needs two plain stretchers, the other needs a plain one at its outer end and a slotted one at the end which is closest to the pulley-belt of the dynamo. The castings are all white-metal, very heavy and crude by the best standards of today but fit for purpose provide you can live without brake shoes or yokes, as none are supplied. It seems a strange philosophy to have drawn a body to the nth degree of detail and yet to offer bogies with no etched parts at all. Modification: bolster with 6BA screw rather than 6BA nut.

I built the 7ft ‘heavies’ using 70 degree low-melt. You may well need to drill out the rear of the axleboxes to provide enough depth for your chosen bearings. Considerable modification would be needed if you want any form of compensation. I built mine rigid and without bearings as I had some second-hand steel wheels with snub-ended axles, and they were a good fit in the axle-boxes once I had drilled the holes a little. With a touch of light oil they run freely and sweetly despite the lack of pinpointed axles or brass bearings.

A selection of double-limbed and single limbed cast bogies steps is provided but the smaller ones are not needed for the 7ft bogies fitted to non-passenger vehicles, and there were only two of the larger ones, whereas four are needed, one at each outer corner of the vehicle. I managed to dig out some etched brass replacements from my pile of spares, and put all the cast ones in the bin.

A modification: a small rectangle of 0.018in brass sheet was sweated onto each bearing pad to eliminate any tendency for the body to rock laterally. After a trial fit of bogies to body I was happy with running quality, but not very happy about the lack of bogie brakes, but I decided to sleep on it. Brass rubbing pads fitted to the bogie stretcher to provide stable running. The glaring lack of brake rigging is very obvious.

The next day it was even more glaringly obvious than it had been the night before that the coach was ’non-fitted’ in that the bogies were completely free of brakes, and I decided I could not live with it like that, so more rummaging turned up a set of old Blacksmith yokes and some pairs of brass brake shoes from heaven knows where, and I spent most of a morning adding the absent rigging. At this point the vehicle was ready for painting and I reckon I had clocked up about 40 hours of work, which was way longer than it need have been had the kit been better thought out and presented. Completed bogie after Blacksmith yokes had been added.

It’s a good job it was just for me and not for a client as it would have been economic suicide to build at a price anyone would be happy paying.

Twopence coloured Painting is a relatively simple task apart from masking that roof. The undercoat for the entire vehicle was satin black from an aerosol, which also serves as a top coat for ends and underframe. The sides are the wonderful Comet cellulose early BR Lake (ie carmine, the pinkish shade, not the later more maroon shade), which will go on top of an acrylic undercoat without causing a crackle reaction if you mist it on diluted and applied gently from an airbrush at a fairly low pressure. The lovely old Simoniz cellulose black undercoat is no longer available.

Pressfix transfers are from the HMRS GWR freight sheet, as SIPHON does not exist on the BR Gill Sans sheet, but there’s a precedent, as photo evidence shows that Swindon carried on using up its stock of GWR font lettering well after nationalisation. The body was sealed with petrol-thinned airbrushed Wilkinson exterior satin varnish (outdoors of course).Body detail, the lack of rivets on the hinges is not too apparent. The lettering is from the HMRS GWR freight sheet.

After 48 hours for the varnish to harden the body was masked off and the roof was airbrushed in Humbrol 66 Olive Drab. The masking tape lifted a couple of small areas of carmine on the louvres (which is why I hate the fixed roof method of construction) so I had a small amount of retouching to do.

Weathering is a mixture of airbrushed various matt gunge colours and matt varnish that gives an overall ‘in-service’ look. Final detailed weathering was with powders and dry-brush technique. Overall, worth the effort and in my humble opinion it looks the part. But it could have been made so much easier with better and more consistent design.