This shows the new grid benchwork in the loop area, sitting snuggly on top of the desk corner section. The new grid section fits right in but at this point is easy to lift out and move it to where all sides are more accessible. The wood is 2x2 in the center, 1/2 on the edges, screwed together. Where the 2x2 sections meet I used U-shaped cuts to slot them together. This is more work but makes the grid stronger and stable laterally. 1/2" insulation foam tape is used underneath for sound deadening and to protect what is left of the desk finish. I settled on the exact measurements by using a piece of 18" radius subroadbed from the previous staging to figure out the optimal placements of the grid joists.
Three days later, on December 21, I took the above picture showing the same grid but with the newly-cut 1/2" plywood subroadbed for the lowest tier lying in place (not fastened down). In order to do this a little more of the old staging area was removed.
3/4" is commonly recommended for model railroad subroadbed, and I've used it in the past. In fact I bought high quality birch 3/4" plywood for the main area of this layout. However, I learned a few things from that. First, even the best 3/4" plywood still can warp if it is not kept perfectly (I plead guilty), and once warped 3/4" plywood is more resistant to being bent straight, while 1/2" plywood will lay nicely flat/level if you have supports 1' apart and use a couple other tricks that I'll show later (and flat/level is the most important factor in subroadbed). Second, I think 3/4" is great for HO and larger scales but the lighter N scale cars gain no benefit from it.
This next picture, taken on the same day, shows the subroadbed of the middle tier laid in place for measurement:
The 1% grade limitation means, of course, that it takes a lot of length for a train to climb any appreciable height. To gain a minimum 2 1/8" vertical separation between tiers you need to climb 212.5" -- about 17.5'. Given this, the size of the room, and the placement of the layout and the height of the main lines as they exit the layout, this means that the three tiers have to be as close together as possible. I tried 2" separation on the first staging and found that this left no margin for error with the highest double stack trains, so now I'm using 2 1/8" (roadbed surface to roadbed surface).
This in turn requires a the thinnest possible subroadbed for the middle and top tiers. But what to use? You want a material that is stiff enough to maintain a level surface even though supported by piers that may be spaced as much as 12" apart (which is why most thin plywood won't work). Yet one that has a surface which can be easily penetrated by pins (for setting track, for example), accepts glue nicely, and can be assembled with screws. I used some sort of 1/4" composite board for the first layout and it was sufficiently stiff but the surface too hard.
This time I found some 2x4 sheets of 5.2mm Luaun plywood at the local Home Depot very cheap ($5?) and bought two to try them out. They have worked very nicely, I just wish they had 4x4 sheets so I had fewer joints between sections.
You'll note that the middle tier sheet of subroadbed is not cut in a nice circle. The intent is to allow the track to be in a pure circle, but the subroadbed sticks out at spots to allow for support piers alongside the track. As you'll see this did work out, but if I do it again I'll make some adjustments to the technique.
No comments:
Post a Comment