To the Thread Originator:
I'm going to share with you some thoughts on HO scale, 3-rail, and O 2-rail.
As one that has modeled primarily in HO for the past 60 years, I can share some experience in that scale. I have found that derailments in HO are generally attributed to:
* Switches
* Rough track joints
* Kinks
* Poor curvature (too tight for the intended model)
* Wheel gauge
* Wheel profile
* Couplers
Looking briefly at each one:
SWITCHES:
Do NOT cut corners on switches. Atlas "Snap Track" switches (and similarly low priced switches) are the lowest rung of the ladder for a prefab switch. Use QUALITY switches, such as Atlas "Custom Line", or switches from Peco's line, the Walthers line, and such.
Using less expensive switches typically results in stamped points that are prone to being "picked" by the equipment's wheel flanges, poor frog standards, and such as that. Grief WILL follow. Yes, inexpensive switches can be "tuned" to be more reliable, but that requires knowing what you're doing and being willing to piddle with them.
TRACK (Rough joints, kinks, poor curvature):
Rough Joints/kinks - IF you use sectional track, you will have more joints to deal with, thus more opportunity for a rough joint for the wheel flanges to find and pick at. Using sectional track, each joint must be square (to avoid kinking), and smooth on the inside of the gauge. I prefer to use a quality brand of flex track as much as possible.
Poor curvature: IF using sectional curved track, equipment that is too big for the curvature will cause that engine piece to consistently derail. That is, large steam on 18" radius curves, or large diesels and such combos as that. Typically, 18" curves are best suited to small steam, 4-axle diesels, 40'-50' equipment. ANYTHING larger can result in issues. Thus, one needs to make SURE their mainline and pass track curves are compatible with the LARGEST equipment you intend to run.
WHEEL GAUGE/PROFILE:
Wheels must be in gauge. You will need an HO "Standards" gauge so you can check the gauge of your wheels. Rolling stock is typically very easy to re-gauge to proper gauge if too wide/too narrow. Simply remove the truck and twist as you pull/push the wheel that moves.
You need to consider standardizing on the NMRA Recommended "RP25" wheel profile for code 110 wheels. (The "more scale looking" code 88 wheels require tighter track tolerances.) The code 110's w/RP25 contours will perform better over quality switches than the larger, sharp flanges, that often come on rolling stock of European mfg'er.
COUPLERS:
You need to standardize on "knuckle-type" couplers, preferrably from a single mfg'er. (I use Kadee Products). IF the car is equipped with the old "Horn Hook" HO coupler, remove it IMMEDIATELY and replace with the knuckle of your choice.
ALL couplers need to be BODY MOUNTED. There is no way a truck mounted coupler will EVER be conducive to shoving moves through switches/etc. The nature of the design will force outward pressure in opposite directions, resulting in the flanges looking (and finding) the slightest irregularity in the track.
(The ONLY reason truck-mounted couplers work in 3-rail is because of the extra large flanges on the wheels.)
O SCALE IN GENERAL:
IF you're going to O scale because of the size, AND you're wanting less opportunity for derailment, then 3-rail wheel profiles will offer the best way to fulfill that desire.
IF you want the larger size AND the closer to scale appearance of 2-rail O scale: Then ALL OF THE ABOVE POINTS I shared for HO scale APPLY TO O SCALE 2 RAIL!!
In O 2-rail, larger does not AUTOMATICALLY mean better on-track performance, in fact, it can exacerbate the issue in regard to needed curvature. (You will be alarmed at what a large radius a large steam engine or diesel engine will require.)
ALSO, be reminded that nearly ALL O rail 2-rail is built for track that is a scale of 5' gauge, and not to a prototypical scale of 4' 8.5" gauge. May not bother you, but you need to be aware of it.
Best of luck in your model railroading journey, regardless of what you decide to do.
Andre