Converting Scales to Metric

El Gato · Post by **El Gato** » Tue Apr 21, 2009 10:03 pm

From my drafting days, I know that a 1/72 scale is that a model that is 1' tall is 72' in real life. What happens is the only measurements you have of the real subject is in meters? Should I convert the measurements to English and go about it that way or is there an easier method (such as for established English scales the metric scale is X)?

Stu Pidasso · Post by **Stu Pidasso** » Tue Apr 21, 2009 10:04 pm

www.onlineconversion.com

El Gato · Post by **El Gato** » Tue Apr 21, 2009 10:12 pm

Thanks, bud! Sure beats doing the math...

Kylwell · Post by **Kylwell** » Wed Apr 22, 2009 11:16 am

Uhm... just divide the measurement by 72 if it's 1/72. Doesn't matter what the original measurement is so long as you keep it in the same units.

Chacal · Post by **Chacal** » Wed Apr 22, 2009 8:14 pm

1 m on the original = 13.8 mm on the model;

10 mm on the model = .72m on the original.

Original is 17.4 m in length, model will be 17.4 x 13.8 = 240.12 mm

Model part is 22.5 mm, original is 22.5 x 72 = 1620 mm or 1.62 m.

El Gato · Post by **El Gato** » Wed Apr 22, 2009 10:51 pm

Kylwell, Chacal, yeah, but that just means I have to do all of my measuring in metric and stuff.....................................................................

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Chacal · Post by **Chacal** » Thu Apr 30, 2009 7:43 am

Oh. From metric original to scaled imperial. Big problem is that calculators will give you decimal inch values. You got a decimal inch ruler? If so:

10 m = 5.467636 in.
1 m = 0.5467636 in.
10 cm = 0.0546764 in.
1 cm = 0.0054676 in.

For standard inch fractions, it takes a lot of math to work out the actual sizes.

Marco Scheloske · Post by **Marco Scheloske** » Thu Apr 30, 2009 8:09 am

Chacal wrote:Oh. From metric original to scaled imperial. Big problem is that calculators will give you decimal inch values. You got a decimal inch ruler? If so:

10 m = 5.467636 in.
1 m = 0.5467636 in.
10 cm = 0.0546764 in.
1 cm = 0.0054676 in.

What kind of numbers are those???

1 Inch = 2.54 cm

1 cm = 0.3937 inch

Kylwell · Post by **Kylwell** » Thu Apr 30, 2009 9:24 am

Marco Scheloske wrote:
Chacal wrote:Oh. From metric original to scaled imperial. Big problem is that calculators will give you decimal inch values. You got a decimal inch ruler? If so:

10 m = 5.467636 in.
1 m = 0.5467636 in.
10 cm = 0.0546764 in.
1 cm = 0.0054676 in.

What kind of numbers are those???

1 Inch = 2.54 cm

1 cm = 0.3937 inch

Metric original to scaled imperial... the scaled being the tricky part.

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Thu Apr 30, 2009 11:30 am

I don't seem to care what measurement the actual or model is made in.

If I have a 32meter boat, and I want it in 1/72nd scale, then,
32m ÷ 72 inches = 17.49"

Okay, cool,... a 17.5" long model.

Now, Lets say I have plans that are 7.375" long.
I need a factor for enlargment.

17.5 ÷ 7.375 = 2.37

So everything on my plan needs to be enlarged by 237%

Now, whether I measure the plans using an imperal ruler, or metric,
the factor of enlargement is still 237% or multiply all measurments by 2.37.

Sometimes I use inches, sometimes I use millimeters to take my
measurments. The deciding factor is typically which ruler lines
up closest to a direct measurement(falls on a line).

Each time I measure the plan all I have to do is
apply the factor, and measure out the part I need.
It is just a matter of using the same ruler that scaled
the plan, to measure out the part.

Marco Scheloske · Post by **Marco Scheloske** » Sat May 02, 2009 7:02 am

Kylwell wrote:
Marco Scheloske wrote:
Chacal wrote:Oh. From metric original to scaled imperial. Big problem is that calculators will give you decimal inch values. You got a decimal inch ruler? If so:

10 m = 5.467636 in.
1 m = 0.5467636 in.
10 cm = 0.0546764 in.
1 cm = 0.0054676 in.

What kind of numbers are those???

1 Inch = 2.54 cm

1 cm = 0.3937 inch
Metric original to scaled imperial... the scaled being the tricky part.

Why?

First do the math for metric to imperial, then divide through every scale you want (for example divide through 72 for 1:72 scale). Or calculate the scale first, then divide through 2.54 to get the imperial sizes. No difference.

Where is the problem?

naoto · Post by **naoto** » Sat May 02, 2009 11:44 am

Marco Scheloske wrote:
Kylwell wrote:
Marco Scheloske wrote: What kind of numbers are those???

1 Inch = 2.54 cm

1 cm = 0.3937 inch
Metric original to scaled imperial... the scaled being the tricky part.
Why?

First do the math for metric to imperial, then divide through every scale you want (for example divide through 72 for 1:72 scale). Or calculate the scale first, then divide through 2.54 to get the imperial sizes. No difference.

Where is the problem?

I think it's that "math phobia" thing...

I believe part of it has to do with not trying to understand the problem in the first place and getting confused. The typical problem I see is folks not breaking down the problems into simpler steps -- they try "keeping things simple" by solving the problem in one fell swoop (looking for some "magical" formula) and ending up with a confusing jumble of conversion factors and scaling factors.
step 1: Try to understand what you're trying to do. It would really help if you understand what is meant by scale.
step 2: Convert measurements into single set of units. Inches or centimetres it doesn't matter. If you're starting with feet and inches -- convert everything to inches rather than feet (and ending up with fractions).
step 3: Scale up or down the measurements. Usually means you multiply or divide by some value.
step 4: Convert scaled measurements to more convenient set of units (if necessary). Typically this would be where you're scaling something up (e.g. finding out the size of the real article based on measurements of model of specified scale).

One thing that needs to be made clear -- sometimes scales are given in terms of units to get a general idea of what you're dealing with:
1/72 -- 1" = 6'
1/32 -- 3/8" = 1'
1/48 -- 1/4" = 1'
1/96 -- 1/8" = 1'
but you shouldn't be using these when performing computations when scaling up/down -- mainly because they mix different units. They also tend to use fractions which often gets messy.

For the often-asked question of "if I've got a model of so-and-so scale, what would be the model in such-and-such scale be?" -- break it down into two different questions:
1. what's the size of the "real" article of the model in so-and-so scale
2. what's the size of the model in such-and-such scale of the "real" article'
each can can solved relatively easily. If you're observant, then you'll probably notice the answer staring you in the face.

Say for example you've got a 1/32 scale model and you want to find the dimensions of of a model in 1:144 scale. So let's break down the problem into the two separate questions:
Q1. what's the size of the "real" article if we've got a 1:32 model
A. A model in 1:32 scale is 1/32 the size of the "real" thing. Turn that statement around and we get: the "real" thing is 32 times the size of the model. So we take the measurement of the model and multiply by 32
Q2. what's the size of a 1:144 scale model of the object?
A. The model is 1/144 the size of the "real" thing. This means we take the measurement of the "real" thing and divide by 144.
... and if you're paying attention, you'll notice that the answer to the original question is now staring you in the face.

BTW... Just in case there are folks who haven't gotten a handle on what "percent" means -- it's referring to the number of hundreths -- basically X% means X/100.