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Simply 7/8ths scale Dennis

by Doc Turner

7/8ths Dennis at Summerlands (CB)

After a year or so building to 16mm scale, I found that I needed something to re-stimulate my creativity and had become interested in small industrial locomotives following a couple of visits to Statfold Barn. It seemed to me that with 32mm gauge track, the very biggest locomotives I could build would be 7/8ths scale which would mean that they were running on 18 inch gauge track, not uncommon in small industrial complexes. An additional attraction was that that image that attracts me, that of a large bulk of locomotive balanced on a narrow track was even more extreme. It's how I see them when I visit the full-scale jobs at Statfold Barn open days, where, interestingly the liveries are somehow more vibrant.

Not too many in our hobby go for 7/8ths scale which means that it is not possible to just buy locomotives or rolling stock 'off the peg'. Well, that was true once; now you can buy an Accucraft Quarry Hunslet in this scale. Actually, I don't like the look of it one bit so haven't bought one. I don't know why they don't appeal and I'm forced to admit that they seem excellent value for money and with such high detail too. I suppose I'm less into ready to run locos that those who actually steam them. I get more kicks from making them. No, I don't make them, I assemble them. Precisely.

Simply 7/8ths

Simply 7/8ths is the name of a company that makes 7/8ths scale body kits to fit onto Roundhouse Billy boiler and chassis or Accucraft Edrig and Ragleth power units with no or minimal fuss. The excellent kits are available from Mikes Models in the west midlands. Various suppliers make accessories in brass, probably the most important being Talisman and DJB. Probably the most important reason for choosing this scale is to be obliged to scratch build so much. Another is that it is near enough to the 1/12th of dollhouse scale so I can use the 1/12th stencils from Bromley to make suitable buildings and buy any amount of compatible bits and pieces like buckets, tools and other paraphernalia you'd expect to see lurking about.

Building a Dennis

I'd had experience of building a loco from a kit of parts. Indeed the very first loco I made was a Roundhouse Lady Anne and that was the best thing i could have done. Quite apart from learning how to work with brass and solder, undercoating and painting, I really got to grips with how a steam locomotive works. I really fell in love with Lady Anne but I made her far too pretty for my current taste and have subsequently totally rebuilt and re-liveried her. In black she looks far more business-like as far as I am concerned.


Lady Anne reliveried, blower, westinghouse,oilers, clack valves and extended footplates.

The big guiding light in this hobby is the taste of the individual and I'm pleased to discover that my tastes have changed with time and experience. I can't tell you how long it took me to make up my mind about which kit to choose. One problem was the simply dreadful images on offer on the Simply 7/8ths website. Part of me wanted to buy a new Ragleth power unit because having had one fitted to a Swift 16 Owain, I knew how effective and practical they are. I was obliged to restrict my choice to their 18 inch gauge models as my track is 32mm.

It makes sense to explain here what the scale and gauge issues are about when we model to 16mm to the foot and also in 7/8ths. In garden railway, the commonly available track comes in a choice of 32mm gauge representing 24 inches between the rails and 45mm, representing 36 inches when we think of a scale of 16mm to the foot or about 1/19th scale. At this scale we can get away with things that are 1/18th scale or 1/20th scale, such as model cars and motorbikes and even just about 1/24th scale buildings, brick and stone stencils. The approximately 2 foot wide tracks were common in Welsh narrow gauge railways, whereas the 3 foot were more common in Ireland. Just to be complete, some modellers of Irish narrow gauge use the 45mm track for 3 foot gauge but pedantically, but accurately point out that, for true scale modelling, we ought to use 15mm to the foot, and they do just that. They are a fairly small select group for that reason.

When we want bigger vehicles, if we stay with the same commercially convenient track, the biggest we can possibly go to is about 50% larger with the 32mm track now representing 18 inch gauge and the wider 45mm representing 24 inch gauge, more or less. So, as you see, I was restricted to a modest range but should I go for the Accucraft based or the Roundhouse based vehicles?

Ultimately, the decision was made easier for me. At the Llanfair show, Simon Whenmouth had a Katie kit without body parts, already made up and compressed air tested. Ideally, the Simply 7/8ths kits are made for a Billy kit but a quick chat to someone on the Roundhouse stand gave me the confidence to go for it. How would it matter? The chassis is the same 0-4-0 and identical in length. The differences include a rather nicer smokebox on the Katie and a better position for the safety valve in my view, further towards the cab. Not so useful for the Dennis body that would suit it is that the Billy boiler is held 7.5mm higher than the Katie's. How could I know that? Roundhouse' website has superb scale drawings with all the measurements so that you can compare the two chassis/boiler kits. How would I resolve that difference? A phone call to Roundhouse resolved the problem at the rear. They would send me the rather higher Billy boiler rear support and all I would have to do is find an elegant way to jack the front up by that 7.5mm.


