HO vs OO

Dear all On Nov 27th I will be hosting an open house on Atlanta's Layout tour.

formatting link
I know the American railroad modelers are going to ask me why we run 4mm on HO track, and I need a concise answer, can anyone help? Thanks Rob

Reply to
Rob Kemp
Loading thread data ...

I always understood it was because the British manufacturers could not get the mechanisms to fit in a 3.5mm model, due to the smaller loading gauge of our prototype, so they enlarged the scale slightly but kept the same track for compatibility.

Andrew

Reply to
google

Thanks a lot, that's the story Ill use then! Rob

Reply to
Rob Kemp

It's rather more complicated than that, and whichever story you choose you will find advocates for the alternatives. You can offer either of two concise alternatives:

  1. A historical accident back in the last century.

  1. We don't think its worth the effort to build correct gauge track and change the wheels.

Keith

Reply to
Keith

Because we can?

-- Steve

Reply to
Steve

Actually, the 4mm scale on 16.5mm gauge tyrack is mostly due to an error on the part of Henry Greenly, a pioneer in railway modelling. His book, Model Railways (Cassell, London, 1924) had a great influence on the standardisation of scales. I have a copy - it's an excellent book on all counts (especially track and signalling), except the issue of OO gauge/scale.

Greenly's summary of scales and gauges "No.00 Gauge "Table" Railways. -- This standard gauge has been recently introduced by the writer at the instance of Mr. J. W Basset-Lowke to provide for thow who are limited in space to that of an ordinary dining room rable. Clockwork and electric locomotives are supplied. The actual gauge is 16mm (5/8 in) and the scale is 4mm to the foot..."

Note that Greenly calls this a "standard gauge", and modestly refers to himself as the inventro of the gauge/scale. Why did he not sepcify a

3/4" gauge, which would have been almost exact? From a manufacturing point of view, there would have been little difference in cost, even in an age when material costs were relatively higher compared to labour and machinery than they are today. Bassett-Lowke was the premier maker of model as opposed to toy trains in the first half of the last century: their live steam offerings in the larger scales are justly famous not only for their scale fidelity but also for their technical perfection. Greenly designed many of these locos. Like many people who pioneer a technology and come to dominate the field, he wasn't easily, um, persuaded that he had made an error, and those who looked to hima sa an expert were unlikely to criticise his errors, let alone try to correct them.

Bassett-Lowke also imported a good deal of material from Germany, and the German toymakers of course made the product to the specs supplied by Bassett-Lowke, but to avoid retooling their track making machines, they supplied 16.5mm gauge instead of 5/8 in gauge - a slight difference, and oine within henry's rather loose standrads of precision. When Hornby decided to build toy and model trains in competition with Bassett-Lowke, he pretty well had to follow their lead, as did all other toy/model train makers. So the hybrid OO scale - HO gauge combination endured and became entrenched. And although it would be child's play to make true HO scale British trains these days, the market just won't support that.

The reasons for Greenly's choice of scale and gauge will IMO remain a mystery, but I think it was a simple error, of the kind that once made escapes the notice of the perpetrator until it is too late to rectify it.

Reply to
Wolf Kirchmeir

Better not mention the war then :-)

Reply to
Rob Kemp

Wolf,

Probably because he had extreme difficulty fitting outside motion to model locos that didn't make the cylinders look like Mickey mouse's ears on the sides of locos. Considering that designers of full size British locos had problems squeezing all the outside motion and cylinders into the loading gauge, Henry Greenly would have had even greater problems with over width wheels and the relatively coarser manufacturing tolerances of the motion in 4mm scale. So the answer was obvious - move the wheels in on their axles and leave the cylinders in pretty much the correct position. The same argument holds for Greenly's 7mm scale - our 0 Scale - but in the larger scale, the relative narrowing of the gauge is not so much, probably because he could work to slightly tighter tolerances in the larger scale.

BTW, I think I can remember using 5/8" as the gauge for 00. My first train sets were Trix Twin and I am almost sure that they referred to the gauge as 5/8" - possibly a hangover from associations with Greenly/B-L before WW2. My first train set was given to me at the end of the war and my father had to make the track himself and I'm sure he used 5/8" gauge. The loco was a pre-war Trix 0-4-0 British outline tank which he modified to a 4-4-0 (very Clydeside where the NB and Caley had used 4-4-0 passenger tanks), and the coaches were scratchbuilt from aluminium sheet offcuts scrounged from the Blackburn factory where he worked - they had just stopped making Sunderland flying boats and started making pre-fabs. :-)

Jim.

Reply to
Jim Guthrie

It's to help disguise the pastry cutter flanges which were necessary in the early days when running on H0 scale track. They are not so noticeable on a

4mm/ft model.

(kim)

Reply to
kim

It's to help disguise the pastry cutter flanges which were necessary in the early days when running on H0 scale track. They are not so noticeable on a

4mm/ft model.

(kim)

Reply to
kim

Interesting observation, and lovely anecdote. I'm keeping your post for my History of Model Railways files. Thanks!

Reply to
Wolf Kirchmeir

In message , Keith writes

Actually, you might tell your audience that there are quite a number of people who think it _is_ worth the effort, hence EM gauge (18 mm, and later 18.2 mm) and EEM gauge (18.8 mm) which later became P4 (18.83 mm). That should confuse all of those who are not paying proper attention.

Reply to
Jane Sullivan

Perhaps he was distracted by the rable in the dining room. I know that when my mob of a family come round for dinner, I can hardly think straight.

Cheers, Steve

Reply to
Steve W

God Help Us if Ettore had ever been responsible for model railway designs, they'd have been far too complicated for the average person. Ettore was not one for simple solutions. Regards, Bill.

Reply to
William Pearce

Didn't he get the RHDR wrong, with the locos to one scale and the track to another?

Reply to
Jane Sullivan

"Now I realise that, technically speaking, that's only one flaw but I thought it was such a big one it was worth mentioning twice. " [Kryten, Red Dwarf Season 5, Episode 1 "Holoship"]

Reply to
kim

But he did it with style. In fact he had an incomplete Midland Compound in something like 12inch gauge, presumably a simple was not good enough for him:)

Ken.

Reply to
Ken Parkes

New one on me, but southern England is a long way from my interests.

Ken.

Reply to
Ken Parkes

Quite so, Greenly did it on purpose, not by mistake, it was not an error to him. Keith

Reply to
Keith

By the time that the Gresley Pacifics were designed, cylinders were right out to the maximum of the loading gauge. That set the centerline of the cylinders which in turn restricted the width of the coupling and connecting rod bearings. Bearing sizes etc etc don't necessarily scale particularly well so the extra width afforded by a narrower gauge would be particularly useful in designing a reliable and reasonably low maintainance working locomotive. In the OO vs HO debate, cylinder centers have to be far enough outboard of the wheel face to allow for coupling and connecting rods and their associated crankpin. As we can't use a headless pin there is a finite width required, beyond the OO wheel faces which must be almost as wide (scale) as the prototype wheels are, given the extra width of OO wheels over scale width wheels.

Regards, Greg.P.

Reply to
Greg Procter

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.