View single post by Robert Comerford
 Posted: Tue Aug 18th, 2015 01:30 am
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Robert Comerford


Joined: Thu Feb 14th, 2013
Location: Glen Innes, Australia
Posts: 588
O gauge as invented by the Germans was to 1:45.
It is not hard to see how such anomalies as 7mm came about. To cater for their main market at the time, the cashed up British middle and upper classes, an easy conversion was needed for a metricated work force and plans arriving in feet and inches. Hence the mm to the foot rule.
With metric measuring tools like hens teeth in the USA then 1/4" to the foot became a convenient measurement when they got into O gauge.
What surprised me was to discover recently that the French used 7mm as I had always taken all of continental Europe to use the original correct scale.
I can remember articles about some American modellers using 17/64" as the 1:45 conversion ratio to make their models more closely aligned to the track gauge. I can't think of a more awkward measurement to work with so I guess they made their own scale rules or perhaps converted everything to inches and divided by 45 on a slide rule.

Bob Comerford

again,good luck.

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