Drones go mainstream

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By Steve Hargreaves @CNNMoneyTech January 9, 2013: 4:30 PM ET

After a crash, two of the arms on my 3DR Hex shifted slightly.  Enough that the props overlapped.  I didn't notice it for a while, but on a subsequent flight, they prop tips touched.  The hex didn't crash but the noise it made certainly got my attention.

My solution was to add more sonar mounting brackets to beef up the arm placements.  It also gave me more places to mount stuff.  (Copter is upside-down in the photo).

I seem to be removing my props often, and I worry that my hand holding the motor while I torque the collett on or off is not strong enough and I certainly don't want to use a steel tool like a Channel Lock.  So, I use a small plumbers strap wrench, pictured below.

This one is overkill because it is made for, well, plumbing.  Specifically for attaching chrome or polished stainless fixtures to pipe stubs without scratching them.  You can find cheaper, smaller and better strap wrenches at Grainger or Home Depot.  In fact, the cheaper the better - you shouldn't have to pay more than $10 for an adequate one.  The benefit of a strap wrench is that it applies pressure evenly all the way around the motor.

Here's a source of 3mm standoffs, like the ones under my GPS module.  They are available at any computer store that sells PC parts.  Fry's and Microcenter come to mind.

I accidentally discovered a perfectly fitting cover for my APM stack:

Yup - a cold-cuts box.

I am using a set of thumbscrews to hold my stack to the hexacopter frame , and the cold cuts plastic box fits over the thumbscrews perfectly.  The cover doesn't budge in a hard landing or while carrying the hexacopter.

And it looks cool in the dark.  (Not that I am planning night flying).

The first line in the flight manual should read: "You will crash".

The stock landing gear on my 3DR hexacopter are fine for experienced pilots, but while learning to fly, you will crash.  At the very least you will make hard landings.

I removed the surviving polycarbon landing gear and replaced them with much more forgiving parts.

I Ty-wrapped three 1/2-inch foam pipe insulators purchased at our local home improvement store.  Then I cut the top of three Easton 9-inch practice balls and shoved them into the "T".  While this photo doesn't show it, one of the Ty-Wraps goes through the ball to help keep it secure on the insulator "T".

Do not try to use the hard plastic Whiffle balls from Target or Wal Mart.  They are not flexible and difficult to work with. The Easton practice balls are pliable and can be cut with scissors.

Note also that I painted the outboard balls black and left the "forward" ball in its native fluorescent green.  This really helps with my orientation of the copter in flight.

These are temporary while I learn to fly proficiently.  The balls are in the direct down-wash of the propellers and have to be contributing to my yaw problem.  I suspect that this is because the training wheels are on the arms for all of the CCW props, and the CW props are not similarly compromised.

I plan to soon add a camera gimbal, and the balls are too low to the ground, so another solution has to be engineered.

The micro USB connector on the APM boards is extremely fragile and easily damaged.

My solution was to insert a Micro USB to Mini USB adapter to the copter:

This way, I just use any Mini USB while on the ground or bench, and leave the adapter cable on the copter.

Here's an example:

Female-Micro-Adapter-Cable

Do not try to use a similar appearing charger adapter.  They typically lack the data wires.

On the other hand, I do use a USB charger to power the APM without connecting the LiPo.  This lets me safely communicate with the APM over the 3DRadio.

Here is how I made a parallel battery adapter.  Mostly because I didn't want to wait for an order from Hong Kong, but also because the commercially available parallel adapter uses #14 AWG wire, which is probably too small for my Hexacopter.


I tried to make one with wires, but I was never happy with my soldering.
I had the two male connectors on my bench when I realized that wires aren't needed:


I laid a piece of #12 solid wire across the three connectors as a bus, and soldered them together.
Then used a piece of heat-shrink that I had on hand to hide the burn marks from the soldering iron.

It definitely worked well.  I got probably ten minutes out of today's combination of two cheap 2200's.



If you decide to make one yourself. I hesitate putting two high-power batteries in parallel without some kind of isolation.
Never store the batteries connected together.  If one cell drops even a tenth of a volt, you have a dead short to the other battery. Use an inexpensive alarm on both batteries so that if either battery goes below 9V, an alarm starts beeping.
gh my phone.

While building and balancing my hexacopter (and rebuilding it after learning crashes) I frequently move the radios. Note the white tabs under the radios.  These are 3M Command adhesive strips.  By using these removable strips I can simply pull the tab to remove the strip and relocate the radios as needed.

(Note also the copious amount of Velcro on other parts.)