A 1:20.3 scale street lamp post

The design of the actual lamp post came from a cruise around the local ACE Hardware store. While I know what a street lamp post looks like, I had prepared before my trip with a quick visit to Google Images, looking at various types of lamp posts through history. The K&S Engineering display of brass and metals at the hardware store (I have found similar displays at most hobby stores) had plenty of nice pieces of tubing that looked to scale pretty well to round-shaft lamp posts. I was somewhat concerned about bending tubing to get a crook in lamp post, but was willing to give it a try.

I was about to scout the store to find something that I could use for a reflector and lamp shade when my eye caught a display next to the tubing that held a variety of drawer-pulls and the like.

There I found a crome-plated knob backplate, which had a square hole in it (Amerock BP30361-26); a quick measure showed it to be a little less than 1/4-inch. Unfortunately, a 7/32-square K&S tube didn’t actually fit into the hole, but a 3/16 did, though with a little slop.

In my mind, the lamp post quickly came together: a series of increasingly smaller square tubes reaching up to a right-angle, which then stretched over “into the street,” as it were, another right-angle and down to the reflector. I bought a couple of pieces each of 1/4, 7/32 and 3/16 square brass tube (which each comes in 12-inch lengths), a couple of back plates and went back to the workshop.

I sketched a layout, looking at my 1:20.3 conversion table all the while. Twelve inches at 1.20.3 is a little under 21 feet — just about the right height for a lamp post. To most economically use the tubing, each segment is evenly divisable by 12; the 1/4-inch tube is cut to six inches; the 7/32-inch tube is cut to four inches and the 3/16-inch tube to three inches, two inches and one inch. So, each lamp post takes one-half of a 1/4-inch tube, one-third of a 7/32-inch tube and one-half of a 3/16-inch tube.

The 3/16-inch tube is cut at 45-degree angles using a mitre box.

I used standard plumbing-like soldering techniques to join the materials; I’m sure you could use another type of adhesive, taking into consideration the outdoor nature of the lamp. I found, though, that there wasn’t enough “grab” space on the 3/16-inch tube, 45-degree cuts to solder correctly. Further, through trial and error — lots of error — I found that the wire couldn’t be forced down the 90-degree angles after the soldering and would melt if inserted into the tubes before the soldering.

Back to ACE, where the K&S rack had a stick of 5/32-brass C-channel tube. In the workshop, I cut 1-inch pieces of the C-channel, and put a notch in the middle of each. But even with these “clips,” as I call them, in place, the heat of the soldering still melted away the insulation of the wire. I finally realized that a segment of heat-shrink tubing inside the clip will keep the insulation from melting, especially if low-temperature soldering techniques are used (see instructions).

I cast about for quite a while looking for a lamp shade. Finally, one afternoon when I was cleaning out the kitchen “junk” drawer, I found an old cap to an Air Wick air freshener. I had thrown the cap into the drawer because of the unique styling — and the sheer size and weight of the plastic — I had known this cap eventually had an afterlife. I took it down to the workshop and, amazingly, the size of the hole in the cap was exactly 10mm — the LED slid into the cap perfectly! A little silicon caulking and the cap easily attached to the reflector and provided good diffusion.

That was the good news; the bad news was that the manufacturer of the Air Wick product, Reckitt Benckiser, had just stopped using that cap and almost all the products on store shelves used a new cap that didn’t have the great styling of the old cap. Here and there at drug and grocery stores you could find products with the old cap (usually at the back of the shelf, behind products with the new cap). Ultimately, I found a case of 12 fresheners on eBay that had the old cap and snapped them up. (I also bought a couple of new air freshener dispensers and installed them near the cat boxes, thereby solving two problems at once.)

There are other alternatives available: the white cap from an aerosole can of whipped cream will also work; the measuring cup that comes on the top of Pepto-Bismol bottles will work as well.

The base for the lamp post (because my railway is on a shelf, or a deck, it’s not easy to just stick the post into the ground) turned out to be a piece of 1-by-3 pine lumber, cut 2¾-wide, to make a square. A 1/4-inch hole is drilled into the top of the lumber to accept the brass tubing; another 1/4-inch hole is drilled into the side to give the lamp cord egress, and a 1-inch hole is drilled half-way through the bottom to provide space for the rectifier and the resistor.

The electrical (and electronic) components of the lamp post are typical for my railway; you can read in detail how I discovered the best ways to work. Suffice it to say, I use a 3.3 volt, 10mm, warm white LED, a 330-ohm resistor and a bridge rectifer of at least 12 volts and 1 amp.

The wire internal to the lamp post is 22-gauge, single-strand copper wire; I have a spare roll of CAT5 computer cable in the workshop, left over from wiring the house, and I cut off an 18-inch hunk of it, pulling out two individual wires. Radio Shack or a hardware store will sell you 22-gauge wire without having to buy a 50-foot roll of CAT5.

The LED is soldered to the 22-gauge wire with heat-shrink insulation (be certain to note the polarity of the LED before cutting off the leads), the LED is placed into the plastic cap and all are sealed with the silicon caulking to the reflector. The bridge rectifier and resistor are soldered to the 22-gauge wire at the bottom of the base, are stuffed into the 1-inch hole and held in place with, first glue, and then silicon caulking. The lead out the back of the base is 20-gauge “zip” cord (I buy rolls of speaker wire at Radio Shack). I painted the posts with multiple coats of flat gray primer.

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