Build Your Own Combat Robot

200 Build Your Own Combat Robot
deformed (smashed), whereas others use a plastic insert that resists unscrewing. In
addition, special liquids such as Loctite can be applied to nuts to prevent them
from coming unscrewed at the wrong time.
The use of a torque wrench is common in automobile engine assembly and repair,
but is rarely needed to determine bolt tightness in robot construction. The
large, bending-bar type of torque wrench is generally in ranges too high for bolts
used in even the largest robots, but the click type of torque wrenches can be useful
in multibolt pattern tightening. A pattern of bolts with known tightness better distributes
loads on the structure. In most cases, making a habit of tightening all bolts
after assembly or repairs is more than sufficient for most designs. The use of a
torque wrench set at a value you’ve determined from experimentation helps.
Self-Tapping or Sheet Metal Screws
As mentioned earlier, a self-tapping screw looks a lot like a wood screw, but the
former is designed for metal and is the type of screw you see in common household
electronic equipment. The threads are coarse like a wood screw, but generally the
taper of the screw changes at the end, becoming narrow quickly. This allows the
person assembling the item to start the screw easily in the pilot hole; then it becomes
tighter as the screw cuts into the metal.
Many times, these screws have a hexagonal head for a nut driver and a slot for a
screwdriver. Longer versions are also tapered but have two indentations at the
bottom to aid in cutting into the metal like a drill (thus the self-tapping moniker).
These types of screws are not recommended for any type of combat robot
BattleBot that takes a lot of vibration, especially if you have to remove and insert
them several times.
Blind and Pop Rivets
Rivets seem like a strong fastening method, and they really are. They look great on
airplanes and tanks, and even on robots. When people finally decide to go the
“rivet route,” there are questions about just how to install rivets. Most builders finally
decide to use the blind, or pop rivet. But using these rivets is a major mistake,
especially in combat robots.
Rivets, just like welds, are pretty permanent, making it hard, if not impossible,
to change them in the field. If you have to remove a pop rivet, it has to be drilled
out—leaving bits of steel or aluminum shavings hiding in the corners of your robot’s
chassis, ready to sneak into your electronics at the wrong moment. Most pop
rivets found in typical hardware stores are made of aluminum; and although basically
“permanent,” they are about the weakest way to attach two pieces of metal.
They have poor shear strength, even the mild steel varieties.
When the rivet tool pulls on the pin to cause the rivet to deform and fill the hole,
the pin breaks in half after the operation is over. Even though a rivet holds two
pieces of metal together, the other piece of the metal pin can come loose during