be effective in both close combat and for throwing
at foes. An axe — with the center of mass firmly at
the end of the haft — would be an ideal way to
ensure a heavy load at the end of a long lever arm
for testing our superpowered servo.
The axe we had in mind was a double-bladed
battle weapon that was about three pounds and a
bit under two feet long — which normally made its
home as a wall display in a bedroom.
Despite their prevalence in popular culture, the
double-bladed twibill design was somewhat
uncommon, but the basic dimensions of the axe are
close to what a Viking might have used. Also, it’s
We envisioned a simple arm made from a flat
plate of aluminum attached to the ServoBlock hub.
One thing that we are very pleased to report is that
mounting things to the servo hub is super
easy. Not only do the technical drawings
on the ServoCity website include detailed
information about the positioning of the
mounting holes on the hub, but the holes
on the hub itself are through holes.
We opted to used our automatic
center punch to site our holes on one end
of the plate and drilled them out for 6-32
clearance holes. The plate fit on the hub
like a charm, and the next task was to
figure out how to attach the axe to the
We drilled out pairs of holes spaced a
couple of inches apart throughout the
length of the plate to accommodate zip
ties. We’re sure the Vikings would have
loved the effective simplicity of zip ties if
they had them. They certainly worked well
enough to attach the axe to the plate.
However, we couldn’t just have a 3 lb axe
hanging off the end of a servo — the servo needed
some sort of mount. We needed something stout so
that the entire assembly didn’t tip over.
We settled on a wide square tube of aluminum
that could accommodate the servo through the top
plate, while leaving plenty of room inside for devising
further mounting solutions — even something as
simple as some heavy weights to keep everything in
We center punched the corner holes of the
ServoBlock bottom plate, drilled them with the press,
and then traced the inside of the opening for the
servo while the frame was bolted in place. We drilled
holes in the corner of the traced rectangle and cut
out most of the opening with a coping saw.
Some brute force with some metal files finessed
the shape of the opening so that it could
SERVO 01.2018 57
OUR WEAPON OF CHOICE.
FABRICATING A LEVER ARM.
BUILDING A HOME FOR THE SERVO.