Hi;
Anyone with helix experience. I am thinking this would have some advantages over a circular helix. Easier to cut and less plywood wasted. What would the pitfalls be?
Thank you in advance.
Mark
I suppose it depends on how you do your joints. One advantage to using curving sections is that you can use two layers of plywood (each one being half the thickness that you want the final roadbed to be) and stagger the joints, making for a strong, continuous spiral. Doing that with straight sections isn't going to work that well because there will be a lot of areas where the two layers aren't overlapping each other.
If you plan to do a single layer of plywood by butt-jointing the ends and using another small piece of ply under the joint, then it wouldn't really matter. The disadvantage to this is that the extra piece of ply is going to add to the thickness, thus reducing clearance.
Steve S
presumably this is easier and less wasteful because it can be formed from straight pieces of wood with appropriately angled ends.
you could make it with two layers. If the layers are offset, the joints wouldn't overlap.
how wide do the pieces need to be?
greg - Philadelphia & Reading / Reading
My experience: I built a double helix with staging rising 27" total. The helix has been in place roughly 8 years now and works flawlessly.
The biggest drawback is the extra time it takes to glue eight pieces of wood together for each rotation. I used a design that cut the circle into quarters and that was tedious enough. There are those that overlap the layers, essentially doubling the number of pieces. I didn't find the overall strength of the stack to be enough of an issue to warant the extra effort.
I my helix design I wanted tracks to pass each other very tightly going around the helix. The curves gave me a tighter fit than sharp octagonal angles would have, thus allowing me to use less space for the helix area.
My two cents,
Guy
see stuff at: the Willoughby Line Site
I see no pitfalls whatsoever. My current layout has three such helixes. I assembled all the sections using a biscuit joiner, which makes for solid joints without needing splice plates.
Rob Spangler
Thanks to recent developments in CAM woodworking (Computer Aided Manufacturing) there are now companies that can cut semi-circular pieces out of plywood sheet very quickly and easily, and at a reasonable price. I did the math for a 60" dia. helix and I could get 12 - 90 degree curves 5 7/8" wide from a 4 x 8 sheet of plywood.
To do a 27" high x 60" dia. circular helix with 4" between layers you would need 6 3/4 turns (@ approx. 2% grade). That equals 28 pieces if you are biscuit joining them, or 56 pieces if you were laminating them.
To do an octagonal 27" helix you would need 56 pieces if you are biscuit joining them or 112 pieces if you were laminating them.
I hope my math is correct.
Both solutions will work.
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
hon30critterThanks to recent developments in CAM woodworking (Computer Aided Manufacturing) there are now companies that can cut semi-circular pieces out of plywood sheet very quickly and easily, and at a reasonable price.
That's how I did my helix parts. I dropped off 3 sheets of 1/8" birch and a DXF file and picked up these a few days later.
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
Hi Carl:
Actually, it was your post that spurred me to find a local company who could do the same thing, and I did find one that is about 25 minutes away.
Can you explain a little bit more about what is involved in creating a DXF file and what program(s) would be needed?
Thanks
Hi again Carl:
I need you to help me out a bit please. I thought that I had bookmarked the woodworking shop that had the equipment to do the cutting of the helix parts, but alas it has disappeared from my favourites list. Can you post a link to the thread where you talked about getting the helix parts cut so I have a better idea of what to search for?
No need. I found the company.
Hi Markie,
To get back to your original question, that is how I made mine. 28" radius, 5 loops and I just used pieces about 6" long glued and screwed underneith the joints.
It has been there for about 4 years now and has worked well.
I was a little intimindated when I started but, it went together easily and not with the extensive engineering that I had read was necessary.
Go for it.... It certainly is the economical way to go.
Johnboy out...................................
from Saskatchewan, in the Great White North..
We have met the enemy, and he is us............ (Pogo)
hon30critterCan you explain a little bit more about what is involved in creating a DXF file and what program(s) would be needed?
You don't even have to use a full-blown CAD program. A vector drawing program like Inkscape can output in DXF format that should be able to be read by the CAM software. Inkscape should be a lot quicker to learn than a CAD app. You can download it for free at...
https://inkscape.org/en/
Here is a detail for a dodecagon (12-sided) helix. It is N-scale and single track, but the dimensions can be changed to accomodate multiple tracks or different scales. It is not as complicated as you might think. A table saw and a chop saw are needed, but those are pretty common shop tools. All components are exactly the same size, so setting up some sort of jig would speed up production.
