Eastfield MkIII - 00 4 track roundy-roundy in 12'9" x 9'4"

[Dr.Glum]

Eastfield Mk1 was in the loft until 2013, Eastfield 2 was designed after a divorce and house move, and  supposed to be made up of major elements from Mk1. Some of the redesign and rebuild was described in:

Eastfield II - phoenix from the ruins - Layout topics - RMweb

Last year, having admitted it affected living here too much as I was now trying to live with someone else in the house, so one day I admitted to myself I needed something more modest that I might finish and enjoy before the drink or old age finally caught up with me. So I spent some enjoyable time using CAD to design a four-track roundy-roundy.

First I had to dismantle a lot of the existing boards.

 

The photo shows stripping down a board that was made from an old door that has already been through two rebuilds from 1999 to 2016! Note the hole for a turntable. (My strategic reserve of bog roll is exposed!) I've removed the extension (leaning against the shed), stripped everything right off, and (since that photo was taken) cut the board to shape to fit its new location, repainted, covered it with cork to get a fair surface. Now I've been laying track - hooray!

Edited November 8, 2022 by Dr.Glum
Clarify the topic name

[Dr.Glum]

As usual I enjoyed working up a design using CAD. A work in

progress  below. (Sorry about the fuzzy screenshot - but you get the idea.)

 

Unfortunately the elderly computer that ran Autocad with a parallel port dongle gave up the ghost part way through, so at some stage I'll have to learn Templot so I can make a record of the design. But I have plenty to do, working on the boards that are in the upper part of the drawing. There will have to be two lift out sections, upper right and bottom middle.

 

Above. The cutaway to clear the door is being checked here. 

The image above was taken during the process of sticking down the cork to obtain a decent surface. PVA very slightly diluted applied with a 2" brush - leave overnight under weights, but it is reluctant to stay stuck down. I was pleased that I could find all the salvaged bits associated with the turntable.

Below was taken while wiring up the underside of the Board 1. All very old-fashioned I know, but no outlay, as I'm using everything 'in stock' or recovered from the previous version. 

 

Edited April 11, 2022 by Dr.Glum

[Dr.Glum]

The image below was taken during the 'design' of the loco yard behind the running lines. Positions of track and what was possible was pinned by the location of the turntable hole. The white piece of paper is a track template that just fits inside the sleeper ends of Peco track. (I used to have an office next to a drawing office, which was very handy for free use of Autocad and an A0 roll plotter.) That one is 30 inch radius, the minimum on the layout.

Next (below), things have moved on, and I've discovered the way to maximise the turntable is to have the diesel depot (Hornby clip-together kit) opposite the Metcalfe steam shed. This is nothing like I had originally envisaged, but then, that's the joy!

Here I'm testing the elevation of the track ends to give a smooth ride on and off the turntable.

Although I'm unlikely to go for full scenic treatment, later there will be signature structures in the loco area e.g. coaling tower (Ratio kit), water tanks and water columns (Dapol, etc), bike sheds (Wills), Knightwing oil tanks, and so on. Below, I'm installing ash pits on the entry loop.

Finally, this picture was taken while I was test levelling the board in place. The chest of drawers was a bargain from British Heart Foundation and has already proved brilliant for storing tools and clutter that you need while making a layout. The height of the layout surface is 1220mm /4ft, chosen for the future days when I'm just watching the trains go by. The step stool is significant, as a result.

 

Edited April 11, 2022 by Dr.Glum

[Dr.Glum]

I had been distracted by reading a long Topic about motorising the Peco turntable and the difficulties some people (not all) had with slack in the drive system causing difficulties lining up tracks when turning. Put me off spending money on a motor system. Instead went and found the mechanical system my father made for a 3mm scale home-made turntable.

The TT layout he built it for was definitely at a house we moved out of in 1960, so this item is at least sixty years old. Note the hefty soldering. The next shot is a close-up of the wheel that deals with the polarity problem in exactly the same way that Peco chose. It has two sprung contacts (ball bearings in brass tubes, pointing downwards in the photo). Originally there were wires soldered to the ends. I don't like getting rid of things, even when I see no immediate need for them!

