Someone in another thread asked about Mushroom layout design, so I thought it might be good to start another thread to discuss it.
If you are new to the hobby, you may not know anything about the mushroom layout configuration. In the 1970s, the famous (now deceased) trackplan guru, John Armstrong, proposed being able to fit more layout into your space by double-decking your layout design.
In 1975, a gentleman named Richard Benjamin quietly took John’s double decking idea and added a unique twist – he flipped one deck the opposite direction and then built the design. By having one deck facing the other way, you could use a raised floor and have both the lower and upper decks be at a similar viewing height.
John also came up with the idea of flipping one of the two decks around, and he published a track plan design in the October 1987 MR using the concept, and he dubbed it the “mushroom”. If you see the cutaway diagram of my layout benchwork below, you can see why John called it a mushroom. If you take a cross-section of the layout benchwork, the upper deck and aisle forms a T shape, sort of like a mushroom.
(click to see a larger image)
I also independently came up with flipping the two decks in the mid 1980s when I was drawing lots of track plans, looking for a good “dream layout” design. However, Richard Benjamin first originated the idea in the 1970s and he also built a mushroom! John was the first to publi***he idea in the 1987 MR, and I wrote an in depth look at the mushroom design in the January and February 1997 MR.
So that’s an introduction to what a mushroom is. If you want to learn about my own Siskiyou Line layout and it’s mushroom design, you can click on the link in my signature. It will take you to my web site which has dozens of pages of photos and text about various aspects of my layout.
Thanks for posting this. I visited the Canandaigua Southern a few months ago, when the Armstrong family opened house for the Potomac Division of the NMRA. It struck me that John had developed some, although not all of the ideas that you’ve just illustrated in that design. It had some impressive qualities - since the aisles weren’t perfectly linear, they gave the impression that the space you were in was much larger than it actually was. The curve of the aisles and the high tormentors kept me focused on the scenes in front, and I was struck by the job he had done of designing the layout so that the visitor would get a series of perspectives as he walked through - most of them trackside-level broadside views, but a few of them angled views of large sections of the mainline and Cattaraugus Yard.
I think it is a good idea but there were some valid concerns raised by a fireman when the first drawings appeared. One is the need to tie the floor joists together with bridging to prevent collapse. Another was adequate emergency lighting in the event of a fire. i hadn’t considered a mushroom and need to relook at my plan to see if it is a viable alternative to a nolix or helix.
I can see the advantages…efficiency in space usage chiefly among them. My first thought, though, echoed what ndbprr expressed; if one used a wall-to-wall layout of that nature, emergency exit/fire/wiring access issues come to play. While not insurmountable, it complicates the design.
That said, I am increasingly feeling constrained by the space I have. And She says that’s as good as it gets (I have to agree). So, some gee-whiz, why don’t I…?, if I did this…, and what are others doing? is where I am at the moment. If I want that nice slow curve, a long run, and a yard, I had better get thinking outside the box.
Thanks, once again, for sharing your experience with us, Joe.
I would have liked to use the mushroom design on my own layout, but one of the requirements is that you have a full-height room in which to build it. Since my basement ceileing is only about 6’6" above the floor (most old houses with basements I’ve seen have a clearnce of only 6’ or a little more), the mushroom wouldn’t work. So I had to live with a standard double-deck.
How do you support the upper deck sufficiently in a manner that is unobtrusive to the scene below? I seam to remember seeing a quip attributed to Armstrong paraphrased as “I just designed it, you need to figure out how to build it.”
Obviously he did actually built it also, but even in your cutaway, there isn’t any support for the upper deck illustrated. So, what techniques and tricks have been developed to overcome this issue?
The club I’m in has a section done this way (the levels are connected by the helix I’ve mentioned in other posts). We do have the advantage of a high ceiling (the old firehouse part of the building), so headroom wasn’t a problem. The main advantage is it visually isolates parts of the railroad; ie: you can’t see the whole layout at once, meaning you perceive the layout to be larger than it really is. There is an elevated tower in the room, only accessible to operators, that you can see most of the layout. Also, with the walkaround controls, it makes you move around more to follow your train, enhancing this perception.
And you are less aware that it’s a double deck because of the vertical separation between the levels. The effect will be better once we get the “ceiling” on the bottom of the upper deck.
More layout possible in the space, but without the visual clutter of traditional double-decked
Each deck can be near optimum viewing height
Upper deck support is easier - the front of the upper deck is supported by the lower deck backdrop and the back of the upper deck can be supported from the ceiling.
The greater distance from the floor of the upper deck makes nod under or even walk under access possible from that side of the room
Visual separation of the decks makes the layout seem much larger
Mushroom cons:
Difficult to visualize when designing in 2 dimensions. You may need to do some 3D mockups to clearly determine dimensions like deck height, deck separation, distance of the upper deck from the ceiling, etc.
Need some way to get from the lower deck to the upper deck, like using a helix. A helix can take a lot of floor space, and is difficult to scenic realistically (same issue as a traditional double deck, however).
More complex benchwork than single deck (but simpler than traditional double-decked)
Lower deck scenery is height constrained in the upward direction and upper deck scenery is constrained in the downard direction (traditional double-decked design has this issue too).
