My experience is with N-Scale, but temporarily lacking room for even a modest layout in that scale, I am excited with the idea of scaling down my first layout that I built as a teenager in N-Sale to Z-Scale. The plan will have a cross over, so I need to know the minimum vertical clearance, minimum radii, and track spacing— but the real issue is grade as, ultimately, it is going to define the length and width of the layout.
A quarter inch in height at a 2% grade is a 12-1/2” increase in needed length and, in my case, that could be a project ender. I want to meet a minimum, but I simply do not have room to afford to exceed that minimum.
The vertical clearance for N-scale, according the NMRA, is 1 21/32”. Simple math from scale-to-scale suggests that the Z-Scale equivalent would be about 1 13/64”; but I am not comfortable proceeding until I have some input from those experienced with Z scale. So, could someone provide experience with Z-Scale?
Minimum Radius
Vertical Clearance
Track Spacing
Cork “roadbed” thickness and track base-to-railtop?
That is an excellent question. I would not be shocked it they sit a little high, just to physically make things work. I would think no more than 1/8th, probably less, but that’s completely uninformed opinion. One good thing is that the weight should be low enough that you can really go thin with the roadbed.
I agree with you about the weight and roadbed, and think I should be fine with 1/4" ply for the roadbed.
Also, I just found that the NMRA has standards for Z Scale tucked inside the “modules” section of the recommendations and standards. I am making an assumption that modules, intended for club use, will anticipate the greatest variety of rolling stock and clearance needs (I noted that the N-Trak module standard minimum radius is 3 1/2" larger than the NMRA standard for class P!). Yet, I also note that the beautiful Z-Scale layout featured in the December MR, has used 10" as its minimum.
From the NMRA Module standards pages:
Minimum Radius = 7"
Track Centers Clearance = 1"
Grade = 4% (What? Using cogs?! Someone else can try that concept-- not me!)
Vertical Clearance = 1 19/64" (3/32" more than my calculation-- not even an eighth—you were right!)
Track and cork “roadbed” = still unknown, but less than N-Scale.
I am going to presume that those reading this thread are also interested in planning so I’ll add a bit of my thoughts:
I am not forgetting the need to allow height to pass under the portion of the bridge structure that extends beneath the ties of the cross-over track, but can safely assume that even a store-bought will be less than the 1/4" ply roadbed—and if I am wrong, I can
If you need to I bet you could go less than 1/4" for the distance where you need the clearance. Or maybe a different material, like 1/16" sheet metal, or something. I would think you could insulate it to keep it from being troublesome.
I still have not heard back from Micro-Trains, but it is now weekend. I hope, mostly, the confirm my cork “roadbed” height approximation (below) and how one makes the transition from cork and flex-track to the pre-ballasted turnouts.
Here is what I found:
Minimum Radius = 7 1/2” (NMRA MRP-1.0).
Vertical Clearance = 1-19/64” (NMRA MS 1.0)
Track Spacing = 1” (NMRA MS-1.0)
Non-NMRA data (can anyone verify?):
Cork “roadbed” thickness = UNKNOWN; estimating 2.5mm=3/32” ( based upon found data that HO is at 5mm, and N is at 3mm; I assume, then, that Z would be just over 2mm);
Track height ties and rail = 2.6mm= 7/64” (Found track profile image with metric dimensions on track laying article on Z-Scale user site).
The total climb necessary to exit a tunnel at the lowest level and cross over that lowest level is exactly 1-3/4" based upon my data and findings if I use 1/4" plywood roadbed.
I have adjusted the plan to use the above figures, and have a final dimension of 34" by 58", with a 10-1/2" minimum radius (equivalent to N-Scale 14-1/2”); 2-1/2" track center to edge of layout; 2.5% grade on straight ascent; 2% grade on ascent curves (each quarter-turn broken by 6" straight also at 2% to relieve load).
Thanks for any advice,
Crews
P.S. If anyone is questioning my 34" width with 10-1/2" radius, separated by 6" straight, and adding a 2-1/2" out
My gut says you’ll be ok. I think you can steal another 1/8 in. in the roadbed at the critical spot if you need to, you could make a U type of trough, very thing roadbed, with short verticals to stop it flexing. Almost like a real bridge.
I think you are correct, and I had not considered that I could go DOWN should I have a small fraction here or there to make-up. For that matter, I could probably just use a plane and shave the cork a bit below the cross-over.
It is nice, since I felt comfortable enough with my overall climb calculation, because out came the graph paper, compass, pencils, and I now have the mainline down on paper; all radius centers marked; and discovering I can get just a bit more “yard” than I had expected. It never was an “operations” layout, but I might come up with a switching puzzle or two to make it interesting for guests. By mid-week, I’ll have both a cut list and a materials list.
If I find an error in my math or obtain the definative word on the open questions, I’ll share that on this thread.