A Billy support to replace the lower Katie one arrived overnight once I rang Roundhouse.

Here's where I found a bit of luck. I was introduced to Paul Miles who has started up the Milepost Engineering firm. Fully equipped and highly competent, with a good knowledge of the hobby, Paul was able to cut me a brass fillet 7.5mm thick to sit neatly under the Katie smokebox support and with a cut out to enable exhaust pipes to rise up through the chimney as before. He went one better. Having received the smokebox by post, Paul saw that it would be no good merely to make a symmetrical block as the smokebox itself was askew. What Paul sent me was absolutely excellent. As well as raising the boiler by the prescribed amount, now the chimney was perfectly centred.


New custom made brass block 7.5mm thick raises and levels the smokebox 

So far so good. It seemed that the differences issues I had brought about by acquiring a Katie rather than the Billy had been overcome very simply. Some hope! It transpired that there were more differences that had to be overcome before the job was a good'un.

The Dennis kit comes with new footplates, on for the front and one for the cab floor and they both need some amendments to cope with a Katie. At the front, the slot for the exhaust pipes is far too short and must be enlarged to permit the necessary forward slope of the pipes for fitting the smokebox onto the chassis and just over the boiler. Naturally enough the holes in the Dennis footplate were designed for the Billy smokebox and these are in a different place from ones that would allow the Katie smokebox to be bolted on. The front central hole was, thankfully, the same and one hex bolt is all that is needed to securely fix the footplate to the chassis.


While the rear alignment and central front holes match the two footplates, new holes, 
forward and wider apart must be drilled to allow fixing of the new heightened smokebox.
The four smaller holes in the picture are tapped and ready for screws provided that
hold the body in place within the two sand boxes, a very neat design. That slot is too 
short for Katie's exhaust pipes and will have to be lengthened as shown below.


Front footplate showing increased slot enabling full forward slope of exhaust pipes

I was lucky enough that Chris Bird could adapt a chuffer to fit these pipes and make that job of fitting easier than with a pair of pipes. The supplied higher chimney stack wasn't tall enough to my eye and being turned specifically to fit the smokebox and the brass cap, seemed to me to be too narrow in the bore to accommodate a decently functional chuffer and allow easy lighting. A new chimney stack from K&S brass tubing, using short sections of the stack provided as joiners solved both problems. In addition, the holes in the footplate that should marry up to the smokebox did not do so and had to be drilled appropriately.

The rear footplate had several problems for Katie. Most important of these related to the gas tank. Katie's tank has an L shaped plate welded to its base, enabling it to be bolted to the vertical frame on the right. The much bigger rear footplate supplied with the Dennis kit covered that area completely.


The new Dennis footplate when dropped onto the frames, totally covers them, 
making it impossible to mount Katie's gas tank to the frames as before.

 I decided not to cut the L plate off the tank but see how I could incorporate it. To accommodate the vertical plate, I elected to cut a slot in the footplate. 


Maybe not the neatest slot but it allows the gas tank flap to sit where it was designed to be

Once the pipework was reunited and with the tongue in the slot, there was no need to bolt the tank more firmly. Its base sat flat on the footplate and the tank had nowhere to go once that slot was filled.


Gas tank now sits on footplate where it was meant to be. Once connected up, even
unbolted to the frames, that's going nowhere.

I wanted Dennis to be radio controlled. Roundhouse swiftly supplied me with the Katie R/C kit which had the subtly different regulator, pillars to mount the reverser servo and linkages. The problem was that I simply could not understand how to mount the regulator servo. Something seemed to be missing. It was. had I been supplied with a Katie body kit, it would have come with the servo mounting. That would have been one expensive part, considering I wouldn't be using the rest of it to make a Katie! Another phone call to Roundhouse saw one on the mat next day. It comes as an etching which is folded up and has tongues at right angles that allow it to be fixed to the footplate. This means cutting a couple of new slots.


Slots drilled and filed for the servo support tabs. They are not pretty. Who's looking?


Servo support with servo offered up to show how it aligns to the regulator.
(Note how invisible those vile slots are now.)

Adding the details

One of the best elements of adapting to 7/8ths is the very good Talisman brass castings available from Si Harris of ModelEarth. Again, that 50% increase allows for better proportions and more detail. Chains hooks and rings look completely real,as far as my own eye is concerned. It seems to be the difference between 'representing' items like rivets and bolt heads and being miniature versions of those. 


Talisman coupling and chains, here combined with a single link to avoid track fouling
when not in use. Believe me, on my line, that makes sense!

Even the surface texture looks right. I chose the couplings, safety chains, Roscoe lubricators and whistle. Just to illustrate what I mean about the realism of the castings, examine for a moment the whistle with separate steam pipe. I think we'd be hard pressed to make such a casting at 16mm scale.


