Dan’s Train Blog

Yes, I’m still futzing with the track and that darn hill. As I described last time, the hill was too steep and I lowered the end height ¾” and estimated that I had brought the grade down to 6%.

Was it really 6%? I decided to do what I should have done in the first place, really measure the grade. With a ruler and a level-bubble I was able to estimate the grade easily enough, but I could see that the hill was steeper in some places than others. I decided I needed better measurements to not just tell me the grade but tell me how much I should correct elevations along the grade to smooth things out.

Couldn’t I do this with the CAD system? Not really. Something 3rd PlanIt does not do well is vertical transitions and what I’m talking about here is an eight foot ribbon of plywood that eases up to the grade, climbs (and goes around an 18″ radius turn), and finally levels off at the top.

So I got out a ruler and measured the height of the roadbed every three inches to the nearest 1/16th of an inch, entered the measurements into a spreadsheet and found some trouble. The average grade was 5.8% — very close to and below the original estimate. However, that average was made up of sections at about 4% and others at 8%.

Making the speadsheet also made it easy to calculate which risers needed to be adjusted and by how much.

While I was at it I decided to try to pull off another ¾” from the overall climb. To reduce the need to climb I had to change the type of bridge from this:

to a plate girder type bridge like shown below which allows a minimum rail-head to rail-head distance. The bridge shown is a standard Atlas bridge which is not realistic if examined closely — I’ll have to take care with detailing and finishing.

And lose that beautiful Howe truss bridge? No, I’ll simply shorten the wood bridge and it will continue to the left.

 The good news is that the reduction in height reduces this grade to 4.5%. The climb up the other side of the hill becomes 3.7% (same climb but longer run). Now that (admittedly still steep) grade is even with no sudden steeper parts.

Lesson learned: measure, test, measure, and measure again.