The On-Line Magazine of Rideable Model Railroading
© April 12, 2015
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Constructing a Diamond Junction
Written by Laurence Johnson
“In U.S. railroad practice, a level junction (or in the United Kingdom a flat crossing) is a railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other that require trains to cross over in front of opposing traffic at grade (i.e. on the level). The cross-over structure is sometimes called a diamond junction or diamond crossing in reference to the diamond-shaped center.” (from wikipedia)
Not every train layout has need of a diamond junction and almost never need more than one. My club asked me to build them a 30E diamond. I decided to make it by welding steel rail and angle iron pieces. For layout reinforcement purposes I used 4” longer cross ties in the junction area thereby adding to the overall stability and to get good ballast support I used a full 2 x 4. The Club’s Cross Tie Standard calls for a 15” length which gives three inches from the end of the crosstie to the rail base; in the diamond crossing that distance would then be five inches. For the crossties under the diamond, they are laid perpendicular to a line through the long points of the diamond. With the rails are coming together, each crosstie is progressively longer when laying out from the short corners of the diamond. These crosstie lengths can be determined by making a full size layout or, as I did, by CAD where dimensioning is a very simple operation.
To facilitate the positioning of the crossties I welded a metal frame using 1/8” x 3” strap steel as shown here. Careful positioning and much measuring is required before fastening the steel to the bottom of the crossties. I’ll never use strap steel again, I now recommend the use of 1” angle iron bolted to the bottom of each crosstie directly below the rails! This might be a bit stiffer but will make things easier for the track crew when they tamp in the ballast when building this section of track.
The main problem in cutting the diamond rail parts is, in this case 30E, all saws don’t pinch any closer than 45E (left). I made a special setup on my abrasive wheel chop saw (right) clamping the rail to a section of square tubing and checking often with a machinist’s protractor. For the rail guard I chose to use 1” angle iron rather than milling down the sides of the mating rails.
Again, the dilemma of the small angle plus there is the intersection of the top of the rail or rail guard going over the base of the mating rail. For that cutting I used a milling machine; here I show my setup; other times the rail or angle iron are upside down and held to a block. Again, measure more than once and, if in doubt, cut long and sand/grind to fit. More so in a diamond crossing than in a switch, the back dimension is as important as the front dimension for the flange of the wheels. To maintain this spacing I discovered I could use 7/16” nuts wedged just under the rail head to hold the rail guard to make the proper flange gap.
I marked the position for the angle iron guard by making a chisel cut into the base of the rail and then filling it with soapstone. You will find you might need another hand or two while making the clamp up for welding. I chose to stick weld here so I could get good penetration without the need for grinding. This close up shows the dressed weld. Notice the protruding sections that will be close with the side of the rail. I used straight rail in one direction and rail sections in the other. Where the wheels passed thru the rail I simply ground a notch in the rail head with a my right angle grinder.
* E is a drafting term meaning "angle" in degrees.
I have CAD drawings for diamond crossings from 30E to 90E by 10E progressions and when it comes your turn to build a diamond,
just email me at this address:
Written by Laurence Johnson
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The On-Line Magazine of Ridable Model Railroading