Ergo Tip of the Month
November 2005
Sandalwood Enterprises is a consulting firm that specializes in Ergonomics, Process Optimization, and Information Management. The Ergo Tip of the Month is offered to our customers and friends for the benefit of the Ergonomics community. If you choose not to receive future editions, contact us at ergotip@sandalwood.com
The Benefit of Virtual Ergonomic Tools
In order to stay competitive in the market,
manufacturers have to shorten the development time for a new product in order to respond to trends
more quickly, reduce costs and increase the number of products introduced in a given time period.
This goal has been accomplished largely due to the use of computer-aided design tools. Within
ergonomics, computer generated environments and digital humans allow analyses to be performed early
on, without ever
requiring physical data or prototypes. A variety of ergonomic analyses (such as clearance, posture, reach, line of sight and strength predictions) can be performed to predict the success of a product or workstation layout.
Are you a Jack Classic (UGS) or 3DSSPP (University of Michigan) User?
Jack Classic is
a digital human model that allows the user to perform a number of ergonomic assessments, including a
3D Static Strength Posture Prediction (3DSSPP). The strength prediction tool within Jack Classic is
based on data from the Center for Ergonomics at the University of Michigan.
Did you know the
strength capabilities of the left hand and arm are, on average, 10% lower than the right hand and arm
(HumanScale, 1981). The population strength data included in Jack and 3DSSPP automatically discount
the left arm. Therefore, if you are conducting an ergonomic analysis using Jack or 3DSSPP to predict
the strength capability for your workers, there is no need to 'double discount' the left arm, this has
already been done for you. No matter what anthropometry you are assessing or the percent of the
population you choose to accommodate, the capabilities of the left arm will always be approximately 10%
lower.
The population maximum strength data from Jack and 3DSSPP is shown for both the left and
right arms. The strength difference between the 2 arms ranges from 6 to 11%.
| Joint | Maximum Strength of Left Shoulder (Nm) | Maximum Strength of Right Shoulder (Nm) | Difference in Maximum Strength for the Left and Right Arm |
| Elbow Flexion/ Extension | 33 | 36 | 9% |
| Shoulder Abduction/ Adduction | 44 | 47 | 6% |
| Shoulder Forward/ Backward Rotation | 48 | 52 | 8% |
| Shoulder Humeral Rotation | 18 | 20 | 11% |
References:
Classic Jack - Sandalwood
Classic Jack - Technomatix
3DSSPP
Henry Dreyfuss Associates (1981). Humanscale. Cambridge, Massachusetts.
Massachusetts Institute of Technology Press.