Ergonomics - Atlas Copco

EXTERNAL LOAD
For evaluation purposes, it is assumed that
the tool is being used for riveting in the
aircraft industry. The tool is mainly used on
vertical surfaces and the height is adjusted
to allow a comfortable posture for pushing
the tool horizontally. The tool is used by a
male operator. The damping system starts
attenuating vibration at a feed force of
50 N. A feed force of up to 220 N can then be
applied before bottoming occurs. The opera-
tor applies sufficient feed force to prevent
the head of the rivet from jumping out of the
countersinking and spoiling the panel.
The bucking bar has built-in vibration
isolation, and the spring is designed to
give a force of 100 N at the foot of the rivet
when in use. Thus the operator must apply
greater force. A trained operator applies an
average force of 125 N during the riveting
process.
When the tool is used with a high grip
no torque is required to operate it. When
Table 4.8 Evaluation of external load for the Riveting Hammer RRH 06.
the index finger is used for triggering,
together with a low grip, an ulnar flex-
ion torque is required. This torque can be
estimated as the vertical distance from the
middle of the handle to the center of the
tool, times the push force. In this case the
distance is 70 mm and the ulnar flexion
torque can be calculated as follows:
Ulnar flexion torque.
= 125 N • 0.07 m = 8.75 Nm
When the tool is taken from the tool rest
to the rivet, or moved between rivets, the
weight of the tool is supported by the hand
holding the trigger handle. In this case a
radial flexion torque must be applied that
equals the horizontal distance from the mid-
dle of the handle to the center of gravity,
times the weight of the tool, times gravity.
Radial flexion torque
= 0.1 • 1.3 • 9.81 = 1.3 Nm
Force/Torque MVC Safety factors Reduced Real load Real / Score
N/Nm Speed Frequency Duration MVC N/Nm Reduced
Trigger 130 N a1=1 a2=1 a3=1 130 N 16 N 0.12 1
Push forward
straight arm 450 N 450 N 125 N 0.28 2.5
Ulnar fl exion 15 Nm 15 Nm 8.75 Nm 0.58 5
Radial fl exion 15 Nm 15 Nm 1.3 Nm 0.09 1
Total score: 9.5
147