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Building easy sub-roadbed


switch machines to small plywood pads which are screwed to the sub-roadbed. (The switch machines are Hoffman from Aspen Models.) Once the sub-roadbed is level, it is


time to make it look like a railroad. We use DAP Alex® Plus caulking com- pound to secure the cork roadbed to the sub-roadbed. Apply a liberal bead of caulk to the sub-roadbed, then spread it out smoothly with a putty knife. The cork roadbed can then be pinned to the sub-roadbed using push pins. After 30 minutes or so, the pins can be removed. When the cork is firmly in place,


The caulk has been spread (left) and is ready for the cork which will be pressed into it. Then push pins will be used to help hold the cork in place. Once the roadbed is laid down (right), the flex track can be laid. Ballast and scenery come next. This system makes smooth and strong trackwork, and it reduces the sound transmission from the roadbed.


usually by two inches or more. The one place where the ends will be even is at the ends of the straight sections that have had strips applied. Cutting the re- inforcing strips to whatever length you need couldn’t be easier. Buy an inex- pensive bolt cutter. It works perfectly. As can be seen in the photos, it is nec-


essary to cut away the hot glue from the supports on the side of the center spline to which you are applying the re- inforcing strips. This insures that the additional strips stay at least close to level with the center strip. Once all the strips have been applied to one side, re- move the glue from the supports on the other side. When the roadbed is full width, it will be incredibly strong and will retain the shape you have given it. The whole structure can be lifted slightly to squeeze a blob of hot glue onto the support, fixing it in place. But hold on. The top of the sub- roadbed will be anything but level. You need three things to fix this: an inex- pensive (I was going to say cheap) pow- er planer is the first item. We tried us- ing an orbital sander but it proved ineffective. The second essential item is a decent shop vacuum. The third item is a second set of hands. The Black and Decker two blade


planer we use has a place to attach a vacuum hose. This is a must. (Remember our experience in the garage earlier.) With the planer set for a shallow cut, begin making passes over the roadbed. With the shop vacu- um hose attached you won’t end up


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with dust everywhere. The second set of hands is to hold the vacuum and keep the hose out of the way. At this stage, be very careful to keep


the planer level. You can build in su- per-elevation; just be sure the surface tilts the right way when you are done. There will be spots where the strips are not perfectly level all the way across the surface, leaving little holes or ditch- es. That is okay. Bumps caused by one or two strips sticking up above the rest are not. The caulk used to hold the cork in place during the next step takes care of any slight dips. Turnouts are next. They are done by


first building up the main or straight portion of the sub-roadbed until it is full width. At the point where the points join the stock rail, hot glue a new center spline to the divergent side of the roadbed. Glue the divergent spline to the existing sub-roadbed up to a point between the points and the frog. Bend the divergent spline to conform to the shape of the turnout it will support. Continue to hot glue this spline to the supports for the new roadbed. Once the center spline is in place,


add short, three- or four-foot reinforc- ing strips to the outside, staggering the strips about one inch until the roadbed is a good width to support the turnout. Once the outside is complete, glue strips to the inside to complete the roadbed. If a slot is necessary for a throw bar, clamp the roadbed to pre- vent de-lamination and drill a ³/₈″ or ¹/₂″ hole in the roadbed. We mount the


spread caulk on the upper surface of the cork and lay in your track. We use flexible track that can be secured using the same push-pins used to hold the cork to the sub-roadbed. The slow set time for caulk allows for adjustments and corrections after everything is in place. Once it has set and the pins are pulled, it is time to run some trains. The first roadbed structure we built


this way has been in place for six-plus years without any signs of sag or move- ment. Wherever we have a bridge planned, we just lay up the spline sub- roadbed. When the time comes to put the bridge in place, we use a saw to cut out the appropriate section. In several cases, the sub-roadbed ended up cantilevered out eight or nine inches with no sag. How long can a section be without support? There are several places on the railroad where the spline structure spans three plus feet in anticipation of a bridge to come with intermediate piers. None of these sections have shown any sag or movement. How does this sub-roadbed deal with grades? On our layout, the junction at Fort Seward is on a one percent grade. The high line to the lumber show at Eel Rock is reached via a six percent grade. The vertical transitions are every bit as smooth as the horizontal curves on the mainline.


Hardboard spline roadbed requires


some equipment and a learning curve, but it is worth it. The resulting roadbed structure is rock-solid. It doesn’t move, it doesn’t sag, it makes its own ease- ments, and it transmits almost no sound. And, it is fast to put up. The sec- tion in the photos accompanying this article is 16 feet long. Once the up- rights were in place, the roadbed was done in two hours. Leveling with the planer took 30 minutes after the planer was found, (Oops!), and hooked up. Laying the rail, including soldering the rail joints, took a second evening. I encourage you to use this informa-


tion as a starting point for helping you build a great model railroad. If you find a way to do something that really works, share it with the rest of us.


DECEMBER 2011


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