Model Railroading > Define HO Scale

This is going to sound like a stupid question, but, what is the actual ratio for HO Scale? I can never remember and can't find it anywhere. If it is not 1:120, what scale is 1:120, N?

Thanks

DelMonteX wrote:
>
> This is going to sound like a stupid question, but, what is the
> actual ratio for HO Scale? I can never remember and can't find
> it anywhere. If it is not 1:120, what scale is 1:120, N?
>
> Thanks

HO is 1:87.

Jeff
<a href="http://www.trainweb.org/cnotp&quot;&gt;Norfolk Southern CNO&TP Home Page</a>
<a href="http://groups.yahoo.com/group/nscnotp&quot;&gt;CNO&amp;TP Site Update Subscription Page</a>

Most people use the 1:87 to define HO scale. It is really one of two common scales that is metric at 3.5mm = 1 foot. The other being OO scale that is 4.0mm = 1 foot. OO is very common across the pond in the UK. "N" scale is 1:160. 1:120 is TT scale.

Isn't HO actually 1/87.1 or something like that?

HO is 1/87th of an inch to the scale foot.

bessemerlakeerie wrote:
>
> Isn't HO actually 1/87.1 or something like that?

Yeah, but the fraction is exceptionally irrelevant at the scale. I think you're right, though. 1:87.1 sounds like the true figure.

Jeff
<a href="http://www.trainweb.org/cnotp&quot;&gt;Norfolk Southern CNO&TP Home Page</a>
<a href="http://groups.yahoo.com/group/nscnotp&quot;&gt;CNO&amp;TP Site Update Subscription Page</a>

H0 originally ment Half 0 in the old days.
At that time there were a few toy train manufactrers on both side of the atlantic making 0 scale (32mm gauge) model trains. Märklin and Lionel and several others. The need for something smaller started in europe and a guy at the US embassy in Sweden took it to the USA.
The gauge 16.5 mm became standard right after that but then the problem started since there was no definition of 0 scale.

I think Allen Rice should be called "the father of H0 in USA" and I hope he is remembered in the NMRA hall of fame

DelMonteX wrote:
> what is the actual ratio for HO Scale?

Interesting question in that it generated so many answers. This got me thinking about the answers and trying to calculate the "actual ratio" DelMonteX asked for. This is NOT intended to flame anyone, just some thoughts on a question that I found hard to give an exact answer to.

(1) HO is 1:87. - close enough for practical purposes, but is it the "actual ratio"?

(2) 3.5mm = 1 foot. - this defines the scale but is it a ratio?

(3) HO actually 1/87.1 - getting closer.

(4) HO is 1/87th of an inch to the scale foot - a slip of the tongue? This would be 1:1044.

(5) 1:87.1 sounds like - same as (3) but as a ratio.

(6) The gauge 16.5 mm became standard - interesting history, and I also understand that historically HO means Half O gauge. HO was originally a gauge, not a scale!

So what is the "actual ratio"? Using the definition 3.5 mm = 1 foot we can first convert the 1 foot to 304.8 mm (real world definition of a foot) and then divide 304.8 by 3.5 to give 87.0857142857142857142857142857143. This would make the actual ratio 1:87.0857142 with the last 6 decimals repeated indefinitely.

So 1:87 works just fine and 1:87.1 is even closer. Personally, I have built a lot of structures using 1/8" = 1 foot or 1/96 full size just because they are a little undersize and emphasise the trains a tiny bit.

-trainman-

Thanks everyone for your help. The reason for the question was a purchase via Ebay of a Lionel engine, advertised in the HO Scale category. I know the old adage, buyer beware, and if I had looked closely, I would have noticed it was 1:120 scale not HO or 1:87.1. I should have also translated the word "decorative" to dummy or unpowered.

In the end I bought a real nice looking tin GP9 in Black Widow for my son, instead of for me. Just burns me that the seller was less than straighforward about what was being sold. Live and learn.

Could you please be a little more specific? Just kidding, great answer to the question, of course until somebody else asks it next week. Good job!

