I have at least 5 #4 Walther's Shinohara Code 83 turnouts in my yard and all of my 2-8-8-2's and 4-8-8-4's go thru them without any problems. Two of the approach tracks to the turntable go thru these #4 turnouts, so I have to negotiate them quite often.
-Bob
Life is what happens while you are making other plans!
PK, I don't have any fancy brass or high dollar loco's but will offer what I can. My layout is all #4 Atlas turnouts. My loco's: Mantua and IHC 2-8-2's, Bachmann 4-8-4's, Mantua and Rivarrossi 4-6-2's, and an older Athearn Genesis 4-6-6-4, as well as a few other various smaller or smaller drivered steamers. All negotiate my turnouts fine whether going through divergent route regardless of direction.
You've already said you will build a test section which is great; definately can't go wrong that way before building permanent.
Happy RR'ing!
Duane
Jim-
You said the magic word/letters. My 2-8-2 is a USRA light mountain, I'm using Atlas turnouts as well. I'll build a "Test Run" section tomorrow and see how it goes. If not I'll just have to wait for the elves in the brown truck to bring me some #5 or #6 turnouts.
Modeling BNSF and Milwaukee Road in SW Wisconsin
I have a lot of #4 Shinohara turnouts and even Decopods are fine and have many 0-8-0's, not the same and I can not check at the moment but I probly run 2-8-2's also.
I'd also think about whether that 2-8-2 will be taking the divergent path on those turnouts. I only use shorter switch engines in my yards.
It takes an iron man to play with a toy iron horse.
For commercial turnouts, Paul nailed the critical point - the tight closure radius of an accurately-built (to NMRA spec) #4 turnout. Atlas #4 turnouts were actually #4.5, which brought the key radius above 18 inches - adequate for most (but hardly all) mass market locomotives.
I hand-lay #5 turnouts, but my minimum radius is driven by some stiff catenary motors that get actively unhappy if forced under 24" radius.
One possible trick, since a 2-8-2 is road power. Lay the arrival/departure track(s) with #5, then go to #4 for body tracks that will only be entered by a short-wheelbase switcher. Embargoing long/heavy locomotives from certain trackage is certainly prototypical.
Another useful trick is to use a compound ladder - the turnouts are #5, but the ladder angle is effectively #2.5. If your space is wide but short, that will let you lay a couple of additional classification/storage tracks.
Chuck (Modeling Central Japan in September, 1964)
I'll offer the following NMRA info for comparisons, namely Recommended Practices 12.0 (turnouts) and 12.3 HO turnouts, both pdf files you can open here:
http://www.nmra.org/index-nmra-standards-and-recommended-practices
If I interpret these correctly, the closure rail radii may be the critical spec of concern. For a #4 it's only 15", where for a #5 it's a much more generous 26". Maybe someone can confirm I'm looking at this data correctly. Whether that's an issue for your mikado I imagine would depend on it's specs, but I'd guess many 4-axle steamers (like my BLI 2-8-2) certain specify 18" or more. So it could be a problem.
Do note that you can compact yard turnouts somewhat by trimming the track ends so they butt together more closely, which I did with #5s in my yards. So suggest make some #5 paper copies and play with same to see if #5s won't simply work where you want them. But don't trim inside any jumpers (my Walthers-Shinoharas have jumpers you can see underneath).
Paul
Modeling HO with a transition era UP bent
Some 2-8-2's will probably work fine, others not so much. I suggest you do a test. Build a temporary yard with a couple of #4 turnouts arranged similar to what you plan for your yard. You will find your answer then.
Hoping to lay some track this holiday and have thought myself into a knot.
On main line my crossovers and turnouts are all #6 or #8 but in my yards and spurs I planned to use #4. Will that give me trouble with a 2-8-2 loco?
I know it might not look "prototypical" if longer cars are used but these are going to carry 1950's freigh and industry.