what's in a gauge

[abby]

Could some kindly knowledgeable person please illuminate me.
What is the correct gauge width for gauge1 ?
The G1MRA web-site states 45.0 mm +0-0.5 mm , and goes on to give the imperial measurements as 1.772 in +0-0.020 in.
45.0 mm is 1.800 in , which is of course +0.028 over the stated 1.772.
if the correct figure is 1.800 in then this equates to a scale of 1:31.388.
It goes without saying that I have been using a gauge of 1.772 for scaling my G1 black 5 which gives a scale factor of 1:31.88 , nearer to 1:32 but which figures are correct ?
I know these differences are small but for example on a driving wheel this is almost 1/16" on the diameter.

[havoc]

NEM 010 gives 45mm with a 1/32 scale for standard gauge.

[abby]

Which means what Havoc? does no-one else have any comments ?

[baggo]

Hi Abby,

How do you get 45mm to be 1.8". It's 1.77165"
Or have I misunderstood you?

John

[havoc]

Which means what Havoc?

Nothing more than it says: the european standard says it is 45mm. So I think that is what to use.

[abby]

LOL !John you hit the nail on the head , I feel like a right pratt now . As I rarely work in metric I think of 6" = 150mm , 1" =25mm so 45 mm =1.8". Thanks to both of you for putting me right.

[GWRdriver]

Abby,
In order to become Metric-functional I decided to memorize the value .03937" which is the Imperial equivalent of 1.0mm. Most people memorize 25.4, the number of mm/inch, but .03937 seemed more logical and easier to use to me. (To each his own . . .) Now any time I encounter a metric dimension which I need to convert I simply multiply the number of mm's by .03937 and I have inches, or conversely divide inches by .03937 to get mms.

[abby]

Thanks Harry, I have made a spread sheet with full size - 5" gauge size and G1 size , now I can enter any measurement I have , and all the empty boxes are filled in with imperial and metric sizes , so no excuse for mistakes any more.
One headache is that G1MRA standard wheel widths are actually wider than scaled down wheels , which means making adjustments to compensate but 3D modeling has found most of the problems for me before cutting metal.