Risers for track elevation starting from L-girders and gridwork

[riogrande5761]

Crossthedog,

There are more construction photos in the link starting at the beginning of the process a little over a year ago.

https://atlasrescueforum.proboards.com/thread/3737/jims-layout-topic-blog?page=5

 I've made liberal use of c clamps during assembly.

[crossthedog]

Guys, thanks. Mike, you've correctly seen through the clutter that I've got some plywood subroadbed in mind, but that's half-inch in the photo, and I'm considering going to 3/4". Those are just scraps I had lying around. There are some triangulating braces on the far side, and on the far end, which you can't really see. Those are temporary until I figure out where my access tunnel will be. Sadly, I have to store stuff under the layout, so I'm going to frame in some shelving, but I'll leave a pathway into the interior access hole(s).

Selector, great tip about using clamps.

Wayne, I'm amazed to say it, but I actually was able to follow your entire procedure. It took me a few passes to understand what you and Selector meant by superelevation, but once I grokked that you were talking about tilting the curve inward I was onboard, so to speak. I had wondered about that. In fact I had wondered if raising one end of a plywood curve wouldn't twist part of the curve AWAY from the center (to disastrous effect, naturally). I'm glad both of you addressed this.

I thought at first that "superelevation" meant "going really high", and I was going to report that I've pretty much decided to stay as flat as possible. I'll have a mainline oval, basically, and the only grade I'll have is where the branch departs toward the inside and has to get up and over the mainline to the town area over by the wall. But I'm still going to elevate everything off the stringers enough to level the mainline, so this is all helpful. 

Thanks again, all.

-Matt

 

[doctorwayne]

riogrande5761

L-girder is the posh route but I just go open grid and try to have cross members about ever 16" or less for risers.

I agree...L-girder is useful in some instances but open grid is easy to build and easy to modify as needed, and less wasteful of lumber, too.

Most of my track, and all of the curved track, is on cut-out 3/4" plywood sub-roadbed.
For the grade from the main level to the partial upper level, I simply placed the roadbed segments atop the open grid, then cut more 3/4" thick segments to use as joiners under the individual segments, assembling them until the entire 45' long roadbed was one unit (another 2' of grade was added at the top when the partial upper level was finally constructed).

Next, I attached one end of the grade's roadbed to that at the bottom of the grade, then affixed the top end of the grade to the point where the partial upper level would eventually be built.

Next, using a train of fixed-length as a measuring device, I determined the mid-point of the grade's length, and added a riser there, placing the track at that position at an elevation half that of the entire rise.
This had the effect of automatically creating vertical easements at both the bottom and top of the grade.  From there onward, additional risers were added simply by making them to a length suitable to the elevation of the roadbed at each particular point, a benefit of using thick plywood for the sub-roadbed.

To created superelevation... 

If your track is on risers (it doesn't have to be on a grade) it's easy to add superelevation.
Draw a pencil line on each riser where they attach to the crossmembers of the layout structure - this is to ensure that the risers will be at the proper height after the superelevation is imparted.
Place (or run) a train onto the curve - it should extend completely through the entire length of the curve, even if you'd never run a train of that length.  
Next, unscrew, from the crossmembers, all of the risers supporting the curve.  The roadbed will likely sag somewhat, depending on the thickness of your sub-roadbed - I used 3/4" plywood, so the sag was minimal.  Now, select the riser closest to the mid-point of the curve, raise it so that the pencil line aligns with its crossmember, then push the bottom of the riser towards the outside of the curve, thereby imparting some degree of superelevation to the track.  Manually adjust the amount of offset until the train looks good to your eye...a noticeable tilt that you'd consider appropriate to the speeds at which trains would pass through that curve.  
Line-up the inside point of the pencil mark on the riser with the top of its joist, and then clamp or screw it in place.  The outside end of the pencil mark will now be somewhat above the joist.
Next, pick a riser mid-way between the one you just attached and the beginning or end of the curve.  You'll notice that the pencil line on it is now also not-level, as the entire sub-roadbed of the curve has twisted with the re-positioning of the riser at the mid-point of the curve.  This twist diminishes as it gets farther away from the mid-point of the curve, which imparts the vertical easements into and out of the curve.