Lastly, on Tuesday I took delivery of a kit of parts for the next two baseboards, from Tim Horn. Laser cut birch ply, 9mm and 6mm. My partner had suggested that I "buy a baseboard so that you finish this year". Yes, well. (All the boards in the previous layout were mostly comprised of reclaimed material; I think I spend at most about £30 over the years, and that was for a layout approx. 24ft x 7ft.) I thought the idea was daft, but did look into it. Delivery times were an issue, but I read a complaint about Tim Horn in a RMweb topic. When I read on, there were a lot of good testimonials refuting the complainer. I contacted him and very quickly my order was in the queue.

Above: one of three big packs of bits for along the wall and more than half way across the room.

Edited April 11, 2022 by Dr.Glum
Typo

[Dr.Glum]

The turntable turned into a bit of a nightmare, mainly due to the main shaft not being absolutely straight. To cut a long story short, the red box holding the worm gear now floats unattached to the underside of the baseboard, free apart from the vertical shaft being glued into the underside of the turntable deck using PVA. (Initially I used Loctite but it never set: magically the turntable would rotate clockwise, but if you wound the handle the other way, the deck stayed put. Ha!) Anyway it works now. Both ways.

Track planning and track laying continues. The last points and wiring are done on Board 1. Track that continues onto Board 2 will be laid once the two boards are up and joined. The photo below shows them clamped together so that I can mark the bolt holes underneath.

I have continued to tweak the track alignments because I plan to have the four running tracks meet the far edge of Board 2 at right angles to the edge. The rail joints there will be of unsoldered rail joiners, so that if necessary the layout can be split at that point in future. I can't manage the first two boards when they're joined together, but I could with a helper.

After much fiddling, I appear to have found how to run an ash and coal siding next to the ash pits and the coal tower. The corner posts from the Ratio kit are at the correct spacing.

And below, not so much fun as jiggling bits of track - varnish the bare wood of Boards 2 and 3. When dry, turn over and do the insides.

 

Edited April 11, 2022 by Dr.Glum

[Dr.Glum]

Been busy even though the colder weather has made it a bit nippy in the conservatory, to say the least! (Must get on with speccing the insulation work.) Decided to revamp the cabling from the controller so that the programming track supply could be switched to the long siding at the back of layout Board 1, with the idea that it would be handy for programming mulitple units. Made it all, but (for now) a waste of time as the system cannot detect a response from the unit being programmed. Presumably the leads are too long/ too far away. Programming does still work on that short length of track that sits next to the controller.

I have been raiding Dunelm for net curtains and rods so that I can have some privacy and remove the temporary sheets I hung up with sellotape. Another distraction was making legs from tubular ali. After considering all sorts of brackets, I made 'sockets' to be expoxied onto the leg end. The legs are cut slightly short and height adjustment is by card shims at the top. Socket shown is upside down.

Next I looked ahead and did enough leg work to do a trial 'offering up' of Boards 3 and 4 (as 1 & 2 are now permanently joined).

By today's date I have now laid all bar one short siding on Board 1 &2, so tonight I put a bit of stock on to get a feel of how it will look.

 

Lots of work to do yet, filling in sleepers, a few more droppers, etc.

Edited April 11, 2022 by Dr.Glum

[Dr.Glum]

I have to be realistic and think it’s going to be months (at least) before I can run trains on complete circuits all around the room. So I looked again at the question of a temporary headshunt board to stand in the doorway and allow transfers between the four running lines, and the engine yard on the outside, and the goods sidings on the inside.

While hunting in the shed for something, I contemplated the remaining boards from the old loft layout. A bit of doodling on paper showed that I could re-use at least two of them, making a straight run into the house. I brought two of them into the conservatory, see below.

Both had sections of incline that were added during the big rebuild in 2006 to 2007; I had to now remove those. The boards are made as per my standard of the time, from contiboard shelving strengthed by a batten underneath. All the points were motorised so the boards are quite heavy. The next image shows all the gubbins of accessory decoders, CDUs and H&M point motors.

 

One end will rest on the ledge of Board 1, but new supports are needed. I was concerned about stability; the baseboard top is 1.225m high (just over 4 feet). I raided the stored woodwork that used to support the loft layout and made this shown below.

It is reasonably stable and a coat of grey or black will improve it.

The next photo was taken while I was checking that track alignments were going to be feasible, and before I put blocks in to raise the end to datum.

Although using an existing board was going to be a great time saver, there was still an amount of work. There was some redundant wiring to remove and checks that all rail sections had feeds, in case supply to any rails was from adjacent boards in the old layout. Here it is upsidedown.

