I know this will sound ignorant but I have seen 87 and 87.1 used as the divisor/multiplier for HO scale. I was under the impression HO scale is 1/87.
Set me straight before I get into a mess.
The official ratio is 1:87.1, as if that .1 makes much of a difference. You’ll find the rest of them here:
http://www.nmra.org/standards/sandrp/pdf/S-1.2%202009.07.pdf
On your HO layout, multiply stuff by 87 for full scale dimensions. Full scale dimensions, divide by 87. Very simple.
Rich
For those of us who want our HO rivets to be just a little bit closer to exact scale, a more accurate scale ratio is (drumroll please):
1/87.085887
Or, 1 inch = 87.085887 inches
Ed
Someone pointed out once that HO scale (3.5mm=1 foot) is perhaps the only example that mixes metric and inch systems. Except for perhaps that “other” O scale (7mm=1 foot).
1 inch on an HO model represents 87.1 inches on the prototype item; i.e., a scale represented as 1:87.1.
The scale is defined as 3.5mm to the foot. 87 or 87.1 is the close approximation depending on how much accuracy is desired.
Enjoy
Paul
87.1 instead of 87? oh shucks, no wonder nothing fits!!!
grizlump