Helix construction methods???

[KingConrail76]

I've been thinking of adding a second level to my layout since I am horazonally challanged in my given space.

I know how to plan my Helix, and the dimensions I want to use.

What I don't know is: What size/type of material should I use to get the thinest subroadbed, with the greatest strength and easiest splices?  3/8 inch underlayment plywood, 1/8 inch or 1/4 inch masonite, something else?

Also, How much (degrees of curve) should each section of raw material turn to get the best end result? (when I layout my "sections" to be cut from my 4 x 8 sheet, how will I get "best yield"?)

I am modeling in HO scale, would like to have maximum 36 inch radius, with maximum 2.5% grade. I run Modern Equipment including Double Stack Well cars (seems to be my highest equipment)-hence, my need for thin subroadbed.

Any thoughts?

[concretelackey]

Having experience in both steel fabrication and custom concrete form building I will say that having the goal of BEST YEILD is not always the best method. Best yeild from a woodworking point of veiw means limiting/eliminating waste, however, doing so can create additional costs beyond the monetary factor. In your case, best yeild for narrow strips of radiused cuts from a rectangular sheet means going with short peices with a lot of splices. This means loss of overhead height at the splices and additional construction time. Longer cut peices mean less splices, less construction time but more potential waste.

I've no experience with helix construction but perhaps a hybrid will work. Using splined roadbed construction (1/4" masonite strips 1'' wide laminated together) with the threaded rod hanger system ( I think it was BRUNTON that posted some pics of his back in November). If you have access to a table saw with a thin kerf blade you should be able to get about 40-42 strips 1 inch wide from a 48" wide sheet of masonite. Standing them on edge it would take 12 strips to make a 3" wide bed, so 40 strips would yeild about 24 linear feet of bed with 6 strips left for the next 24' run (OR 2 4x8 sheets should give enough to do about 60 feet of bed). The last time I bought masonite it was about $10 a sheet.

Quick thought if you have Atlas RTS. Make a 4x8 layout outline and see how many curved sections (of what length/degree of curvature) you can fit in it. It may not be 100% accurate but should be close

my

[concretelackey]

You could probably do the splined bed at 3/4" thick and use simple 1/8"x3/4"x4" flat brackets from lowes/HD connected to the threaded rods. The brackets would lay flat under the bed.

[dehusman]

I have tried a couple methods. 

You can use a "thicker" plywood (1/2-3/4") and then rout the ends so they overlap. You can use the thicker plywood and use a bisquit joiner to attach butt ends.  You can use a thin splice plate of 1/8 hardboard or an even thinner one made from those metal construction splice plates (a flat metal plate with hole punched in it, only glued, not screwed under the helix.)  I tried laminating two layers of 1/4" plywood to completely eliminate splices.  Getting the clamped flat is the hard part.

A friend has a layout with several helixes in it.  One he made using curved pieces of plywood cut with a saber saw, the other with octagonal sections from an article in RMC.  The octagonal one was easiest to cut (all straight lines on a table saw and chop saw) but it actually used more lumber eventhough the curved pieces had more "waste".  The octagonal design had more joints in it, which I didn't like.

There are also several methods of making the helix.  Threaded rods with nuts and washers to set the levels.  Spacer blocks between each level.  Notched risers that the helix fits into.

Good Luck.

Dave H.

[last mountain & eastern hogger]

Good Morning King Conrail,

I have a helix (four loop) on a center penninsula to lower Staging and classification yards.Built with straight sections and 22.5 degree ends. This has butt ends and splice boards  and threaded rods. has worked well for me,

If you go to the bottom of this or any thread and go to the search bar and type in HELIX, it will take you some reading but your questions can be answered as we have gone through this many times. There are numerous entries on this subject there.

Good luck, take your time, calculate properly and build sturdy and you will find that it is a worth while project.

Johnboy out...............

James:1 Verse:5

The "wobbly" is wobbling in the snow.

[ndbprr]

In my opinion the highest yield method will also equal a very string method.  Rip plywood into straight lengths 8' long.  If 6" wide you get 8 strips 8' long or 64 lineal feet.  The trick is to miter the ends to make pieces that are trapezoid shaped.  In a simple explanation the outside instead of being round will look like a hexagon but will have many more sides. Use small pieces of splice plates place and screwed from the bottom and top as well as glue  to hold the pieces together.  The hang threaded rod from the rafters and drill holes in the helix so it can be adjusted later if needed.  Use double nuts under each section to level and hold it in place.

