Even though postwar American Flyer track has no center rail to measure, you can still use the method I described above to find the radius to the center of the track. Just measure from end to end of the two rails that you have and average the measurements. Then use that number instead of the center-rail measurement called for by the method.
Bob Nelson
Major,
Thanks for the response. I am in post war S scale, and currently only have the original Flyer Track. This seems to measure about 38" between rail centers. I know what is referred to as 54" curve track is available but I don't know what teh actual rail center to center measurement is.
I am planning a new layout, and am looking for this information to help me in design. If anyone has this information and or knows of other track options please let me know.
Thank you,
George
phillyreading lionelsoni: Lee, you're not thinking of Marx O34, are you? Bob, I don't have the track in my possesion any more, but I know it was 027 size rails in an 031 curve. Matched up pretty well to a section of 031 curve. Not sure but I think the track pins almost look like nails that had their head cut off. Not positive who made this track but I think it was Ives, and I know it wasn't Lionel track. Lee F.
lionelsoni: Lee, you're not thinking of Marx O34, are you?
Lee, you're not thinking of Marx O34, are you?
Bob,
I don't have the track in my possesion any more, but I know it was 027 size rails in an 031 curve. Matched up pretty well to a section of 031 curve. Not sure but I think the track pins almost look like nails that had their head cut off. Not positive who made this track but I think it was Ives, and I know it wasn't Lionel track.
Lee F.
That would be Marx 034. Do you remember if the center rail tabs were crimped along with the outside rails? That would further identify it as Marx.
lionelsoni Lee, you're not thinking of Marx O34, are you?
aflyer Hi, This is a great post, and provides a good education for layout and benchwork planning. Does anyone have the same information for Ameriocan flyer tracks? Thanks, George
Hi,
This is a great post, and provides a good education for layout and benchwork planning.
Does anyone have the same information for Ameriocan flyer tracks?
Thanks,
I have AC Gilbert pre war O gauge Track and switches. They stated that they were 40" in diameter, but that was to the outside rail. The curve track was made in 30 degree sections 12 section made a circle. It appears that AC Gilbert use this same track geometry when he produce his post war S gauge track. Of course this meant that gaps in the track of passing sidings did not line up with the main line and we had to make short sections of track to get them to join together.
That would be very interesting reading, Martin.
Generally speaking, the track sizes and diameters are mainly Lionel tubular track. If you have Gargraves 042 and larger track, you can add at least quarter of an inch to the radius, sometimes more.
The old Ives 027 or maybe somebody else's 027 has the same size curves as 031 but has the rails in 027 heigth, there are some varitions of track sizes made through the years from the 1930's. Some of the pre war(pre WW-2) track I have come across has differant sizes.
Some years ago (probably more than 20 by now) the late Max Knocklein -- train collector & historian extraordinaire -- wrote a series of articles published in the TCA's Train Collector Quarterly on the history of Lionel track. In one of the articles on the earlier years of O gauge, he said that Lionel fiddled repeatedly with the exact lengths of the sections -- straight and curved -- and the exact geometry of the track, trying to get everything to fit together right. He documented the different lengths, etc., though I don't remember any of the specifics. (I have the magazines around somewhere, but can't lay my hands on them right now.) This changing went on for years from the start of Lionel O in 1915, finally settling down by about 1930, IIRC.
He also said that for a while, as part of this fiddling, they even produced 40-degree crossings rather than 45-degrees. I can testify to this -- I have one. It has the green sheetmetal base. I bought it at a train show, probably in the early '90s, with the idea that it was 45 degrees, but when I got it home I realized that it didn't look quite right and then measured it at 40 degrees. A few years later I got some back issues of the TQQ, and there was Knocklein's article, reassuring me that I hadn't been going crazy!
Martin
lionelsoniI am convinced that the original scheme for O27 and (so-called) O31 tubular track was to coordinate the curved and straight sections so that the joints in a siding alongside a straight main line would match those of the main line. This assures that a passing siding can be made using only standard sections.
Precisely.
