When super-elevating curves, with tape I assume, do you put the tape between the roadbed and track, or under the roadbed? Any better ideas other than using tape?

Really, you can put the tape anywhere.

You can use cardstock shims. You can lay the roadbed flat, glue it, and then sand it so that its top surface is offering a cant to the tracks. Theoretically, you could even sand the ties, but it would be a heck of a job.

The nice thing about spline roadbed, and even cookie cutter if you sand it, is that you can do this and then just lay the tracks. The splines can be torsioned slightly by swinging their risers'/piers' bottom ends to one side prior to mounting them on their anchoring points.

Crandell

If you use open grid or L-girder benchwork, superelevation is easy to add, including the vertical easements into and out of the curve.
I use 3/4" plywood as a sub-roadbed, but any similar-type material, or even spline roadbed should also work.  Install the straight roadbed on either side of the curve by fastening the risers to the joists - leave the last riser beyond both ends of the curve unfastened.  Install risers to the underside of the curved roadbed, but don't fasten them to the benchwork just yet.  If your curve is on a grade, as most of mine are, raise the roadbed through the curve to the proper height, then mark a pencil line on each riser which corresponds to the top of the benchwork to which it will eventually be fastened.  If the track through the curve is to be level, adjust the risers accordingly, then make the lines.  Next, choose the riser closest to the mid-point of the curve, raise it to the proper height, then push the bottom end of the riser towards the outside of the curve.  Re-align the height line on the riser so that its inner end corresponds to the top of its benchwork member (the height line will be tilted, with the end on the outside of the curve somewhat above the benchwork).  I've found that the best way to establish the amount of superelevation is by placing a train on the curve, then adjusting the off-set of the bottom of the riser until it "looks right".  I use a C-clamp while I'm making the visual adjustments, then, when I'm satisfied with the appearance, that mid-point riser is screwed to the benchwork.  Because the roadbed is torsionally flexible, each riser on either side of the mid-point will now be off-set from the vertical, to diminishing degrees, as the distance from the mid-point increases.  Working from the mid-point of the curve, carefully raise each riser so that the inside end of the height mark aligns with the top of the benchwork to which it will be fastened, making sure to not change the angle of off-set, then screw the risers to the benchwork.  I did all of mine with the trackwork in place.
Here's a sketch of the layout room:


As you can see, lots of need for curves. The low level trackage at Dunnville and the low speed curve between Lowbanks and Port Maitland aren't superelevated, but all other curves are. Maximum track speed on the layout is 45 mph, but the limit is 30 mph or less in most areas.

Here's a train approaching South Cayuga from Dunnville. While it's not overly apparent in photos, the slight superelevation is definitely noticeable during operations:


A westbound crossing Chippawa Creek, heading for Lowbanks:


Looking south at Dunnville, all of the upper level tracks, including the approach to the coal dealer's siding, have superelevated curves. However, I goofed and used a single wide subroadbed for the two main lines: to be more prototypical, each track should be on its own subroadbed, and superelevated individually.



Here is a couple of views of the roadbed-on-riser method of construct:




And a short on-board video of a train on the curves shown above:


Wayne

I cut styrene curved strips (about 1/4" wide) to match the outer rail of the flex track curve I created, then slid it into place beneath the rail ties and glued it in place. The whole assembly was then ballasted. For Nscale, even a very small elevation makes a difference in "look" and a slight difference in operation.

FYI: a 16 degree curve ( approximately 50" radius in HO ) would have 4" elevation ( outer rail head 4" above the inner rail head ), which is 0.0459768" in HO, The allowable speed of train in that situation would be 10 MPH ( the gauge would be widened to 4' 9-1/2" ).
Super elevation, in the real world compensated for centrifugal force. In the model world there isn't enough CF to be compensated for. the elevation leans the cars into the curve, and as draw bar pull increases ( longer trains ), or "top weight" increases ( taller trains ), the tendancy of super elevation, is to dump the train to the inside of the curve ( at almost any speed ).
It does look really good to see trains " leaning into the curve", but I'd recommend no more than 5 degrees of lean ( the above results in about 8 degrees of lean )

Here are the actual tables from 49 CFR. I found over years of watching wheel sets in curves that widening the gauge on curves is not needed, in fact, you can drop in easier on a curve than on tangent track. A wheel set doesn't go around a curve evenly, they tend to skew which in fact makes the wheel set width narrower. The trouble with super elevations and freight trains is they have to maintain track speed or the weight does go to the low rail and it will look like a washboard if this happens frequently.
Charlie

Perhaps just a slight super elevation is in order then. Thanks all.

When did super-elevation come into common usage?

" When did super-elevation come into common usage? "
The information I posted came from the 1903 edition of "The Mechanics' HANDBOOK ", so it was in use then. The original copyright was 1893, but I can't be sure the information was included in the first publication.

MountainMan Wrote:When did super-elevation come into common usage?

As soon as a road gang gathered tools, some ballast, and headed out to where some passengers left smelly bodily fluids on their seats when the first fast-moving passenger car did a two-wheeled balancing act around a curve at speed. It was probably a summer's day in 1879.

Crandell

Selector Wrote:

MountainMan Wrote:When did super-elevation come into common usage?

As soon as a road gang gathered tools, some ballast, and headed out to where some passengers left smelly bodily fluids on their seats when the first fast-moving passenger car did a two-wheeled balancing act around a curve at speed. It was probably a summer's day in 1879.

Crandell