How to Draw Gears in Inkscape

Define the color. Metallic is not a color, it is created by light reflection, so this article will use a multi-stop gradient (a gradient with more than two colors).

1. For gold it should contain a succession of lighter and darker shades of yellow, maybe also a bit of orange.
2. For bronze, yellow with a shade of green (copper oxidation is green),
3. For steel it should contains greys.
4. The chrome is also greys but more reflective (more contrast, from almost black to almost white), silver is less reflective grey and so on.

For a 3D look, add a drop shadow (duplicate, make it black, move a few pixels down and right, move it under the wheel, add a bit of blur and maybe decrease the opacity).

1. The gear does not stay on air, so add a background, and use the same golden gradient (if using this example). For the sake of simplicity, you can use a different one, maybe darker.

Add some more gears (all your golden gears).

1. Note the usefulness of the drop shadow, without it it would be hard to set apart the gear from the background, now they are distinct objects.

Apply the gradient to some wheels.

1. Here is one trick to get some of the wheels richer, not that plain and boring: add a groove - two smaller circles, aligned to the center of the gear, filled with the same grey gradient, the larger in an opposite direction, the smaller in the same direction as the rest of the wheel.

Put the steel gears in the device (just take care to not couple steel gears with gold gears: steel with steel and gold with gold).

1. Now for some axles: small circles, made from gold, steel, ruby or sapphire. Do not forget the drop shadow and consider a white highlight.

Add some screws holding the device. They are easy to do: create a steel circle, subtract a rectangle to create the groove, add a darker steel rectangle, the bottom of the groove, rotate the screw to a random angle (we don't want all the screws to have parallel grooves, that would be repeating and boring), fix the gradient and add a drop shadow. Maybe a hole: a larger circle colored with the same gradient as the background but with an opposed orientation. (I increased the zoom level in this step for a clearer illustration)

Give the gears an aged look. Now is the time to try about the completely different approach, making the gears look like old schematics, old writing on old paper, where we will work on the strokes.

'Set the stroke color and unset the fill color. This will get you something like this, with overlapping contours, we will have to get rid of.

Now make the drawing look rough. But it has a large number of nodes, it will take quite a while to edit them manually for the desired rough look, so, here is an automatic simplify operation (shown at an increased zoom level).

Now define a multi-stop gradient for the paper - light brown/yellow for old paper or dark blues if we want to go with a blueprint (I have not decided yet about the way to go).

1. A multi-stop gradient is needed for ink also (not shown), and it has to have fitting colors but good contrast with the paper (like browns for old paper and light blue for blueprints). Apply the gradients.

Then add some texture to the paper: draw a random blob with the freehand tool, will it in a color similar with the background (but slightly darker or lighter), unset the stroke, simplify if needed and blur a lot: