UP THE CREEK: Peninsula Construction!
A regular report on the construction of a 1950s-something layout
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Part 2 - Finishing the helix and expanding the helix table benchwork ...
I
n the last episode we left our intrepid helix heros hard at work laying flex track on the inner and outer routes of the helix. Lots of progress and no visible signs of dizziness (yet). Before tackling the second lap, it is a good idea to drill any needed holes in the roadbed and solder all track feeder wires. Doing this after the lower lap is covered isn’t fun. You’d be amazed at how easy it is to forget that drilling a hole works best when there’s room for the drill – or maybe you wouldn’t?
Optical Detector Holes Charlie Comstock became the MRH editor in the March 2011 issue. Click here to learn more about Charlie.
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Page 29 • Feb 2012 MRH Column – Up the Creek, page 1
I plan to make my own optical train detectors with an infrared LED shining upward and an infrared photo transistor detecting reflections from the bottom of passing cars and locomotives (figure 1). I made a jig out of a scrap piece of oak to guide the drill when boring the holes between the rails (figure 2). Positioning counts. With a band saw, I cut grooves that slip over the rails to center the holes under the track. I’m planning four sets of detectors for each lap in the helix (eight detectors per track, 16 overall). They’ll allow crews who don’t want to bend over and peer under the upper deck to keep track of their train’s progress up
BC&SJ 3272
Infrared light bounces off bottom of car and down to IR photo diode
Infrared LED
Plywood roadbed
Two 3/16” holes on 3/8” centers
Infrared photo transistor Figure 1
Figure 1: Holes in the roadbed contain an infrared LED and photo transistor. Light bouncing off the bottom of a passing train is detected by the photo transistor. Figure 2: Hole drilling jig for lining up the holes in the roadbed for the infrared LED and photo transistor. and down the double-track helix. I’ll be writing more about optical detector electronics when I build and install it. In the meanwhile, I need to remove three ties and drill a pair of holes at each detector location.
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3/16” holes 3/8”
Grooves fit over rails
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