 

While sorting out to minor changes to the track alignments I was disturbed to find two rails were going to be too short i.e. leave too big a gap (although it always surprises me how large a gap stock will tolerate). I left the job overnight at that point.

Edited April 12, 2022 by Dr.Glum

[Dr.Glum]

Next day I found that in a previous rebuild the end of the board had been built up, and by scraping it off, my rails were now long enough. Phew!

Tracks were re-aligned, the board offered up, the electrics checked – no shorts. All OK, except no loco would run on the board. At least eight years of no running or cleaning had left a non-conductive patina on the nickel silver. (It then took a long time to clean it all with a glass fibre pencil.) While it was connected I thought, “I’ll try the point motors”. After all this time, I had to look up what the command was. I tried all three on that board – nothing. “Oh well, perhaps it was asking a lot for them to remember their addresses”. I was even willing to believe some of the electronics had failed.

Durr! I had switched the track power off. (I didn’t install a separate bus for the points on the old layout and I’d never had a problem.) With the power on, blow me, they all remembered their addresses and they all worked.

Next day, with cleaned track, I did some test running. The image below shows crossing from the new headshunt of the Outer Loop across to the Inner Main.

 

Edited April 12, 2022 by Dr.Glum

[Dr.Glum]

Been quite a lot of progress since late January. All three extension boards are operational and allow a bit of a run while the circuit round the room hasn't yet been built.

I can remove the board that straddles the doorway if I want to shut the doors between sessions, but I've found to my cost that that removes the end-to-end stability. I sent one board flying by bumping into the end. Result: one knackered point motor that landed on the door frame. It's still definitely a worthwhile project.

I've laid temporary track round onto boards 3 & 4, to get maximum run for playing. After I have a visit from an old school chum in five weeks time, I'll take everything down so that the ceiling can be insulated.

Next

[Dr.Glum]

Time to strip another of the old boards. I'm particularly after the double cross-over which I hoped to re-use to link the outer loop with the outer main on Board 4. For operating flexibility there will be three places around the room where it is/will be possible to change between loop and main. Because I had found hacking standard Peco points and crossing led to a non-symmetrical result (or at least with the amount of cutting I was prepared to attempt 15 years ago) this will be the only example of both inwards and outwards at the same place.

The next shot show how I have traced the rails of the junction and then found the positions of all the droppers that are soldered on. There are so many because the junction is fully switched for the two routes A and B across, as this was the only way I could get good slow running with even the shortest wheelbase (well, I didn't own a 0-4-0 then) and also avoid some locos shorting sometimes. Choose A, and all B rails are dead, including an approach length and vice versa.

[Below] I've eased up and removed all the track pins, and the two nearer points on the loop have come away because there were no rail joiners attaching them. Reason? Geometry made it impossible to put it together, even when isolating joiners flex. (I did not have derailments.)

Finally I took advantage of the baseboard being white before it and the track were sprayed grey, so now I could line up the tracing, check its veracity and poke a biro end into the dropper holes to make an accurate mask for when I lay the track again.

"Why bother with all this namby-pamby arty-farty tracing business?", I hear you ask. Well when I lay this on the new layout I want to keep the dropper holes as small as possible, and avoid new droppers at all costs. Soldering on some of them was a nightmare in the confined places on the crossing.

[Dr.Glum]

For a bit of fun when a friend was coming round for a look, I dug out and put together this small bit of scenery from the old layout. The buildings are detachable and may find a home  on this layout, but not on this triangular base. The lights all worked except the one in the phone box (hardly visible behind the right hand bus), which may not have been connected.

[Dr.Glum]

A friend helped me offer up the next (last) board supplied by Tim Horn. It didn't fit. Some numpty had specified the length to exactly fill the space to the window glass, instead of that length minus the 6cm allowance. I am an idiot.

However, I started looking at how it would be if the board was applied the other way round. There's no real reason why the layout this side of the room has to be the absolute minimum footprint. So I've trialled it rotated by 90 degrees.

The extra area has led to all sorts of interesting changes to my thinking of how the tracks will lie. More of that anon.

I spent a long time measuring and discovering the geometry of the gap. It turns out that the board 4 (on the right above) is not parallel to the end windows by a small amount, but I can't change that as it is governed by position constraints on all the other boards bolted together. So that gap filler is to be slightly irregular as I do want the sections down the left windows to be parallel to the windows. In the end I decided I wanted to build it myself, mainly because if necessary I could change the design as I progressed. No, mainly because I was too impatient.

