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A new lighting beam for Splitveld Fabriek.

Several invitations to public shows speeded up the construction of a new lighting beam om my layout Splitveld Fabriek.

My layout Splitveld Fabriek is an organically growing object, it changes over time without advanced development plan like nature. The center part is now about 25 years old. Most organically growing objects generally profit from a good prune now and than and after that it blossoms again on new extensions. After the layout went through its the sixth incarnation the existing lighting rig didn't fit any longer.
The layout was displayed in Bournemoor where it was clear that the display would have profited from a good lighting rig. The old lighting rig was based on a set gallows that carried an aluminium/foamboard top fascia with a set of 3 small fluorescent tubes of 15-20W. The main problem was that is was rather flimsy, awkward to set up and the light was too yellow to my taste. With 2 new invitations from Belgium in the inbox, I decided that it was time to put some effort into a new lighting beam based on leds and take into account tips and tricks of Ian Rice's cameo experiences. The current layout is 3.05 m long but a 3 m long lighting beam won't fit my car. Thus with keeping the number of sections to a minimum, 2 parts of 1.53 m needed to be coupled up into a rigid construction such that it is possible to use only 2 posts at the outer ends. To light the front fa├žade of the Siropery, which is directly at the front of the layout, it needs to hang several cm in front of the modules. This of course depends on the light cone of the used leds but flat leds come close to 180 degrees angle per plane. Further with only 2 posts to hang it on it helps minimise weight. To make it rigid in all directions an L-girder cross section is the logical approach such that lighting can be directed from the inner part. I choose to produce something from 3 mm ply. The ply that I used is of lowest quality and stems from packaging to protect higher value goods. The pro was that the length sufficed and it came entirely free. One practical problem is that you cannot cut it with a saw because this results in huge splinters and coarse edges, thus you have to cut with a Stanley knife. Not that easy, because the knife wants to follow the wood grain, thus you need to apply force and make lots of cuts. I did cut 4 strips, 2 of 10 cm for the actual top fascia and 2 of 8 cm as horizontal reinforcement. These dimensions were choosen on basis of the resulting light angle. The 42 degrees is an angle on the middle of the day in summer. These ply strips were glued together with a piece of 12 x 12 mm white pine (just because it was available, smaller will do too) and 4 triangular reinforcements of 6 mm poplar ply, one per 50 cm.

crosssection"
cross section of lighting beam.

Diagram 1 shows the cross section. These triangles have one large hole, originally meant for maybe an extra feed wire, and some smaller holes to be able to align the end. You only need the alignment holes on the center ends. These triangles were CNC cut therefore I made them all identical. The edges of the ply were rounded to prevent splinters coming off and the round edges are less damage prone in transport. This required a further small strip of 5 mm white pine on the lower edge otherwise it would have become too thin. After gluing and sanding the whole lot was tested on the layout to see how it kept. Disappointingly it sagged in the center over at least 2 cm and applying more pressure on the wing bolts in the alignment holes didn't help. Something had to be done about this sagging.

I came up with the idea that it needs another 2 triangles and a metal bar to help to keep it straight. Thus I glued in 2 extra triangles at 15 cm from the center ends. The larger center hole was used to insert a 30 cm long tube of 12mm diameter (actually an offcut of a piece of lightweight steel curtain rail). Through this I fitted an M8 threaded stud with a wing nut and 2 fixed nuts. The tube has a sliding fit through the center holes of the reinforcement triangles, therefor the parts of the beam have hardly any space left to move out of alignment. However to create an upward tendency for bending I fitted a piece of 1 mm material at the top edge in between the beams. If you now apply force over the M8 stud then the beam is forced into an upward curve and it can actually be adjusted a few mm into a single straight item. The weak point is that the triangles of poplar ply are not strong enough to take the forces of the wing nut and deform by creep, thus these will get an extra support of a birch ply version. Take care that you apply the force over the stud on to the light beam and not on the tube thus fit a wide ring over the tube. I used a piece of 8 mm ply with a 15 mm hole as a sort of washer that sits over the tube end.

reinforcement for straightening
View on the lengthwise construction to counter sagging.

In the test phase I rigged it up with 2 posts. These are lightweight 6 mm poplar ply constructions with a trapezium crossection. But as the left hand post hindered the view on the nice flowing track formation I replaced that with a better version of the old gallows. This has a post of 25 mm square aluminium tubing with a T-bone outrigger from 9 mm birch ply. The post is bolted to the module with a set of 2 M6 wing bolts and wing nuts.

I was a bit uncertain about the colour for the light beam as the nut brown of the fascia looked too dark. After a consult of the VAG using a series of photoshopped pictures I settled on a bold colour of red-orange, this reflects the colour of the buildings but it is also attractive and it may help to draw public. Note that this is in contrast to the advice of the guru for finishing your cameo layout. Most choices went for a finish in a different colour being either a neutral pale blue or bold colour like the red-orange chosen. To finish the lot, the right hand post is a 2-coloured affair. At the height of the fascia it is nut brown but the section between fascia and light beam is in a neutral cream. In the mean time this post was replaced by a copy of the lefthand version with 25mm square tube being less intrusive. view from public
Display on a public show in Antwerp in 2017

Henk Oversloot date: 20 August 2017

copyright: Henk Oversloot
date: 20 aug 2017 originally published in the 2mm SA magazine.