I found myself having to help my nephew enlarge a drawing, printed on an A4 sheet, to transfer it onto a much larger one. The drawing was of Santa's reindeer (free from www.hiclipart.com). The final measurements should be 440mm by 1200mm, while my nephew's drawing only measures around 110mm by 300mm.

I know that whenever you need to get an enlarged reproduction of a drawing or image, the easiest way is to use one of the many PC graphics programs on the market to modify the original drawing and then print it using paper of the desired dimensions. Many printers also have this functionality in their software without having to process anything externally. But a printer capable of printing that size would be expensive and probably hard to find.

I think you can turn to one of the many companies that can print the enlarged drawing on such a large paper support. Or you could print all the parts of the drawing on many sheets and then glue them all together, like a puzzle.

However, there are at least two other methods for enlarging (or shrinking) a drawing: the projection lines method and the pantograph method. Let's see in detail what these two methods are.

Step 1: Enlarge With the Projection Lines Method

With this method you have to arrange the sheet with the model to be enlarged and the target sheet on which to draw it, with a common vertex. Then you measure the distance from that vertex to a vertex in the model (the red line in the figure). By multiplying this value by the desired factor and maintaining the same direction, the distance from the vertex where to place the new point (the blue line) is found. It's easy isn't it?

However, if you don't have much available space, instead of positioning the sheets with a common vertex in a corner, you can use the centre of both sheets and proceed in a similar way.

Step 2: Enlarge With the Pantograph Method

A pantograph is simply a device that facilitates copying drawings, images or figures by enlarging them (or even making them smaller), and is made up of metal, plastic or wooden bars connected together to form a parallelogram. Let's see how it works.

Let's consider the pantograph in the figure. It is made so that segment AB and AC are of the same length. Point E is located exactly halfway through segment AB, and segment EF is half the length of AB. Similarly point D is halfway of segment AC and segment DF is half of AC. The various segments are fixed together, or rather held together, at points A, D, E and F, with screws and washers but are still free to rotate. It can be seen that the distance BC is exactly double that of BF. So if you fix point B and move point F in any direction, you will see that point C will move similarly to F following its movements but with double distances.

Let's now look at modifying our pantograph. We position a new point H at 1/4 of the distance BA from point B and point G similarly at 1/4 of the distance AC from point A. We made a segment HK which is 1/4 of AB long and a second segment KG which is 3/4 of AB. We unscrew the segments EF and FD and screw on the two new segments HK and KG. In this case it can be noted that the distance BC is exactly four times that of BK. So if you fix point B and move point K in any direction, you will see that point C will move similarly to K following its movements but with quadruple distances.

Similarly to points E (1/2) and H (1/4), it is possible to position other points simply by placing them at a distance from B of 1/3 (M), 1/5 (L) and 1/6 (J) of segment AB. Using the different holes and maintaining the geometry of the pantograph, we will move point C relative to B by 2x, 3x, 4x, 5x and 6x the distance that point K will move from B.

Step 3:

Material

An aluminium bar two meters long, 15 mm wide and 2 mm thick
6 M5 wing nuts
6 M5 nuts
2 M4 screws with nuts
1 M3 nut
4 Carriage bolt 50mm M5
Some M3, M4 and M5 washers
An old drawing compass lead holder
A hacksaw
A drill with an M3, M4, M5 and M9 bits
A small round file

Step 4: How Big I Want My Pantograph?

As expressed before I want to build a pantograph that can zoom up to 6 times, and I would like to have the different holes placed at integer values distance. Since the segment AB must be divided into 2, 3, 4, 5 and 6 parts, I calculated the least common multiple of these values and obtained 60. In fact, if I divide 60 by these numbers I get 30, 20, 15, 12 and 10 which are actually integers. This combination is also repeated for multiples of 60.

I opted to build a 480mm pantograph (8 time 60), and using that dimension for arm AB (and AC of course), the hole locations will be 80, 96, 120, 160 and 240mm from point B. Eventually, we will have the dimensions as in the picture.

As you can see the first bar (AC) was cut shorter. This is because I preferred to make the pencil point removable to allow at least two different interchangeable pencil point versions as needed.

First of all I cut the bars according to the measurements indicated and then drilled them with a 5mm bit. I drilled two 4mm holes on the AC bar to fix the pencil point.

Step 5: How to Assemble the Tracing Point, the Pencil Point and the Pivoting Points

For the tracing point I sharpened a bolt. Be careful not to sharpen the tip too much to avoid tearing the underlying drawing material.

I had an old, unused drawing compass and took it apart to use the lead holder. Obviously I had to secure the support stem with an M4 bolt. This allows it to be screwed to the pantograph structure allowing the lead to be replaced very quickly.

The pivot points are made through the use of carriage bolts. This type of bolt has a completely smooth head and no screwdriver cuts. This allows the pivoting points to slide better on the surface of the underlying drawing material.

For tracing point and pivot points ensure that the wing nut is tight enough, but that the joint remains soft to allow the segments to rotate without loosening. For the pencil point this is not important, as it does not have to rotate.

Keep in mind that the tip of the pencil point is the only part of the pantograph that should be touched when transferring the drawing. Your eyes will be focused on the original, moving the tip of the tracing point along the lines to be copied, while the pads of your fingers will maintain light pressure on the tip of the pencil point as you make the copy.

Unfortunately the tip of the pencil was higher than the other tips and, in order not to increase the height of the articulation points too much which would have made the entire structure more unstable, I filled the difference in height by shaping a piece of aluminium bar.

Step 6: A Different Pencil Point

I made also a pen holder by bending the end of a scrap aluminium bar which I drilled with a 9mm bit. Then I made a square aluminium nut that I threaded M5 and lastly added a knob nut to tighten the pencil.

Using two small screws you can easily interchange between the two different types of pencil tips. The height of the entire pantograph can also be adjusted by acting on the nuts of the various pivot points.

To transfer the reindeer drawing to a larger sheet I used both enlargement methods: projection lines and pantograph. And it worked perfectly, much to my nephew's delight.

I hope you enjoyed my Instructable. Feel free to leave your comments and feedback in the comment section.