Shive Wave Machine
standing waves - traveling waves - transverse waves
What it shows:
Mechanical demonstration of transverse standing or traveling waves using the Shive wave machine.
How it works:
The Shive wave machine consists of a series of horizontal metal rods 1.25 cm apart coupled by a torsion wire.
The unit comes in three parts, one having 46cm long rods, one 23cm rods and an 'impedance matching'
section with intermediate lengths. The 23cm rod section has a wave propagation velocity three times that
of the 46cm section. A pulse can be sent down the machine by displacing the end rods (doing this by hand,
pull down on more than one rod as the connections are delicate and do break). The far end can be clamped
for rigid termination to show reflections, or damped using a dashpot which absorbs the energy and prevents reflections.
Setting it up:
The wave machine is mounted on its own foldable base. The tips of the rods on our machine are coated with
fluorescent paint; with the hall lights down and a 4ft black light placed in front and below the rod level, only
the tips can are visible, making the wave motion beautifully clear. The dashpot
1
is attached to the last rod in the line (how far down the length of the rod for best damping takes a bit of
experimenting, although when found it can be marked with a piece of tape). The driver attaches by an
alligator clip to a taped loop over the first rod.
Comments:
The Shive wave machine was developed at Bell Labs by John Shive. His handbook (see reference) is a
good accompaniment. Our Shive wave machine is from Pasco Scientific (SE-9600); Cenco have a similar machine
(32694). The 46cm section is usually used alone. Rating ****
The wave machine can be driven with a 12V DC motor
2
controlled by a multi-turn pot, the driving cam illustrated in figure 1 attaches by alligator clip to a taped loop over the first rod.
Reference:
J. N. Shive: Similarities in wave behavior Bell Telephone Laboratories (1973)
1
Adjustable air dashpot by Airpot Corp. Norwalk Conn.
2
12V DC motor CYQM42810-31-5 Barber Colman, Rockford, Ill.