I was trying to find the same ply that Tom Horn uses, and failed. But I did find a local builders merchants that had in stock 9mm marine ply (that over the years I read so much about).

My sheet 2400mm x 1225mm x 9mm cost me £54.26 plus £2.40 to clean cut it into three section so I could get it into the car. It's a lot for one bit of wood, but it's fair value as it should be enough for the rest of the layout.

For the life of me I cannot keep to a line with an electric saw, so it took me most of a day to manually saw all the pieces for Board 5. I had to rest between sessions to prevent a terrible knotting behind my right shoulder.

So I've created the kit of parts (nearly all shown above). Let mayhem and gluing and screwing and cursing and bodging ensue! I numbered everything, and tried to mark which were the gluing areas on the parts, so how come I so often stuck things on upsidedown, or failed to see the block wasn't lined up correctly, or other stupid mistakes? I do despair sometimes. 🤪 Nearly finished, below.

If all my edges were perfect like Tim Horn's laser cut ones, I could have used wood glue. I used the equivalent of Evostick. Then 20mm screws. It's finished now and I recovered from all the bodges and it's strong and I'm pleased. 😄

[Dr.Glum]

Finished Board 5 (on right) clamped to Board 6 as a trial. I separated them, attended to proud screw heads on Board 6, back together and, joy, the surfaces form a plane. Because all my timber is 9mm nominal, the two boards weigh about the same.

After bolting them together, I lifted them into position with the help of a friend. This morning I've levelled them with shims, drilled bolt holes between 5 and 4 and locked it in place. I can now extend some temporary track round the corner.

So my mistake with dimension of Board 6 has actually improved what is possible in this area, with a bit more space for the end of the goods yard in front. I'm aware it's quite a reach to the far corner, but most of the curves can be laid next time the boards are down. The scenic stuff and colliery tracks will be on top of the tunnels made as a removable layer so I'll be able to get at all sides of that. Build it, and then plonk it in place.

Once I know where the ground level track curves will be, I shall make access holes in the board surface so I can reach up through and deal with any (unlikely) derailments or collisions (more likely) in the tunnels.

[Dr.Glum]

Update  since April 22nd.

I’ve continued to lay temporary track to check that my plans are feasible. The corner shown below will have the four tracks in tunnels. I had to make up Scalescenes tunnel mouths to find my minimum spacing. The other tunnel mouths will be roughly at the RH edge of the picture. (I wish I’d remembered to apply the darkening option when I printed the sheets: my stonework looks like it was built yesterday and no smoky trains been near it.)

In the following image you can see the temporary ledge on the end of the baseboard. The grey board with 4 tracks on it (on the settee, lower right) sits on this and spans across the doorway to the garden, giving me about 6 feet extra run, for now. I have yet to build the permanent wedge shaped board that’ll bolt on to the face you can see.

The railway arches (above) are a scenic module from off the old layout. I’m thinking about how they (and others) can be used on this one, but not where you see now.

The next view is taken from the ‘previous’ corner. The sidings won’t necessarily be like that. I allow minimum radius 24 inches in goods sidings where space is squeezed.

About ten days ago I was stood looking at the layout late one evening, musing with a drink in hand, and rather than just plan to progress the build on the end that I had reached, I was suddenly taken with the urge to tackle the difficult bit at the other end of the layout. I had to have a lift-out section spanning a 1.5m gap for 4 tracks and a spur off leading into the house. I started next day. I’ve documented it in a separate post:

 

For now, here’s a view of it awaiting final fettling so that the edge walling will fit vertically, before track laying begins.

[Dr.Glum]

And here it is, nearly finished and in use, playing trains.

It turns out (quite fortuitously) that there is just clearance to put the board up with the door to the house closed if I don't need to run into the house during a session. I'll have a better view of the MPD. I'll think about a drop in building to fill the gap between boards.

and

[Dr.Glum]

Spurred up by seeing trains on the curves of Board 8, I started on the woodwork of the adjacent corner Board 7. A temporary measuring jig made from foamboard showed me the corner was a right angle, which simplified matters.

This board is to be of 9mm marine ply. Having cut out the top I wanted to see what it was going to look like. It sits between two doorways.

