Saturday, April 20, 2013

How I installed optical fibres in the WSMoftheWBB* sign

I’ve been putting off writing about the ins and outs of the optical fibre installation job on the WSMoftheWBB* project until I was satisfied with how it turned out. Well, it works, and there’s light, but the whole thing was a big learning experience. I installed a lot of messiness inside the building’s shell before I got the hang of things, so I’m not completely satisfied with the internals, but, as I said, it does work. Here are a few pictures I shot as the job progressed.
Here’s a $2 LED light unit stripped of its outer shell. It’s a rather clean design. I wanted the building to be battery powered so I could place it wherever I wanted and not be dependent upon an external power source, so these things I left as battery powered – they need 3 AAAs. There are 4 inside the building.
I found some styrene tube in my scrapbox that fits snuggly over the LEDs and cut it into lengths that are about 15 mm taller than the LEDs. These were then slipped over the LEDs and glued in place with sparing amounts of super-glue.  These tubes are to hold the fibre ends in place over the LEDs. More on this later.
I added some more internal structure to both add stiffness to the shell and provide a base to mount the LED units. The inside surfaces were painted flat black to help prevent light from bleeding through the walls. The inside surface of the sign is also painted black.
This is a test placement of the LED units. I had to make sure that I could replace the batteries from the bottom and nothing was blocking. Once I was satisfied with the placement, I glued them in with superglue.
Before gluing the sign in place, I added a number of styrene blocks cut from square-section styrene tube to the inside lower edge of the sign so there was something to securely attach the bottom of the sign to the top of the front brick wall.
The front wall was painted with Krylon red spray paint, and when completely dry after a few days, was washed with a loose mixture of flat black and Tamyia Smoke to tone it down and bring definition to the bricks. The service door entries and street level vents were given a little extra black wash to deepen their shadows. When I'm walking over the to real WBB from Yonge St., this is the view that I see, so it was the one that 'clicked' in my mind that I was close to capturing a likeness of the building. Seeing the entire model head on with all the lights lit is a little odd, because one can never actually see that sort of view from street-level.
Here's the back wall while the paint was drying. I have no idea what the real one looks like, so this is completely freelanced. The brick stripe is the same Krylon red as the front wall, but the main surface is loosely brush painted with Poly-Scale aged concrete, flat black, and Poly-Scale L & N gray. It dries to a nice grimy, flat finish.
These are - I think - all the tools I used to install the fibres. I used plain old sprue cutters to cut the fibres.
I had a 50 ft roll of 1mm diameter optical fibre on hand, and bought two more 100 foot rolls so I'd have enough to finish this job and extra for future projects. I estimate that I used around 130 feet for this project - that includes waste and test pieces. The roll on the left is a complete 100 foot roll, and the one on the right is the remnants of a second 100 footer after the job was done. The original 50 footer was used up.
It's a little hard to see, but that is the business end of a 1 mm diameter fibre. 
I used my old - they're probably 10 years old - sprue cutters for cutting the fibre, and along the way I broke its return spring. They still cut, but they're now a little awkward to use.
Over each of the styrene tubes I slid onto the LEDs, I then slipped a piece of shrink tube. The shrink tube was about 15 mm taller than the inner styrene tube. I had this idea that I'd fill each styrene tube up with fibre ends and then heat up the shrink tube with a hair dryer to collapse the shrink tube tightly around the fibres, and presto, they would all be held firmly in place. It didn't quite work out that way - more on this later.

Here's what I did to install each fibre.

1. Make sure the hole into which the fibre will be inserted is completely clear of plastic debris from drilling and any residual glue. I re-drilled many of the holes, and widened some with an exacto knife to make sure they were clear.

2. I unspooled some fibre from the roll and clipped the end to a point with the sprue cutters. This makes it easer to thread the fibre into the hole.

3. Once the fibre is through the hole and a decent length is pulled into the building, use the sprue cutters to cut the free end square. 

