MECHANICS FOR ROBOT
HANDS AND ARMS
by Tom Carroll
Our recent series of military actions in the Middle East have resulted in many of
our fighting men and women returning home with missing hands, arms, and legs.
Many of these marvels of mechanics, electronics and computer science are quite
complicated and literally cost an “arm and a leg,” certainly no pun intended. Sometimes
purely mechanical solutions seem to work best in many situations where one tends to
first look at an electro-mechanical solution. It is these mechanical solutions to robot
hand and arm designs that I’d like to discuss.
Imagine yourself in the field of battle. It’s four years into the new century and you’re 24 years old with seven years
of military experience behind you. In the heat of battle,
you’re struck in the arm, not by a mere bullet but by a
cannon round and shrapnel of broken bits of metal. You’re
bleeding severely and fellow soldiers help you aside and
tend to you before medical help comes to your rescue.
Later, to your shock, you are told that your hand has been
severed and your lower arm is so mangled that it must be
fighting is in
What can be
done to give you back your arm? One that can move? One
that can manipulate things? As you slowly heal, the first
prosthetic hand that you are given is nothing more than a
stiff mitt with mere claws for fingers. You ask for a better
hand and arm, and finally a mechanical prosthetic solution
is custom-made for you with articulated fingers that can
grasp and manipulate objects. Oh, the joys of modern
medical science and artisans that can create mechanical
miracles to assist wounded soldiers.
The Götz Iron Hand
Am I describing a soldier injured in one of the Middle
East wars of 2004? Actually, the year is 1504 and I am
speaking of Gottfried “Götz” Von Berlichingen (shown in
Figure 1) — a soldier of fortune or mercenary for hire.
Figure 2 shows the artificial hand and lower arm that he
was given. The term ‘prosthetic arm’ was not used back
then; it was commonly called the Götz Iron Hand and was
a mechanical masterpiece. Most
accounts of Götz’s injury speak of
a cannon blast severing his hand,
and shrapnel from his sword and
armor severely injuring his lower
arm. However, there are several
accounts that speak of an
altercation with a farm hand that
resulted in the lower arm being
cut off by a sword. Possibly Götz
FIGURE 2. The Götz iron hand.
76 SERVO 09.2011