No. 459 May 1997

U.S. Department of Health and Human Services

Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Ergonomic Seat Reduces Shock for Low-Seam

Shuttle Car Operators

Objective

To improve seats on mine shuttle cars with ergonomic design

and by reducing shock impact transmitted through the mine vehicle

seat to the vehicle operator.

Background

Operators of underground mobile equipment, particularly

shuttle cars, are often exposed to significant levels of shock and

whole-body vibration. Past studies have reported that as many as

one-third of underground equipment operators could be exposed

to adverse levels of shock and whole-body vibration. Moreover,

seats on mining equipment, historically, are inadequate relative to

the ergonomic needs of the equipment operator. In the extreme, a

mine vehicle seat has sometimes consisted of blocks of wood or a

bent steel plate bolted to the machine frame. Also, the lack of sufficient vertical clearance in some underground mines is an impediment to providing adequate shock isolation systems on mine

equipment seats.

Approach

The NIOSH Pittsburgh Research Center (PRC) is conducting

research with viscoelastic foams to improve seats on mine shuttle

cars. Viscoelastic foams were used in an ergonomically designed

seat to reduce the amount of shock transmitted through the mine

vehicle seat to the vehicle operator. Data on selected viscoelastic

foams were analyzed from laboratory shock tests at PRC. Using

information from the analysis, two ergonomic seats incorporating

selected foam were constructed for in-mine testing on a shuttle car

(Joy 21SC) in eastern Kentucky. The shuttle car operated in a 35-

in-thick coal seam with an approximate mining height of 43 in.

Operational data were recorded on the ergonomic and original

seats. Further, the shuttle car operator was asked to compare these

seats. 

Results

When comparing the original seat (figure 1) with the ergonomic

seat (figure 2), the shuttle car operator described the ergonomic seat

as generally “much better” than the original seat. The operator

explained. “It’s just easy to adjust. And it’s got the lower lumbar

support. And the pad is thicker. It’s just much better all the way

around.” He added, “It does support you more and [there is] less

shock when you hit a hole...I liked the lower lumbar support.

That’s where most of your shock is at, in your lower back.”

The operational data supported the operator’s comments. In the

full-load case, significant improvements in isolation were achieved

(down to 15 Hz) with the ergonomic seat. Additional laboratory

testing of seven viscoelastic foams was done to further improve the

level of isolation from shock and better characterize the material

properties of each foam. Data from this testing were used in an

analytical model of the seat pan isolation system. Results showed

that two of the viscoelastic foams, SUN-MATE EXTRA-SOFT and

PUDGEE, gave the most effective shock isolation of the seven

materials tested. A composite of EXTRA-SOFT and PUDGEE

foams improved the isolation characteristics of the seat pan to

approximately 4 Hz. Similarly, EXTRA-SOFT by itself provided

isolation to 5 Hz. These results will be validated with future inmine measurements.

Cooperative Research Opportunity

NIOSH is seeking cooperators to assist in further research and

development of this technology. Additional information on

cooperative reseach may be obtained by contacting Jacqueline H.

Jansky, Technology Transfer Officer, NIOSH Pittsburgh Research

Center, P.O. Box 18070, Cochrans Mill Rd., Pittsburgh, PA 15236-

0070, phone: (412) 892-6615, fax: (412) 892-6678, e-mail:

jgj7@cdc.gov
Figure 1.–Original seat.

Figure 2.–Ergonomic seat.

For More Information

For more information regarding this new technology, contact

Alan G. Mayton or Sean Gallagher, NIOSH Pittsburgh Research

Center, Cochrans Mill Rd., P.O. Box 18070, Pittsburgh, PA 15236-

0070, phone (412) 892-4078 or (412) 892-6445, fax (412) 892-

6567, e-mail: anm9@cdc.gov or sfg9@cdc.gov

Mention or any company name or product does not constitute

endorsement by the National Institute for Occupational Safety and

Health.

To receive additional information about mining issues

or other occupational safety and health problems, call 1-800-

35-NIOSH (1-800-356-4674), or visit the NIOSH Home Page

on the World Wide Web at http://www.cdc.

gov/niosh/homepage.html 

As of October 1996 the safety and health research functions

of the former U.S. Bureau of Mines are now located in the

National Institute for Occupational Safety and Health

(NIOSH).