The white item is a microwave bracket from B&Q (SWL 10Kg) and will be the support at the LH edge of the brickwork.

After a while I bowed to the bloomin’ obvious, and took the trouble to clamp the pieces I was sawing. It was well worth it, even if the clamp has to be moved part way through the cut. It improved my ability to keep to the line and to make a vertical edge (well nearly, most of the time). The pink glove is left over from my days working on the farm and is to protect against splinters from ply edges, and from tiny slivers that even come off the surface (until it is sealed).

The existing blocks have been screwed from both directions for extra strength. A boring day making a kit of parts; a lot of ply to saw. After they’re all glued in, it will need more blocks at the new joints and then they’ll need screwing up too.

I’ve sorted out suitable chocblocks, wires and cabling for the track and there are enough holes for wires to reach anywhere. There will be streetlights and maybe lit buildings, but I don’t know where yet.

[Dr.Glum]

The board 7 is finished, apart from varnishing, wiring, cork laying and spraying the top surface. And laying track and adding edge walls. And scenery. At the moment it weighs about 13lb / 6kg. The focus has been to get the supports right. The board is now anchored and level (temporarily) in the picture below.

The depth is quite shallow (58mm), but it’s not a big board and “she’ll be right!”

Above:  Bridging The Gap. Having established both boards in the exact right place and absolutely level, I’m measuring the gap and shape. To the nearest half millimetre is the best I can hope to build. That should be no problem for the track gaps.

Earlier in the week I thought that somehow, despite calculations and care, it was going to end up about 3mm higher than the adjacent board, which was a very disturbing thought. In the event, now that the supports are stable, I find it naturally sits 3mm lower, which is an ideal situation, right in the range I was hoping for. You can always shim up, but sawing thin slices off the top of supports and moving wall brackets? Nooo thank you very much.

[Graham108]

On 21/08/2022 at 21:50, Dr.Glum said:

 

 

Why didn't you clamp it in such a way that the cut went down the middle of the work mate?

[Dr.Glum]

Graham108 - you have a point.

a) I didn't at the time think of it and b) at either end of the Workmate there's a cross-strut and the end of the saw connects annoyingly except over a short range, so I'd have had to move the piece and the clamp as I progressed anyway.

But mainly I didn't think about that, at least, not consciously!

[Dr.Glum]

So I have to extend the surface (to be level and plane with the existing foamboard) and extend the load bearing frame member. First I have to remove a block (which I actually hadn’t needed to fit yet) and make holes for short wood to be glued alongside the main frame.

The impact adhesive had really got a hold of it, so I did a lot of damage removing it. The next shot shows the frame extender glued in. The white areas are setting PVA spread to strengthen the damaged underside of the board surface. Strengthening pieces were later added.

In the next shot you can see me struggling to make a level surface for the track. I’ve had to use filler because the surface foam board had become slightly curved downwards when I was wrestling with removing the wood underneath.

It proved to be a right old game, as I had failed to get that plate of mdf on the end absolutely true. Lots of wasted hours.

Next picture is the result of testing curves and track positions. It convinced me I needed to widen the end of the board, so I eased the side wall away. In the view, I am measuring up for a surface filler (long thin ‘wedge’) and wall extensions.

Below the view is along the tracks from Board 8 to Board 7. (Left hand track cut to length and fettled ready, but the end not pinned yet.) The alignments are good enough for very smooth running, but cosmetically I didn’t quite get the second track from the right (Up Main) as I would wish. There is a rail joint a few inches in from the end of the board that jars (my eye, not the trains). But mostly I won’t get this view, and it’s stuck down and pinned and it’ll have to do. (Minimum radius ahead is 30 inches.)

Edited September 21, 2022 by Dr.Glum
To clarify what jarred.

[Dr.Glum]

Uploaded a brief video to Youtube of three trains running.

https://youtu.be/H_jtX0qptnQ

Cheers

[Dr.Glum]

Before I finished laying the outer loop and its point, my thought turned to scenic treatment of the area. The length of curve on the outer tracks would support platforms long enough for at least three carriages (short locals) and I fancied a bridge as a scenic break for the curves. I have the Scalescene downloads for an arch bridge (R011) and a plate girder bridge (R012A) and in the view below I am using bits of printout to see what’s feasible.

The geometry of the curves arising from the presence of the point meant that there would have been an unsightly gap between the outer loop and the down main, but the presence of a bridge pillar makes it logical. In the next image I’ve started building the structure and am checking clearances (again).

