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Table 1.

Fitting terms from least squares linear regressions of log10Maximum force output (N) as a function of log10 Motor mass (kg) for different types of motors

Motor typeInterceptSloper2Ns.e.m. slopeMin massMax 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 5.87×105 
Winches 3.251 0.736 0.852 0.154 14.5 1361 
Linear actuators 3.048 0.612 0.656 0.167 0.34 2587 
Mean 3.008 0.686      
Group 2        
Running animals 1.703 0.949 0.998 0.023 0.00004 32.7 
Swimming animals 1.672 0.924 0.992 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 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 4264 
Turbofans 1.793 0.986 0.934 30 0.049 64 6804 
Electric rotary motors 1.739 1.078 0.999 10 0.013 0.04 558 
Linear induction motors 1.825 0.854 0.940 0.096 1.9 32.6 
Piston engines 1.719 1.016 0.988 31 0.021 0.165 2744 
Mean 1.726 0.977      
Motor typeInterceptSloper2Ns.e.m. slopeMin massMax 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 5.87×105 
Winches 3.251 0.736 0.852 0.154 14.5 1361 
Linear actuators 3.048 0.612 0.656 0.167 0.34 2587 
Mean 3.008 0.686      
Group 2        
Running animals 1.703 0.949 0.998 0.023 0.00004 32.7 
Swimming animals 1.672 0.924 0.992 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 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 4264 
Turbofans 1.793 0.986 0.934 30 0.049 64 6804 
Electric rotary motors 1.739 1.078 0.999 10 0.013 0.04 558 
Linear induction motors 1.825 0.854 0.940 0.096 1.9 32.6 
Piston engines 1.719 1.016 0.988 31 0.021 0.165 2744 
Mean 1.726 0.977      

N shows the sample size within each category of motor; s.e.m. is the standard error of the least squares regression slope. Minimum and maximum motor masses (kg) are shown for each category. Single molecules that create translational motion (myosin, kinesin, dynein, RNA polymerase) are included here with muscle cells and whole muscles (treating muscles alone yields a nearly identical scaling equation). Piston engines greater than 4400 kg mass are excluded because they scale differently than smaller piston engines (see text and Fig. 10).

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