Without applying any outward force, carefully lift it until the inside end of the pencil line aligns with the top of its riser, and fasten it in place.  Repeat this procedure for the riser on the mid-point between the first-done centre one and the other end of the curve.
  
You should then be able to repeat this operation for all intermediate risers, taking care to only lift until the pencil line on the inside of the curve aligns with the top of its joist.  Do not apply any force outwards.
  Each portion of an ess-curve is done in the same manner, and as long as the distances are great enough between the changes of direction, the superelevation will automatically transition to suit the curves.
It's a pleasure to watch a train snake through the curves, tilting in and out as the cars and locos respond to the superelevation.

Wayne

[selector]

You need to plot your 3D path in your mind, and place risers under the imagined roadbed.  But the trick is to use clamps. Situate risers of a reasonable length where you imagine they'll be needed, but clamped only.  Then, fashion your roadbed elements and place them atop the risers.  Continue to fiddle until you have the geometry you need there, including the grades up and descending.  Once you are happy, AND YOU KNOW YOUR TRAINS WILL HANDLE WHAT YOU ARE LAYING FOR THEM, you can adjust the lengths of the risers or simply commence screwing them to the joists or cleats.

Note that you can, and probably ought to, cant the risers to accommodate super-elevation if and where you'll want it.  Don't overdo this!  Two-three degrees of cant is lots, even on our layouts.  But the tilted tops of those canted risers will securely hold the thin sub-roadbed in the proper attitude if you use glue, a single countersunk wood screw, or both.

[crossthedog]

Rio, that's exactly what I imagined, but it's hard to see what the supports look like for the curves at the far end of the photo. I see at the near end that you've got some serious carpentry going on, which enables the supports to be properly crosswise under the roadbed. I haven't that skill. My layout is basically an indoor tree-fort. I was hoping that I could do my track leveling with the risers. Thanks for showing that photo. Helpful, and slightly intimidating. :)

[riogrande5761]

L-girder is the posh route but I just go open grid and try to have cross members about ever 16"  or less for risers.  I use 1x3's but 1x2's should work too.

This is open grad - works as well as L-girder and a bit simpler to build.

[crossthedog]

Awrighty, next question. How do you attach risers from gridwork in such a way that they'll support the subroadbed wheree'r it doth go? My basic benchwork looks like this so far, pardon the mess:

It's not really even a grid. There are 3 L-girders, one short one attached to the wall and two 10-footers out in the garage space, the one nearest to the camera being 8 feet out. They are spanned by 1x4s on end, supported with brackets.

I saw this arrangement online somewhere last year and it showed how to attach risers for subroadbed, but I can no longer find that article. I'm not sure that copying it was the greatest idea, especially since I had to space my "joists" or spanning pieces unevenly, due to a host of reasons including future access holes inconveniently placed electrical wells, and a subtle angle in the finished wall that I'd actually never noticed before (it's been behind shelving since we moved in). 

So what are some ways to skin the cat of laying subroadbed here? I've seen layouts where you lay a first (sub-sub) roadbed directly flat on the grid, with risers standing on that, and then mirror the first roadbed with a second bed at elevation. But I didn't need to build gridwork just to place a prefabbed viaduct on a flat surface.

I had originally thought the standard practice was to bolt risers to the gridwork, and that's what I've been planning to do. But how do you get the supports to orient properly with track curves? I suppose I could make mini L-girders out of 1x2 so that roadbed supports could be affixed to the riser no matter which way the roadbed was oriented. 

Ideas? Does what I'm asking make sense? Has anyone else addressed this issue?

As always, thanks in advance for any and all help.

Matt