Robert and carl425:
I question the need for the washers at all. If the nuts and washers as shown in Robert's side view were to be tightened down securely the resulting pressure on the helix slope would tend to flatten the slopes out. If the washers were left out and the nuts were not tightened then the helix could retain its natural grade.
In fact, if my theory is correct, you wouldn't need the upper nuts either, except perhaps to keep things stable if the helix had to be moved about. Once the proper grade has been established by adjusting the lower nuts they could be locked in place with a little CA, and the slope of the helix would simply rest against them on a slight angle. The threaded rods would be bolted securely into the bottom 2 x 4 frame and once the top of the helix is attached to the upper bench work I think things would be quite stable. That is, unless you live in New Zealand or Japan!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Dave,
I have been involved in the construction of two helix structures. The current one at the club is 4 1/2 turns of double track(33"/36" radius). It is built out of double laminated 1/2" plywood with 10 3/8" threaded rods. The large washers prevent the nuts from digging into the wood. Something this large & heavy is not going to be moved! There is NO flattening of the grade. And I would never glue the nuts to the threaded rod - What if you needed to adjust it? Actually, I suspect 'super glue' would not work as it really has no shear strength like epoxy. Our helix has been in operation for over 10 years...
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Super glue and threadlockers like loktite are both acrylates. If you feel you need one, use blue loktite, which comes apart with reasonable force. Red may not, without heat.
Henry
COB Potomac & Northern
Shenandoah Valley
jrbernier Dave, I have been involved in the construction of two helix structures. The current one at the club is 4 1/2 turns of double track(33"/36" radius). It is built out of double laminated 1/2" plywood with 10 3/8" threaded rods. The large washers prevent the nuts from digging into the wood. Something this large & heavy is not going to be moved! There is NO flattening of the grade. And I would never glue the nuts to the threaded rod - What if you needed to adjust it? Actually, I suspect 'super glue' would not work as it really has no shear strength like epoxy. Our helix has been in operation for over 10 years... Jim
I agree. Last sketch.
OPTION 1 Also known as The Original Plan. ¼” plywood deck, ¼” plywood glued gusset plate connectors. Despite having flunked statics, I think the plywood is sufficiently stiff and the geometry is sufficiently stable that deflection will be minimal (and within acceptable range) considering the relatively short distance between supports and the light load of a fully-consisted N-scale train. The simplicity of the design does not require fabrication of a bunch of little fiddly bits to beef up the moment connection at the columns. The slightly oversize holes in the gussets allow some wiggle room for adjustments and imperfections of craftsmanship (and any perturbations of live load) as well as accommodating the 2-percent (1.15-degree) slope of the deck. Slightly smaller washers.
OPTION 2 3/8” plywood deck, 1/8” plywood gusset plates. The gusset plate was never under concern regarding shear or deflection of the deck. It was there to simply join the pieces of decking, serving the same function as a biscuit, and to provide a tab to attach the deck to the all-thread columns. 3/8” plywood would provide better resistance to longitudinal deflection and torsional rotation of the deck at mid-span while not reducing overhead clearances.
OPTION 3 1/2” plywood deck, 1/8” plywood gusset plates. More stiffness, less deflection. Reduces clearance slightly, but the 3-1/2” helix pitch always provided more than enough. Plus, I have a bunch of ½” plywood on hand, and I think it might actually be a little cheaper than the ¼” stuff at the big box stores (due to sales volume, I imagine).
OPTION 4 The Full Monty. ½” plywood deck, ¼” plywood gussets. Reduces clearance to 2-3/4”, but that is still sufficient for N-scale and if it seems a little crowded I can increase the pitch of the helix slightly to compensate.
OPTION 5 Has always been available as Fallback Plan B for all options. Adding a vertical structural member to the outboard edge. Increases stiffness significantly while providing a barrier to prevent trains from taking that 500-foot plunge off the cliff. Doesn’t impact accessibility of the 0-5-0 or MOW equipment or obscure sight lines too much. The straight lines of the decking (dodecagon remember) makes fabrication easy.
Thanks to everyone. I always appreciate thoughtful comments and constructive criticism. Now . . . after having sufficiently hijacked the Octagon Helix thread (apologies all around) I will retire to my workshop and piddle with a few ideas.
LINK to SNSR Blog
Hi Jim:
Actually, my suggestion of using CA to 'lock' the nuts in place once everything was adjusted was based on the fact that the CA doesn't have a lot of shear strength. If adjustment became necessary the nuts would pop loose fairly easily (at least in theory). Same thing with blue Locktite. The CA would prevent the nuts from vibrating out of place (again, theoretically) especially if they weren't tightened securely (which seems to be a moot point now anyhow).
I was concerned about the helix deflecting when the nuts were tightened because Robert was initially proposing to use 1/8" ply. I can see that being much less of a factor when thicker materials are used.
