My buddy has O scale and says the largest radius the make is 36"
That is like 18" in HO and yet they make all the big Articulateds which he has and runs
From what I have seen they look downright weird on that 36" radius
What was the rational for only 36" radius
Whatever you do, don’t make the mistake I made, and I’m sure you wouldn’t, of confusing radius with diameter. A 36" o-scale 1:48 radius in 1:24 large-scale would amount to a six-foot radius, or twelve-foot diameter, if I am calculating correctly. That is not ANYWHERE big enough to run realistic looking large-scale trains; specifically, nowhere near big enough to prevent the overhangs and twisting that look so toy-like. As far as the rationale goes, maybe it’s the same rationale that prompted Aristo to call their five-foot diameter (diameter, not radius, as I learned so painfully) curves “wide radius” curves. Yeah, right.
Could this be for tinplate type trains rather than scale? Those can negotiate some tight radius, but are made with a lot of scale compromises to do it. Seem to recall from somewhere that O72 is 36 inch radius, though I’m not knowledgeable enough on tinplate to be sure.
Calculating that 36 radius in O would be a 20 in HO
Both are too tight for decent appearance
And passenger cars of any thing bigger than an Overland would be even worse
Please don’t confuse O scale (2-rail, prototype-looking track, small flanges) with O gauge (tinplate or Hi-Rail) with its 3 rail track and deep flanges - and huge compromises to make big locomotives take street corner curves.
36 inch radius (aka O72) is the largest LIONEL curve available, but true O scale rolling stock won’t even run on that ugly round-topped rail. A serious hi-railer would be more likely to lay GarGraves flex to as generous a radius as possible, while an O scaler would probably fight for a radius in the 60 < 72 inch realm if big articulateds, stiff 4-8-4s and full-length pullmans were part of the roster.
Chuck (Modeling Central Japan in September, 1964 - with radii measured in millimeters)
It’s likely you are confusing O scale and O gauge – defintiely not the same thing.
But even in O Gauge, your buddy is wrong. There are much broader sectional curves available. Gargaves (for one) sells sectional curves up to 138" diameter. This is measured to the outside of the track (as traditional for O Gauge), so the equivalent radius is something like 67". That would be the equivalent of about 36" radius in HO.
Nope it is O Scale like Lionel
Terminology issue. O yes, Scale no. Lionel is O-Gauge. The track is actually the equivalent of 5 feet between the rails not 4’ 8 and 1/2". The Lionel curves are measured in diameters not radius. For example a Lionel O-27 curve measures 27" diameter on the curve. Standard O-gauge is O-31 or 31" diameter of a circle of track. Formerly their large track was O-72 so called “Super O” which was 72" diameter or 36" radius. That could be what your buddy was talking about. More recently they have introduced O-45 and O-54 track with appropriate diameter curves.
I have no idea what the rational was. I know O-27 was cheap. I am guessing O-31 was originally made so that an oval could be nailed to a 3" x 6’ sheet of plywood. For the O-72 I am guessing that was the largest they considered reasonable. Remember that the average house in the US when all this stuff was being worked out in the 1950s and 60s was only 1200 square feet.
But your are right. It looks really silly to have those massive locomotives going around such sharp corners. Most O-scale people I know (2 rail stuff) run a minimum of 48" radius curves. That would be a Lionel equivalent of O-96 if they made such a thing. Oh and they don’t run massive equipment around it either.
Lionel is not O scale. It’s O gauge.
In the 3 rail world curves are measured by diameter not by radius and are usually measured to the outside rail not the center. O72 is the largest diameter that Lionel uses and they make all their trains to run on O72 or less curves. This involves several compromises the most notable of which is the very oversized flanges.
Lionel also makes two grades of track, O31 (usually just labeled Lionel track) and O27 (usually designated O27). O31 has taller rails and more robust turnouts and is more expensive. O27 is smaller and cheaper. O31 's tightest curve is 31" diameter and O27’s 27". Both lines have larger radius curves - the largest is O72 for O31 track and O54 for O27 track. All Lionel trains will run on straight track of either kind. They will also run on curves of both as long as the curve is wide enough for the particular train. 3rd party manufacturers may have other sizes than Lionel.
