After visiting the idea of doing large scale and deciding I am unable to pursue it at this time I am revisiting the idea of making a perminant HO layout and there are a few pointers I’m not quite sure on in regards to construction.
The main issues I have right now are height, grade, and multi-track easement requirements. I have a 20x30 foot room to take advantage of and I’ve already drawn up a track plan on paper but these particular points I am still having trouble with. On the main I will have a minimum radius of 22" and the largest peaces of equipment would probably be a big boy for locos, double stacks for height requirements and a 16 axle generator car for width and overhang in turns. About 2/3 of the layout is going to be double tracked and I will be putting in atleast one helix which I need to figure out the requirements for.
I have noticed when trying to re-draw the route on the AnyRail design program (something I’ve found to work better than XTrkCad) that the spacing of the tracks might need to be widened but I don’t know what would be advisable with the size of equipment I want to allow for.
A 22" radius may be a little to tight to run the equipment you mentioned, better go for 24" and even larger. A Big Boy looks toy-like even on a 24" curve.
As for the track spacing, 2" from center to center will be OK on a straight line, but in curves you´d better go for a 2 1/4" spacing. The rule of thumb is the wider the curve, the less space you need between parallel tracks.
Check the NMRA standards on track centers here! You need to scroll down to find the ones for HO scale.
The NMRA Standards and Recommended Practices are your friend. At the very least, they provide a good starting point for your planning. In reality, cheating on the RPs and SPs will make your ability to make all the desired rolling stock work reliably and consistently much more difficult. In particular, the new draft S7 (http://www.nmra.org/standards/sandrp/pdf/s-7_update_draft.pdf) lays out some of the increases in height and width needed for modern rolling stock like your double stacks and generator loads.
Can you tighten things up beyond the recommendations? Yes, but. The further you deviate from the recommended minimums, the more likely at least some of your rolling stock is going to need modification to operate reliably. And the more likely you will need a test program to find those issues in advance. For instance, if you choose 28" and 30.25" radius concentric curves, I would build a test case to make sure you are not side swiping, and that the cars will track reliably. And I would carefully measure before committing to an overhead clearance of just 3".
I would strongly recommend using 30" radius for a Big Boy. I have 2 of them and my mainline has 30" as a minimum and it looks and runs great. I have a couple of 24" radius curves on branch tacks and the Big Boy just doesn’t look right so I don’t run them in those areas. Also, if you can keep the spacing on parallel curves to at least 2 1/2 to 3 inches you will not have any problems with clearances for long engines and passenger cars. With a 20x30 room you should be able to make these standards unless your track plan is so crammed in. Good luck and enjoy the hobby.
22" radius in HO is too tight for the equipment you want to run.
In that much space, you can have a fine layout even with broader curves. Why so tight? I’ve desgned a number of layouts in that size range that offered a lot of operating potential and scenery opportunities with broader curves.
If you haven’t studied in detail John Armstrong’s book Track Planning for Realistic Operation, you’ll probably be lacking much of the knowledge you need to design a successful layout of that size. Many of the answers you are seeking are contained in its pages.
For everyone saying that 22" radius is too tight. I don’t know about the generator car but every manufacture I’ve looked up on including the discontinued riverosi big boys gives a minimum recommended radius of 22". For most of the layout I am trying to go big with 36" on outside curves.
Edit: I’ve started looking at the links and it looks like the layout would be a mixture of class 1a (main) and class 2 (on the branchline).
One other question I have that hasn’t been addressed is track easement from walls and the like. On my initial design I tried to keep a minimum of 3" from the track centers and I’m not sure if I should widen that even more.
The equipment will run on the 22" radius you have planned (I have a 4-6-6-4 Challenger & 2-8-8-2 that operat just fine on a 22" radius curve), it just that the units don’t look right on that radius.
However since we don’t have unlimited space like our 1:1 counterparts you have to make compromises somewhere. Try to visually obstruct the curves (like with brush, buildings or trees) and the ‘wrong’ won’t be so noticable.
You are right - most plastic models of articulated locomotives unrealistically pivot both engines to allow the HO model to go around 22" radius curves or better. There are also other models of Big Boys and articulated locomotives that keep the rear engine aligned with the frame and boiler. These models will not do 22" radius curves.
Passenger cars are another example. Athearn and others made “shorties” - models of shorter prototypes or shortened models to permit operation around 18" radius curves. Walters makes well-detailed full length models of passenger cars that are advertised to go around 24" radius curves. More than a couple of posters on this forum alone have complained about the modifications (cutting away of underbody detail) they had to make so that the Walters model would stay on the track on 24" radius curves.
You didn’t say who made your double stack cars, or what the stated minimum radius is. These are typically quite long in length, and often need a 26" or 28" minimum radius to stay on the track. According to the reports on this forum, there are intermodal cars that won’t operate successfully on 22" radius curves.
And that was my point. The NMRA recommended minimum radius is based on the worst case, not the best case. If you follow NMRA recommendations, you are highly unlikely to run into derailments because of curves being too sharp. On the other hand, when you use 22" radius curves where 32" minimum is recommended, t