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Helix design alternatives

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Helix design alternatives
Posted by tstage on Thursday, March 16, 2023 11:51 PM

Greetings,

Most of the helixes that I've seen constructed for layouts spiral in a uniform column circular pattern:

I am contemplating incorporating a helix in my next layout but I would like it to have broad curves > than R30".

My basement area where the layout would be is 10.5 x 18.7'.  A conventional column-type helix with R30" curves would eat up a large area of real estate in one corner, which doesn't appeal to me.

One thought I had was building an "open" helix design that spirals both upward AND outward as it ascends and descends; following the footprint of the layout directly above it, in a rounded triangle pattern.  However, I don't ever recollect seeing any helix designed like this.

Here is a diagram showing a cross-sectional view of how the open helix would look, with the profiles & dimensions of various rolling stock operating on it: (Click photo to enlarge)

As noted in the specs, the minimum radius of the curves would be R31", with the largest R36".  My largest locomotives would be 4-8-2 Mohawks, a 4-8-4 Niagara, and a 2-6-6-2 Mallet.

My question for the panel of experts: Are there any inherent issues or problems with an open helix design for ascending or descending to different levels that I may not be seeing or considering?

One plus to the design - as I see it - is that all the structural aspects of the helix are behind the track rather than surrounding or enveloping the track, as seen in the first photo.  This allows for easier access and visability of the trains.

One minus would be how close the trains are to each 3" drop-off to the level below it - e.g. in the event of a derailment.  I think this could be mitigated using a plexiglas guard rail in the event that a derailment did occur.  I would need to determine if the guard rail might interfere with any outward clearance issues from either locomotives or rolling stock.

I appreciate any comments and questions you might have.

Thanks,

Tom

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Posted by ATLANTIC CENTRAL on Friday, March 17, 2023 12:22 AM

I'm having a hard time visualizing the foot print or the advantage?

I've designed a numbr of layouts for others using the helix. One of which was a double track continious layout with a helix at each end to access lower lever staging. Scenically it was a single deck layout, so the helixes were completely hidden with scenery over them. Trains went in a tunnel, and down 14" to 18" to a staging yard, then came back up at the other end of the layout.

My new layout incorporates two mini helixes which are only one loop to change elevation in a short distance and increase the illusion of distance. At the end of a peninsula trains enter a tunnel on one side of a backdrop, and reappear on the other side of the back drop at a lower or higher elevation of 4"-5".

Even when I built a double deck layout, which I would never do again, I did not use a helix to get from level to level. I used progressive staggered levels and hidden track behind the scenery.

So I feel like I need more info to understand your idea.

And in any case, I would never recommend a helix of less than 36" radius - forreasons of grade mainly.

Sheldon  

    

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Posted by "JaBear" on Friday, March 17, 2023 4:13 AM
Gidday Tom, a helix is a space gobbler, and especially in a small area, having it completely hidden is, IMO a bit of a waste of viewing availability.  I think what you’re proposing is completely “doable.”
 
The only questions I have is whereabouts in your layout space would the helix be positioned, and can it be viewed from all sides?
 
I say this because if there is part of the helix that can’t be viewed, then I’d be considering stacking the tracks in that area above each other, like in a conventional helix. While the “circle” would be elliptical, it would allow you a slightly larger radius and or a little more edge distance, and while I fundamentally agree with Sheldon as in a large radius, sometimes we must compromise and do the best with the area available.
 
I know I enter into the realms of heresy, and would be far more generous with the radius and use less of a grade on my own future layout, than this 4%, 18-inch minimum radius helix, but it has the “Look” I’d like to capture.
 
 
¼ My 2 Cents Cheers, the Bear.

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Posted by tstage on Friday, March 17, 2023 7:04 AM

ATLANTIC CENTRAL
I'm having a hard time visualizing the foot print or the advantage?

Sheldon & Bear,

Thanks for your input.  I will try and post a diagram & description later this morning that I hope will help with the visualization.

Tom

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Posted by Onewolf42 on Friday, March 17, 2023 1:09 PM

I think what OP is proposing is a wedding cake style layered helix.  The radius gets smaller as it ascends each layer.  I don't see the advantage. My previous layout had a double track (37.5", 40") helix and I had no trouble getting access to or maintaining the helix track/traffic.

