07-20-2009, 11:59 AM
Josh, the radius of a helix not only allows for the use of long equipment, but also allows for reasonable grades. You probably need about 3.5-4 inches from the rail top to the bottom of the next level of the helix. You don't need road bed on a hidden helix, but you will need it to be strong enough not to flex. If it is made of 1/2 inch plywood, with 1/4 inch allowed for the rails, you are looking at going up 4 3/4 inches in each revolution of the helix. If I have figured the math correctly, you are looking at slightly more than a 3% grade, but you are going to tie up a space of nearly 48 x 48 inches for the helix. An alternative might be to put Modesto Yard on an "elevator" traversing between the 2 levels of the layout.