garden roadbed and tracklaying
Plastic trenching and sharp sand ballast make tracklaying go quickly and adjust easily. Soldering a jumper across every joint makes it go much more slowly!
Dig out to 100mm below track grade (within about 20mm) using shovel and laser-level. I'm blessed with nice sandy soil - makes it easy. !-break-->
Two strips of 100mm recycled-plastic garden edging form a trench, held in place with temporary wire "staples", or bricks, or sometimes just a little soil. used 200mmm edging in one area where track is below ground level, forms a 80mm "cutting".
Geotextile (weed-stop) cloth is spread on the base of trench (I used a handsaw to cut 300mm lengths of the whole roll)
Standard sharp builders mix or paving sand goes in. Sizes from about 3mm down to dust. Would like more dust in it to bind it up but seem to settle pretty stable. The local sand here will blow in and lock it further. I may wash rock dust into it later if need be. I am also experimenting with ash from our woodburner - cinders worked as ballast for the prototype. Ash is very fine and sets up pretty hard.
I tamp it down with a bit of fencepost and much walking on it (lately I just walk a lot and let it settle for a few days). The plastic sides are allowed to slope out a bit. I've let the edging get a bit high and protrude 10 or 20 mm. Next time I may set it lower and bury it, allow ballast to spill over a bit.
I stamp the sand, then leave it for a few days. Rain helps. Then I level the sand with a plasterer's float, spirit-level and laser-level, to within about 20mm of correct height, and lay the track.
All joints screwed, one or two soldered where necessary. I've not left many expansion gaps - there are lots of curves and the tracjk is llose int he ballast - we shall see when summer comes. Temperatures seldom get above 30 deg C here (or below freezing).
Tracks cut with hacksaw, new screw holes drilled but not tapped. Jumper wires soldered across every gap - tedious but worthwhile. using zinc chloride flux and 60W soldering bolt with rosin-cored solder.
I'm using standard-radius curved track sections, but I bend it to other radii, and to put easements in between curves and straights. I bend track by hand or across my knee or my belly. Gauge is checked with a track gauge, level and gradient checked with a metre-long spirit level, curvature is checked using the eyecrometer.
Another layer of builders mix on top, sometimes spread by my son's grader :) Tamped lightly then watered in and left for a few days.
Because the drainage is so good here, the ballast is level between the plastic sides: no roadbed, no camber. Easy and stable. I may experiment with putting sloping sides outside the plastic to make it look more realistic.
We get no frosts, no ice, no snow, no burrowing animals other than our bloody terrier. I don't want anything concreted or built on wood unless I have to - I want to be able to move/adjust it later if the whim takes me. And when we move house all the track will come up easily and move with me unless the new buyer wants it.
The ballast is proving delightfully easy to adjust, yet quite stable when walked on, or dug or jumped on by the dog.