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Posted by Overmod on Friday, March 17, 2023 1:29 PM

Onewolf42

I think what OP is proposing is a wedding cake style layered helix.  The radius gets smaller as it ascends each layer.

I thought he was proposing just the opposite, spiraling outward like a strip mine or TCA.

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Posted by tstage on Friday, March 17, 2023 1:52 PM

I was at the doctor's office this morning and tried to post the following diagram.  Unfortunately, I couldn't access the photos on my website from my smartphone. Sad

Anyhow, below is a diagram showing the lower level of the layout.  The upper portion shows the staging yard (@ 0" elevation) and the "open" helix spiraling upward and outward (w/2.5" CTC track spacing), as it ascends or descends to and from the mainline or yard:

The lift-out at the left leads to the laundry room and the one at the bottom leads to the landing for the stairs that goes up to the kitchen.

The open helix crosses over the staging yard throat twice at two different elevations and levels off @ +9" until it emerges from underneath the upper mainline level (@ +12"), which is represented by the dotted line pointing 9:30/3:30 on the right side.

At that location there is a #6 turnout.  Heading straight leads to a reversing loop back to the helix and downward to the staging yard.  The diverging route climbs the final +3" to connect to the mainline track.

I'm still working through some design issues with the current iteration.  However, what I'm mainly interested in is whether incorporating an "open" helix poses any unforeseen issues.  I've never seen one designed but I can't see why it wouldn't work.

Hopefully that's a help.  Thanks for the input...

Tom

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Posted by tstage on Friday, March 17, 2023 1:54 PM

Overmod
Onewolf42

I think what OP is proposing is a wedding cake style layered helix.  The radius gets smaller as it ascends each layer.

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Posted by mbinsewi on Friday, March 17, 2023 2:17 PM

tstage
  The strip mine illustration is exactly what I had in mind.

Like a terraced landscape feature.  I've never done a helix, but I like this over the convential enclosed spiral design.

At least you could have a backdrop with scenery on it.

I've thought about something along the same lines to get to and from a staging area.

I like it.

Mike.

 

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Posted by tstage on Friday, March 17, 2023 2:24 PM

Mike,

The open helix would be directly beneath the upper mainline level so you would only see it from within the upper open area.  With 2.5" CTC track spacing, it would be a bit tight for any backdrop and not really serve much purpose.

Tom

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Posted by "JaBear" on Friday, March 17, 2023 2:52 PM

Overmod
I thought he was proposing just the opposite, spiraling outward like a strip mine or TCA

Thank goodness for ffolkes with a clearer vision than the Bear! Bang Head
 
Am I to take it Tom, that the helix will not have any scenery as such, just open bench/trackwork? Hence your proposed use of a plexiglass guard, if the clearances are right.
 
Bottom line, provided that the construction is top notch, I see no good reason why your helix should not work satisfactorily.
 
½ My 2 Cents Cheers, the Bear.Smile

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Posted by tstage on Friday, March 17, 2023 3:21 PM

Am I to take it Tom, that the helix will not have any scenery as such, just open bench/trackwork? Hence your proposed use of a plexiglass guard, if the clearances are right.

Correct, Bear.  No scenery - just like a strip mine. Wink

The only "tight" accessibility would be the 12" wide isthmus - i.e. between the top of the +9" elevation and the bottom side of the upper layout where the mainline is located, prior to the track emerging into the opening.  On further consideration, I might need to come up with a way to remove (slide) both sets of #6 turnouts - or the mainline directly above it - should I need to access the turnouts for maintenance purposes.

Tom

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Posted by Lakeshore Sub on Friday, March 17, 2023 4:10 PM

Tom,

One question,  how does one get into the middle of the helix?   Wasn't quite sure on the height at the lowest level.

Scott Sonntag

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Posted by tstage on Friday, March 17, 2023 4:41 PM

A very good question, Scott.  My initial thought would be a swing gate (shown below), which would require the side with the latch to angle outward for clearance.  (Same for the track)  I'm not sure how feasible that would be to implement.  Sheldon should have some good insight in that regard.

