Conversion factors

[timmy wheeler]

I'm pretty sure I've seen them here before....but I can't find now. Can somebody post the conversion factors to convert prototype measurements (12"=1') to 1.5" scale and 2.5" scale. Thanks, Timmy

[ccvstmr]

TW...

1.5" Scale refers to 1.5 model inches per foot of the actual item. 12 in/ft divided by 1.5 scale = 8. This is your conversion factor. 1.5" scale is the same as 1/8 scale. Example: if you have a 40 foot long freight car, your model will be 1/8 that length or 5 feet. Don't forget to keep the units the same. Works the other way too...40 feet x 1.5 in/foot = 60 inches or 5 feet.

2.5" Scale works similarly...12 in/ft divided by 2.5 scale = 4.8. This is your conversion factor. If you're trying to do a quick calc in your head...use 5 or 1/5. Example: if you have a 40 foot long freight car, the quick calc would tell you your model will be around 8 feet. More accurately, your model will be 1/4.8ths of the real thing or 8.33 feet. The other way...40 feet x 2.5 in/foot = 100 inches or 8.33 feet.

Hope that helps you. Carl B.

[timmy wheeler]

That does help, thank you. Are their decimal conversion factors for working in prototype inches? Example convert 9 prototype inches to ______ in 1.5" scale (or 2.5" scale). I'm trying to scale down freight car components (frame members) so they can be accurately reproduced on the model. Timmy

[David_T]

As already stated, converting feet is easy feet times 1.5 or 1.6"
Make up your own table for the inches, there are only 11 of them.
1" divided by 12" equals .0833. Take that time your scale. .0833 X 1.5 =.125" for 1 scale inch.
This can be further divided by 4 or 8 for scale 1/8's and 1/4's".
Busy work with a calculator. Make seveal copies, so you only have to do it once. I can never remember where I filed my orginals.

[sabin]

So many prototype dimensions are in feet and inches, I convert them all to inches and then divide by the conversion factor. Example: 3ft 6in= 36in + 6in=42in divided by 8= 5.25in. Hope this helps

[Greg_Lewis]

For little stuff in 1.5, one prototype inch equals 1/8 inch. So something that is 9 inches on the prototype is 9 8ths on the model. A real inch equals 8 inches on the model. No math needed there. An architect's scale will have a 1/8-inch scale on it.

[Bulbous]

For a nice quick calculator setup, use this one from SMEX.net.au:

http://www.smex.net.au/Index.php

Click on 'Reference' up the top, and scroll down to the 'Articles and Drawings' section, and at the bottom of the first column on the left is the link to 'Scale Dimensions Calculator'. Works with both metric and imperial measurements, and works in both directions if required.

For some work I was doing, I knocked up a quick Excel table with lookup formulas - made the conversion work from engineering drawings in inches and feet nice and fast for me (used to metric over here!). I will see if I can find it again.