I’m sure the more knowledgeable among you get weary of this discussion. I just again checked Lionel’s web page - under ‘guage’ they list 042 curves as being 027 ‘profile’, supposedly meaning 7/16" hright profile (versus 11/16" height profile for “0”). Yet under 'Products" they list 042 curves and switches under “0” guage!
Of course, in addition to this they describe their curves as 031/042/054/072 DIAMETER, while I have again confirmed for myself (because I always forget this stuff after 6 months to a year) that 031 curves, measured on the center rail, make a 28 1/2" diameter circle. Which measures approximately 31" from outside tie edge to outside tie edge. The other curves presumably follow suit. And they never explain how they measure the curves. Only a hands on test with 8 sections of 031 curves provides clarity. God only knows how they measure Fastrack.
I give up! And these nitwits expect me to happily buy their stuff.
Lionel markets their own O-42 in O-27 profile and the old K-Line O-31 profile switch in O-42 form to compliment their own 0-22 (6-14062,6-14063) (which is actually O-31 curve) and their O-72 switch.
It can be a tad confusing. In reality the “Gauge” is all the same whether it “027” or “0” or even “Fasttrack”, the “Gauge” being the width between the outter rails. Initially the “027” track was just that, a 27" diameter with the lower profile and only in “O” track could you get larger diameter starting with 31".
When looking at the Lionel website for track check by the track name that they use such as “027”. this will give you a listing of all diameter curve track using the “027” profile.
Don’t stress, it gets better with age. Until you get to old and start forgetting the stuff you learned earlier in life.
This is because it’s all true! Both track types are still made.
FasTrack & Super “O” is measured 36" diameter to the center rail. O-72 is 35.88" radius to the center rail. O-27 is 12.37" radius to the center rail, “O”(31) is 14.14" radius to the center rail, O-42 is 20.17" radius to the center rail, O-54 is 26.60" radius to the center rail.
Not to worry… it’s a passing fad. The stuff has only been around since 1915.
I’m fully aware of Lionel’s three (four?Super Snap?) track offerings. Whether they made the 042 curves and switches in "031’ profile or only in 027 profile was somewhat unclear from their web site.
What’s been driving me nuts is determining the center rail to center rail diameters - for layout planning purposes (I use compass and graph paper).
First, while I don’t doubt that the theoretical diameter of 031 is 14.14" (what is the calculation by the way?), I do doubt that anyone can actually put together a circle that small. Best I can do is about 28 7/16".
Second, The previous not withstanding, say an 031 cirlce measures about 28 3/8" (splitting the diff above), and almost 31" to outside of ties, a diff of 2 5/8. Why then would a 031 profile (so called 0 guage track), 072 circle (at 35.88 r) measure 71 3/4" TO THE CENTER RAILS, and not approximately 72" TO THE OUTSIDE OF THE TIES like the so called 031 radius does? I would have thought that there would be some consistency of measurement within ONE track product from ONE mfgr! Barring that, Lionel could at least have the true dimensions clearly indicated in their web site section on “guage” or in their track descriptions. How do they expect anyone to plan layouts when the actual radius of the curves is not given and furthermore is misrepresented and inconsistently so. [end of rant[|(]
So finally, Rob,
I’m assuming that ALL the measurements you provided above, except the 36", are for 031 profile track.
Pick up a CTT INC Tinplate Track gauge. Most hobby shops have them. Kinda lime green in color. Even come with a centering hole for O27, O42, O54, and O72 curves. No muss, no fuss, and no more guessing.
Thank you - both are sanity maintaining ideas that I’ll keep in mind. I. like all of us I suppose, get in a rut on how I approach and try to solve problems.
Fife- what scale is that guage? I do most of my planning at 1" = 1’ (more ruts).
14.14" is the radius, not the diameter. Your 28 7/16"(28.4375") is pretty darn close to my 28.28" diameter(1/2 of 1%).
No, it includes Lionel, Marx, & K-Line products made in both “O” & “O-27”(I didn’t get into Marx O-27(34) but could do those calculations from a piece of straight track). The height of the rails & ties, and the gauge of the steel used are not mutually exclusive to the geometric calculations.
The radius of those track systems, like O27 and O31, that use 8 curved sections for a complete circle is the length of a straight section multiplied by the square-root of 2. The idea is that a passing siding constructed alongside a straight track will have its track joints aligned with those of the main line and can therefore be constructed from standard sections. If you look at a turnout like an 022 or 5121, you will see that the end of the center rail of the curved path is directly adjacent to the end of the center rail of the straight path. Likewise, if you recurve the track with a curved section turning the other way, its rail joints will line up with the next straight section coming from the straight path.