Tom

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Posted by Lakeshore Sub on Friday, March 17, 2023 4:53 PM

It is a bit of a quandry.   I don't have helix but I do have a semi-circle train elevator that requires crawling under the 40" lower benchworkConfused Getting harder and harder to do that and since your helix has is quite solid like my elevator, i'm curious to see what your solution will be.

Scott Sonntag

 

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Posted by ATLANTIC CENTRAL on Friday, March 17, 2023 9:57 PM

I guess I would like to see the rest of the track plan and have some better understanding of its scenic and operational goals.

From a simple logistics standpoint what you have on the drawing works.

10 x 18? Is that the total available space including aisle space?

I am considering a swing gate, if built correctly they work fine, there ars a number of well tested examples. But having room for it to swing is the issue I might be having with my layout plan.

Not sure if it isd worth the complexity.

Would getting inside the helix only be a maintenance thing? If so I would skip the gate or a lift out and crawl under.

Sheldon

    

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Posted by SeeYou190 on Friday, March 17, 2023 10:03 PM

I built SGRR layout #3 the same time my friend Randy and I were building his Norfolk Southern layout. Both were in N scale, both had a helix.

I will never have a helix again, I would not even consider it.

The amount of time the train is out-of-view is a true obstacle to enjoyment.

I would only suggest a helix (of any design) if you have experience with them, and find they are worth it to you.

-Kevin

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Posted by tstage on Friday, March 17, 2023 11:08 PM

ATLANTIC CENTRAL

I guess I would like to see the rest of the track plan and have some better understanding of its scenic and operational goals.

From a simple logistics standpoint what you have on the drawing works.

I am not able to do that at the moment, Sheldon, but at some point I will.  What I was primarily interested in is whether there was some inherent problem with an open helix design.  Thanks for confirming that the design should work.

10 x 18? Is that the total available space including aisle space?

Correct.  It's 1/2 a finished basement and it's nearly twice as long as it is wide.  I'm merely trying to utilize the area within the confines of what I have to work with - without turning it into a "spaghetti bowl".

I am considering a swing gate, if built correctly they work fine, there ars a number of well tested examples. But having room for it to swing is the issue I might be having with my layout plan.

Not sure if it isd worth the complexity.

Would getting inside the helix only be a maintenance thing? If so I would skip the gate or a lift out and crawl under.

Sheldon

The maximum height of the basement ceiling in my 75-year old house is < than 7' (82"), leaving me about 6" of head room.  The upper level mainline would be 42 - 48" high.  The drop to the staging yard would be ~12" below that, making the lower level 30 - 36" above the basement floor.

I'd like to have access to the inside of the upper portion for maintenance, modeling, and operation purposes.  Crawling under the layout is not a problem per say...but it could get old real fast.

The lift outs are very important because my dear wife (and I) need to access the laundry room and there is but one doorway to that.  (See above diagram)  Therefore, a duck under is out of the question - especially when a basket full of laundry or hanging clothes is involved.

Tom

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Posted by tstage on Saturday, March 18, 2023 4:46 AM

SeeYou190
I built SGRR layout #3 the same time my friend Randy and I were building his Norfolk Southern layout. Both were in N scale, both had a helix.

I will never have a helix again, I would not even consider it.

The amount of time the train is out-of-view is a true obstacle to enjoyment.

I would only suggest a helix (of any design) if you have experience with them, and find they are worth it to you.

-Kevin

Kevin,

Then I take it you would never have any hidden staging on your layout?  On some layouts the train would and could be out of view as long as (or longer than) a helix.

With the open helix that I'm describing, the trains are visible; it just isn't visible with scenery.  You could also liken it to a gradual grade up a narrow shelf layout; the grade is just concentrated more over one area vs the entire layout - again, w/o scenery.

The upper level will be the showcase for continual running on a double-main and follow the flattish, prototype "waterlevel route" of the NYC.  It will also allow the outside & inside mains to interchange with one another at two separate locations; one requiring a interlocking tower.

The open helix also allows movement of locomotives, rolling stock, and passenger cars from the lower staging area up to the mainline.  Otherwise, I would need a large yard on the upper level to store my nearly 250 pieces of rolling stock.  Given the dimensional confines of my 1/2 basement, I want the upper level to have more of an open feel, with scenery and prototypical structures as the highlights.

