Building a Bridge

Apr 20, 2015
Well, it's not about building a real bridge, but a model of one. But there is more to it.

A while ago a friend, knowing my avionics background, ask me to assess an antiquated lift-span bridge console. The local maritime museum acquisitioned the console and wanted to know if it could be used as an interactive display. They hoped it could operate a model of the local bridge that the console came from. I soon found out that the museum had no model or anybody to build one.

Though I had never built a model before, or any electronics for a few decades, I knew I could do this. Though I felt confident, prudence told me to say a prayer before consenting to the tasks required - "May God favour the bold or the foolish".

Because this museum is totally run by volunteers, I too became a volunteer to fulfill their request. At first they wanted to assign some helpers. Then I found out that there were no plans available for both the console or the bridge. That meant the bridge had to be built from scratch, and the console reverse engineered. Nobody had the skills to do either, or wanted to get involved or have a go at it. So I took it on alone.

As the project started, hundreds of questions arose as to the display scale, how to operate the console, drawing up the plans and schematics, designing the electronics, researching and ordering parts, and putting it all together. The complexity of the project started to dawn on me. There was so much to learn and consider. The museum is on a small budget. Many parts were sourced from unlikely places and homemade.

The project is still going. This thread will be a sort of a journal-story of Building a Bridge. There are challenges to overcome, little miracles of creativity along the way, and heaps of praise for God's helping hands.

To start with, here are some photographs of the actual lift-span bridge, and the old console that came from it.

0_Wardell Lift-Span Bridge.jpg

control panel.jpg

Further posts will follow on nearly a daily basis until I reach the point where I am at with the ongoing project. Then the posts will be spasmodic according to tasks completed. Hope you will enjoy the story.

Please feel free to post any questions of comments along the way.
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Apr 20, 2015
The first task was to understand the control panel of the console. Some of it did not make sense to me. A meeting with the bridge operator, though he has never seen the control panel before, was able to explain it to me. It turned out that the console was installed in 1962 and replaced in 1995.

500 x 460px or 25 x 23 inch scale.jpg

Drew the control panel for easier reading. Note: An Operating and Troubleshooting Manual is being compiled as the project progresses.
Control panel drawing.jpg
For those that wish to know what is involved in operating this lift-span bridge.
  1. First the usual reason to operate the bridge is to allow a vessel, too tall to go under the bridge, to pass through. The bridge operator needs to know from which side (upstream or downstream) the vessel is waiting from. The operator communicates for the vessel to follow the vessel traffic signals (red/green) on the top of the lift-span itself.
  2. The operator turns the power on to the bridge via the CHANGEOVER switch to NORMAL. This turns the road traffic lights on and to GREEN.
  3. Then turns the NAVIGATIONAL LIGHTS switch to either up/down stream. At this stage both Up & Down stream traffic lights are RED. No boats are to pass under the bridge at this stage.
  4. The operator waits for a clear spell in the flow of road traffic.
  5. The road traffic lights CONTROL SWITCH is turned to CONTROL, and the unlabeled traffic control switch [bottom left] is turned to NORMAL. This turns the road traffic signal lights to AMBER (flashing) for 15 seconds (plus an alarm bell). If more time is needed for road and pedestrians to clear the bridge area, the operator switches this switch from NORMAL to EXTEND.
  6. The operator today has closed circuit TV, but pre 1995, the operator used an upside down periscope to view the road and pathways on the lift-span (operating hut is on top of the span). So once all is clear, the road traffic switch (back in NORMAL) will (after 15 seconds) will turn from flashing AMBER to RED.
  7. Once traffic has actually stopped at both ends GATE switches 1-4 are closed across the roadway.
  8. Then the lift-span bridge is unlocked (by a lever next to the console - much like ones seen in a railway signal box).
  9. The Bridge is raised by the SPAN CONTROL pushbuttons. The span has to raises to the top before the vessel traffic lights switch over to GREEN.
  10. The operator signals the boat to pass under the span,
The rest of the procedure is basically in reverse order.

So you can see that it really is not a simple matter of flicking a switch for up or down. Now here is a problem with allowing the public to operate the model bridge - it has to be childproof. That is, any out off-sequence use of the switches and buttons ought not to work. This part of the design has not yet been resolved, but I know I can work it out once I get to the electronic design stages.

Here is how the model bridge ought to operate:

Wardell Bridge anigif 1.gif
Apr 20, 2015
The curator was always complaining that there was not enough space in the museum. So my plan was to design a compact display with the console as the larger piece. To my surprise the curator would not condone the idea. He insisted I use the space allotted for the project. He showed me a huge 2.4 x 1.2 x 2.0 m (8 x 4 x 6.5 feet) space. He wanted the whole bridge with river banks. In other words, a diorama. :eek:

God sure has a sense of humour. Obviously He thinks I can deal with it. That is one of the beautiful things about God, He knows me better than I know myself.

