Lionel clock - Classic Toy Trains Magazine

Sorry, but Lionel's nominal O scale, and American O scale generally, is 1/48. The toy-train track gauge is Maerklin's number zero ("O"), 1 1/4 inches, which is too wide. American scale modelers fix this by using a narrower gauge.

On the European continent, they use an O scale of 1/45, which corresponds to the Maerklin O gauge of 32 millimeters (virtually the same as 1 1/4 inches). Thus ETS trains can run on Lionel track, even though they are built to a slightly larger scale. The British like an O gauge of 33 millimeters and a scale of 1/43.5, which they prefer to think of as 7 millimeters per foot. This is the O that HO is half of.

So HO is 1/87 and 16.5 millimeters. The British, ever eccentric, however prefer what they call OO, which uses a scale of 1/76 on HO-gauge track. American OO, once built by Lionel, uses the correct 3/4-inch-gauge track. American Flyer's S scale was 1/64, which ran on 1 1/4-inch three-rail track before the war and the correct 7/8-inch two-rail after.

"Standard" gauge was the result of Joshua Lionel Cowen's misunderstanding of Maerklin's number-two gauge, which he thought was 2 1/8 inches but which actually was 2 inches. Other American manufacturers were forced to call it "wide gauge". G gauge is Maerklin's number one, at 45 millimeters; but the scale is all over the place as a result of its being originally used to model narrow-gauge trains in its modern revival.

TT, at 1/120 and 12 millimeters is almost extinct.