I agree that a helix (and a swing gate) would be a learning curve and require precison, as well as the need for fine tuning and adjustment.  But experience is only gained by doing it.  If I took that approach to my music earlier in my life, I would not have gotten as far as I did.

So, in my case - for the reasons given above - this unconventual helix (and its challenges) would be worth it to me. Big Smile

Tom

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Posted by richhotrain on Saturday, March 18, 2023 5:09 AM

I think that in Tom's case, the "helix" makes perfect sense. Given the dimensions of the space and the need to store trains, the OP has no other choice. I would also point out that Tom's solution to the problem isn't really a helix, at least in the classic sense of a stand alone spiral. It is more of a gradually rise from under the layout, using the perimeters of a long but narrow space. 

Rich

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Posted by gregc on Saturday, March 18, 2023 5:10 AM

i'm curious where the vertical supports will be if the helix spirals outward?   wouldn't each layer need to be the width of the benchwork wider?

greg - Philadelphia & Reading / Reading

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Posted by tstage on Saturday, March 18, 2023 6:05 AM

gregc
i'm curious where the vertical supports will be if the helix spirals outward?

A very good question, Greg - Thanks.  I will definitely have to think that one through.

My initial thought for the underside of the helix is to use the same support concept as a stair stringer, with the tread angling at a 2% grade (using wedges?) to support the tread base of the track.

There is a 3" buffer along the edges of the layout so I think that should allow for adequate room for support of the helix and upper level, as well as clearances for locomotives and rolling stock.

For stability I would consider using hardwood stringers 16" apart and 1/4" plywood for the treads.  I don't know if this approach would be problematic.  Again, Sheldon's experience in construction would be welcome and insightful.

Tom

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Posted by ATLANTIC CENTRAL on Saturday, March 18, 2023 7:41 AM

OK Tom, that was enough explaination, I get it now.

As for building the support for the semi-helix, it appears that nothing is below it except where it crosses the yard lead, so simple risers can support from a table top or open grid construction - Don't make it harder than it is.

Skip the third liftout/gate to the helix pit - you already have too much going on in the way of lift outs.

I'm in a similar position with my new layout - two liftouts that are complex because they contain multiple tracks at differnet elevations. I have not decided if the gate idea makes that better or worse. 

Liftouts and gates are a compromise. In my case, the perfect solution would have been for the basement stairs to come down somewhere in the middle of the basement. BUT, this is otherwise the perfect house for us, so I will live with the liftout/gate issue.

The idea of being "inside" the layout and maintaining the "left is west, right is east" viewing feature is very important to my design. Maybe my brain is handicapped, but I dislike layouts were some of the time you are standing on the south side of the tracks and sometimes on the north side. It disrupts my sense of "going somewhere".

Kevin's comment about the length of time trains are in a helix rings true with me. The layout I described before had lots of "down time" especially in the larger helix. I have other friends with multi deck layouts with the same issue.

The hidden trackage on my layout is a fair amount, but for the most part it is behind the trackage you see, not 18" below it. This allows a number of things. The mainline goes twice around the room, one of those trips is thru the staging and is "mostly" hidden. There are multiple small staging yards rather than one big one. In fact they are more like "staging sidings". The double track mainline becomes 6 tracks at three places. And there are no crossovers from "east to west" tracks in the hidden trackage.

BUT, that route around the room is a bit shorter, it has spots where the trains are visible in the "background" or appear to be a separate route or different railroad, and there is a "cutoff route" that bypasses the staging loop for some of the optional operational and display modes.

Additionally trains can enter/leave the staging loop at 4 different places, proving lots of options for train movements. Some of these simulate interchanges with the B&O and C&O.

Long explaination, but all of this works to minimize the "missing train syndrome" common with the helix.

So here is my track plan again in case it offers any help. Note the one turn helix on the two peninsulas and you will note they are not true concentric circles.

Again, now that I have enough of the big picture, I think your plan will work fine.

Sheldon 

    

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Posted by SeeYou190 on Saturday, March 18, 2023 7:50 AM

tstage
Kevin, Then I take it you would never have any hidden staging on your layout?