Excellent Talisman whistle casting

I always like the appearance of a blowpipe and the Katie smokebox comes with a pre-formed dimple on the left side, making drilling the hole for the excellent brass fitting from DJB. I drilled a hole into the bottom of the front wall of the cab to receive the supplied brass rod which I also bent to lie closer to the boiler. That it is somewhat fatter than perhaps is commonplace but for me it adds to the illusion that this is a very small locomotive in full scale terms. I found the Talisman Roscoes tricky to assemble as the wheels come separate and i found it necessary to deepen the holes provided before soldering. Added to that, the tiny projection for fixing to the smokebox was entirely inadequate. A nut was ground down to lose the slot then a hole drilled in that and then soldered on. Getting it aligned was a game but at least then I had a nut and bolt to fix the entire assembly securely to the loco.


Talisman Roscoe and DJB blower

Only one boiler band was provided with the Katie kit and that was needed at the rear, within the cab to assist with holding the boiler onto the rear support. I decided that the Dennis boiler would need another pair of bands, one at the cab front junction and one adjacent to the smokebox. I realised that these ought to be wider than those on a 16mm scale boiler so I made some using 4.8mm brass strip, bought in a convenient pack from Atropos at Exeter Show.  I felt that, out of the pack, these would look too pristine so I pre-blacked them with Carrs Brass Black and once installed, rubbed some of that off. I find this leaves a much more realistic look.


Just the new blackened off the brasses looks better to me

Finally, this Talisman lamp caught my eye and I just had to have it. It comes with a fitting and support peg and that rather nice glass cabochon.


Talisman headlamp and support. It doesn't work but it could easily be made to
if I have a time on my hands.

Afterthought rivets

Once the body was fully painted and assembled, I found the side tanks just a touch too bare and bland and I searched online for examples of tank sides to glean inspiration. The one image that appealed to me was one of our very own Steph's. She had run a single vertical line of rivets at the cab front junction and it looked as if they were doing a job as well as breaking up the tank side desert.  But how to do it without lousing up the paint job? I thought of using Cambrian plastic rivets and gluing them on but two things put me off. I am appallingly clumsy and have a poor eye for a line. I knew I would leave glue dabs all over the place and touching up with green paint would merely add to the mess.

In the end, I elected to pre-paint brass snap-head rivets, setting them up on a drilled card and of course the process was, as ever, clean, acid etch and two coats of coloured paint. Now for the holes

I have a pillar unit onto which I can mount my beloved cordless Dremel. I had already made sure that the paint on the tank sides was fully set by subjecting the painted parts to cooking in the oven for 20 minutes at 100 degrees. That meant that the paint finish would tolerate the necessary handling of assembly but, most vitally, at this stage, I could trust it to withstand strips of masking tape. 


Ready for drilling

Once these were in place, I could mark the places I wanted the rivets to go and, resting the loco on its side on the thoughtfully now padded drill bench, carefully drill the holes, ensuring they were a snug fit for the rivets. Of course, I had to be careful not to push the rivets home with a tool that would remove the paint from their heads and I would now cook those too if I did this sort of thing again. It worked well. Now all that was required was to dab some wet paint into the holes, push home the rivets and all was as I had hoped.


Tidy enough I think. Note the feeble attempt at ingratiation and the Busybody
driver who needed amputation of the right leg at the buttock to sit on the lubricator.
He also needed his left foot to be hollowed out to sit over the lube outlet nut.

I only discovered the problem I had caused myself when I was obliged to remove the body from the chassis and came to realise that it would have been wise to cut off the rivet shanks as they protruded inwards. It was easily done with a sidecutter but showed that my paint glue idea would have worked better had I not had to mess with the rivets again!

This job was so easy, I may well adorn other more bland side tanks the same way and, indeed, the Dennis buffer beams look a lot better with a few well chosen rivets. It almost goes without saying that those were pre-painted red! Derr!

Radio control wrinkles

While this Dennis kit is excellent, as with most of life, there are a few little matters that need to be resolved when you add radio control. For example, when you fit the regulator servo support and insert the tabs through the slots you've cut, you interfere with the fitting of the right hand cab steps which are designed to be held under the footplate with a pair of screws into ready tapped holes. I probably could have bent those tabs the opposite way the that which I chose had I thought it through before bending. On the left side, there is a tendency for the reverser link rod to bind on the body shell. I was obliged to file off a couple of mm from the edge of the small folded brass plate that acts as a roof to the cutaway section at the bottom of the tank. 


While now there is clearance, it is still mean and I may do more

I had enough room to store a power pack in the right tank and the kit comes with a plate to convert the space under he cab floor into a useful place for a receiver.


Not the ideal place for the switch, given where the steps have to go but the slot is provided
on both sides in the frames. Note how the ventilated floor to the back box is secured with
screws through tabs outside the frames.


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