

Making Scale Models
Name: Melinda
Status: student
Grade: 912
Location: CA
Country: N/A
Date: 4/27/2005
Question:
I am doing a project on similarity for my geometry class.
I have to make a small scale replica of the roller coaster Superman the
Escape. I know I have to multiply all the measurements by like 1/205 to
make it around two feet tall, but how do I figure out the curve of the
ride and how wide to make it? Any help would be gratefully accepted!!
Replies:
This is tricky without seeing the plans you are working with  it could
be "trial and error". A relation that might prove useful is: The arc
length of a circular arc, call it "L", is given by: L = R x , where "R"
is the radius that forms the circular arc, and is the angle expressed
in radians. So if you can divide segments of the curved parts into a
series of circles  a French curve may be useful  then you will be able
to construct the curved parts by "n" successive circles: L1, L2, ..., Ln.
If you are working from a diagram, and you know (or can find someone who
knows) calculus, the length of the arc formed by a function, f(x) from x=a
to x=b is: Iab = (1 + [f '(x)]^2) dx, where Iab is the integral from 'a'
to 'b', and f ' is the derivative of f(x) with respect to x. If you don't
know f(x) you can resort to numerical integration using Simpson's rule, or
some other numerical device. A nonmathematical approach would be to use a
flexible spline. These are lengths of flexible metal or rubber that can be
bent/molded to the desired shape. You can then piece together the model
material to fit the spline. These splines can be found at hobby stores or
off the Internet if you "Google" search for suppliers that serve model
railroading and/or ship building hobbiests. I think one supplier is "Micro
Mart" or "Micro Market"  I forget their exact name. What you are trying
to do, model builders do all the time, so you may be able to get some
easier way to do what you want to do.
Vince Calder
Small scale models are more of an art form than a science, so please forgive
me if some of my answers seem "unscientific". Also, it is not quite clear to
me exactly what you have to work from, other than the height of the primary
drop.
For the width, I'll assume you have a width of the actual roller coaster.
Your best bet is typically to convert this number to a smaller unit of
measurement. As I recall, that roller coaster is about 20 feet wide.
Dividing that by 205 will yield a small an relatively unusable fraction.
Multiplying it by 12 will yield 240 inches wide, which can be divided by 205
to give about 1 11/64ths inches. If the actual ride is closer to 17 feet,
it would only need to be 1" wide for the model.
You have correctly judged the curve to be the hardest part to model. If you
have a picture of the side of it, you can scale the picture up or down as
necessary. If you have the approximate dimensions, you can build that
portion of the model separately, using a circular template to build the
structure around.
Ryan Belscamper
You are on the right track regarding scale.
The accepted practice uses rulers
marked off in given distances. An architectural
scale,is triangular shape, with 12 different scales.
The explanation in words gets complicated.
The scales are used to convert something
in feet to inches, either for drawings
or models. Something 12 feet becomes
at an 1/8 th inch equals a foot scale
one and a half inches.
Let us look at your model, you did not
mention the height but a guess, say 50 feet.
or 50 x 12 = 600 inches. If the model was
1 inch equals 1 inch, that is "full scale"
or a 50 foot high model.
But if 1/8 inch equals one foot, that is
50 X 1/8 "= 6.25 inches. More convenient
for drawings, or models.
The other common scale in use is an engineers scale.
Like the architectural it has 12 scales, but instead
of feet and inches, it is metric, or in 10 ths.
It is used more for larger distances, like trying
to make a drawing for something 200 foot long.
Back to your roller coaster. The physical construction
related to scale, may be issues. For example,
the rails. It could be their width is no more
than a line width, will you try for three dimensions,
or just opt out for drawing a line. Same goes for
the railroad ties , their spacing. Often, it is best
to think backwards, how big is the final product,
how will you get it to where you want to go. It very
well may be partial disassembly. It will be best
to make those plans from the beginning. Their is
a classic joke of building a boat in your garage,
then having to tear the garage down to get the boat out.
James Przewoznik
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Update: June 2012