Scale is another issue with Lionel. O27 trains are not full O scale. While not scaled down directly they are usually considered closest to 1:55. Many Lionel O trains are 1:48, but there are exceptions. Large locomotives are frequently made to smaller scales - some as small as 1:64. All the while using O gauge track, some with amazing overhang.
2 rail O scale is almost always 1:48. Some manufacturers (not Lionel) such as Atlas and Weaver offer their cars and locomotives in both 3 rail and 2 rail versions. The 3 rail versions run on O72 or less curves. Atlas also offers both 3 rail and 2 rail solid rail track. In the 2 rail world 36" radius (equivalent to HO 20") is usually considered the minimum, suitable for smaller locomotives and cars.
A fundamental choice with O is whether to go 3 rail or 2 rail.
Enjoy
Paul
Ok that is for the track ?
All his engines are MTH
I assume that is O scale and he is using O72 track
Which is 36" radius or as stated above about 20" in HO
And he has 4884s–2666s–2884s–4664s running
BUT as long as they go around the curves they look OK on the straightaways and he is happy so I don’t know why I should criticize
MTH is a company that seems to want to appeal to the O gauge and O scale crowd at the same time. They offer both 2 rail and 3 rail versions of their locos.
While their locos are close to scale in size they are heavily modified to negotiate very tight curves. Blind drivers and swivelling pilots allow for this, as well as other modifications. I do not consider this to be O scale when a pilot is not attached to the body of a diesel loco. Same with the couplers. They are attached to the trucks, not the body.
The scale engines made for 2 rails by atlas, weaver and multiple brass importers are not made to negotiate these tight curves, most large steam engines need a 60" radius (O120) to operate reliably.
As for the track, 3 rail track is sold in curved sections by diameter (O27, 31, etc.) There are also suppliers of flex track for three rail but from what I’ve seen most O gauge guys use individual curved sections.
Most scale guys do not use curved track sections for their layouts, they use flex track or, like myself, handlay the track using wood ties and steel or nickel silver rail. For us Oscalers, it doesn’t matter what radius curves are available, we make what we need.
The minimum radius on my layout is 72" (O144) on the main line. I will go down to 48" only in area where I know that no large locos will be running.
Ahhhh, the Myths of O Scale…
(Resident O scaler chiming in here.)
Yes, it’s almost normal to confuse Q gauge, O Scale, P-48, 17/64s OW5, and O Scale.
Most 4 axle diesels WILL negotiate 36r. Atlas makes 36, 40.5 and (I think) 44r. 6 Axle will also operate on that, BUT can look very stupid doing it. Steam, 2-8-2s, 4-6-2s, small articulateds (2-6-6-2s such as the C&O H-4) will also mechanically do it, but. they don’t always look good at it.
Some MTH locomotives ARE full scale, many of their diesels are available with fixed pilots, ready for Kadees, but the dual vertical motor drives are less than stellar at low speeds. Same can be said for current production Atlas and Weaver. Lionel will not enter the two rail market.
O scale can be done on a budget. If one wants to get their hands dirty, there are plenty of 3 rail Weaver locomotives out there for little dollars that can be easily converted to 2 rail There are also old Atlas F-9s, Red Caboose GP-9s, and the occasional brass diesel that has fallen prey to cold solder joints and needs rebuilt. (I paid $50 for mine)
Cars, Weaver is the most common, are readily available, and there is a large secondary market for scale stuff. I built a B&O passenger train, Walther’s cars, added details from Kiel-Line, seven cars, less than $100!
My layout uses Atlas flex, their 36 and 40.5 “snap track” Atlas #4 switches in my yard and switching sections, handlaid (with a FastTracks jig 
) #6 on code 148 rail.
But then, I’m restricted to four axles diesels on the switching railroad, the “railfan” loop is 56" and 62" which gets me by with SD-40-2s, (CLW for you O scalers out there) Atlas SD-35s, and 2-8-2 “excursion” locomotives.