The plan I am working with now has three hidden staging areas. Two are behind the backdrop and one is in a dead-ended tunnel.

I say "Working With", because I found out my room is 6 inches more narrow in one area than I was aware, and now my plan needs some major re-work to fit.

tstage
So, in my case - for the reasons given above - this unconventual helix (and its challenges) would be worth it to me.

That is all that matters.

-Kevin

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Posted by ATLANTIC CENTRAL on Saturday, March 18, 2023 8:01 AM

SeeYou190

 

 
tstage
Kevin, Then I take it you would never have any hidden staging on your layout?

 

The plan I am working with now has three hidden staging areas. Two are behind the backdrop and one is in a dead-ended tunnel.

I say "Working With", because I found out my room is 6 inches more narrow in one area than I was aware, and now my plan needs some major re-work to fit.

 

 
tstage
So, in my case - for the reasons given above - this unconventual helix (and its challenges) would be worth it to me.

 

That is all that matters.

-Kevin

 

Kevin, it is amazing how we think alike on some of this stuff. Your staging plan is basically identical to mine.

My very first layout, build by my father, had "behind the backdrop" staging, way back in 1968 - I guess my father was ahead of his time in model railroading.....

Sheldon

    

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Posted by Overmod on Saturday, March 18, 2023 11:00 AM

tstage
My initial thought would be a swing gate (shown below), which would require the side with the latch to angle outward for clearance.  (Same for the track)  I'm not sure how feasible that would be to implement.

I don't have software to draw it, but why not make it as a segment of a curve, opening outward?  That automatically gives you your 'bevel' for swing, but avoids having to make and align 'skew' joints in the trackwork.

I'd make it just like a 'drop-in' but with very short alignable wedges to keep the piece in line.  Tinker with it so it is rock-solid with aligned track on it.  Then use a vertically-extended hinge pin.  You pull up on the drop-in an inch or so, and then pivot it outward, making some kind of cam or stop on the hinge side to support it when open.  Then you swing it nearly closed, lift it up and swing the rest of the way, and drop it down into assured millimetric alignment...

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Posted by ndbprr on Saturday, March 18, 2023 11:27 AM

I find the stair stringer idea to have some merit. cutting 4" high and wide steps with adding an increasing height base to each one would make construction  much easier.  If you allow 4" clearance for each loop five loops would yield 20"  of height differential and the helix would be offset by 20". three inch wide steps would only be offset by 15" and 2.5" width would only be offset by 12.5".  Cerainly something to think about if a helix is called for. I would consider using say a 16 " wide piece of 3/4" plywood for the stringers standing them  vertically,  then there is no offset balance problem. three could be made from a standard sheet which would yield two supports each if then cut out with a saber saw.  A lot easier then all the rods and leveling needed

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Posted by Overmod on Saturday, March 18, 2023 11:37 AM

Stair stringer approach only needs rods at the 'outside' if hung in tension (e.g. using threaded rod and turnbuckling for alignment) or compression construction if supported from underneath, for example simple vertical benchwork in birdsmouth cuts in the bottom of the 'stringer'.  I'd think pinning the 'stringers' at the inside corner, plus one compression member about ¾ out, would be stable whether or not you tied the stringers circumferentially.

There is clearly room between the 'tiers' for multiple tension rods between the tracks, if overhead clearance and access permits.  I would be tempted to 'electrify' with cat bridges incorporating the tension rods, then paint the part above them like the backdrop...

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Posted by mbinsewi on Saturday, March 18, 2023 11:55 AM

I don't get why he would even need any type of rods, using the stair stringer.

I'm still trying to put together a 3d image in my mind of Tom's track plan.

I'll have to check out the elevation numbers again.

I like the idea though.  My first layout plan, before I built what I have now, was to have something similar on each end of a "round the room" layout to get from a lower staging track to the mainline and running level.

I wish I would've figured out some sort of staging for what I ended up building.

I was more interested in building something I could "finish" in a resonable amount of time, and not get overwhelmed with a larger layout.

Mike.

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Posted by gregc on Saturday, March 18, 2023 1:56 PM

mbinsewi
I'm still trying to put together a 3d image

height assuming 2% grade

greg - Philadelphia & Reading / Reading

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