Helix question

[FJ and G]

I'm going to start this week on building a helix in my HVAC storage room. I'm using aluminum shelving attached to studs. Planning on using 1/2 inch particle board. Problem is, where the particle boards.

Some questions:

1. What type of wood or other material do you use for the helix; not the vertical part but the roadbed? Thinner is obviously better.

2. What do you use to connect the sections of roadbed together?

3. My helix will be a weird looking blob, not round, as it coils around the HVAC room. How do you determine the slope; just use the slope=rise over run formula or, do you test your heaviest train to see how it pulls up the steepest slope and then use that slope. In other words, do you set the slope first or do you find the steepest slope possible by testing your train first?

Thanks.

Dave

[Anonymous]

QUOTE: Originally posted by FJ and G

I'm going to start this week on building a helix in my HVAC storage room. I'm using aluminum shelving attached to studs. Planning on using 1/2 inch particle board. Problem is, where the particle boards.

Some questions:

1. What type of wood or other material do you use for the helix; not the vertical part but the roadbed? Thinner is obviously better.

2. What do you use to connect the sections of roadbed together?

3. My helix will be a weird looking blob, not round, as it coils around the HVAC room. How do you determine the slope; just use the slope=rise over run formula or, do you test your heaviest train to see how it pulls up the steepest slope and then use that slope. In other words, do you set the slope first or do you find the steepest slope possible by testing your train first?

Thanks.

Dave

David:

In case you don't have it, here's a link to a helix grade calculator site:

http://www.trainweb.org/s-trains/helix/percent_grade.htm

I believe this one assumes that the helix will be round, but you can still get some good info off of it.

Essentally, the grade is run over rise. If you have two 180 degree curves of the same radius connected by straights, then the run is the perimeter of a circle with the same radius plus twice the length of one straight run. If your helix looks like a hexagon with O72 curves in the corners, it would be (Pi * 72) + (6 * the length of one side).

As for materials, you might consider MDF or Homasote for the roadbed in the helix itself. It's not like you're going to scenic it, especially if it's in your HVAC closet. Plus, you want to make everything as thin as it can be & still support your trains, since the mateiral thickness contributes to the rise & so affects the grade.

Hope this helps!

Tony

[FJ and G]

Thx, Tony,

I mispoke; not planning on roadbed; just "structural support" as labeled in your link.

Problem with my helix is that it won't be a particular shape; just a sort of blob as it winds thru the HVAC elements. Figuring it would be a nightmare; or rather a dream if you are into geometry.

The challenges for me will be accessibility and easy-to-remove helix, to get to the various HVAC elements if repairs ever become necessary. it definitely will be one of a kind.

I already layed a temporary lower shelf (to store all my trains on while I scenic the upper shelf). Thus, i have the distance down that the helix needs to coil; about 20 inches.

I'm just curious, for those of you who have helixes, how you arrived at the percent slope. Did you just pick a number, say 2% or, perhaps you calculated the depth from shelf to shelf and then how many coils were necessary.

dave

[FJ and G]

One other question is how did you join the "structural supports" without appreciatively increasing the thickness? I'm thinking metal joiners instead of wood to join the sections. Am I on to something here?

dav

[Anonymous]

David:

Is that 20 inches the circumference, or the rise? If it's the run, you're going to have a very steep helix indeed!

Here's a way to connect the structural supports, if they're made of hardboard or wood: tongue & groove. Or half-lap. Both allow you to connect the pieces without adding a joiner plate. Half-lap would be easiest. Just use your table saw or router to remove half the thickness on two pieces & glue & screw & you're done.

Half-lap will work for the lift-out sections too. You can use dowels as locking pins through holes drilled through the overlapping pieces. Just yank the dowels, then lift the section out. You might tie the dowels to the helix with fishign line to keep from losing them, though it would be easy enough to cut new pieces.

Regarding the slope, it's just rise over run. Let's work a theoretical here.

If you need the helix to rise a total of 20 inches, you want to do that with as gentle a slope as possible. You want to keep it in the 1%-2% range if you can. You have to go around all of your HVAC equipment; let's say you can do that with an 8 foot diameter circle. I know you've got a "blob," but let's keep with workable numbers.

Now, an 8 ft circle has a perimeter of about 301.6 inches. Let's say each coil of the helix has to rise 10 inches, in order to do th total 20 inch rise in 2 coils. That grade is then

10 / 301.6 = 3.32%.

If you do a 6 2/3 inch rise, you come out with 2.21%. This is much better, though you need to go around three times and you may be limited in your choice of rolling stock that can go through the helix.

I hope this helps

Tony

[lionelsoni]

Dave, I used plain O27-profile tubular track attached to the wall with corner braces--no shelf at all except in the corners--for an around-the-walls track. I spiral (inside) corners keep the track close to the walls.

[FJ and G]

Tony,

Rise.

Wow, you just solved my problem! Thanks!!!!!!!!!!!!!!!!!!!

