Tinplate Attitude In HO Scale

 This is my current test setup - 

Just a circle of HO tinplate track. 

A very tight circle, in fact, about 22.5" (57cm) across the outer rails. This track came with those Nomura/Cragstan tin locomotives. I have enough for two complete loops, plus a couple of straight pieces. 

This track, like those diesels, are copied from Distler, a West German company. They, in turn, apparently copied their track from Fleischmann, which made a huge range of tinplate HO. I also have two Fleischmann turnouts, though I don't really have the room for them yet.

But, let's say that this track was O gauge instead of HO. That's an increase in diameter for this test track of 192%. That gives us circle of track 43" (109cm) or so across. 

That's a bit larger than O27, the most common O gauge train for years. decades even.

Entire railroad empires were made in O27.

Of course, there were caveats. 

First, the wheelbase on steam locomotives had to be short. This meant that most O27 locomotives were 0-4-0 or variants on the four coupled theme. There were a few six coupled designs, like Lionel's "Baby Hudson" or Marx's lone Pacific/Hudson, but they worked around this by having smaller diameter driving wheels. In fact, most O27 steam locomotives are sub-scale, with the exceptions being models of switchers.

Diesels are, of course, another story, but even then there are three that I can think of that are scale (American O scale, 1/48) that will go around O27 curves - the Lionel F3, the Marx #21 (F unit of sorts), and the Unique Arts #2000, which at 14" were the longest O27 diesels for a long time.

Yet modern  HO scale isn't like that.

Since the founding of the NMRA, the preferred minimum radius track has been 18" (46cm). Atlas and a few other companies did make 15" radius track, but as models became more scale like these tighter tracks had to be dropped. 

My Athearn F7 with the famous Hi F rubber band transmission will not handle anything less than a 15" radius apparently. The trucks won't even settle properly on this 11" radius. Another work in progress, a Marx F3 battery set unit also balks at this, though Marx made tight track for their "toy" sets.

The thing is, the two Nomura locomotives are the same size as the proper "scale" models and included this track in their sets (apparently the original Distler sets had a slightly larger radius, though I haven't confirmed this yet). 

What gives?

Compromises, folks. 

The Nomura diesels, and their Distler forebears, while scale size (well, closer to 1/90 instead of 1/87) are not scale-like. The wheelbases on the trucks are short, and they pivot closer to the center of the locomotive.  Also, little protuberances like steps are omitted. This is also how the larger scale achieved those tight turns.

What about a true equivalent of O27 in HO?

That would be about a 7" (17.5cm) radius. 

Can this be achieved?

HO gauge was originally OO gauge (confusing, but hear me out). When Bing introduced the gauge in the 1920's it was originally considered "table top". Tight radii were the norm.

I am going to look into this more.

Of course.