My Styrofoam Size is 3 Feet X 3 feet X 2 inch
And the size of mountain i'm thinking of is for the Layout of 10.5 feet X 3 Feet. My idea is to make Whole place in a mountain Scene with bridges and tunnels and valleys. I got the Layout plan for tracks if u want me to try get picture of it. Its from my Lima Layout Book.
If this is your first layout, it sounds overly ambitious. Also, is your layout size to be 10.5 by 3 feet? In HO scale, that will only give you room for a 16 inch radius curve, which is very tight by HO standards.
I'm not familiar with the Lima Layout book, so I'm not sure what you're trying to build.
Unless you are using a dual axle engine, your layout size seems very restricted, as Tom suggests above. You can use small industrial engines on the curves you would be able to place in the confined space you describe, such as the Shay steamers and small diesels. But the space you describe would be far more suited to a bench switching style layout. For all practical purposes, the minimum radius in HO scale has been 18", which means the outer rail on your curves would hang out over the lip of your 36" wide foam including the ties under them. That's a recipe for disaster when your rolling stock and engine tumbles to the ground for some reason. So, you need a wider bench design or you need tighter curves than the recommended minimum for HO scale...except for small industrial switching, as I mentioned.
I think we could use more of an idea of your interests for this space. What do you have in mind? Can you get a few more square feet...beg if you have to?
The SAR Engines i'm using for my layout are 8 and 12 wheeled and goods are 4 and coaches are 8