Can’t see the whole layout as a sweeping vista (but this is also true of traditional double decked designs)
The mushroom takes a fairly wide room in order to fit. Minimum room width is about 12 feet although you can cram something into 11 feet if you compromise aisle width and/or benchwork width down to bare minimums.
Raised floor construction needs to be robust (translation: be ready to spend money to do it right)
Comments
I started my Siksiyou Line layout in 1991 and designed it to use the mushroom concept. It was tough to determine the exact dimensions in 2D on a flat piece of paper,
Joe, I’m really glad you brought this up. I have a question regarding the transition from one level to the other. How is it accomplished? Is there a realistic (read NO helix) way to go about this? If there is, can you please spell it out for the intelligence challenged me? Thanks.
Joe, right now I’m planning a double deck layout and the support for the upper deck is a big problem. I have a couple of ideas but I’m not satisfied. So you are absolutely right when you wrote the following:
Upper deck support is easier - the front of the upper deck is supported by the lower deck backdrop and the back of the upper deck can be supported from the ceiling.
What do you suggest for a traditional double deck layout if I want to have the upper deck 24" maximum? Is there a common solution to the ‘upper deck support’ problem?
The moat mushroom design will allow the levels to be connected without a helix.
With a moat mushroom, the center part of the layout is mushroomed and it’s in the middle of the room with an aisle all the way around it (the “moat”), then along the walls of the room you have a single narrow deck that climbs from the lower deck to the upper deck. That narrow shelf can be fully scenicked, and be one long helper grade, making for a lot of fun if you like to run trains with helpers (which I happen to like to do).
However, to build a moat mushroom, your room width needs to support a center layout with a mushroom (need about 7 feet of width for that), then room for an aisle on each side (for 3 foot aisles that 3x2 or 6 feet more), then perhaps a shelf a foot wide past that (another 2 feet in total width for the 1 foot shelf on each wall of the room), for a total of about 15 feet of room width – minimum.
I have what’s called a “partial mushroom” as my layout design. In a partial mushroom, one peninsula down the center of the room is double-decked (and face opposite directions), and that’s all. The layout deck along the outside walls of the room are single decked.
I was able to start at the far end of the mushroomed peninsula on the lower deck and climb upgrade for the length of the peninsula, then go along one wall and keep climbing upgrade down the length of the room. By the time I got to the other end of the room, a one and a half turns in a helix got me over to the upper deck in the center of the room. If my room was another 10 feet longer, I could have gotten to the upper deck level
The best approach I’ve seen for doing a solid upper deck is like what my friend Charlie Comstock is doing. He makes his own wood brackets and attaches them to the wall. This section on his website talks about spline roadbed, but it introduces how he does his wall brackets for deck support as well:
If you look at this photo you can see how he does his upper deck brackets. He cuts the tips of the brackets off at a slight angle so the front of the deck is narrower than the back against the wall (where you need more depth for good support):
As a builder of a large mushroom layout (26’ x 52’) in n-scale, there is a lot of
preplaning involved. As Joe wrote, I will agree on the pros and cons. About 15
years ago I drew up a basic dream layout plan (basic benchwork with no track
drawn in) to get a idea to what size would be needed to get a 24" min separtion
for the mushroom part of the layout. In 1998 I started building my house and I had
10 foot walls poured for the basement. It took a year and a half of weekends for
me to buid it by myself.I did everything except fin***he sheetrock. It took another
two and a half years to get started on the layout.
The layout starts at the far end of the penninsula on the lower half, and stays
level along it till it comes to the perimeter wall and the 1 1/2% grade starts here.
With the grade along the entire perimeter walls with the exception of Keddie yard
(about 30’ long), I gained 28" . Where it comes back to the penninsula the track
is 80" off of the floor. This is were you enter the layout room, walking under and
up to the step to the raised floor, which is 22" off of the concrete floor. I used 2x6s
as joist and 3/4 t&g plywood, no short cuts here. The track hieght on the lower
mushroom is 54" and on the upper is about 58". At the far end of the penninsula
is a 9 1/2 turn 2% grade 56" x 80" helix that connects the two leves and the staging
yard that is 90" off of the floor.
Rodney
Joe, thanks for the links. It looks like a very good idea, simple construction. Is it possible to send a email to your friend Charlie and ask some questions? I don’t see any email adress on his webpage. It would be very interesting to discuss this subject futher with him.
John - just curious about the history of this type of layout. Are you saying Armstrong came up with the “half a mushroom” layout, and you and Richard Benjamin independently came up with the “Full Mushroom”?
Then you ended up building a “Half Mushroom” due to your space constraints, right?
Just trying to follow the history - I don’t know why, but the history of model railroading is sort of interesting to me.
I didn’t realize you came up with that - that is pretty cool!
Actually, I haven’t thought about who came up with what variation, since Richard B. came up with the original concept of reversing one of the decks in the 1970s, he gets the credit of being first with the idea. The fact Richard actually built a mushroom in the 1970s before any of the rest of us had even started drawing it on paper pretty much cinches it that Richard invented the idea.
But John A. gets the credit for being the first to get the idea into print. And I gues you could say I have helped popularize the idea with my two-parter that both discusses the idea in some depth and presents a real layout that was built using the ideas – taking it out of the theoretical and grounding it in reality.
