Turnouts test-fit in place but not spiked down at the east end of Santiago Yard.
Having found a little time to build turnouts and lay turnout ties down, it’s time to lay the yard tracks that will store cars at Santiago Yard.
I want to use thinner ties in the yard tracks than are used on the main track, to simulate the yard tracks being lower than the main track of the Campbellford Sub. Along with the use of Code 55 or Code 60 rail representing 80- or 85-pound per yard rail in the yard tracks compared to the Code 70 rail modelling 100-pound rail on the main as well as the use of cinders in the yard tracks versus gravel ballast on the main, the purpose of the different tracks should be plainly visible to even the casual viewer.
Following CN practice, the main track uses scale 6″ thick by 8″ wide Micro Engineering ties; turnouts use scale 7″ x 9″ Mount Albert Scale Lumber turnout ties. The yard tracks will use Campbell Scale Models and custom-cut scale 4″ thick by 8″ wide ties. Campbell to my knowledge no longer makes their excellent HO scale ties, but I can cut similar ties from Mount Albert Scale Lumber HO scale 4″ x 8″ stripwood stock, which I buy in bulk.
The difference in tie thickness is negligible between HO scale Mount Albert and Micro Engineering ties, both being about .082″– ,085″ thick. I need to make a height transition between these and the scale 4″ .044″ thick Campbell ties. As well, the difference in height between Code 70 rail in turnouts and Code 55 or 60 rail in the yard tracks must be addressed. Vertical curves, though with a total difference in rail top height not more than about .050″ between turnouts and yard tracks, still call for some planning to ease the transition between ties thicknesses and rail heights.
Four-wheel-trucked diesel locomotives or four-wheel driver steam locomotives are very tolerant of vertical curves. Not so for eight-coupled steam like a Mikado, or at most a Northern. A CN Northern has a wheelbase of twenty feet for the drivers alone; a Mikado which I will run on the Midland’s grain trains far more often has a fixed driver wheelbase of about sixteen feet. Fortunately there is enough vertical play to let the lead and rear drivers drop a little to start into vertical curves.
I measured some sample Campbell, Micro-Engineering, and Mount Albert ties to determine their thickness. The prototype railways set the ties into the ballast and raises or lowers them to make up differences in desired track height; we modellers don’t have that device to use on our layouts. I also measured the thicknesses of regular 20-pound paper and a standard 3 by 5 inch index card. Also measured were the thicknesses of some scale lumber in one- and two-inch thicknesses.
Wanting a replicable formula for use on the layout, I calculated the thicknesses of various combinations of card, paper, wood and track ties to deduce some tie thicknesses and shim combinations to make a smooth transition from thicker ties to thinner ones. The above sheet shows what I came up with initially.
I used a home-made 16-tie-per-33-foot-rail tie spacing jig to place some yard track ties. Ties 1, 2, and 3 are Mount Albert scale 7″ x 9″ wide ties; ties 4 through 13 are intended to make the transition to ties 14 through 18, which are .044″ thick scale 4″ height Campbell yard track ties.
Combinations of paper strips, scale lumber, and ties were white-glued together using the determined dimensions in my calculations on the above sheet to obtain suitable tie thicknesses for the planned tie height transition. I measured the thickness of each tie/shim combination using a digital vernier caliper to determine the total tie thickness before placing it in the tie jig.
Above the tie jig are some of those strips of scale lumber, paper, and card used as shims under the ties. The bottom of ties 4 through 13 are marked with each tie’s measured thickness. I found that even the white glue added a few thou to what was the calculated thickness of many ties, calling for some re-placing of the shimmed ties in the jig.
Next step will be to make some more shimmed ties of various thicknesses and try this out at the diverging end of a turnout in Santiago Yard. And I have not figured out the rail transitions next, so there may be a few tie height tweaks to come. This 1925 CN standard rail distribution diagram may help.