kit was the weight and robustness of it. The square tube
itself is anodized 6061 T6 aluminum. The output shaft —
which comes assembled in the bearings even for the
“unassembled” gearbox version — is 1/2” diameter hollow
steel tube and is supported by a pair of ABEC- 5 double-shielded ball bearings.
Unlike many products from ServoCity, the gearboxes
come with a sheet of instructions in the box. The assembly
of the gearbox is so intuitive that step-by-step instructions
are not really necessary, but they give some helpful tips
The servo goes in first, so we removed the flimsy plastic
servo horn and inserted the servo into the square tube.
Short 6-32 screws fasten the servo to the tube, but getting
them in place can be a bit challenging. The holes in the
tube are tapped, and the tabs on the side of the servo
body sit on the inside of the tube, so the screws have to be
tightened from the inside of the tube. Getting the short
screws placed is a bit of a fiddly proposition, but with a
little patience and focus it can be done without too much
gnashing of teeth.
Once the servo is in (though not tightened down
completely to allow for adjustment), the small 12-tooth gear
is next. The small gear comes with the spindle pattern on
one side, so it slides onto the servo snugly and is secured
with the standard spindle screw. Before installing the large
84-tooth gear, the collar has to go on first. More 6-32
screws fasten the parts together, but unfortunately, this
isn’t a part you can hold off on tightening down to
promote fine adjustment.
When the gear is installed in the gearbox, the screw
heads are facing the square tube, as hidden away as a
walker bite on a character from The Walking Dead not
quite ready to give up the ghost. Just be sure that when
tightening the screws the heads don’t impinge on the hole
for the shaft.
Once the collar is on, the large gear is installed on the
shaft, and it’s a snug fit. Getting the teeth to mesh is the
only trick, and it can require a bit of pressing on the
servo to ensure that everything falls into place.
Once the gears mesh, everything can be tightened
down like the iron grip of a crocodile’s bite before it
spins into a death roll. We put together a second
gearbox and were ready to answer the immortal
question: Will it crush?
Getting in Gear
Crushers have a long and illustrious history in
combat robots. Robot Wars’ Razer might be the most
successful crusher ever, with over 40 fights and
numerous championships to its name. Beginning in 1998,
Razer has left a trail of destruction and pierced armor
with its hydraulic crusher. The Season 1 incarnation of
Chomp that appeared on ABC’s revived BattleBots™ was
equipped with perhaps the most powerful combat crusher
ever. However, the bot experienced greater success with a
hammer in Season 2. This year, Spectre is biting into the
SERVO 03.2018 55
BEAUTIFUL INVOLUTE TEETH.
THE SQUARE TUBE STYLE GEARBOX.
JUST ADD SERVOS.