The slats are 3-1/2" across and are cut from 1/4" plywood. You can cut 14 8-foot long by 3-1/2" wide strips from a single sheet, and get 6 slats per strip or 84 slats all totaled. The glue-reinforcement pieces are 8" long and you can get 12 pieces from each 8-foot strip. For this particular helix you need 12 slats per level times 3.5 levels or 42 slats all totaled. Plus an equal amount of the 8" corner reinforcement pieces. Notice that you can use dimension lumber, but my plan is to use 1/4" plywood to keep the thickness of the helix ramp to 1/2" to accomodate the vertical clearance. The little holes on the inside vertices are for 1/2" all-thread rods to support the ramp. There are 12 holes, but I might only use 6 (every other one). Yeah, I haven't actually built this thing, but theoretically it should work.
My first photo attachment. I read Steve's instructions, but even so I'm not sure how it will come out.
Robert
LINK to SNSR Blog
Steve:
Thanks for the link to Inkscape.
Robert:
Your photo posted just fine.
Interesting design! Almost no waste! Easily adapted to HO scale too.
How are you going to attach the pieces together? Glue?
hon30critter Interesting design! Almost no waste! Easily adapted to HO scale too. How are you going to attach the pieces together? Glue? Dave
Hey Dave-
Well, you know . . . Saturday afternoon, nothing else to do, so why not take a sheet of 1/4" plywood and rip it into a bunch of 3-1/2" strips?
Yeah, glue. Smear a thin layer onto the 8"x3-1/2" connectors (shown as dashed lines in the drawing) and clamp them to the bottom of the angled joints of the slats. When dry, the yellow glue becomes just as strong as the plywood itself. The effective thickness of the ramp is 1/2", leaving 3" clearance (in this case) between levels. 1x4 dimension lumber could be used and joined with biscuits as described in a previous post, but that would decrease the clearance and then the pitch and grade would need to be adjusted.
Hex nuts are placed just under the glue boards along the 1/2" diameter all-thread vertical columns, and they allow very minor adjustments to smooth out the grade.
The 28.25" radius is pretty generous for N-scale, and that was used because I have a shoebox full of Kato Unitrak.
Somebody did an article about an octagonal helix about ten years ago or so, don't remember which magazine it was in.
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
Howdy, Robert.
I have one helix in an equalateral dodecagon, same shape as yours but fabricated from steel stud material. I expect to use the same system for some other hidden curves, but haven't worked out the precise geometry yet.
The stud, positioned like a rain gutter, is cut at right angles, leaving the outer 'wall' uncut. The 'floor' overlaps, and is screwed together to hold the angle. The inner 'wall' is cut free of the 'floor,' bent out 30 degrees, then screwed to the 'wall' of the next segment. A couple of risers were screwed to the 'walls' and continue upward to support the covering landform. Others hit the bottom of the 'floor' and were screwed up from below, taking care to keep the screws where they wouldn't interfere with passing rolling stock. The risers are also steel stud material, and the screws are those little things meant for steel stud assembly.
The whole purpose of using steel studs was to hold the grade to a minimum, on a hairy 350mm (sub-14 inch) radius curve! The route is operated with very short 1:80 scale cars and locomotives, and embargoed to anything long that isn't also super-flexible. Total thickness, railhead to bottom of 'floor,' is about a quarter inch.
Chuck (Modeling Central Japan in September, 1964)
Here are a couple of sketches showing construction details of the base for my 12-sided helix. The location and spacing of the little circles around the perimeter of the helix as shown in a previous post determined the size and layout of the base.
A specific design criteria is that I have to be able to duck under the benchwork and stand up inside the helix. Directly above the helix on the upper level is a steel mill, and there is a 28"x42" lift-out section. It is constructed of rigid styrofoam and other lighweight modelling stuff and it lifts out like a big deli platter. It contains some of the main buildings (blast furnaces, rolling mills, blower buildings, etc). Being able to lift it out makes it convenient to assemble the buildings and structures and whatnot and paint and weather and scenick the area comfortably on my workbench instead of trying to work in situ.
Your helix base design is very simple. Thanks for the example.
I have had some difficulty designing the bases for my helices. You have given me some better ideas as to how to address the problem.
Keep up the good work!
Here's a sketch of the helix assembly.
The distance between decks is 18". Three-and-a-half turns of a 3.5" pitch helix is 12.25". The other 6 inches or so is made up by a pretty long run between the decks. The sketch only shows a short run-in and run-out approach to the helix.
ROBERT PETRICKHere's a sketch of the helix assembly.
No support for the outside edge of the helix?
carl425 ROBERT PETRICK Here's a sketch of the helix assembly.
ROBERT PETRICK Here's a sketch of the helix assembly.
ROBERT PETRICKThe way this helix is configured is similar to a residential spiral staircase that is supported by a single pole at the center.
Every one of those pictures you linked (except the 2nd one that is just a pencil drawing rather than something somebody actually built) has a structural element to support the outer edge of the helix that your design doesn't.