Since no plans were available for the bridge, I had to measure it myself in a round about way. Photographing the bridge was sort of fun. I crossed this bridge hundreds of times before but never really took much notice of it. Now I know ever nook and cranny. Then I only took two measurements, the width of the road and the length of the span. From this, and measuring parts of the photographs, I was able to create a scale drawing of the bridge. It turned out that a very popular modelling scale of 72:1 fitted the whole bridge into the 2.4 m length of the display space. Meaning, that I could purchase scale vehicles and figurines to place in the diorama.

Bridge display layout drawing.png
As you may have guessed, there is also a boat involved. (I told you it would get more complicated).

bridge display idea -large.png
Because there will be a boat actually travelling under the bridge, its control will need to be managed under the table. The boat will be moving along a slot cut into the display table. Also, the electric motor for the lift-span is too large to fit in the operations hut. So it too will be managed under the table, with its control cables actually going through the display table too.

motor positioning plan_1.png
SM = Span Motor.
BM = Boat Motor.

As you can see, it is getting quite complex and at times daunting. Each piece, in one way or another, effects the surrounding pieces with it. Because of this, I sometimes feel overwhelmed by juggling it all in my mind. When this happens I drop everything and go for a long bicycle ride to clear my mind.

As this project unfolds, the museum staff can't understand how one person can do all this. I wonder too sometimes! However, it has not yet scared me off. At this point in time it is all just on the drawing board. Many detailed plans were drawn for the bridge, display table, and the Control Box with motors and electronics to fit under the display table.

After about a month of drawing the plans, it was time to have a meeting with the museum president, curator, and treasurer about the costs. They gave me free rein, knowing that I will be frugal and prudent with sourcing and costing---what a relief that was. The last thing I needed was to be questioned for every cent spent.

Now came to big step in faith, to purchase parts and building materials to put the plans into actual physical creativity.

Fish Catcher Jim

Feb 7, 2015
Hi Peter Luke
I am enjoying this thread very much.
Along the great loop there are many, many different types of Lift Bridges and I have not found one that did not simply amaze me.

This might be a little off topic but I wanted to share this with you.

Also a piece of the great loop is the Trent Severn Waterway which host several of the most unique locks I have ever seen.
These are old school designs and we're originally meant to be replaced but worked so well they never did.

This one is as good as any amusement park ride. Lol, you actually float up on a platform which you are then strapped up and lifted up onto a rail system which takes you up and over unto the other side.
It's pretty wild.

This was built with the same intentions but is still in operation today.
It's two huge concrete tubs if you will. You float in and one lowers as the other rises and the water and hydraulics system is purely amazing.

If you get a chance, check out some videos on you tube.

Again I apologize for going off topic a bit but I thought you might truly enjoy them.

Looking forward to you next entry.
Apr 20, 2015
Not a problem Jim.
Very interesting design features. Never seen anything like it. I also liked the model shown in the last link.
Thanks for showing us a different type of lift apparatus.
Apr 20, 2015
While waiting for certain parts and materials to arrive I started to disassemble the console. The wiring needed re-doing to operate a completely different setup.

2_Bridge Model update_ Stripping Wiring Harness.jpg

The switches were heavy industrial types, The larger ones were hand-made (1961) for a specific task.

CONTROL SWITCH connections.jpg
These switches and pushbuttons had to be deciphered in terms of what and how contacts were arranged. Drawings were then made from the decipher, such as:

Apr 20, 2015
Due to the museum workshop being too small for this long-term project, I opted to have it built in my place (a small unit). Not having a garage the project has to be in my lounde-room come studio-workshop (the privileges of being a hermit who does not have a TV or radio).

