Servo Magazine ( August 2016 )
Getting from A to B
Those of you that are into training and physical fitness know that it’s not about getting from A to B, but how you get there that matters. If you’re training for a 10K road race, for example, it’s one thing to train running 10K at an easy pace and another to mix it up with sprints and other speed work.
It’s the same for robotics. If you want to get into drones, you can stop by RadioShack, plunk down $50, and get a pair of “combat” drones, complete with controllers. For your money, you get a few hours of play time until you crash the drones into each other or an unlucky tree. Not a bad thing, if your goal is to fly a quadcopter.
However, if you want to learn robotics principles, you should at least perform a post-mortem teardown of your downed quadcopters. Teardowns are a great way to discover what works and what doesn’t, and what techniques are worth borrowing. For example, in one quadcopter I picked up as a present, one motor simply tore off from the mount and started spinning wildly, tethered by the power leads. Turns out that the “mount” was nothing more than a dollop of hot glue. Sure, it was lightweight compared with a bolted-on mount, but it was also an accident waiting to happen.
A better way of getting from A to B — that is, to pick up robotics skills related to quadcopters — is to build your own. You can go all-out and create the frame with a 3D printer and get the parts from sources like SparkFun and Tower Hobbies. The upside of this approach is the ability to fabricate spare frame parts in an afternoon, or to create a completely new frame in a weekend.
The downside is durability — especially on the larger frames. I’ve found that the standard ABS plastic filament has only a fair durability to weight ratio. Larger frames are just heavier than the lightweight fiberglass reinforced plastic frames available commercially. However, for a 10 to 12 inch quadcopter, straight ABS plastic is fine.
Alternatively, it’s a simple matter to find a nice frame and electronic components online. Hobby King has an amazing assortment of affordable miniature hardware, electric motors, and the rest — as long as you can tolerate the shipping delay from Hong Kong. I’ve used their super-durable reinforced plastic frame components as well as their lightweight carbon fiber frames, all with great success. Make sure you order spares of everything — from nuts and bolts to motors and frame components. Shipping from Hobby King is a major component of the cost, so try to get everything you need in one order.
(Of course, you can follow along with our new series here in SERVO — The Multi-Rotor Hobbyist with John Leeman — as he takes us from beginning principles to a finished working quadcopter.)
So, let’s say you opt for the 3D printer approach to acquiring a drone. In getting from A to B, you’ll have to understand strength of materials, how and where to cut back on plastic on the frame, and how to source all the electronics, cables, and motors. Your creation will likely not leave the earth — much less fly — on your first few attempts.
In figuring out balance and center of gravity, you’ll likely try several designs and break a few props before you have a flight-worthy craft. Long after the quadcopter has run into its last tree, you’ll have retained the lessons of robotics that you can apply to your next project. So, next time you consider taking a shortcut from A to B, consider what you might be missing along the way. SV