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1/72 Bridge Diorama


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A year ago the local maritime museum obtained the original (1964) console for Wardell (NSW - Australia) lift-span bridge.


Museum staff wondered if it could be used as an interactive display, such as flicking a switch to turn a panel light on. One of the staff, knowing my background in electronics, asked me to appraise the situation. At the end of the day I found myself not only having to make the console operate a model bridge, but to build a model of Wardell bridge as well. This will be my first model building project. Below is a photo of the bridge.


A few weeks later, the curator allocated the display area. At first I said it was too big. I planned to only build a portion of the bridge, and to be no wider than the console. He said that I had to fill in that space somehow. It is 4 x 8 feet (1200 x 2400 mm). 


There was no console schematics, nor bridge plans, available. The console had to be reverse engineered. The bridge plans had to be, from two reference measurements, extrapolated from photographs. It turned out that a 1/72 scale would allow the whole bridge to fit across the 8 foot display area. It was at this point when I discovered a new word _ diorama. So now, the model will not only have a boat traversing under the raised bridge, but also a replication of the river banks.


This is a large project, with many photographs. It will take a long time to complete. The diorama, to date, is about 2/3 completed. I am building the diorama in my spare time, as a volunteer. I don't get paid, but the museum will be paying for the materials I will be using. The museum is a non-profit organisation. So I have to be frugal.

I will be posting images, most days, until I catch up to my current status. Then updates will be sporadic.

Please feel free, at any time, to ask any questions about this build.

to be continued...

Edited by Peter
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Hi, Peter,

This is a great way to introduce yourself to us.  You only get one chance to make a good first impression, and yours is a whopper.  I know I will enjoy seeing your work-in-progress pictures.  Thanks for alerting us to this project.  Welcome to the Forum.


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Spent a fair bit of time drawing up plans for the display. Used the standard MS Paint program.


How the lift-span bridge operates, for allowing tall vessels to pass under the bridge.


Decided to us a pulley-cable system to operate the raising and lowering of the bridge span, and for traversing the model boat under it.


Examining the console wiring, and stripping the excess (wires cut loose or extracting the console).


The control panel could not be removed to access the wiring to the various switches etc. It was all tied down to the three vertical terminal strips within the console. Had to strip all the wires to pull out the control panel. This made it easier to figure out all the terminals to the instruments. Then I drew schematic diagrams for each type of instrument.




After all of this, I still did not know how to operate the lift-span. Had to interviewed the current bridge operator. Though he had never seen this original console before, he was able to understand it. He was not allowed to tell me how to operate the bridge for security reasons. But he was able to tell me the function of each switch. From this, I was able to get a good idea of the operating sequence. It is definitely not a simple matter of flicking a switch to raise and/or lower the bridge. Much is needed to be known and controlled throughout the operation. Road traffic, pedestrians, river traffic, navigational lights and signalling, let alone operating the bridge span itself.

Then a problem arose, that is still not completely figured out. Museum visitors are to be encouraged to operate the model bridge. Naturally they will need to follow a stepped sequence. The problem is, the operation needs to be child-proof. In other words, I have to make sure that nothing can be operated out of sequence. Such as dropping the bridge span on the traversing boat.

I am old school when it comes to electronics. PIC microcontrollers, and the like, which would make things easier. But these are outside of my knowledge base. So it's going to be based on analogue circuits and some logic circuits too.

Spent some time designing a DC power supply circuit for the electronics. Will be using 5 volts for logic circuits, 12 volts for motor and relay circuits, and 24 volts for relays and lighting.



Next update will be about building the display platform and the bridge.



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Thanks Rusty for visiting, responding, and following this build. Much appreciated.

6 hours ago, Rusty White said:

This your first MODEL?  I would be intimidated as heck.  Good luck and I'll follow along.

:laugh:  I have asked myself a few times "what have I got myself into now?"  

Fortunately I do not believe anything is impossible. I have tried many firsts, like anybody else, in the last fifty years. Most things we do require transferable skills. So I am not that easily phased out. Actually, I really enjoy the challenge, because it brings the creativity out of us _ the very essence of inspiration. It makes life so meaningful.

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The display tabletop. Note the slit across the table. This is for the boat keel/vane to pass through to the pulley system. The slot also guides the boat back and forth under the bridge.


Built a control box that fits under the table, and directly under the bridge. This will house the motors, pulley systems and various electronics. The box has two hinged doors for accessing its contents for maintenance and repairs.


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Cut, filed, and Inserted the bridge footings.


Added bridge piers. Each set had its own length so as to create the desired curvature of the bridge road. Wood putty was applied around the base of the footings. This is to eliminate any shadows that may suggest that the footing is afloat.


Display side walls were added. Girders added onto the piers.


It is starting to look like a bridge.