When the timber was delivered I measured and marked out everything according to my drawings. Such as:

Below: Those grey bits in the drawing is a steel framework that is a fixture already in the display space. I had to design the display table around it. The box under the table is for housing the motors, pulley system and electronics.
Bridge display plan.png

I am an old fashioned tinkerer and all my tools are the same (hand saw, hammer and chisel, etc)
Left: All timber cut to size.
Right: Display tabletop assembled; all screw countersunk and filled with wood putty. Notice the gap-slot for guiding the boat.
Bottom: Table supported on two carpenter's horses, sanded and ready for the bridge-work. This is a later photo, after I built the control box.
PS. my desk, with the laptop, is both dinning table and office - where I am now sitting typing this report on this forum. as you can see, there is not much room to get around. It's been like this for many months, and still is.
3_Bridge Model update_display table.jpg

Top L-R: Assembling the Control Box; Notice the gap slot has two wooden slats on the edges to deepen the slot for steadier guidance.
Center L-R: Control Box access doors for future maintenance and/or repairs.
Bottom L-R: Interior view.
4_Bridge Model update_working compartment Box.jpg
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Apr 20, 2015
By this stage some electronics parts arrived. I thought good, I need a break from carpentry. Besides, its been thirty odd years since I done any electronics (old fashioned in that department too). I was looking forward to designing circuits, testing them out on a circuit breadboard, and designing a circuit board, etching the board, assembling the components, and trialing it. This last bit is always that part of an experiment where you will find out if it will blow-up in your face or not.

The first circuit to build is the Power Supply Unit (PSU). From this, all other circuits can be tested and run from it. There is three voltages. +24 volts for panel lamps, +12 volts for relays and motors, and +5 volts for logic circuits.

Here is the PSU circuit diagram (after a few drafts and modifications):

Designing the printed circuit board (PCB)

Testing the PSU.
As it turned out, all worked perfectly fine at the initial switch-on.
PS, Those aluminium heatsinks, on the printed circuit board, came from a few computer PSUs I cannibalized the previous week. The metal strip is part of the console interior. The PSU will be located in the console.
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Apr 20, 2015
Back to the display table. Here are my plans for the bridge.

Bridge plans.png

I had trouble sourcing the right dowel, or wooden pole size, for bridge footings. I had to cut them out myself and shape them with a file.

6_Bridge Model update _footings.jpg

I used wood putty around the footings to display table (river) to eliminate seeing a gap-line which would make the footings look like they were floating on water, but in fact are large concrete pylons into the riverbed.
7_Bridge Model update _piers.jpg

At last, some resemblance of a bridge is coming together .

I always emailed these photographs to the museum president and curator. This gives them an update in what I am doing.

At this stage of the project the curator was perplexed that I would put so much effort into scaling the size and curving the bridge instead of simple and straight. Apparently, other museum staff were saying the same. Yet the museum has many examples of very fine model boats and ships, all built from scratch, and to scale. I thought it was odd. Perhaps they were taking the working part of this model too much for granted. So, I arranged a brief meeting with the committee members to explain my reasoning.

I explained that any working model will one day break down and become irreparable due to sourcing parts and/or nobody wanting to repair it. On that day, the model can no longer rely on its attraction based on working parts. It is then my plan to build a bridge as best I can, to resemble the actual structure and its surrounds, so it can stand by itself as an attractive aesthetic and static display. That being said, they gave me the go ahead to do it the way I thought it would work best.
Apr 20, 2015
Bridge lifts-span platform, girders, and an underpass are installed.
8_Bridge Model update _girders.jpg

An undercoat of paint is applied to the bridge sub-structure before the road base gets put on. The river part has been undercoated too. The river banks and road is left raw for adhering the landscape too.
9_Bridge Model update _under-structure undercoat.jpg
Above. The holes you see in the girder edge is for contact wires for carrying signals and power to the lift-span when it is docked (explained later).

Below. Fender pylons (aka Dolphins). The outer Dolphins accommodate the river navigational lights (red and green) from the centre pylons.
10_Bridge Model update _Fender piles.jpg
Apr 20, 2015
Thank you all for your likes.

At this stage I was still waiting for certain parts for making the traffic lights. The lights, and wiring, had to be installed before installing the road base.
So in the meantime my attention went back to the console.

All the wiring and electronics will be located in two areas, in the console and under the display table. Both need to be connected to each other via connectors. I decided to use the common computer type D-Connectors. Holes were cut out to accommodate these connectors and a mains power plug connector as well.

12-Bridge Model update_Console connectors.jpg

Also, there will be some sound effects incorporated with this project, such as the alarm bell, and the sound of the boat diesel engines chugging along as the boat passes under the bridge. Speakers were obtained from cannibalizing my old analogue TV set. However, they could not be properly used without making a bracket for them. Otherwise the speaker diaphragm would be suppressed and muffled.
13_Bridge Model update_Speaker encasement.jpg

These speakers would be installed into the back of the console, so another tow cut-outs were required.

The museum president mentioned that it was a pity that the console internals could not be seen. He said it would provide some education for the children about what was involved in making the bridge operate. I suggested that we could replace the front metal panel with a thick sheet of perspex, and turn the interior into another diorama in itself. I added that we could cover the bottom portion of the perspex with sheet metal to stop peoples shoes from kicking and or breaking the perspex. In this way, it would be added safety precautions to inadvertent access to the mains power source. Another added piece of complexity.