I'll be getting out the table saw.

GREAT advice!

Dave

[FJ and G]

Bob,

Didn't see you post. Actually, I priced out the braces and the aluminum vertical posts with holes AND the brackets that come with them at home depot, price well compared with the metal angles I saw there, and, since the vertical aluminum posts have many holes, I can simply use them for each ring of the helix.

Each post can be slightly offset on the stud as well so the slope is just right.

I'll be doing a lot of experimenting before putting it up and once it's up I'll test it a bunch of times with the longest and heaviest stuff I have.

thx

Dave

[Anonymous]

David:

Glad I could help! I'd overlap the two for about 4 inches to ensure a good physical connection.

Tony

[FJ and G]

Good thinking! I'm going then w/3/4-inch particle board so the overlaps are thicker as well. I've used the table saw to do things like you mentioned; but never thought of using it for the helix. The table saw was a great investment.

Also, your lift out idea could have other applications as well (as in a liftout section crossing a door)

Always wear goggles and am carefull around it too. I respect it a lot.

Thanks.

Dave

[Big_Boy_4005]

Dave, sorry I was sleeping. When I built this helix I used two layers of 3/8" plywood and laminated them together, and totally overlapped.

It is best to make all of the turns the same shape and size, even if they aren't a perfect circle.

Grade is rise per 100 units of run, so 100" of track gaining 4" is 4% grade.

[FJ and G]

Elliot,

Nice photos, I've often admired your helix but these pictures really show the steps. Nice work!

How did you arrive at 4%. Did you test your trains on 4%? If you had to do your helix over again, would you do anything different?

It looks like double-track. Will there just be 2 exits from the helix (top and bottom?) or are you planning more than that? Also, can your helix be used as a return loop or once you enter the helix, you must go up or down? And if not, have you considered using the helix as a same-level return loop?

Sorry about all the questions. Just trying to pick brains for ideas.

BTW, using Tony's idea of overlap 4" rather than total overlap; because it will facilitate removing sections for access to the HVAC.

Dave

[Big_Boy_4005]

Dave, the 4% was just an example. Mine is more like 2%. That is so shallow that I have to keep giving the cars a push just to get them down. I think it would be very helpful to try and keep the grade as constant as possible during the entire climb, so you aren't having to constantly adjust the throttle and worry about the train stalling.

My helix is something like an octopus.

Two tracks start at the bottom, after 2.25 turns the outer track exits at the main level, and the inner track goes on.

At 2.625 turns there is a turnout for the inner track to exit on the main level, or continue.

At 4.0 turns, there is an entrance through another turnout. this is a hidden track that forms the continuous run of the mainline, and brings trains back from a different part of the main level.

At turn 5.625 there is a turnout allowing trains to go one direction on the upper level.

And finally at turn 6.0 the track swings out one track width to allow for the headspace on turn 5. The track crests the hill gradually, and gently moves off center and makes a final quarter turn to end on the upper level heading in the opposite direction.

This helix is the key to the entire operation.

The layout design does the looping parts on the levels of the layout. I suppose it could be done to have a reverse loop in a helix, but I'm not sure why you would want to, since the goal of the helix is to get up and down.

[FJ and G]

My helix, actually, will be at one end of an elongated layout, about 30 feet opposite of another return loop (but not a helix). Your helix appears to be in the middle. Thus, the thought of a return loop so that my train doesn't have to go down to the next level and can simply cruise back to its return loop at the other end.

In this way, I could, if I wish, have a train topside and below, cruising independently back and forth; each on its own level, without going up or down.

The helix would be for variety; you know, sending some cars up for switching duty or something.

What I might do to facilitate the return loops inside the helix is make the helix all single tracked except for the return loops inside the helix.

Am I making sense & is this as clear as mud?

[Roger Bielen]

Dave,

If your going to determin your grade via testing remember the additional drag caused by a train being in a constant curve in the helix.

[Big_Boy_4005]

Maybe this will clear up some of the mud Dave.[;)]



This is a simple schematic of what I mean, click on it to enlarge it.

[FJ and G]

Yes, that is the return loop. Now, imagine a track peeling off from either the loop or the stem, spiriling up or down the helix. The drawing would have to be in 3-D to show that.

Thanks.

Gotta run to eat but will be back to tell you how I plan to bust thru the wall.

dave

[Big_Boy_4005]

OK Dave, while you were at lunch I drew this.



The top two are useful, the bottom one, WELL....................[swg]

[FJ and G]

OK, back from lunch. Ate lots of onions so pardon my bad breath.

Anyway, where was I? Oh, yes, I'll be busting thru the drywall of the HVAC where the helix will be located. As the train exits thru the wall, it crosses a great chasm, which is my 7 ft wide hallway. Instead of a bridge, I'm building a removable extension of the layout that will be scenicked as desert.

I may design a portal on the wall where the train exits/enters. Actually, based on the above Elliot diagram, 2 portals thru the wall, because once inside the HVAC, there's no room for the Wye split.

