I am in the evaluation/design stages of a room sized HO rr in a room that is 20’ long, 12’ wide at one end and 10’ wide at the other end. The difference is the product of a 12.5 cabinet, 25" deep and 36" high, that runs in recess along one wall. I would like to run my pike at about 42" high in this area, a desire that would leave only 6" from cabinet top to track for below grade construction and maintenance. I’m thinking of things like later installation of signals, installation and maintenance of switch machines and the like. I’ve seen any number of plans and pictures that provide for staging just a few inches under the main railroad, but without any description of how below grade maintenance is done. I’m thinking that one or more removable scenery sections are probably the best approach to this problem, but I can’t help but wonder if there’s something painfully simple that I’m just not seeing. Thanks in advance Bob
A suggestion I have not tried:
Assuming the layout over the cabinet is a shelf 25" or less deep, and is cantilevered off the wall, build it in about 6ft long sections that hinge near the back. Bring the switch machines and wiring out to the front edge. Use rods to link the switchmachines to the turnouts. With the combination of being able to hinge a section up, and most of the key elements near the front edge, the situation should be manageable.
The hinge should be a few inches from the back edge to provide clearance for scenery and structures when the section is in the up position.
my thoughts, your choices
Fred W
Howdy, Bob,
Painfully simple, Si. Obvious, NO.
While I have easy access to the underside of my layout, I prefer not to use the subterraineous approach. Instead, I bring everything that has to be maintained (or just installed) out to the fascia line, where I can work seated in a chair in the aisleway. My switch actuators (switch being defined here as the points of a turnout) are all readily accessible, as are the terminals for rail drops and such. I feed rail drops down from the top, then fish them out with a straightened wire coathanger. When I install signaling, I will use the same method - put the wires down the hole, plug the bottom of the signal into it and bring the wires out to the logic module right on the aisle.
To simplify my electricals, I use stud-and-nut terminal blocks made from plain-Jane #6 or #8 machine screws mounted to an insulating substrate with two washers and a nut. Wires are stacked on the stud with washers between, and anchored by a second nut. By leaving space between the rows of studs, I can label each terminal with a simple (to me) code that exactly describes that circuit’s origin, destination and function.
My switch machine linkages (from machine to points) are lengths of fishing line - the points are held in the ‘normal’ position by suspended weights. When using Peco switch machines with Peco turnouts, the machine snaps to the underside of the turnout and is installed from the top down. As long as the wires are soldered on first, that works just the way I described above for signals.
Chuck (Modeling Central Japan in September, 1964 - with easy-to-maintain electricals)
Painfully simple indeed !! But am I ever glad I asked. I have much the same feeling I used to have in various classes when I blew a problem and the right answer was explained. Thanks very much.
Hi Bob from Bob, In addition to the solutions mentioned already, the following photos show a couple of other solutions, that i use on my 24’x24’ garage loft layout. 
To gain access to the end loop of an N scale dog bone loop, I first cut out a hole for working on the mountain. I then happened to have a Styrofoam cello packing case, to form a “lift-out mountain”, that I cut to fit, spray painted, and covered with a canopy of Fall colored Deciduous trees. 
Bob Hahn Click on any photo to enlarge it. Then, click on the photo series to the left, to view other parts of my layout. In order to gain access to the area behind my sawmill & pond complex. I constructed them on a pull-out drawer. 
Totally agree with the “hanging wire syndrome” and “cabled & labeled” solutions noted. Whatever access you do end up with needs to be unhampered access.
For easy slide-in & slide-out from under the layout – consider “1/2-inch thumbtack-like” floor-glides, handy for wooden chairs. bookcases, etc.