The outer platform will run under the arch and the inner one under the plate bridge. (I don't really expect to run HST's on the outer loops, but it gives the max overhang.)

[Dr.Glum]

I need 2 curved platforms. Last time I started such things, I made a tracing of the track on the curve (on multiple pieces of paper) and used that to cut the platform surface. It was not a success, as the paper moves while you’re pressing it on the rail heads, and generally it is too prone to creeping errors. I was just too impatient to get started.

This time I did start with a tracing of the rail head, but only to get an approximate line to cut paper templates to stick down. I drew a pencil line 7mm inside the centre line of the rail head impression on my tracings and then cut that with scissors. The image below shows the pieces of A3 paper taped down.

The offcut of old platform (on end) shows the profile I will build, this time with greyboard. 1mm of lip, 2mm of coping, 2mm of platform side, foamboard base inside.

BR standard platform height to railhead is 3 feet – 12mm. Add 4½mm for Peco code 100 track height gives 16½mm, but I chose to make a little test piece at 15½mm as the story is that this is an old station.

Next I have to determine my minimum clearance distance: platform edge to sleeper ends. I used my paper template (30 inch radius) to see if there was a minimum radius curve location: there was a few inches exactly at 30 inch radius. A Mk1 carriage would be the longest vehicle on the inner loop (as I had no intention of running HSTs along there). See next image with the height test piece.

I found a minimum of 6mm from sleeper ends. I did wonder about the steps on steam locomotives, but it quickly became clear this wasn’t an issue. Job done. Or so I thought.

While collecting suitable sheets of greyboard (or rather, brownboard now it’s treated with knotting fluid) I was troubled by a niggle. What about the fuel tanks and gubbins under my diesels? As soon as I opened a loco box, there was the massive length of the Deltic. I measured up again.

Clearance was 9½mm from sleeper end; call that 10mm for construction tolerance. Good job I checked. I made a pen holder that I could slide along the rails making a clean line on my template paper. It was a right faff drilling out a shaped hole to present the pen point at 17mm from the face of the block of rail guide. I imitated the farmer in Shaun the Sheep when he’s angry, when I finished the tedious job and discovered I been drilling from the wrong side. Rather than start from scratch, I opened up the other side enough to just get the pen point through and used two hands: one to move it, one to ensure the pen was upright and drew a line.

Nice line. Job done. Or so I thought. I put a Mk1 carriage on the track. Oh. That’s an awful gap at the carriage ends. Shame I can’t have 5ft radius curves – hah! But I had a think and decided that operationally I could cope if the Deltic was banned from that part of the line. I need Ml1s to be able to pass here, but 57ft suburbans or 63ft Gresley’s don’t look too bad at the Mk1 6mm spacing (for posed photos when it’s built). So I’ll draw a line 4mm outside the present one before or after transferring to brownboard.

[Dr.Glum]

The paper templates are down and marked with the curves for both the inside and outside platforms. The bridge is now finished. Well almost; I havn't glued the girder parapets in yet, in case I need to separate the parts (arch, roadway, RH buttress) while constructing further walling and everything that will adjoin what you see.

Everything is upright; my camera distorts close objects.

[Dr.Glum]

I have cut out the greyboard platform surfaces and made up some temporary ‘stands’ (visible below) to raise them up to the design height (15½mm). That allowed me to check clearances with carriages. So then I find out that the headstocks on Gresleys and Hawksworths stick out a bit more than Mk1s at my platform edge height and I need a bit more clearance.

Once the platform edge was established, I drew round the curved outline onto foamboard. Using an offcut of card 6mm wide, I marked an offset from that line (2mm sidewall + 2mm coping + 2mm platform overhang) all along the curve and then cut the foamboard.

I had earlier made three locating ‘plates’ for the foot of the bridge abutments (visible below) and glued them to the baseboard. In the next photo I have cut holes in the base and platform surface for one abutment and am about the measure up for the other two. Right old game, that was!

After some adjustments (bodging) I could put the outside platform in place with the bridge piers passing down through. And that’s what’s shown in the next photo.

[BTW yes I know I could have made the abutments not so tall and stood them on the platforms. But when I built the bridge I hadn’t planned the platforms and other scenery in enough detail. Now I don’t trust my ability to accurately shorten them and have resulting gaps.]