Thanks for all of your great suggestions. Sorry for the bad smell but it's even worse when I put raw garlic on my sardines.

Dave V.

[Big_Boy_4005]

Dave you don't need the wye near the helix if this is the top or bottom level. The wye can be a part of the main layout, like the first diagram. I suppose the "I don't know" could be used for a middle level if you didn't have room for the wye.

[FJ and G]

Thanks, Elliot,

I see the diagrams now!

[fjerome]

"The challenges for me will be accessibility and easy-to-remove helix, to get to the various HVAC elements if repairs ever become necessary. it definitely will be one of a kind."

geez, dave, you don't set your sights low, do you? [:D]

[daan]

To get gradient right in a helix, you could use threaded wire and nuts (don't know if that's the correct name for it). Inside and outside the helix you locate one, and by turning the nuts you can finetune the level you need to have.

[FJ and G]

Forrest,

I crawled around the HVAC room last night with sections of track, measuring and pondering. I think you are right; the HVAC room may get too crowded for a helix, so now I'm seriously considering a helix in my daughter's bedroom at the opposite end of the basement and instead of helix in the HVAC room, simple return loops for theupper and lower shelves.

So, now I have to start the whole thought process over again!

If I place a helix in her bedroom, I don't want it to be too big for obvious reasons. (Actually, the bedroom is about 19X19 & she's going to college this year and may not use the room that often).

I was thinking 042 helix; because that's the size all my trains can negotiate.

Which leads to more questions!

1. At 042, what grade would you suggest; 2%?

2. Elliot used wood for his vertical supports. I've heard tell that some use long threaded screws. Pros & cons?

3. Elliot uses a double track helix. What are the pros and cons of single vs. double tracked helix?

Thanks.

Dave.

[Big_Boy_4005]

Good morning Dave, unfortunately you can't simply pick your grade out of the air. Grade is tied to radius and verticle spacing. Using your 042 and multiplying by Pi, we get about 140" run per loop. Each loop needs to gain about 6" in height in order to give you the head space to run traditional O gauge trains. Scale takes even more clearance.

Doing the math, an 042 helix with 6" spacing comes out to about 4.2%. Move up to 054, and the grade comes down to 3.5%. If you need more head space for larger cars, the grades get steeper again. Keep in mind 4% should be your max, because you want the engine to be able to pull the cars up.

Wood is just handy for me, I cut spacers all the same size, and I'm off to the races. The threaded rods are small and pretty, but I don't just have them laying around.

I built what I needed, part double, and the rest single. The decision is based on layout design, and nothing more. I've seen a 4 track helix in HO before.[swg]

[FJ and G]

Thanks; 054 sounds good. Too bad there are no helixes in real railroading. At 054, with that much space, would look good with scenery. perhaps an inside-out open pit mine? Hmmmmmm?!~

[Anonymous]

Dave:

You can also decrease the grade without increasing the radius by making it an oval shape instead of a circular shape. That is, add, say 3' to a side. In that case, the total length of one circuit becomes

{(Pi * 54) + 72 = 242

With a 6" rise, that gives you a 2.5% grade.

It seems to me that the best way to construct a helix is with wooden spacers between levels. It's real easy to make sure that they're all the same length, so you end up with even spacing. You could bore a hole through the spacers & put threaded rods through them. Then the rods can be used for suppot & to tighten up the whole assembly.

The threaded rod wouldn't be absolutely necessary, though.

Tony

[Anonymous]

Oh, and David? Regarding helixes in real railroading...

We (you & I & others) had a thread on OGR before the upgrade where we talked about & identified what were essentially one-level helixes in the real world. As I recall, there's one in the Canadian Rockies that CN uses to lower the tracks 50 feet (it has a diameter or radius of one mile, I believe) and so bypass having to climb a mountain.

There's also one on the Darjeeling railroad in India at the top of a mountain. The railroad climbs this mountain using a series of switchbacks, then, when it gets to the top, uses a loop to start its descent down the other side.

A number of other folks pointed out one or two other examples.

No, there are no multiple level helixes like are sometimes used by modelers, but the real guys use 'em when they have to!

Tony

[Big_Boy_4005]

Dave, I whipped up a little table for common circle diameters, and different height gains. The formula is pretty simple: height gain / (Pi x Diameter). My Helix turns out to be 2.12%, that's 8"/ (Pi x 120"). The helix is 10 feet across.[swg]

The numbers are acceptable for 054 up to 7" height gain. The 063 numbers are good up to 8".

Remember, height gain includes roadbed and track!!!! Make sure there is enough clearance for your trains.

[Big_Boy_4005]

Tony is absolutely correct, adding straight sections to any diameter circle, is the same as increasing the diameter, just that you are only doing it in one direction instead of two.

There are a lot of examples of single turn loops around the world. The real railroads want to keep their grade down too.[swg]