Another issue you have to deal with that those examples don't is that in addition to providing support to the outer edge, since you are working with 1/4" plywood, you have to have additional support in place to make sure it won't warp.
I looked at the idea of eliminating the support at the outer edge of my own helix as a way to get the largest radius in the smallest footprint. Ignoring the matter of long term rigidity, I found in my experiments that without some structure at the outer edge I could not keep the roadbed level from side to side.
I know it's always fun to invent your own wheel, but in this case I'd encourage you to stick with one of the proven designs.
ROBERT PETRICKNo. Doesn't need it. The way this helix is configured is similar to a residential spiral staircase that is supported by a single pole at the center. The theory is that a spiral ramp will act as a simple beam (even though it is curled up) that is supported in all axes of three dimensional space.
Someone here would have flunked statics if they had studied it.
You need explicit sections for lateral bending; the helix as drawn is not 'dimensionally stable' in the lateral plane, and certainly 1/4" plywood will deflect down at the outside edge unless (1) you explicitly design for the cantilevering, or (2) you provide explicit support of that outer edge in some way, sufficient to control the bending within necessary limits. I suspect you are not designing this as a box beam (for vertical clearance reasons alone) so I'd go with external supports, but...
What I would do if I were building this is provide tension members around the edges of the helix, more of them between the coils than are needed to suspend the entire helix.
The existing design (with threaded rod) explicitly works with this design, if you rig the rods to be supported at their tops and free at their bottoms. All that is necessary to adjust the pitch of the helix, and hence the grade in each section, is to have doubled nuts either side of a flat bracket.
The outside 'reinforcement' can be simple wire or cable with turnbuckles or other fine adjustment to just the right height or to eliminate twist. These would be relatively easy to reach in past, and are also easy to install and adjust compared to pieces of 1x4 or whatever (and are inherently stable against bangs and other 'perturbing forces' common in layout construction and operation). You can build a compression frame internal to or external to the helix, with brackets appropriately out to where the tension risers come up, and in fact you can build the brackets with crossbeams centered on columns and 'tension' on both ends to make construction and adjustment somewhat easier. I think you can use elastomer isolators to reduce some of the noise.
Another sketch showing a typical section through the columns and a typical longitudinal profile of the deck.
The plan is to use plain old ordinary 3-ply 1/4" AB sanded plywood from Menard's. I have some 7-ply Baltic birch plywood, but that is a little too fancy for everyday use.
I noticed a small discrepency between the top view of your helix and the side view showing the threaded rod and nuts/washers. In the top view the rods do not go through the main sections of the helix. They only go through the joining plates. In the side view, you show the rods going through both layers of plywood.
It certainly isn't a game changer, but you may have to make the main sections wider if you want to bolt through them too. Otherwise, going by the top view, the washers won't be able to sit flat on the plywood. They will be half on/half off the main sections of the helix. Certainly it would seem wise to put the rods through both layers of plywood if you are not going to have any outer supports.
hon30critter Robert: I noticed a small discrepency between the top view of your helix and the side view showing the threaded rod and nuts/washers. In the top view the rods do not go through the main sections of the helix. They only go through the joining plates. In the side view, you show the rods going through both layers of plywood. It certainly isn't a game changer, but you may have to make the main sections wider if you want to bolt through them too. Otherwise, going by the top view, the washers won't be able to sit flat on the plywood. They will be half on/half off the main sections of the helix. Certainly it would seem wise to put the rods through both layers of plywood if you are not going to have any outer supports. Dave
Holy cow! Very astute observation! I knew about that discrepancy, but it is heartening to see that others actually look at the sketches.
The overhead plan view is correct. This is where I have an unfair advantage . . . I have a milling machine. I will cut out small triangular wedges and glue them to the plywood reinforcement joiner in that sliver of space. They will kinda act like a long, skinny 1/4" wooden washer underneath the steel washer. The theory is that glued joints are just as strong as the fibers of the plywood itself, and the sliver will become integral to the joiner.
Did you also notice that I sneaked up the size of those joiner strips to 4"x8" instead of 3-1/2"x8"? Gives a little more room on the inboard side so that that long skinny triangular sliver is not too skinny. Want to have a lot of surface area for the glue to bond the pieces.
ROBERT PETRICKit is heartening to see that others actually look at the sketches.
I got 100% in my drafting classes in High School! (Not so good in other subjects.)
hon30critter I got 100% in my drafting classes in High School! (Not so good in other subjects.)
I squeaked through with a C. My father, a professional draftsman, was not happy.
CG
ROBERT PETRICK
One thing you may be overlooking is that the roadbed is on a grade. If your rods are vertical, they won't be perpendicular to the roadbed and the big washers that you're relying on to provide rigidity won't work because they aren't lying flat on the roadbed.