Does anyone know what the radius of super O track is? I am thinking about building one of the super O display layouts in Roger Carps book on the subject. Super O track is not available anymore so I thought I would use fast track. I was hoping that the track geometry of the fast track was close to that of the super O.
Thanks,
George
Super O is 36" and Fastrack's minimum radius is also 36".
That is what I thought I remembered. So, fast track geometry is exactly the same as super O and any super O track plan should work with fast track.
Atlas also has a 36" radius track including switches.
My home layout is Fastrack and Super-O, joined in various places. I used a FT to O gauge transition piece, then a short piece of O gauge track with Super-O pins soldered into the other end, and then the Super-O from there. I can't complain about it, I love the look of Super-O and have a bunch of it, so it seemed like a good idea. Good luck!
The radius of Super O is 18 inches, whether to the center rail or what, I do not know. The diameter is 36 inches.
The radius of the tightest Fastrack curve is also 18 inches, to the center rail. The shortest diameter is 36 inches. It is also available with a 36-inch radius and a diameter of 72 inches.
Bob Nelson
Thanks Bob. So many folks seem to have forgotten their high school geometry.
runtime
lionelsoni The radius of Super O is 18 inches, whether to the center rail or what...
The radius of Super O is 18 inches, whether to the center rail or what...
That is correct - to the center rail. Regular curves are 30° compared to 45° for FasTrack.
Rob
Has anybody ever tried to do a D-264 display layout with Fast track? If you did, how did it turn out? Would you do it again? Have you posted photos?
This drives me nuts about tinplate track. Why don't we refer to track with the true centerline radius ? I use good old fashion tubular track. O-31 has a centerline radius = 14.1/4 inches. I am a land surveyor by trade and have staked out real railroad track on the ground. If it is a road or railroad track, we always work with the centerline and need to know the centerline data for a given curve. Same goes for laying out the centerline of trackwork on a layout at home.
Steve
I couldn't agree with you more, Steve. Here is a recent post of mine on this topic:
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.
Bob, when I first read your original posting of this reply I began to hyperventilate, ran upstairs to see if I still had my college handbook. I panicked when I realized I had long since disposed of it. Then I calmed down and realized that, of course, the is an iPhone App for that! I had not needed a cosecant in over 40 years yet here was an elegant application! Thanks for reposting your explanation, I for one really enjoyed the insight it provides into design considerations that likely went into the toy train design process.
My personal opinion the reason the diameter of toy train track was originally quoted as the outside diameter is the size of the layout required was more important to "dad" than the ability to design custom track plans accurately.
Tom
There is plently of Super O on eBay. If you want some further leads contact me: hspanier@aol.com
Mike Spanier
Tom, it's not often that the humble cosecant gets such attention! This is it's 15 minutes of fame. The cosecant of 15 minutes, by the way, is 229.1838453.
I'm sure you're right about "dad's" concern for the layout size.
Our community is FREE to join. To participate you must either login or register for an account.
Get the Classic Toy Trains newsletter delivered to your inbox twice a month