Work In Progress: to date, half completed. Owner: Ballina Naval and Maritime Museum. Display area: 2400 x 1200 mm (8 x 4 feet). Display type: Interactive Dioramas. Designer and Builder: Sparky (museum volunteer). Forum Presentation: Story in pictures. Hopefully one per day.
The museum did not have enough space, in its workshop, to include this project as well. So it is being built in my lounge-dining room (I have no garage).
Building the display table and its control box.
The line across the table is a 3 mm gap used for guiding the boat under the bridge.
The control box has two doors for accessing the motors, pulley-cable systems, and various electronics.
Here is a layout drawing of how the span and boat are to work.
note: There is no return cabling from the span. The counterweights are fake (balsa), and the weight of the span ought to be enough to guide the span downwards during the 'lowering' operation.
The first thing I do about any electronics project is to build its power supply circuit. Often the project may have a unique, or unavailable voltage source, needed to test its designated circuitry. The voltages required for this project will be 24, 12, and 5. Each capable of handling about 2 amps. The 12 volt source may need more current capacity, so I designed the circuit to include another 12 volt regulator if I need it.
Already started to cannibalize old computers, TVs, etc for parts. The aluminium heatsinks came from computer power supply units.
The first thing I did in building the bridge was to locate exactly where the piers and footings go. I drilled wholes for inserting 3 mm bamboo skewers for doweling. Then cut and shaped footings from scrap board (Minimal length for 32 mm curtain rod was 8 feet and too expensive, even second hand). Then glued these and their piers to the doweling.
Filled any gaps between footings and table with wood putty to eliminate appearance of float on water. Added piers and braces.
Added girders. The box section at one end will be for a street to pass under the bridge.
Bishop wrote: I just love watching this stuff. Scratch building is so satisfying. It's the little details like the putty around the footings that will sell it.
Thanks Bishop, I certainly hope to make those little differences that are basically essential. That is, it will be noticed if not done. Yet other details would not be essential (seen) if done or not. But then again it is all relative and subjective. However I am striving to achieve some sort of aesthetic appeal, so the model can stand on its own, without relying on the working parts.
Decided to give the bridge a few coats of white acrylic undercoat before putting in the road base. The river area also got painted.
The holes you see through the bridge ends, where the span goes, is for contact wires. These will provide power and data to the span.
On either side of the bridge span are several Fender Piers. The outer ones have the red and green navigational beacons. Their centre piers have been drilled out to accommodate the wiring. I am using small LEDs for the lights.
Nice work. Sparky, just to let you know, people don't always reply to your posts, but it doesn't mean they're not watching so keep posting. People run out of words after a while and just check in. So fear not, you are not alone in this build.
Throughout the project I have been scavenging parts from unserviceable electrical appliances, TVs, PCs, etc. The heatsinks used on the Power Supply Unit (PSU) were from PC PSUs.
I needed a small pair of speakers for certain sound effects (alarm bell, boat engine, and perhaps a fog horn). Found a good pair speakers from an old analogue TV set. Had to make a mounting bracket so the speaker diaphragm would not touch anything (or it would muffle the sound).
While I was at the museum to cut out speaker holes, etc., from the console, there was talk about showing photographs of the console interior as part of the display. Then I opened my big mouth and said why not replace the front panel with a sheet of thick clear Perspex. So now the console will also be a wiring diorama of sorts. This means that the interior needs to be cleaned up, painted, and revamped. Though the control panel will also be revamped its antiquated looking exterior is to remain as is.
Back to the bridge.
Added 3 mm Masonite sheets for road base, kerbing, and footpath to span plate.
The underside has red and green navigational beacons, plus 8 contacts (shown later). To hide the wires, I decided to carve out trench to route the wires to far side of span where the framework will be. Then the wires can be attached to the framework and routed to the span hut without being too noticeable.
Then I drew up a template for the framework and started making the span frame. Used 2.5 mm bamboo skewer sticks for doweling wherever I could.
While building the frame a solution anchoring the span cables to the frame came to mind. I used half a fishing swivel attached to a bolt head. Any twisting tensions on the cabling will be neutralized by the swivels.
Then I placed the span on the bridge to get an idea of how the rest of the bridge may present itself.
I found some springy shim metal and cut out eight contact plates. Installed the contacts, LED navigational lights, and wiring.
The wires are routed to where the frame vertical beams are, so to guide the wires to the span hut.
I filled the trench work with wood putty (after I checked for electrical continuity). Then sanded and painted the span with white acrylic undercoat.