And all of this is why the Fastrack geometry is so messed up. It's all due to Lionel's insistence that the straight track sections remain 10" long.
Rob
I am convinced that the original scheme for O27 and (so-called) O31 tubular track was to coordinate the curved and straight sections so that the joints in a siding alongside a straight main line would match those of the main line. This assures that a passing siding can be made using only standard sections. With 8 curved sections in a circle, this scheme effectively requires that the radius be the length of a straight section multiplied by the square-root of 2.
It's pretty clear that Lionel intended their straight section to be exactly 10 inches, with the result that the radius is 14.142136 inches, the value that Rob and I agree on. (I think we're using the same reasoning.) When you double this to get the diameter, and add a tie length of 2.25 inches, the overall diameter comes to 30.534271, which is where we get the modern nominal diameter of O31 (but occasionally O30 for the same track).
O27, which I believe Lionel got from Ives, is the other way around. It seems to have been designed with a round number for the overall diameter. So, subtracting the somewhat shorter 2-inch tie and dividing by 2 gives a radius of 12.5 inches. Then, dividing by the square-root of 2, we can back into the "correct" length for the straight section, which comes to an awkward 8.838835 inches. I think that track manufacturers have not generally understood where this number may come from, because straight O27 sections vary quite a bit around this length. Marx was particularly inconsistent.
As Fred suggested, it is quite tedious to get a good measurement, particularly by the obvious method of putting together a full circle and measuring it directly. As Rob pointed out, the joints can vary in tightness; and the track itself is quite flexible (one of its virtues, actually). It is essential to make at least two measurements, at right angles, to have any hope of accuracy.
Because of the difficulty of making a full-circle measurement, even if you are lucky enough to have enough sections for that, I devised the following method that requires only a single section and knowledge of how many sections a circle comprises. It has the useful feature of working better, the more sections are needed for a circle. It is also fairly insensitive to whether the section measured may have been bent a little straighter or more curved than it should be. I have posted it several times before; here it is again:
Measure the chord of a curved section, in a straight line from one end to the other of the center rail. Multiply that number by half the cosecant of half the angle that the section turns. The result is the radius to the center rail.
For example, O42 has 12 sections in a complete circle; so each section turns through 30 degrees. Therefore you multiply by half the cosecant of 15 degrees, or 1.931852. (For 8 sections in a circle, multiply by 1.306563; and for 16 sections, by 2.562915.)
The more careful you are measuring to the exact center of the end of the center rail, the more accurate your result will be.
Here's what I have measured. Since all of them vary slightly this is the closest average that I could get among all of them. I have all of the tubular pieces drawn up in CAD so I can use them as templates. This is measured on the centerline.
O-27 curve = 25" dia.
O-31 curve = 28.58" dia .
O-42 curve = 40.938" dia.
O-54 curve = 51.658" dia.
O-72 curve = 72" dia.
I don't particularly like the look of FasTrack or MTH's integrated roadbed so I will probably avoid them and use MTH ScaleTrax or Atlas-O. And I want as much 072 as possible.
Building the layout - I have some limitations on size and if the outside edge of the ties/road bed is creater than 72 inches I may have to redesign the layout.
Thanks
Scott Q
I'm using 8.875" for a nominal straight track section, that might account for being off by 1.051%! It depends on how tight you can get your track sections connected together.
Rob, I'll have to disagree with you about O27. I say it's 12.5 inches, whether Lionel, Marx, or K-Line.
It's almost a craps shoot, and depends on what you mean by "true" diameter - do you mean along the centerline?
Lionel O-72 is 35.88" center rail radius.
Lionel O is 14.14" center rail radius.
Lionel O-27 is 12.37" center rail radius.
Lionel O-36 Fastrack, & Super-O, are 18" center rail radius.
GarGraves sectional track is different even between plastic tie & wood tie track.
I read something recently and the author indicated 072 was a "nominal" value. If I grabbed a tape measure and measured -
What is the TRUE diamater of O72 Fastrack, ScaleTrax, and Atlas-0 (3 rail)?
Are they measured from the outside rail, the center rail, or elsewhere?
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