Motor type | Intercept | Slope | r^{2} | N | SE slope | Minimum mass | Maximum mass |
---|---|---|---|---|---|---|---|
Group 1 | |||||||
Muscles | 2.995 | 0.677 | 0.997 | 16 | 0.010 | 4.8 × 10^{−22} | 0.014 |
Rockets | 2.737 | 0.719 | 0.988 | 19 | 0.019 | 0.0079 | 5.87 × 10^{5} |
Winches | 3.251 | 0.736 | 0.852 | 6 | 0.154 | 14.5 | 1,361 |
Linear actuators | 3.048 | 0.612 | 0.656 | 9 | 0.167 | 0.34 | 2,587 |
Mean | 3.008 | 0.686 | |||||
Group 2 | |||||||
Running animals | 1.703 | 0.949 | 0.998 | 5 | 0.023 | 0.00004 | 32.7 |
Swimming animals | 1.672 | 0.924 | 0.992 | 8 | 0.033 | 0.0009 | 0.04 |
Flying birds | 1.555 | 0.959 | 0.993 | 11 | 0.026 | 0.002 | 0.37 |
Flying bats | 1.862 | 1.082 | 0.994 | 7 | 0.037 | 0.002 | 0.013 |
Flying insects | 1.583 | 0.959 | 0.982 | 149 | 0.011 | 3.7 × 10^{−7} | 0.008 |
Turbines | 1.811 | 0.963 | 0.993 | 21 | 0.018 | 0.002 | 4,264 |
Turbofans | 1.793 | 0.986 | 0.934 | 30 | 0.049 | 64 | 6,804 |
Electric rotary motors | 1.739 | 1.078 | 0.999 | 10 | 0.013 | 0.04 | 558 |
Linear induction motors | 1.825 | 0.854 | 0.940 | 7 | 0.096 | 1.9 | 32.6 |
Piston engines | 1.719 | 1.016 | 0.988 | 31 | 0.021 | 0.165 | 2,744 |
Mean | 1.726 | 0.977 |
The slope of these log-log regressions is b in the equation y = ax^{b}; the inverse log of the intercept is a. N shows the sample size within each category of motor; SE is the standard error of the least-squares regression slope. Minimum and maximum motor masses (kg) are shown for each category. The data are separated into two groups that are distinguished by slope and intercept. Single molecules that create translational motion (myosin, kinesin, and dynein) are included here with muscle cells and whole muscles (treating muscles alone yields a nearly identical scaling equation). Piston engines greater than 4,400 kg mass are excluded, because they scale differently than smaller piston engines (see text and Fig. 3).