I disagree with the radius of 12.37 for O27, however. This comes from taking the length of a straight section to be 8 3/4 inches, whereas I make it to be (from many measurements) more like 8 27/32, which leads to a radius of 12 1/2 inches.
You can also measure the radius from a single section of curved track. Measure the chord between the ends of the center rail and divide by twice the sine of 22.5 degrees. My chord measurement is 9 9/16 inches, which also leads to 12 1/2 inches.
Except for O27, don’t expect the nominal diameter to equal the actual diameter. For example, I find the radius of Marx O34 track to be about 15 3/4 inches, for a diameter of 33 1/2 inches. For “O31”, the actual diameter is 30,534 inches, which could almost as reasonably be, and has been, called O30. I also find that Marx track tends to be somewhat inconsistent; a single straight section might even have slightly different rail lengths.
BOB, PLEASE! JUST AS i THOUGHT I HAD ALL ‘031’ CURVE RADUII UNDERSTOOD, YOU GO AND CONFUSE ME AGAIN.
I THOUGHT 031 RADIUS TRACK HAD A CENTER TO CENTER RAIL DIAMETER OF 28.28 (2x10"x sq rt 2)- NOW YOU’RE SAYI NG IT IS 30.534. OR ARE YOUI DESCRIBING THE OVERALL OUTSIDE DIAMETER - TIE EDGE TO TIE EDGE?
IT REALLY MAKES THE MOST SENSE TO ME IF ‘DIAMETER’, WITH NO OTHER QUALIFIER.WOULD MEAN CENTER RAIL TO CENTER RAIL, AND ANY OTHER ‘DIAMETER’ WOULD BE APPROPRIATELY DESCRIBED. IF WE COULD ALL GRADUALLY COME TO THAT UNDERSTANDING, IT COULD BE THE GREATEST ADVANCE IN 0 GUAGE RAILROADING IN THE PAST 90 YEARS.
I should have been more specific. I was talking about the diameter to the ends of the ties, which, for O31, is 2 1/4 inches more than the diameter to the center rail.
1"4.14" is the radius, not the diameter. Your 28 7/16"(28.4375") is pretty darn close to my 28.28" diameter(1/2 of 1%)."
I did mean theoretical RADIUS =14.14. And yes, 1/2 of 1% may be nitpicking [:D].
So my final conclusion on curved track radius is:
regardless of mfg or ‘system’(031, Fastrack, Gargraves, etc) measure a standard straight, multiply by sq rt of 2, and that is the radius of the system’s curve, measured center rail to center rail???
The “proper” straight length for O-36 FasTrack is 12.728"… a piece Lionel doesn’t make, and a length that can be made/approximated without cutting only with $$ & space in a large layout using their expensive fitter pieces.
The square-root-of-two rule really works only with track systems that have 8 curved sections in a circle and turnouts with the same proportions as the Lionel and Marx O27, O31, and O34 turnouts. But the chord method works for any track system. All you have to know is how many sections are in a circle. You measure the chord–the straight-line distance between the ends–of the center rail and divide by 2 and by the sine of half the angle that the section represents. Or you can use this handy-dandy table:
For 8 sections per circle, multiply chord by 1.307.
For 12 sections per circle, multiply chord by 1.932.
For 16 sections per circle, multiply chord by 2.563.
For 24 sections per circle, multiply chord by 3.831.
For those who are really into this: This method is not very sensitive to bending of the track; but it becomes even more accurate as the number of sections per circle increases. One trick to improve accuracy is to divide the track section in two, measure the average of the resulting two chords, then multiply by the factor for twice as many sections. For example, I just measured the curve of a 5121 turnout as 9 9/16, multiplied by 1.307, and got 12.498 inches for the radius. Then I measured the part of the rail at the outer end of the curve as 4 31/32 inches and the chord from there to the beginning of the curve as 4 25/32 inches. The average of these is 4 7/8, which, multiplied by 2.563, gives 12.495. Both of these are pretty much 12 1/2 inches. But, if the track had been not a rigid turnout but a slightly bent simple curved section, the second measurement would be more accurate.
Oh my, oh my, oh my… bob, obviously ‘you the man’ when it comes to precisely defining anything related to ‘0’ guage trains. But REALLY, should it be THIS difficult. If I had one of these train company executives here (presumably they have some) I;d want to slap him (couldn’t possibly be a her).
Seriously, not necessarily having pieces of every mfgrs track on hand, I’m left to guessing what “real” (read center rail to center rail) radius everone’s track really has. It;'s enough to make me want to put everything on a display shelf and forget about operating - too much trouble!