Re: Conversion percentages.

Schuyler Larrabee

Rod's point here is a good one. I just emailed Denny off-line that the factor is 0.7348, which is
64/87.1. Some copiers will do this level of precision, but even those are not COMPLETELY reliable.
Using the known length of line to get a reduced length so one can check the machine's capabilities
is a very good idea. One more thing, a machine I had in my office would be different reductions in
the two principal directions. 85% LtoR would be about 83% Top to bottom. That machine got
replaced. But putting lines in both directions will reveal this.

If it's critical, you should get this done photographically. It's increasingly hard to find shops
that can do this, but not impossible.


-----Original Message-----
From: [] On
Behalf Of Rod Miller
Sent: Wednesday, January 18, 2006 9:12 PM
Subject: [STMFC] Re: Conversion percentages.

Hi Denny,

The method Jerry White showed me was to draw/tape a line that
was a specific length in the scale of the image to be
E.g., an O scale (1:48) drawing would have a line, say, 2.5
inches long which represents e.g. 10 feet.

Start with an approximate enlargement/reduction setting and
make a copy. Measure the length of the line on the copy and
determine its scale length for the scale you want. When the
line is 10 e.g. feet long in the scale you want, you have the
correct reduction/enlargement.

E.g., suppose you want to reduce an O scale (1/4 inch = 1
foot) drawing to S scale (3/16 inch = one foot, or 1/64 inch
= 1 inch).

A 10 foot long line in O scale is 10 1/4s or 2.5 inches long.

A 10 foot long line in S scale is 120 1/64s or 1 7/8 or 1.875.

When your line on the copy is 1.875 inches long the copy is
accurate for S scale.

IMHO that is more accurate than calculating a reduction/
enlargement percentage.


Rod Miller

Message: 18
Date: Wed, 18 Jan 2006 13:51:26 -0800
From: Denny Anspach <>
Subject: Re: Conversion percentages.

Off hand, does anyone know what percent rule of thumb
reduction (e.g.
as would be set on a copying machine) to accurately reduce S-gauge
plans to HO (1:76 ---->1/87.1)?


Denny S. Anspach, MD

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