Motor: rotating blades in opposite directions?

I'm asking myself how can I achieve the next solution:
I've a plastic case with the shape like a box, where I've 2 blades: one in the front and the second in the other. My question is how can I rotate the disks in the different direction: one clockwise and the other counter-clockwise.
What mechanical mechanism can I employ to accomplish this?

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Do you have any ideas that you've been considering?

the first and the only idea that I've though about was to use 2 small dc motors each one moving 1 blade at time.
But of course, it would require 2 times more power because I would use 2 motors. Instead, I want to use only 1 motor. That is the main question.. How?

There are many options. Easiest, if the two disks' axles don't have to be collinear, is just to put on on the motor shaft (or shaft coupled with the motor) and put a 1:1 gear or pulley to another shaft for the other disk.

If they do have to be collinear, then off the top of my head I forsee three shafts. One drive shaft from the motor on which there are two pulley wheels. Then each disk axle has it's own shaft and pulley. On one set of pulleys between drive shaft and disk axle you have a normal pulley arrangement, on the other you have a figure eight belt setup.

Or you could use gearing instead of pulleys. Gearing get's more complicated as you'll need another gear+shaft to get one of them to spin the other way, which makes fitting everything in a tight spot a little interesting.

256bits
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Or a bevel gear from the motor running two bevel gears on two colinear shafts.

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oh...haha. Good point.

Bevel gears are the most practice one in the solution I was looking for.