The plan looks fine and could work well with DCC only problem may be the Helix as far as accessability is concerned with a derailment. I wish I thought of something like this before I started my layout. I have ample space 10.49ft x 21.98 and started the benchwork for a layout along the sides of the area varying in with from 2.29 to 1.7 ft to have a long run around. I can still fit a vehicle in the centre of the layout. But a more compact HO layout might have saved a lot of electrical problems.

Did you intend to have a dual-track turntable at the roundhouse?

With a three deck layout, and the entry door in the corner, I think you are going to have a "crawl under" to get to the center of the layout to operate.  What is the radius of the helix?  If I remember correctly you will need a minimum of 3.5 inches between the top of the rails on one level and the bottom of the bench work on the next level.  Don't forget that you need to add in the thickness of the bench work to the 3.5 inches to get the proper clearance.  To do that and keep the grades reasonable takes a lot larger radius than a minimum radius that your equipment will handle.

A 60+ year-old friend is constructing benchwork for a three-deck layout.  It will require a crawl-on-your stomach "duck under."    I can work with a crawl-on-your-hands-and-knees, but haven't been successful in talking the friend into moving the low deck, which contains the staging, above head level making, it the top level.

This looks like quite an ambitious plan for your space!

Comments:

a) the helix appears to be a 30" radius - this implies a minimum grade of around 2.1% with a 1/2" deck thickness to yield a 3.5" clearance above the railheds. Not exceedingly steep. But it you're planning on longish trains you'll need to add about 1% of induced drag from having the train all on the curve.  This implies either lotsa brawny motive power or short trains.

b) The yard area at the peninsula seems designed for a max train length of around 6' which suggests the max train length you run will be around 6' - this should work ok with your helix.  However I'm wondering why the siding areas near Cudahy Bros (left wall, lower deck) has such long sidings on it if you'll be running short trains?  It appears that you're looking for a single track mainline yet much of the mainline "disappears" in the loong (relatively) sidings? Do the sidings have an operational reason for being so long?

c) I don't know this area, and you didn't say whether you were trying to exactly mimic a prototype location but would it make sense that if the Cudahy sidings are length reduced, to add an extra siding across the entry 'bridge' for the Lahish area helping to divide the layout up a bit more on that deck? Of course if these areas were both served from the same siding on the prototype...

d) I'm very confused by your renderings of helices? It appears you have concentric helices where outer loops go from the lower deck to the middle and from the middle to the upper deck and the inner helix goes between the bottom and top decks?  You're definitely right when you say trains will disappear within them for quite a while! In fact you might consider mocking up your decks to see if squeezing them together (elevation wise) is feasible in which case you might be able to loose a loop between the lower and middle decks. The middle deck being relatively narrow will help too...

e) With the upper deck so high I figure either you're a pro NBA player or you're figuring on step stools for operators to see what's going on up there. A mirror in the ceiling about points of interest on the staging level might be able to save some up and downs.

76" is 9" above my eye balls. So to get up high enough so I could see what's happening up there would require an 18" step stool. Which, added on to my 6' height leaves not much room between the top of my head and a typical ceiling. Is there enough space above the top deck to be able to see/reach in without leaving hair and flesh on the ceiling?

Perhaps you can drop the upper deck a couple of inches (while raising the lower deck a couple of inches. The view obstruction of the upper deck will be nil when it's at or above eye level.

f) The helix junction on the upper deck.  Are you planning on a bunch of diamonds here where the inner and outer tracks cross each other? Or is the plan to have the inner helix terminate higher than the outer helix? If the former I'd be concerned about custom, curved track crossings in a hard-to-see location (as well as the potential for T-boning trains there). If the latter, then have you worked out the grades along the right hand wall to see if they are sane? And if the track along the wall will have enough visibility/access for trackwork installation and maintenance (and visibility for operation?

g) I've seen a number of track plans (including some of my own) that put staging on top. I've never seen one that was actually built. Having the staging area in a non-visible-without-a-stool location makes for difficulties when restaging the layout or just trying to mess with consists. Is it feasible to move staging to the bottom and set the (previously) middle deck at 63" and the (previously) lower deck at 45"? If your scenery is relatively flat - no river valleys or canyons - you should be able to keep benchwork thickness for the upper deck at 2" yielding a visible 16" of clearance. With the relatively narrow (previously) middle deck bench that should give you ok access.

Staging is the bugaboo here. You'd be looking a a staging height of around 38" making for a 36" duck/crawl under height at the room entrance. However, that's only a little lower than what you had in your plans. I't might be wise to divide staging into two areas - leftwall and rightwall with a removable bridge between them for the continous run.

h) Lots of holes in the top wall. With trains disappearing into them. What would it take to reverse the direction of the helix and keep those tracks out in the open? Would this allow you to get a continous run on the Cudahy/Lahish deck without having to go all the way up/down the helix and through staging (if desired)?

If the Cudahy/Lahish deck loses the hole in the upper wall, with track running in front of the helix area, what about putting the refridgeration plant in the upper left corner? You might even have enough room for a small industry along the right wall if you desire...

I hope all this is useful and gives you some ideas...

Regards,

Charlie

     I'm sure no track planning whiz, but I'm curious about the extra two feet at the top of the layout plan. Is that a closet? If so, I'm wondering how you're going to be able to construct the shelving, roadbed, and lay the track behind the wall at the top of the plan? Is there access from the closet, or are you employing RR elves.             Gerry S.

You could do an around the walls helix on the back 2 or 3 inches of space with the layout just in front of it.  You would lose that back 3 inches all the way around, but you would gain all of the space currently taken up by the helix.  With a 12 foot by 12 foot diameter, you could greatly reduce your grade and eliminate a long continuous climbing curve to change levels.  You would not have as much restriction on train length.  By eliminating the helix, you might even gain enough real estate to eliminate the third deck.  If you didn't completely eliminate the 3rd deck, you might be able to reduce it's size somewhat.  You could make up for the lost space of that back 2-3 inches by widening the bench work to pick up the lost space to the inside edge of the layout.  The outside helix could be hidden a bit with some scenery, perhaps some tall buildings or grain elevators as required, but you would not want to hide it completely to allow for rerailing if needed.

I'm with Russ - ditch the helix. If you do some math, you'll find half your layout running distance is in the helix, which is hidden trackage - or at least trackage you can't scenic worth a darn.

Imagine running your train around a given deck, then run it around the deck a second time, except close your eyes the second time - that's what running trains in a helix is like. They're a terrible track construct that you need to eliminate if you can. I recognize you can't always get rid of them, but even when you do use a helix, you should use as few tiers as possible.

Better would be to build your entire layout on a slight grade, so that one deck climbs up and over the previous deck - making the layout itself one great big around the walls helix in a sense. The official term for this is a "nolix", it's a way to get rid of the helix and make the layout itself do the work.

It's also much more satisfying to have the trains visible for the entire trip from bottom to top.

 My intent was to have the staging level (76") as a Duck Under, and have the main two levels as swing gates.

 The space behind the wall at the top of the layout is the storage room in my basement.  The furnace is 2' from the wall.