Pusher Props
Pusher props earned the name because they were originally
designed for airplanes with rear-mounted motors (like the
Wright brothers’ first airplane) that would push the plane
through the air, rather than pull it from the front. This is very
similar to propulsion in a boat.
Size and Pitch
Propellers have a hub in the center that mounts directly to the
motor, and two (sometimes more) blades that extend out from
the hub. The size is pretty simple to define: it’s measured in
inches from tip to tip on a two-blade prop. For the Little Dipper,
props in the 5- to 6-inch range are ideal, but some drones can
use props up to 29 inches or more!
Pitch is a little more complicated to explain. Most people
wrongly assume that it is a measurement of degrees that the
prop is pointed up from a flat plane. In reality, the pitch is a
measurement of how far the propeller would move forward if it
were passing through a solid matter with one revolution. Think
of the threads on a wood screw. A fine thread will move a shorter
distance with one revolution compared to a coarse thread.
Props work in the exact same way. A higher-pitched prop on the
front of a plane, or even the back of a boat (in theory) would pro-
pel the craft further with one revolution than a lower-pitched
prop. It’s also harder to turn, just like that coarse screw!
It is outside of the scope of this book to discuss this in much
more detail, but we will mention that the pitch of a propeller is
rarely met in real life (see
). Something called prop slip
always creates a difference between the distance the vehicle
should have moved and how far it actually moved. If you are
interested in that, a ton of websites have a wealth of knowledge
on the topic.
42 Make: Getting Started with Drones
Summary of Contents for Belinda Kilby
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