4. Pull enough fibre through to insert the free end into one of the styrene / shrink tube / LED tubes. Don't make the mistake I did and be too stingy with the fibre. Make sure it goes into the tube parallel with the side walls and doesn't lean against the sides and tilt them - this puts the fibre and the tube in tension, and I found the fibres had an annoying tendency to pop out.

5. I tried to evenly - and somewhat randomly - spread the fibres out amongst the tubes so if an LED fails it wouldn't take out an entire section of the sign, but spread the unlit lights over the whole sign. One drawback of this approach is that the inside of the building becomes a rat's nest of fibres.

6. Once the free end of the fibre is in the LED tube, cut the other end with the sprue cutters. I left 0.5 mm to 1 mm of fibre sticking out from the sign. They could be left flush with the sign, but the light isn't as bright. Friction will hold the fibre in place while you proceed to install more. I'd install 20 or 30 at a time before taking a break.

7. I used a dab of Micro Krystal Klear to hold each fibre against the inside surface of the sign. I stupidly used superglue on the first batch of fibres I installed. I installed maybe 10 or so, put a dab of superglue on each, and turned on the LEDs to check things. I was very happy with the result and went away for an hour to do something else. Upon returning, the LED ends and superglue were just blobs of free-hanging goo! Aargh! I took them out, cleaned things up, re-drilled the holes, and re-threaded the fibres. This time I used Krystal Klear to hold them thinking that it was just a high-quality white glue that isn't reactive. It worked fine.

8. The bottom and side fibres were installed first. The top row was done last.

9. I found that it was useful to temporarily hold some fibres in place with tape. When an LED tube only has a few fibres in it, the fibres can pop out as you work inside the shell if they get brushed up against during the installation of other nearby fibres. Once a tube has 6 to 8 fibres inserted, their mutual friction seems to hold them in place. 
Here's the first fibre I installed. I was very happy!
The lights that are inserted in front brick wall that illuminate part of the sidewalk, and the light  over one of the back entry doors, were also made from optical fibre. I could have used small LEDs, but I was determined to use optical fibre wherever I could :-) Basically, I cut 5, short U-channel pieces from a square section styrene tube, glued 12, 12 inch lengths of 0.5 mm fibre into each piece for each light. The idea was that the dozen fibres at the free end would be inserted into an LED tube. Again I used Krystal Klear to glue the fibres into the U-channel.
That is a 0.5 mm fibre. Very small, and the fibre is very flexible. Each of those U-channels was painted flat black before installation. All 5 of these lights were installed before the top row of sign lights were.
Here's what the back delivery entrance light looks like.
This is one of the front 4 lights. Unfortunately, I didn't get that one installed too squarely, but it lights up fine.

And finally, here's the what it looks like inside from one end to the other.

Not my finest effort, but it does work. 

To secure the fibre ends in the LED tubes I resorted to dabbing a blob of Krystal Klear into each tube, and after it hardened, used a blow dryer to chinch down any remaining flexibility in the shrink tubes. This doesn't completely seal off the LED ends, and some light does still come out. To me this isn't a big deal, since that'll help create a soft light in the main entrance area. Although, light leaks from other parts of the shell may need to be dealt with.

Turns out the fibres move a little as the glue settles and dries. I panicked at first because some fibre ends got spotted with white glue - reducing the light intensity at the sign - others moved slightly out of contact with the LED, also reducing light output. But, after things completely dried - meaning the glue's milky whiteness was all clear - I liked the result better than the super-nova light intensity of the unglued fibres. The sign illumination is dimmed a little and it now has a rather pleasant unevenness from one bulb to the next - the lights have different intensities which I think is more realistic in that real outside bulbs probably age, get dirty, get loose, and maybe even burn out with the result that not all the bulbs burn with the same intensity.

One last thing: the LEDs are switched on and off with a long wooden skewer. 
*World's Smallest Model of the World's Biggest Bookstore

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