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Before adding the road base I needed to apply a few coats of Acrylic primer.


making Fender Piers (aka Dolphins). The outer centre piers are drilled out to accommodate red and/or green navigational lights.


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Could not find any (cheap) narrow pulley wheels needed.  So I made my own from washers. I sweat-soldered them together.

The first one did not work well, but I learnt from that, and the rest turned out okay.


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Adding D-connectors to rear of console. This where two cables will serve as connections between console and the control box (under display table).


I have been cannibalizing old TV sets, computers, etc., to get extra parts for the diorama. Here I am making a bracket for a nice pair of TV speakers. These will be required for sound effects such as an alarm bell, fog horn, and diesel boat engine.


The museum president suggested to take photographs of the console re-wiring. So kids will get an idea what is inside the console. I opened my big mouth and suggested to replace the  front panel with a thick clear Perspex sheet. So now the console too will become a diorama of sorts on its own.

After cutting out the speaker slots, The console interior got sanded and painted for a cleaner presentation.


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Added Masonite road base, footpath and kerbing to the span.


The span will have an operations hut, vessel traffic lights, and navigational lights underneath. Contact points, for when the span is docked onto the bridge, allows electrical connection to the span. The span itself, when undocked, will have its own power from a re-chargeable battery (in the hut). It gets re-charged everytime the span gets docked. Wiring from the contacts and navigational lights need to be trenched into the span base. Then the wires get routed up the span framework to the hut atop of the span.



Building the span framework.



Using fishing swivels, soldered to bolt heads, for pulley-cable anchoring points. The swivel will ensure no twisting tension to the cable.



Just checking to see how the span will look on the bridge.



Any comments would be greatly appreciated.

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Wow quite the undertaking.  The lighting/operating would have stopped me in my tracks.  Outstanding work so far.  

It’s good you’re including a boat as to give people a visual for its size rather than just listing  dimensions.  I’ll be following this one.  😄

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Thank you Kev K. for visiting and following this build log. That has made my day.


to continue...

Used computer ribbon cable for the wiring. 



Then filled in the trench-work with wood putty. Sanded and painted with acrylic undercoat.


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The DC powers supply, as shown previously, got made at this point in the build.

Making the printed circuit boards (PCB)


Testing the 24, 12, and 5 volt outputs.


Since the console will now include an interior diorama, I added a small PCB for a 'blown fuse indicator'. The green LED indicates all is well, but if the red LED turns on instead, it means that it's fuse has blown. Below right, the whole DC power supply got installed into the console.


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Thank you Someone for your 'likes'. Much appreciated.


I draw plans as I go along. Originally done on MS Paint software. But today I just put my hand drawn plans into the files folder. Eventually, this folder will be the service manual.

Here is a plan for the hut base, balconies, and gangways. These are cut out from MDF board.


Used matchsticks for rail posts, and split bamboo skewers for railings.


Sometimes I get carried away with the model building and forget to take photos. Below, you can see that I added the longitudinal bumper rollers to the corners. These were made from microswitch actuation levers/arms. These assure that the span, upon raising and lowering, will not get snagged onto the tower.

In one corner, there is a U-shaped (slot) opto-coupler. This device will trigger the span motor to stop when the span has reached the top of the towers. A fixed vane/flag, on the tower, will come in between a light beam between the U arms. Cutting the light beam will similate 'turning the power off' to the span motor.


Routed the wiring up and along the framework and up through the hut floor.


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Sorry, but your first model is just not complicated enough.

Well, now I have to go shoot myself.  Make sure you keep posting photos.  So my survivors will know why I offed myself.

Edited by Highlander
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Thank you Wee Davey @Highlander for complement. But don't shoot yourself, it's not what it seems.

As a lot of older guys, who have had varying careers, do collect various skill sets. But the trick is to transfer those skills to accomplish other tasks. Though this may be my first model, it definitely is not my first hand in woodwork, electronics, drafting, or designing. Also, I just did not dive straight into building a model. I spent many hours on the Internet looking at what others, such as yourself, have done to make models. A rich source of information was from railway modellers. It is here that I first heard about the word 'diorama'.

To be honest, I discovered that modelling (scratch-building) is very enjoyable. I can easily see myself building lots of models in the future.

Edited by Peter
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Here is an image of the actual bridge bumper rollers. These keep the span in place under high winds.


Added lateral bumper rollers.


Where the huts is, on the span, there is a set of red-green traffic lights for the river vessels.


Around the hut balconies are boxed areas for housing winches, gearbox, and assorted maintenance storage. Below, these are waiting on the windowsill for the paint to dry.


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9 hours ago, pardubak said:

This is truly an impressive and ambitious build, and I can only echo the sentiments of earlier commenters. Thank you also for a detailed build log. Very inspirational :smiley20:

Thanks for kind words.

Here and there, I left out written explanations. Thinkingt that some photos ought to be somewhat self explanatory. Glad you like the build log so far.

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