Tuesday, August 14, 2018

Well, that didn't work out quite as planned!

Well, that didn't work out quite as planned!  As I was carrying our drone to the car last night, I snagged one of the propeller mounts on a stair rail – and just like that, I was out of (drone) action.  I had spare parts (came with the package I bought), so I thought it would be a quick repair.  However, in no time at all I'd managed to strip out the T8 Torx-head bolts that held the mount on.  Dang it!

I put that aside and we went for our wildlife drive anyway.  We saw a bald eagle (likely the same one we've been seeing, as it was in the same place near the Hyrum Power dam), lots and lots of fawns (just now starting to lose their spots), a great viewing of a pair of Sandhill Cranes, and the best viewing of a flock of cedar waxwings that we've ever had.  Great!

Once I'd stripped the screws on the propeller mount, things got much trickier.  First I had to cut away the already broken propeller mount, which is made of carbon-fiber reinforced resin.  That took but a moment.  Then I drilled out the two screw heads – tedious, but not difficult.  However, in the process some steel chips worked their way into the motor, attracted by the powerful permanent magnets in them.  After that happened, the motor no longer turned freely.  Gulp.

I kept going, though, figuring I'd deal with the steel chips later.  At this point I had roughly 3/16" of bolt shaft exposed.  I got a pair of Vise-grips on that, and turned – and nothing.  No movement at all!  WTF?  Some research on the web reveals that DJI (the drone manufacturer) routinely uses red Loctite on these bolts (possibly others, too).  That stuff is like epoxy glue – no way are you going to turn that bolt, unless you heat it.  Now that I had the plastic out of the way, heating was a possibility.  I broke out my big soldering iron and heated one of the shafts up until the motor started getting uncomfortably warm.  Applied Vise-grips again, and ... motion!  I had to repeat the heat/Vise-grips cycle a few times, and this was tedious as heck, as I could only turn the bolt about 60° at a time because of other parts in the way.  Eventually, though, success!  Both the mounting bolts were out of the way.

Then I tried turning the motor by hand again.  There was scraping and grinding as I did so, from those darned steel chips that made it into the motor.  I put the new propeller mount in place, then I decided to try lighting off the drone to see if I could work the chips out by just running it for a while.  A few minutes later, I had the motor spinning – and making a gosh-awful racket.  But after about 30 seconds of this, it suddenly stopped racketing.  After that, the motor spun freely and all appears to be well.  Phew!

I have some foam rubber “booties” designed to protect those parts, and they will be installed from now on.  I don't want to go through that again!

No comments:

Post a Comment