So now the console interior needed to be cleaned up and painted. I chose a darkish blue (ironically called Boatshed Blue). I thought this colour would help to show-up the coloured wiring when it gets installed. I also planned to include internal lighting.

14_Bridge Model update_Speaker slots.jpg
Apr 20, 2015
Back to doing more bridgework.

Masonite (the dark stuff) was added to the base of the lift-span to simulate road, gutter, and footpath surfaces.
Grooves were cut out of the plate to accommodate wiring and (under the bridge) navigational lights (red and green LED lights).
15_Bridge Model update _Span part 1.jpg

Now the framework can be added.
16_Bridge Model update _Span part 2.jpg

Cable anchoring points to the framework were made from fishing line swivels and 3mm (1/8") bolts and nuts.
17_Bridge Model update _Span part 3.jpg

Framework partly completed, placed on the bridge to see how it will look.
18_Bridge Model update _Span part 4.jpg
Apr 20, 2015
Installed the wiring, navigational lights and contacts to the lift-span.
All exiting wires were directed to the vertical beams of the framework (to hide behind).

The entrenched wiring got filled in by wood putty. Then sanded and painted with an acrylic undercoat primer.

Further framework was added. On top of the framework is the Operations Hut where the bridge is operated from. Around the hut are balconies and walkways. They are mainly made from thin Medium-Density Fibreboard (MDF). The notches you see on the drawing is for railings made from matchsticks.

Notice the hut floor plate on top of the base plate; the stepped edges is for guiding and securing the hut walls into place. The rectangular hole is to enable the wiring to enter the hut.

Apr 20, 2015
Before going any further with the walkways I decided to add the longitudinal bumper rollers. These guide and limit the span, while being raised or lowered, from getting caught on the bridge towers. These were adopted from microswitch actuator arms. Also on one corner of the span I added a slit-type photocoupler.

Then I routed all the wiring to the Operations Hut.

Then I added the lateral bumper rollers to stop the span from sideways movement. These too were made from microswitch activator arms.

It's getting a bit compact in the corners of the span. I trusted it will all fit together and the framework will still hold its integrity in terms of strength.
Apr 20, 2015
Vessel traffic lights (red and green LED indicators) were attached to the span framework. Its wires were routed into the hut.

Tools and storage lockers, are placed on the balconies around the hut.
Bottom pictures shows these as blocks, painted grey, drying on the window sill.

Making the Operations Hut walls from MDF, thin clear perspex, and white card-board.

I tell you, it is quite exciting to see how things are coming together. Each step for me is going into unfamiliar territory. As the creation goes deeper each step seems to carry all the preceding steps with it, like a stack of cards. Though I am doing the work, I feel the assistance of God along the way. Much praise is given to God in this project.
Apr 20, 2015
The railings were made from split bamboo skewers, railing posts from matchsticks, and the mesh is fly-screen. It looked better than I imagined.

Painted the whole area bridge grey.
The laptop shows a photo of actual Operations Hut on the span.

Found some narrow washers that fit the navigational lights (LEDs) nicely. Now they look like light beacons.
Railings were added to both the road edges and the footpath.
Apr 20, 2015
Wow, having scanned this thread so far I am sitting here amazed. What a gift~ thanks so much for sharing your bridge project with us, Peter Luke. Blessings. >o<
Thanks for acknowledging the good parts of the work.
I praise the Lord for the gift imparted for me, for I am always grateful to the Lord for it.
The Lord's work is all the good bits, unfortunately all the poor bits is my interference. But that is how it is with us.
The most important bits of the Lord's work is in our heart.
Apr 20, 2015
Since the console is to be a wiring diorama, for extra display value the PSU now has a Blown Fuse Indicator added to it.
While each DC voltage sources are okay, a green LED will be lit. As soon as its fuse is blown, that voltage source will get redirected, from the green LED, through the red LED _ hence, indicating a blown fuse.

Below: The three circuit boards L-R: Blown Fuse Indicators for DC volatges; DC power supply circuitry; Blown Fuse Indicator for AC mains supply. This third circuit is a small red LED indicator embedded in the Panel Meter of the Control panel. If the main fuse blows, all power is switched off except for a 2.7 DC voltage feeding a small red LED light at the meter.

In the console, the three terminal boards have been cleaned and new numbered labels attached to them. The PSU has been installed and connected to one of the terminal boards. The heavy green earth lead is attached to the console, waiting to be connected to another common earthing terminal.