HO Scale vs ON30 Scale

[Sparky782]

Are these actually 2 different scales? If so which one is larger and by about how much?

Thanks David Godwin

[richg]

HO is smaller. Standard gauge.
There is a HOn3 NG, 36 inch and HOn30 NG, 24 inch. Some vary a little from this.

http://en.wikipedia.org/wiki/HO_scale

ON30 is O scale NG.  Usually 36 inch.

http://en.wikipedia.org/wiki/O_scale

Save the Wikipedia link. Usually it is accurate but sometimes an error can be found. I use Wikipedia but sometimes do a cross check.
Take time to read the links. Most questions should be answered.

Rich

[Doneldon]

Sparky-

You can run your O-scale equipment on HO-scale track even though the scales of O and HO are very different. HO is supposedly "half-O", but it's really a little larger than half the dimension (eight time the volume; 2³=2x2x2=8) of O-scale. (A similar situation exists for N and HO. N, at 160:1, is actually a little larger than half -- an eighth -- the size of HO at 87:1.) However, 30" narrow gauge O-scale trains (On30) running on HO track will look funny because it is HO-scale track. That is, operation will be fine but the many, small, close crossties won't look right. People who run O-scale 30" gauge narrow gauge trains on HO track either remove ties (generally half of them or one in three) or, better, buy HO track which is designed for O-scale with fewer but larger, more widely-spaced ties.

Be careful when talking about scale and gauge. Scale refers to the ratio of the model to the prototype. For example, an HO dimension is 1/87^th the size of reality (the prototype). Gauge refers to the distance between the inner surfaces of the railheads. Real, full-size railroads have rails which are 56.5" apart. In HO that is roughly 5/8". (56.5" divided by 87 is .65") O-scale dimensions are 1/48th the size of the prototype. So the distance between the railheads should be a little less than 1.2". (56.5" divided by 48 is 1.18") I'm sure you can see the slight discrepancy between the O-gauge and "half" O-gauge numbers. BUT, and this is a big but, you can run 30" narrow gauge O-scale (1:48 proportion) trains on HO-scale(1:87) track because the scale of those On30-scale trains is still 1:48 but now we're working on track which is only 30" wide in the prototype. (30" divided by 48 is .625")

his might sound like mumbo-jumbo to new model rails, and lots of us are a little sloppy with our inaccurate interchangeable use of the terms, but you'll soon feel comfortable with them. Just remember that scale refers to amount of miniaturization and gauge refers to the distance between the railheads.

Welcome to what I think is one of the most interesting and varied hobbies around. I've enjoyed it for more than 50 years and I'm still learning new things. Even my profession didn't hold my interest that long!
                                                                             -- D

[Jim Banner]

Just to be a little more technical for anyone that might be interested, H0-scale is exactly one half the size (linear dimension) of 0-scale.  But not the slightly undersized 0-scale used in North America, the original 0-scale.  0-scale was originally defined as 7 millimeters to the foot, back in the days when the British measured things in feet.  Because they liked to scale everything as so much "to the foot," 0-scale was often abbreviated as 7 millimeter scale.  To convert this to a fraction, remember that 1 foot is 304.8 millimeters by the definition.  So 0-scale is 7/304.8 = 1/43.54285714 of full size, usually stated as 1/43 scale, or more exactly, 1/43.5 scale.  This 0-scale is still in use in Britain and parts of Europe.  At the time these proportions were being established, we North Americans were clueless about the metric system so we used something close - 17/64" to the foot.  This gave a scale of about 1/45 of full size, a scale still used in parts of Europe but virtually forgotten on our continent.  I suspect the calculations to model in 17/64 scale were so cumbersome in those pre calculator days that modelers spent more time doing the math than building the model.  A solution was to reduce the size of the models to 1/4 inch to the foot or exactly 1/48 of full size as used today in North America.  But that raises a problem.  The NMRA requires 0-gauge track to be 32.2 millimeters between the rail head, making it very close for 1/45 scale, a bit small for 1/43.5 scale and a fair bit too large for 1/48 scale.  In fact, for 0-scale, 32.2 millimeter track works out as just over 5 feet.  Anybody out there modeling in 0w5?

