BUILD REP RT:
Rollin’ With the Punches
● by Andrea Suarez
Win or lose, the best combat robots always put on a show.
That means no drive system failures
unless your robot is in pieces. Bigger
bots can achieve this through
redundancy: four motors, four speed
controllers, etc. However, a single
motor-controller-wheel combo can
be more than 15% of your insect
The first revision of
WhipperSnapper — my one pound
robot with a modular (horizontal or
vertical) five inch spinning disk —
had been cursed with persistent
gearmotor and wheel failures. In
planning for a redesign, choosing
the right components became
essential. I switched from the
Finger Tech Gold Spark to the new
Silver Spark gearmotors with larger
pitch gears for vastly improved
reliability (still under $25).
The Finger Tech Lite hubs are
much lighter than other aluminum
hubs, and they provide two set screws
on each hub. Even other lowest
durometer wheels transferred most
of the shock to the gearbox and
provided little forgiveness during
impacts, so I decided to use the much
softer foam Lite Flite wheels instead.
This new drive combo has
survived its first two full events ( 13
matches) with no drive system failures,
and saved me enough weight for a
much needed weapon upgrade!
The real test to this new setup,
however, came in a
Mecha-Mayhem match-up against Low Blow
from Pretzel Robotics.
Thirty seconds into the
match, Low Blow’s giant
under-cutter got a big hit
wheel, cracking the gray
snap-on plastic and
pulling off the foam. In a
turn of fate,
got wedged between Low Blow’s
spinning bar and the bottom of his
frame, stalling the weapon and
deflecting his bar far enough to
raise both of his wheels off the
My 22.2:1 Silver Sparks survived
the hit and the Finger Tech Lite hub
remained secured to the motor
shaft. The damage was easy to
repair — a dab of CA glue to hold
the foam wheel onto the remaining
Lite Flite plastic and
Lite Flite wheels after Mecha-Mayhem
2011. No Silver Spark gearbox or motor
failures despite an intense event!
WhipperSnapper was back in action.
Having the Lite Flite wheel fail
before the Finger Tech hub insures
that your robot won’t lose its
wheels unless they are destroyed,
saving the embarrassment of
seeing your wheel roll away as the
announcer starts the countdown.
These easy drive changes shot
WhipperSnapper’s record from
3-2 to 14-4 in just two events,
winning 2nd at GCRS 8 and 1st
at Mecha-Mayhem 2011. SV
WhipperSnapper at competition
after drive system redesign.
WhipperSnapper's Lite Flite wheel
jams Low Blow's blade during their
match at Mecha-Mayhem 2011.
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