1:87.something that's almost 1 is the HO scale ratio for length. The next question of course is what is the HO scale ratio for time, like how fast should an HO scale clock be. Most people consider time a universal constant but by gut feel use anything from 6 to 12, with a lot using 10. But if you examine the speedup a motion picture camera must make when filming a model locomotive falling off a trastle to make it look real on the screen (avoiding wrecking real trains in a movie) it turns out that the time ratio is actually the square root of the scale ratio. For HO, this works out to 9.3327..., not too far off from the 10 many use. For O scale, square root of 48 is 6.928..., noit too far from the lower end of the range at 6 many use, and for N scale it's 12.649..., just a smidgen over the 12 which tends to be the upper limit. I think most people set their fast clocks for their convenience thinking there is no "real" scale factor for time, but there is.

Going beyond that, a number of people have further condensed scale miles based on the length ratio to "smiles" by aplying their fast clock ratio. This permits more realistic timetable operation relating fast clocks and distances along the route. Whewreas a straight scale mile would be about 60.62 feet, someone with a fast clock set at 10 would convert that into 6.062 feet of mainline to represent a compressed scale mile or "smile". If we use the correct HO time ratio of 9.33, then the actual distance of 6.497 feet is what represents a compressed scale mile which then relates to a real mile at a ratio of 1:812.683.

To distinguish between the 1:87.1 ratio and the 1:812.683 ratio, I call the latter "HO scale compression ratio". In order to get over the problem of scenes of different towns running into each other, in planning my layout I'm developing a variation table to switch between length and compression ratios to define representations of miles. My basic rule for laying out mains and towns is: any area which is viewable as a unit is to be defined by the actual length of the longest train anticipated to STOP there (Trains passing without stopping don't count). And this area is built to the 1:87.1 length scale ratio. Mainline lengths where trains normally do not stop are not "single view" areas, so can be built to the distance compression ratio of 1:812.683 (in terms of route length, not size of details like trees, buildings which are "single view" items in themselves and done at 1:87.1).

And the transition from one to the other is as smooth as possible a variation based of a default mathematical table I'm working on. Major yards and stations see longer trains stopping than intermediate stops, so the variation itself varies in accordance to the relativity of adjacent stops. I see a certain logic in this approach. although I won't even suggest it's everyone's cup of tea, but I describe it here merely as an example of how it could be done if one wanted to install a bit of logic into lengths of mainline vs size of towns on one's layout. For many it won't be important so just ignore this little exercise, but there may be some out there like me who find this approach a fascinating way to address this issue. And I'm not saying this is the only way, but it makes sense to me for my layout planning.

Sincerely,

Vytautas B. Radzivanas

Mr. Radzivanis' scholarship is evident. However, one must operate at scale speeds to avoid toy-like appearance in operation. Remember too, that human reaction time cannot be speeded up to meet scale time or speeds. Experimentation may show that a 6-1 speed-up of a clock (10 minutes becomes 1 scale hour) is best suited for your use. The late Whit Towers used that ratio for operations over more than 25 years; it satisfied his experienced crew.

No problem for me with what A. Wallace says about scale speed. Even within my "concept" the train itself is still of course at 1:87.1 length ratio wherever along the route it is (cars and locos don't suddenly condense as the train moves between towns, even though the route length does!) and any train is always within a trainlength "single view" of itself, so one's own natural sense of real time determines the scale speed as the scale length relative to real time seconds. So whether my concept is anyone else's cup of tea or not, the scale speed issue still has the same outcome. I just find that for my own interest the variation between length ratio and compression ratio, depending whether I'm in a town where relativity to train length is visually important, or in between where it is not, makes for a more credible timetable operation relative to scale mileage, provided that the equivalent compatible time ratio is used and trains proceed at actual scale speed, plus also making towns more visually compatible with trains likely to service them.

As for time ratios actualy used by modellers, like I did say in my original post, most modellers use whatever is most convienient for their own abilities to react etc, and to each their owm. I guess I was tongue-in-cheek responding to a previous posting which sort of asked for the next question after scale ratio, and that's all I needed! A lot of the intuitively popular range of time ratios are not far off the mark anyway. My posting just sought to share my approach with others in case others of like frame of mind might find it applicable to their own situations.

Wasn't my intention to appear "scholarly", just to share a concept I came up with in my layout planning process, but yes, I do like a bit of rigorous logic behind things, even in proto-freelancing (well, not everything!- I am human), and the challenges it poses in practice, but that's me! Whatever turns you on in this hobby.

Sincerely,

Vytautas B. Radzivanas

The EK sub. of the L&N also operates at 6:1.
Will there be operation on the AEMRC Al?