O Scale Street Light

Once again I have found an excellent resource at Google Books. This time it is “General Catalogue of Electric Light, Railway, Telephone and House Supplies” by electric Appliance Company – 1916

This is the kind of thing that ‘normal’ people are puzzled by anyone being interested .. and then those ‘Abby Normals’ of us are fascinated. There is everything here in this catalogue from the early 20th century, with drawings of the items .. Ceiling Fans, Washing Machines, lighting indoor and out (much of it looks no different a hundred years later).

I was drawn to the pages for Ornamental Street Lighting and I picked the first one shown, a Cutter Ornamental Post called “Commonwealth”..

“Base, 18 inches square, 2 feet high. Column, 8 inches octagon above the base, tapering to 4 inches octagon near the top. height from ground to bottom of pendent globes, 11 feet: to top of top globe, 14 feet 3 inches; to top of globe on the 1-light post, 13 feet 6 inches.”

In 1916 the version with the 1-light (No. 23500) weighed 475 lbs. The cost was $55.00 (globes, wiring and foundation bolts were extra). That would be $1,204.84 a hundred years later. (Inflation Calculator)

Of course making an exact copy is possible. the rounded parts could be turned on a lathe .. but I am not trying to do that .. but use this as a guide. That means I will have to make changes so it will print at Shapeways.

I used the Commonwealth street light described in the paragraph above as a guide for my own version. I brought the drawing taken from the book into Sketchup and traced around the outline to get a place to start. I then went through and taking note of the dimensions given and the constraints imposed by Shapeways for FD plastics came up with this – as rendered through Kerkythea.
The Design
With the prints back from Shapeways I have had time to look them over and discover what worked and what didn’t. Let’s look at my design.

  1. Globe saddle.
  2. This is the socket that is to receive the stud on the globe./li>
  3. Hole at top to fit hypodermic tube
  4. The top of the pole is a 4″ hexagon. This is the thinnest place on the pole
  5. The bottom of the pole is a 8″ hexagon
  6. The pole is hollowed with walls .4 mm thick
  7. The hole down the center of the pole to receive a hypodermic tube
Closer view of the top.

  1. This cups the bottom curve of the globe.
  2. This is the socket that is to receive the stud on the globe. It is 2.4mmm dia and is 1.7mm deep.
  3. Hole at top to fit a 0.043″ dia hypodermic tube. It is 1.08mm in dia.
  4. Since this is the thinnest place on the pole it is most prone to breaking.
Closer view of the bottom.

  1. The widest place at 8″ of the pole
  2. Hollow. The light pole is hollowed so there is a constant .4 mm wall thickness.
  3. Hole at bottom to fit the 0.043″ dia hypodermic tube. Again, 1.08mm dia.
The Good and the Bad
So. With the printed parts in and hypo tubing in hand … I started to fit everything. Had some problems that while can be corrected will need to be addressed in any future prints.

  • A – Fit was perfect .. yea
  • B – The first try the globe won’t fit. A check of the stub on the globe .. and .. ahhh. It is .096″ dia .. or 2.413mm .. arrgh. Too big for the socket by that .013 mm. Simple fix – reamed out with a 3/32″ drill.
  • C – Too tight. I had to drill out the hole. The hole as made in the mesh is 1.08mm. I checked the hypo tubing. In it’s description it says the OD runs .0415/0.0425″. This is 1.05/1.08mm. Since the bottom hole (G) let the hypo tube pass through I suspect there was shrinkage of the FD plastic. Shapeways suggests 0.05 mm clearance and says the accuracy is ± 0.1 – 0.2 mm for every 100 mm. That suggests that I bump the hole to 1.09 mm at minimum.
  • G – Slightly tight but hypo tube went through.Needs adjusting to the same as the upper hole (C) at minimum .. but there is more. This is a small hole and would make sense if the bottom of the light was open to let the wax drain out. That would cause a problem since this small hole supports the end of the hypo tube. It might be possible to rework the design so the pole plugs into the base – or create a small section with the hole to snap into the base. Will have to consider that.
I was going to talk about modifying the globes but think going over a bit about LEDs would be sensible. For these lights I will be using SMD LEDs. The one you use dictates to some extent the modeling of the globe – in this instance – as they have to fit inside etc.

There are two SMD LEDs I have on hand. 0402 and 0603. I have found both of these on eBay where you can purchase them pre-wired. For me this is a major plus as these LEDs are so small that I will gladly pay a bit extra to have someone else solder wires to them.

Here’s 0402 SMD LEDs. The ones in the center of the screen – the little yellow dots are the LEDs – are warm white. The white colored ones on the left are bright white.
The 0402 is very small measuring only 1 mm x .5 mm. Just how the wires are soldered varies as I have seen the wires run down the width and length. Unless you have one in your hand to squint at (yes .. squint) .. you should design for the 1 mm width .. and perhaps a bit extra depending on what that squint reveals.
Here’s 0603 SMD LEDs. While larger than the 0402 LEDS they are still quite small. Everything is relative.
The 0603 is small measuring only 1.6 mm x 1.5 mm. Like I said about the 0402, just how the wires are soldered varies as I have seen the wires run down the width and length. The ones I have sees have the wires run down along the 1.6 mm width.

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