[KingConrail76]

I have tried a couple methods. 

You can use a "thicker" plywood (1/2-3/4") and then rout the ends so they overlap. You can use the thicker plywood and use a bisquit joiner to attach butt ends.  You can use a thin splice plate of 1/8 hardboard or an even thinner one made from those metal construction splice plates (a flat metal plate with hole punched in it, only glued, not screwed under the helix.)  I tried laminating two layers of 1/4" plywood to completely eliminate splices.  Getting the clamped flat is the hard part.

A friend has a layout with several helixes in it.  One he made using curved pieces of plywood cut with a saber saw, the other with octagonal sections from an article in RMC.  The octagonal one was easiest to cut (all straight lines on a table saw and chop saw) but it actually used more lumber eventhough the curved pieces had more "waste".  The octagonal design had more joints in it, which I didn't like.

There are also several methods of making the helix.  Threaded rods with nuts and washers to set the levels.  Spacer blocks between each level.  Notched risers that the helix fits into.

Good Luck.

Dave H.

This method of "rabbiting" the ends to form an overlapping joint was what I thought would give me the most-consistantly thin subroadbed. My concern with this is-Do I lose any measurable strength at the ends of each splice where I only have half a thickness, or in your opinion (or experienced to be fact) is it negligable?

ConcreteLackey,  I saw the post on threaded rod spacers/supports, that's actually what got me thinking about tackling this again. I like the idea of the "strap" supports you mention, but I think I would be just as well off drilling holes right in my subroadbed to reduce total thickness as much as possible. I don't mind having a wide subroadbed, as it affords clearance and a safety factor if anything should derail. To clearify my "best yield" question, as I said, I used to work as a Cabinet Maker, and am well aware that best yield does not equal best results. I guess I was more looking for-Is it worth making half circles over quarter circles, losing the yield to get simpler construction/less joints, or is it "6 of one/half a dozen of the other"?

PDBPRR, Thanks for the much clearer explanation of what JohnBoy was try'n to say. Excellent idea, however as I no longer work as a Cabinet Maker, I have no access to a good "chop" saw, I have to make do with my router, so-so table saw, and Jig saw. (though I think I could make a straight cut 6" long with a jig saw...lol)

 Again, thanks all for the great ideas.

[concretelackey]

A rabbit joint (whoever named this????????????) or also known as a ship-lap would work well since you will have little load on the joint ONCE the entire helix is built, assuming that you can machine the overlaps smooth enough and large enough for solid glue adhesion. What you possibly could do in the situation is build the helix coils as a collapsed structure. Mark your circumference on the floor/table and glue the joints as you go. To prevent the glue from one layer sticking to the next lower/upper layer just place 2 pcs of paper that has a pc of plastic (trash bag plastic) in between. When seperated the paper can be easily sanded off. Doing it this way will give you a consistant circle and afford you the oppurtunity of maximum clamping surfaces with minimum clamps. When the glue has set you can then handle it like a SLINKY, grab the top coil and the rest will follow.

[dehusman]

Possibly the person who named it a "rabbet" joint.

A rabbit joint is what hippie rabbits smoke.

Dave H.

[concretelackey]

Possibly the person who named it a "rabbet" joint.

A rabbit joint is what hippie rabbits smoke.

Dave H.

Oh yeah, his first name is Peter......

[KingConrail76]

A rabbit joint (whoever named this????????????) or also known as a ship-lap would work well since you will have little load on the joint ONCE the entire helix is built, assuming that you can machine the overlaps smooth enough and large enough for solid glue adhesion. What you possibly could do in the situation is build the helix coils as a collapsed structure. Mark your circumference on the floor/table and glue the joints as you go. To prevent the glue from one layer sticking to the next lower/upper layer just place 2 pcs of paper that has a pc of plastic (trash bag plastic) in between. When seperated the paper can be easily sanded off. Doing it this way will give you a consistant circle and afford you the oppurtunity of maximum clamping surfaces with minimum clamps. When the glue has set you can then handle it like a SLINKY, grab the top coil and the rest will follow.

Actually, the "joint" is a ship-lap, and the area removed from the stock material is the rabbit.

Another way to see it, is a Rabbit is an open sided Dado, not to be confused with an open sided daewoo, which is not a Rabbit, but a wreck.

The paper and plastic trick is actually two ways of doing the same thing. Would you like Paper or Plastic?

Waxpaper works well for avoiding glued things that must come apart too.