MDF board

I have used MDF board to my helix.
http://www.smugglers-division.dk/helixam/helixam.html
http://en.wikipedia.org/wiki/Medium-density_fibreboard

Spline

Nominally in a helix, one turn has to have enough climb to clear the equipment and roadbed, it has to climb the distance railhead to railhead.  Lets say the nominal distance from top of rail to bottom of turn above is 3".  You then have to add the thickness of the roadbed and track.  Depending on the thickness of your spline, that can range from a 1/2" to almost 2", that makes the total climb of each turn 3.5" to 5".  The outcome is the thicker your roadbed, the steeper the grade or the larger the radius you need. 

Not Spline But Is Hardboard

I too want to build my helix with hardboard but not in a spline configuration because of headroom problems noted above. My helix design uses 2 laminated pieces of 1/8" forming 1/4" thick sections. The laminated pieces will be offset 1/2 length much like you would stack bricks. This in theory gives me a single continuous helix roadbed from top to bottom while still allowing incremental construction for ease of track laying. The loops are supported and spaced with threaded rod and pvc pipe spacers. Each 120 degree semicircle piece will be cut from a master so they are identical including the holes for the rods. It is a 34" radius single track configuration so the effective roadbed width is fairly narrow at 3-1/2".

The laminated hardboard with the proper number of support rods should provide a solid yet thin roadbed thus minimizing my grade.

Several months ago I assembled a 2/3 loop test piece with rods on 10 degree spacing. Elmers Yellow glue (liberally) and lots of QuikGrip clamps were used during assembly. The pieces were placed rough sides together. It has been in the barn with bricks sitting on it ever since to test the stability. To date there is no negative change to the test piece. 

As was mentioned, thickness of roadbed increases grade or

increases the size of the helix.  One other thing to think of when doing a helix.  A but joint of plywood, hardboard or mdf can result in misalignment or a vertical curve where the pieces join.  I think it is better to laminate two thin pieces and overlap the joints than to make your helix with one thicker piece.

I used strait sections of

I used strait sections of 1/2" ply with angled ends with biscuit joints.  Worked very well and was thin and very strong.

Spline helix

Thank you all for your thoughtful insights.  Hmm - much to think about!

(OOPS-double click).

Spline helix

Thank you all for your thoughtful insights.  Hmm - much to think about!

Spline helix

Excellent point.  Had not thought about that.  Thank you.

I did spline helix - but would do July issue method in future

I've done a spline helix on my Siskiyou Line layout but in the future I would use the method Art Houston shows in the July MRH.

Spline helix has excess depth between levels because of the spline, and maintaining a constant radius with spline requires using a jig to build the spline sections.

Art's method in the July MRH is exceptionally practical and has minimum thickness between levels. All-in-all, Art's method is one of the best I've seen, which is why we wanted very much to run this article. I highly recommend Art's approach as a very painless method with minimum level thickness and no splice plates!

alternate spline use

I used thin plywood, 1/4", with butt joints as roadbed and edged the plywood with vertical spline reinforced with 1/4" square hardboard top and bottom and lots of yellow glue--about as thin as I could get and very strong.  The plywood was cut to radius using an inexpensive band saw and a special jig.  The helix was three track with the minimum radius at 30".  It was used primarily as part of the staging, connecting the ends of the railroad rather than in the middle of the run.

Terry

Spline helix

Thank you, Joe.  I have all your videos and know you were not pleased with your helix.

Art Houston did a beautiful job with his helix masterpiece.  His article and pictures were great.  Frankly, though, his product is intimidating!  Art's carpentry skills, planning, attention to detail, etc. are far beyond my skill level.  Spline seems more forgiving and free form - easy to tweak if I mess up.  If I do more of an oval shape, it might mitigate the depth problem.  I need to ponder and procrastinate some more.

Noticed the time stamp on your post - do you ever sleep?

Thanks again.

You can do it.

The size of Art's helix looks intimidating, but the biggest challenge is to figure out how to get the maximum amount of useful pieces out of a sheet of luan.  You just take your time and do the project one step at a time.

Spline Helix

We just finished up a spline helix on my layout. It has 4 - 36" radius radius turns at about just under 4" apart.. It looks more like an oval though. We had to elongate it to get the grade under 2.5%  It has 3 loops.  My spline is made out of homosote cut in 1 5/8" strips. I also used backer boards to keep the homosote from breaking.  I would not do it again. It took a couple days to get it right. I would use the lamenated plywood way if I were to do another one.

GOOD LUCK

martin

Helix

I have built helices both ways with overlapping joints. They were built essentially the same way and size. The plywood method proved to be more rigid and structurally sound, at least in my experience so if and when I build my third one it will be with plywood. 

Harold

Spline helix

Thanks everyone for your comments.  Sounds like I better avoid spline for the helix and go with plywood.