Hello everybody. Here we have it, another topic on spline roadbed.
After reading more about spline roadbed here and the numerous endorsements, I had a question for you all.
Can spline also be applied effectively to a helix? It would seem that this could be the ideal way to create a helix, as all it would require are a few pseudo-joists spanned from a circular support structure, on which thin splines could be laid.
What issues could you see with such a plan? The splines would no doubt have to be thin in order to maintain maximum clearance, requiring a closely spaced support structure.
I had seen another idea from the BNSF Chilli sub using double layered angle pieces as well. Any thoughts as to which would work better from the perspectives of time, cost, and margin for error?
I am very close to using the BNSF Chilisub idea of helix construction... it would be way faster in my opinion as it can be built in short segments and the screws hold it as the glue dries; you have a level surface to use right away for track laying.
With the spline method, my expectation is that the strips need to be fairly long to get the true benefit of the spline rigidity and trueness. When building a helix, keep in mind that you need to lay track, add feeders etc. as you go. Depending on the spline length, one piece may overlap itself making subsequent track laying difficult.
Also, I'm not sure how much vertical deflection spline roadbed allows.... ie. how much grade can it flex to, or how easily it can transition from say flat track to 2-2.5%?
The purpose of spline, I believe is its vertical rigidity and lack of deflection in the x-axis.
I have never used spline though.... anyone else have any yeah or nay's on what I have said?
Hope I've helped somewhat!
railroadyoshi wrote:Hello everybody. Here we have it, another topic on spline roadbed.After reading more about spline roadbed here and the numerous endorsements, I had a question for you all.Can spline also be applied effectively to a helix? It would seem that this could be the ideal way to create a helix, as all it would require are a few pseudo-joists spanned from a circular support structure, on which thin splines could be laid.What issues could you see with such a plan? The splines would no doubt have to be thin in order to maintain maximum clearance, requiring a closely spaced support structure.I had seen another idea from the BNSF Chilli sub using double layered angle pieces as well. Any thoughts as to which would work better from the perspectives of time, cost, and margin for error?
Dustin and Electro, thanks for your replies.
http://www.bnsfchillisub.com/Local%20Layouts.htm
Helix photos are buried just a little ways down on that page, but "KCT Helix!" is pretty easy to spot as you scroll. The idea is definitely something to try.
The primary reason I was interested in using spline is that there are 2 points mid-helix where tracks must enter, and I thought that making these connections would be easier in a spline design.
Spline roadbed may not be the best choice for a helix because of the vertical thickness of the spline. You have to add that thickness to the vertical climb of each loop. Spline is typically 3/4" or even 1" thick.
If I was going to build a helix, I would use a method I learned at the last club I was at before moving. 1/8" thick plywood was cut into 45 degree arcs of the appropriate radius. Those arcs were laminated into a 1/4" thick sub-roadbed with the joints staggered by about 20 degrees. This resulted in a strong, kink free, 1/4" thick helix sub-roadbed. The track was laid directly on the sub-roadbed to help keep the thickness down and keep the grade minimized. Roadbed (cork, Homabed, foam) isn't necessary as the helix is hidden track anyway. The helix was held in place with 1x2 columns with notches every 45 degrees on both sides, although using nuts on threaded rods would work well too.
ericboone wrote: Spline roadbed may not be the best choice for a helix because of the vertical thickness of the spline. You have to add that thickness to the vertical climb of each loop. Spline is typically 3/4" or even 1" thick.If I was going to build a helix, I would use a method I learned at the last club I was at before moving. 1/8" thick plywood was cut into 45 degree arcs of the appropriate radius. Those arcs were laminated into a 1/4" thick sub-roadbed with the joints staggered by about 20 degrees. This resulted in a strong, kink free, 1/4" thick helix sub-roadbed. The track was laid directly on the sub-roadbed to help keep the thickness down and keep the grade minimized. Roadbed (cork, Homabed, foam) isn't necessary as the helix is hidden track anyway. The helix was held in place with 1x2 columns with notches every 45 degrees on both sides, although using nuts on threaded rods would work well too.
That sounds like a beautiful helix. I can almost see it in minds eye now.
The KCT helix looks good, but it sure looks like a LOT of work!
Here's my own helix:
I cut semi-circles from a sheet of plywood, and spliced 24" straight sections (to reduce the grade) between. I used a lot of sheets of plywood, but all the excess left me with plenty of subroadbed for other trackwork and bases for structures.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton