Link Lengths and Simple Reach Calculations

or Where should I put it?

T. Armstrong

It should go without saying that all work objects -- controls, tools and parts -- should be located within easy reach of the worker. It was Henry ford who said:

The work must be brought to the man; not the man to the work. The work must be brought to the man waist-high. No worker must ever have to stoop to attach a wheel, bolt, screw, or anything else to the moving chassis. Burlingame R: Henry Ford: A Great Life in Brief, p. 75, New York: Alfred A. Knopf, 1966

Yet it is still common to find work objects located such that workers must bend or stretch to the limits of their their capacity to reach for, grasp or use them.

This page provides some basic information that can be used to determine size ranges for female and male workers, their relative proportions and their abilities to reach objects on a bench surface.

1. Begin by selecting specifying a standard worker height1 or a custom worker height

Stature 1504 1618 1730 1636 1755 1880 Width

link Fraction2 Length
1. Stature 1.000 1504
2. Center-Shoulder 0.129 194
3. Center-Hip 0.096 144
4. Floor-Shoulder 0.818 1230
5. Floor-Hip 0.530 797
6. Shoulder-Elbow 0.188 283
7. Elbow-Wrist 0.145 218
8. Hand-Touch 0.108 162
9. Pinch - 65% Hand 0.070 105
10. Grip - 35% Hand 0.038 57
11. Shoulder-Touch 0.441 663
12. Shoulder-Pinch 0.403 606
13. Shoulder-Grip 0.371 558
Link Fractions2

Drillis & Contini Link Proportions

1National Health Survey. For latest data see:
2 Drillis, R., Contini, R., & Bluestein, M. (1966). Body segment parameters. New York University, School of Engineering and Science.

2. Enter Bench Dimensions for sample reach calculations and click on "Compute Reach" to determine how far the worker can reach without bending or stretching.
x Width

Reach distance* = ((Upper Arm + Forearm + Hand Length**)2-(Shoulder Ht - Bench Ht)2))1/2
*Reduce reach distance for belly space.
**Reduce hand length 35% for pinch & 65% for grip.


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