I'm glad the topic has been raised because I will need to construct two - seven level single track helices to get from staging to the main level. The reason for the tall helices is because the staging access has to pass under an 18" - 20" deep river valley. I had been convinced that the best way to build the helices would be to have the plywood cut into semi-circles, but Robert and the OP have shown a much more cost effective way to go about construction. The semi-circles waste a lot of wood whereas the straight sections waste practically nothing. Who cares what it looks like?
markie97 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
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 doubt that there would be less waste with octagonal construction. With straight section construction there is still a lot of waste, its just that the waste material stays on the helix rather than cut to waste. probably best to think about what is easiest for you to fabricate.
I built mine using this method https://www.youtube.com/watch?v=ZdrXH--f41Y
The sections were not pure quarter circles, rather they were whatever I could get out of the width of the sheet so the only waste was a bunch of crescent shaped pieces and a semi circle.
Bill
Bill:
You make a couple of good points.
bagalI doubt that there would be less waste with octagonal construction. With straight section construction there is still a lot of waste, its just that the waste material stays on the helix rather than cut to waste. probably best to think about what is easiest for you to fabricate.
When you do the math, both methods require the same number of sheets of plywood regardless of where the 'waste' ends up (makes sense when you think about it).
I had seen the video before, and it certainly makes it look easy. Glueing and clamping all the straight sections together would seem to add a lot of labour and construction time when compared to using semi-circles. Using blocks as risers would also seem to be less fussy than threaded rods. No offense Robert, but I think I'd go 'nuts' threading all the those nuts onto the rods.
Decisions, decisions!
hon30critter No offense Robert, but I think I'd go 'nuts' threading all the those nuts onto the rods.
No offense Robert, but I think I'd go 'nuts' threading all the those nuts onto the rods.
Hey, I'm always looking for new ways to drive myself nuts. Golf just didn't seem to provide enough opportunities. Then I found N-scale. Life is good.
Robert
A lot of good advice and ideas in this thread. I agree, waste for an octagonal helix will be about the same. However, I believe I can get them at HD to cut the plywood in strips the width that I need and then I have a cut saw that I can use to cut the correct angles and lengths. Much easier then cutting circular sections with a saber saw.
I saw the video before and my thinking is that I can support the octagonal sections in much the same way he does. Maybe the bottom octagon is double thickness to make up for any longer spans made necessary by simpler bench work supporting the helix at the bottom.
Great thread. Thank you all.
markie97I believe I can get them at HD to cut the plywood in strips the width that I need
The HD by me has a sign on their saw that says "no cuts less than 12-inch width".
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.
markie97:
carl425The HD by me has a sign on their saw that says "no cuts less than 12-inch width".
I know that is the case in our local HDs. The vertical saws will not safely hold narrow pieces of wood. Things can go flying.
Look around for a custom woodworking shop. I have one close by that does beautiful cabinet work, but they also will gladly cut lumber for you too. You might also try a private lumber yard, that is if you can still find one in this day and age.
Here is a link to an excell file I made to calculate the size of your segments.
You can change the radii (inner and outer), the number of segments in a circle, and the extra material outside the track. It will give you the sizes of the pieces you will need to cut.
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=567010
Enjoy
Steve
Steve - thanks for the spreadsheet. it works great. I compared the calculations to ones that I previously made for an octagon and they both agreed.
Steve!
Thankyou for taking the time to do the excell file! That sure makes things easy.
Choops Here is a link to an excell file I made to calculate the size of your segments. You can change the radii (inner and outer), the number of segments in a circle, and the extra material outside the track. It will give you the sizes of the pieces you will need to cut. http://www.brickshelf.com/cgi-bin/gallery.cgi?f=567010 Enjoy Steve
Hey Steve.
Clever and useful spreadsheet. I looked at it and wanted to check the calculations, but the worksheet was protected and I couldn't. So, I created my own from scratch based on your scheme. Not trying to re-invent the wheel, and I'm certainly not trying to steal your idea. I figure it's always good to do these sort of mental excercises to clear out the cobwebs.
Can you look it over and check the calcs? Anyone else can as well, if they want to. Some cells are for user input and some are strictly calculations. The calculation cells were locked on purpose to prevent unreal possibilities from producing erroneous numbers. If you need to noodle around, the secret code is '1234' to un-protect the workbook.
Thanks.
Here's a link: https://spaces.hightail.com/space/6E9Cp/fi-b1df69f5-3459-4ed2-9a72-e0a5ee501ba7/fv-d09c9a5a-86ba-4d83-9c70-a28c06f96bb2/HelixSegmentCalc.xlsx
Hello Robert
I looked it over. The calculations look the same.
I Never took a class on it and it became kind of a hobby for me. It's a lot of fun. I use excell a lot at work. I use NX (unigraphixs) at work and all the parts we create have an excell sheet in the background which can be programmed to do any calculations needed.
Anyway the password to my file is TURBINE.