As Donaldon has pointed out, our 0-scale is not exactly twice the size of our H0-scale.  Now you know why.

Jim

p.s. for florynow

H0 is defined as 3.5 millimeters to the foot which is 1:87.0857142857142857142857142  As a fraction, it is a bit less than 1/87.0 and a bit more than 1/87.1      

[Doneldon]

Jim-

Thanks for the clarification on the half-O matter. I've always known of the fact that HO isn't really half of O as we know it but I never knew why. Now I do, and I have you to thank for my understanding. It actually makes me feel a little better to know that there is a real history here, not just someone who was either careless or brainless in devising half-O. Your Canadian heritage makes you much more likely to know the background on this and the English/European influences. Until recently, the metric system in the US was more-or-less something teachers used to torture grade school students (who knew they'd never use it). Now we have lots of metric goods here, foreign cars have been metric forever and we have metric booze. Actually, the liquor industry was the first to completely convert to the metric system, back when the country was supposed to go metric in the 80s or something.
                                                                                                                                                 -- D

[Jim Banner]

Donaldon,

We officially went metric years ago, but in practice we still use a lot of feet, inches, pounds etc.  We still buy 4 x 8 sheets of plywood because that is a lot easier than asking for a 1220 by 2440 millimeter sheet.  The thicknesses are metric but referred to as inches.  If I ask for 1/2" plywood, I get 11 mm plywood.  If I ask for 11 mm plywood, I get a blank stare.  Except if I want plywood to use as flooring underlay.  Then 1/4 inch plywood is 1/4" thick.  This insanity goes on, not just in construction, but at the grocery stores too.  Often things are priced by the kilogram but sold by the pound.

A recent purchase of some clock chain at a hardware store with "Canadian" in its name seemed to take forever.  I needed 6 feet, the chain was priced by the foot, but the measuring machine the store clerks were required to use measured only in meters.  I ended up with three clerks trying to figure out what to do.  I offered to measure the chain for them using a tape measure but that wasn't allowed because none of them knew how to read a tape with both foot and meter markings.  So they had to phone head office for a ruling.  Head office decided that one foot was about equal to 3 meters so 6 feet must be about 18 meters.  I figured the difference paid for my time that they wasted.

One problem that arises every year when I teach model railroading is that the younger people taking the class have learned only metric in school and the retirees still think in feet and inches.  So everything that involved measurements has to be translated and explained twice.  But I guess I am lucky.  With a career building scientific instruments, I spent almost as much time in the machine shop as in the electronics lab.  The machine work was about equally split between English and metric, with a surprising number of jobs being a mix of both.  It helps to be able to select the measuring system depending on the person's age.  But it is crazy world we live in when that becomes necessary.

Jim   

[Doneldon]

Jim-

It's nice, I hope, to hear that things are as crazy in other parts of the world
as they are here. Your hardware store story is priceless. Kind of a catch 2.54
thing. Maybe you and Joseph Heller should write a book!
                                                                                     --D

[Len]

If 'X' is the scale, 'Xn#' is used to represent the gauge of narrow gauge track, with '#' given in feet. So you have:

X = 4ft 8-1/2in Standard Gauge
Xn2 = 2ft Narrow Gauge
Xn2-1/2 = 2-1/2ft Narrow Gauge
Xn3 = 3ft Narrow Gauge

Unfortunately, most computer keyboards don't have a "1/2" key like typewriters do. So in 2009 the NMRA revised the scale standards to show "Xn2-1/2" as "Xn30", representing 2-1/2ft as 30 inches. Which causes all kinds of trouble for Xn3 narrow gauge modelers when they order stuff and end up with Xn30 items instead because the person filling the order thought they left the '0' off.

Len