There are lots of methods for creating curves on your model railroad, from string and pencil to fancy tools. Our trammel kit is a "fancy tool for modelers on a budget".
This kit consists of 5 plastic parts, a steel pin, and 8 screws. Just add a Poplar (or Oak) lattice strip - 1/4x2x48". These are $3-4 at most home centers. Just mark and drill two holes on the end, attach the marking end with two screws, and assemble the pivot point with 6 screws - less than 5 minutes!
This trammel, using a 48" lattice strip, can create curves from 4.5 to 46.75" radius. The marking end is sized for a "Sharpie" brand marker - insert just until the tip extends through the bottom of the of the marking base.
The parts are accurately sized - the point where the lattice enters the marking head is exactly 4" from the marker tip to the pivot point, just create any other marks on your lattice strip from that point as needed. Simply loosen the clamp knob, set the radius and tighten the knob!
Note that the photos show a 12" strip of Poplar lattice to keep the images compact. The lattice should be between 36 and 48 inches long.
The steel pin can be pressed into foam but needs a 1/16" hole drilled at the center point for marking a plywood top.
