9

LENS

sure what happened, but I suspect one of
the relays was mistakenly hooked up to the
NC terminal, and there may have been an
issue with the program as well. Whatever
it was, I took several steps to shore up my
electronics before the next attempt.

ROCKET LAUNCHER, TAKE TWO!
With my self-imposed deadline for publishing
a video about my Rocket Beest (find it here:
hsmag.cc/UStqJp) approaching, I redid the
launching system with
several improvements:

• Code changed so
  that the Arduino
  output pin would
  not even be set
  as an output until
  the fire button
  was activated.
  Normally, you
  declare your ‘pinMode’ in the setup
  section, but here I waited until the
  fire routine was called, to avoid any
  potential issue with it momentarily
  flickering to the wrong state. Firing
  time was increased to three seconds,
  to ensure fuse ignition.


• Made sure that each positive
  rocket lead was hooked into the
  NO terminal. Things got a little
  confusing between the relay being
  active low and switching to a NO
  output terminal, but after careful
  consideration, everything was
  properly connected.


• Instead of powering the Nitinol launch
  wire from the Rocket Beest’s main
  power supply, I added a disposable
  9 V battery to apply voltage separately.
  This was meant to avert potential
  power issues with the rest of the
  Rocket Beest.


• Lever nuts substituted for alligator
  clips. These devices are used in
  place of traditional wire nuts, and
  hold each wire individually with a
  lever mechanism. What I purchased
  was rated for a range of wire sized

between 28 and 12 American Wire

Guage (AWG), and it held my Nitinol

wire, even though it was actually

smaller at 30 AWG.

• Deburred the end of the launcher
  tubes. Cutting had left a rather
  pronounced internal edge, which on
  the first test had caught the rocket
  and caused it to go awry during the
  launch sequence.

With all that done, I again carried the

contraption into the back yard and, even

more gingerly, connected the main power

wires. No initial flames this time – a good

sign – and after connecting to the system’s

Bluetooth module, I hit the launch button on

my Bluetooth-connected smartphone. This

time the Nitinol wire did heat up, followed by

the fizzling and smoke of the rocket’s fuse,

and finally the satisfying ‘woosh’ of success!

The second rocket was also fired

successfully, and coincidentally (?) I could

hear fire engines in the background after

this test. While it turns out my name isn’t

Norman, and Fireman Sam wasn’t coming

to save me from peril, the question of

what my neighbours thought of this activity

wasn’t too far out of mind.

Making the Rocket Beest took

somewhere around a month by itself, and

years if you include its predecessors. Even

with all this effort,

it was a lot of fun to

construct, and I’m

extremely happy with

the results.

While I’ve told

myself and others

many a time that I

would move on to

other projects – and do

make a wide variety of

gadgets both for fun as part of my job – the

Strandbeest concept seems to be quite the

recurring theme.

This, however, is probably the last one I’ll

build... until another ‘must-do’ walker idea

demands to be constructed, of course!

Below

3... 2... 1... Blast-off!

I’m not suggesting that you try

this project, and can’t guarantee

its safety generally