The first two criteria are pretty straightforward. The repair-ability is a bit more important than first meets the eye.
You see, ANY glitch, results in a snap-roll into the ground ( or worse ). You know that nice little motor controller
feature that pulses the power as the battery gets low? Snap roll ( into the ground ). 500 milliseconds of fail-safe
operation? Snap roll (into the ground ) Some data stream in the microprocessor decides to be a trickle-stream?
Snap roll ( into the ground ) Yes, rule # 3 is pretty important, and you can see how it rolls back into rule # 1.
On a multicopter the “arms” connect the motors to the main pod, or body. Thes arms have been found to be the
one point that should be designed to be sacrificial. Just like a Formula 1 car’s suspension is designed to break-away
in a crash, so too should the multicopter’s arms fail and “save” the motors and main pod. I figure a dollar’s worth
of 3/8″ aluminum tube should work just about right.
The main pod is just made of 1/8″ birch plywood. I have to say here that a 6″ X 9″ piece of warped plywood for
6 bucks at the local hobby shops is “over the top” uh, excessive mark-up. I bought a 5′ X 5′ piece of beautiful,
STRAIGHT, three ply,1/8″ birch plywood for fifteen bucks at Frost Hardwood and Lumber on Miramar Rd.
Just so you know.
So much for talk, here are some pictures of my version of a Tricopter airframe.
Picture 1 shows the servo controlled tail motor assemble. It is just a helicopter rotor grip bolted into a piece of aluminum tubing
that has a plywood servo mount epoxied to as well. Pretty simple. Simple is good (rules 1,2,3)
All three motor-nacelles ready for mounting. They are a telescopic fit over the arms and are simply taped
onto the arms. This works quite well , actually ( and fulfills rules 1,2,3 )
The airframe parts ready for assembly. Low parts count fulfills rules 1 and 2.
The arms and nacelles assembled. (Pic missing)
The assembled airframe. Simple, clean and fully functional.
So that’s it for this month’s installment of………… The Next Big Thing .
See you next month.
Rocket (Bob) Kreutzer
