C14 picked out a chassis (frame) today, a 480mm1, S500 Glass Fiber Quadcopter Frame for about $22. He picked this particular chassis because it has landing gear with enough ground clearance to accommodate a cellphone and cellphone cradle. He plans to use one cellphone to capture flight video, and a second cellphone to watch it live via Facetime.
We decided to start with the chassis and work backwards. Picking the chassis first imposes certain constraints on the rest of the design2 and seemed to make selecting the other components a little easier. Some drone websites start the design process elsewhere, but I'm not sure it matters that much. Ultimately, the important thing is to ensure all that the components will work together. To accomplish that, carefully cross-check the component specification (spec) sheets to make sure everything matches. For example, check that the mounting holes on the motor match the holes in the chassis (or be able to drill new ones), and that the electrical parameters (voltage and current) of the motors match the specs of your ESCs (electronic speed controllers) and battery.
Next we'll select the motors, which will be the brushless outrunner type3 as discussed here. But before we buy, we'll make sure the motor mounting holes match the mating holes on the chassis, which are specified as 16~19~25mm. We'll also perform a few calculations as described here to verify that our motors have enough thrust to handle the weight of our drone, plus an extra amount for contingencies.
1The longest distance between motors--488mm in our case--is one way of classifying drones.
2Two constraints are the type of motor used (due to the chassis mounting method), and the propeller size.
3We picked this motor because it's a popular one used for drones and it mounts onto our chassis.
2Two constraints are the type of motor used (due to the chassis mounting method), and the propeller size.
3We picked this motor because it's a popular one used for drones and it mounts onto our chassis.