misplaced my magnifier

Hope you can work out a way to make those pictures bigger; it's a little hard to see what you're doing.  I expect that since you have an oval helix you will be able to make the turns bigger, which will help offset the increased roadbed thickness.  I'm anxious to get a better look.

Using Spline Roadbed in Helix - Part 2A

Sorry about the pictures.  I'm new at uploading and I messed it up by loading the thumbnails. Here are the full size pictures. 

I used the surform tool to smooth out the splines to make the finished surface smooth.  I used a brush dipped in water to spread out the oozing wood glue when the splines were clamped.  That reduced the amount of topside roughness that the surform tool had to deal with.   

This is a picture of one of the straight sections.

This is a picture of my analog gradient tool which is reading about 2%.

This is the helix table that will take trains to and from the hidden staging yard that represents the southwestern & western ATSF destinations.   The two tables in the corner beyond the helix table are only a portion of hidden staging area as there will eventually be a peninsula to the left.  The hidden staging on this end will will consist of two 9 track yards (Yard A andb) with tracks assigned to specific trains.

The spline is built up on temporary risers covered with wax paper on my template table.  The wax paper does do a fair job at preventing the spline from gluing itself to the riser.  When each turn is complete it will be moved to the helix table for assembly.

Looks sharp

It looks clean and well constructed.  It looks like your radius is generous enough that your 2% grade should work out OK.  You have managed to keep your radius pretty constant, which is not trivial with spline, and as an added bonus you have easements going into the curves.  It looks like a good job.

I admire your work ethic....

Spline roadbed always seemed like way too much work to me and the thought of someone doing a helix with it makes me shudder!  I wish you continued success!

Michael

spline=helix

I always thought that it would be a lot of work also, then I started doing spline roadbed for my layout which contains 2 ...count them 2 helixes....I model in HO scale and am using the masonite spline technique.  The hardest part of the Spline construction is "cutting the splines"  Building the spline roadbed is fairly easy and quick.  Anyway...that's my two cents..

later

Amtrak115

It seems to have merit

I only saw a helix made with spline once with my own eyes, and it was a horror story.  Yours is looking a lot more likely to succeed.  One bonus of this technique is it's likely to be smoother than one made from segments of plywood.  The only real stumbling block to me is the thickness of the roadbed, since I like to keep mine 1/2" thick.  I'll have to ponder the problem.  

Maybe a spiral

You could build a helix where the roadbed, rather than being directly above the previous turn, is actually offset with the radius constantly increasing as you go around for each turn. This way the thickness of the roadbed is irrelevant to the grade. It would also allow unimpaired  access to the track from above. One disadvantage might be that the more turns you have in your helix the larger the footprint.

cheers,

Steve  

Size of Spline for Roadbed

Jurgen,

I did not use 1/2" because I felt that it may have been too thin for a double track spline helix.  I have used that size for a single track curve within a micro-engineering brand steel trestle.  It was also enclosed within styrene deck bridge sides with trestle bents to support the overall structure.  Also the 1/2" spline was fairly difficult to cut on my table saw (with a vertical feather board) from a full length sheet of masonite hardboard. Once I switched to a smaller piece of hardboard (maybe a foot wide and 2-3 feet long) I was able to make the rip cuts fairly easily.  For regular mainline and siding spline roadbed, the 1/2" spline would probably be okay since it will be supported by risers.

For the helix that I am currently building, I picked 7/8" spline size for a couple of reasons.  First, when I make the rip cuts to create the splines, the blade takes another 1/8" off the sheet of hardboard. So overall, I am taking an inch off the sheet every time that I make the rip cut. I got 47/48 full strips off the last full sheet that I ripped into splines and one other one broke in half.  The setup that I use is a 10" table saw with an in-feed table behind the saw and an out-feed table in front of the saw.  When ripped, the splines land on the out-feed table.  All that remains when the sheet is done is a foot high pile of hardboard dust. I do this outside on a concrete pad and wear a dust mask.

Second, the helix also needed some surface area on the sides so I could put in the screw eyes to support the threaded rods and I felt that the 7/8" thickness would be better for that application.

Thanks for your interest as it has motivated me to work faster.  I should have the first turn finished this weekend.  I will post some more pictures of progress next week.

John

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