scale help ?

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bobby_hamill

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correct me if i am wrong

ratio of 1:3 = 1/3 scale ?

so to get prototype full size i would multiply 1:3 measurements by 3 ?

exp

3:1 scale measurement = 16.5

16.5 x 3 = 49.5 full size ?

Thanks to help clear the brain fart !
 
Last edited:
Let's see if this helps.

A somewhat popular scale is 1/48 scale. That is also called "quarter inch" scale, since a quarter inch (0.250") in our "real world" is equal to 1 scale foot. For example, in this scale, a six foot man would be an inch an an half (1.500") tall and a 48 foot scale object would be 1 foot long in our "real world".

The formula is this:
"scale length" = ( 1 / 48 ) * 12 * "length of object in real life expressed in decimal feet (e.g., 3 inches would be expressed as 0.25 [ 3 / 12 = 0.25 ] )"

For example, the Sidewinder air-to-air missile has a "real world" diameter of 5 inches. A 1 / 3 scale diameter would be calculated as follows.

Scale factor is equal to ( 1 / 3) * 12 and that is equal to 4. The decimal feet representation is 5 "real world" inches divided by 12, so 5 / 12 ~ 0.41667.

To get our scale diameter, we multiply our factor 4 to the decimal feet representation which is 0.41667. The result is that our 1/3 scale Sidewinder will have a scale diameter of 1.667 inches.

For this kind of work, I usually plug in these values to an Excel spreadsheet and let the machine do the math for me.

HTH.

Greg
 
Last edited:
The formula is this:
"scale length" = ( 1 / 48 ) * 12 * "length of object in real life expressed in decimal feet (e.g., 3 inches would be expressed as 0.25 [ 3 / 12 = 0.25 ] )"

For example, the Sidewinder air-to-air missile has a "real world" diameter of 5 inches. A 1 / 3 scale diameter would be calculated as follows.

Scale factor is equal to ( 1 / 3) * 12 and that is equal to 4. The decimal feet representation is 5 "real world" inches divided by 12, so 5 / 12 ~ 0.41667.
... multiply our factor 4 ... our 1/3 scale Sidewinder will have a scale diameter of 1.667 inches.

This example multiplies and then divides by 12. The transition to Feet is unnecessary.
5 * (1/3) = 5/3 = ~1.667
 
I also got inspired to put together a web-based tool to help scale a prototype rocket down to model dimensions. This not only calculates the scale factor, but also helps translate prototype dimensions to scale.
jcrocket.com/scale-spreadsheet.shtml

Maybe most nifty of all, you can enter the prototype dimensions in the spreadsheet and play around with different scale sizes by selecting standard tubes or entering a custom diameter.
 
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