OO scale is generally only used for models of British prototype. It is 1:76th scale or 4mm to the foot. The trains still run on the same 16.5 mm gauge track as HO models. OO models are slightly larger than HO, but the difference is not normally noticeable. Historically, the reason for this discrepancy appears to be that HO was first introduced in Germany in the 1920’s. Naturally, there was soon demand for similar sized models for the British market. Due to tighter clearances in tunnels, under bridges, in platforms etc., full size British trains are not as tall or wide as those of many other standard gauge railway systems. Therefore there was difficulty fitting the bulky motors of the time into British models made to HO scale. And so they were made slightly larger to overcome this problem. This also made them more visibly compatible, size-wise. Although the scale was larger than HO, the 16.5mm gauge was retained for compatibility.
Club meetings: Daylighters, Saturday
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