1. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Diagram of a wolfrom planetary gear train (left) and the circuit structure (right) Figure Legend:

2. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Diagram of a wolfrom, topologically segmented into two stages, in series, with circuit structures for each stage Figure Legend:

3. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Wolfrom efficiency, as a function of torque ratio and the maximum number of teeth per gear, ranging from 1–10 in (a) to 1–20 in (b) to 1–30 in (c). Wolfrom designs are plotted in black; two-stage planetary stacks are plotted in gray. The two circled points in (c) refer to the examples noted in the text. Figure Legend:

4. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Cycloid assembly includes several parts centered around an input–output axis (including the input shaft, rollers, and output disk), and several parts centered around an eccentric cam (including the offset cam cycloid disk). Figure Legend:

5. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Cycloid planetary gear trains: (a) a simple cycloid and (b) a compound cycloid. Circuit structures are shown to the left. The simple cycloid only uses circuit 1; the compound cycloid uses circuits 1 and 2. Figure Legend:

6. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Examples of cycloids tested. Two designs used N 3 = 10: simple 10:1 cycloids and compound (100:1) cycloids. One design used N 3 = 100 simple 100:1 cycloid. Rollers were either fused to the annulus or free to spin Figure Legend:

7. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Cycloid efficiency: comparison of data from our model and from empirical measurement. Empirical measurements are indicated by asterisk; model estimations are provided by the dashed horizontal line, with a boxed ±0.3% range in friction coefficient. This ±0.3% range without incorporation of the circumference effect (i.e., using η 0 instead of η c ) is indicated by the vertical gray lines for those models that used fused rollers. Ys indicate the presence of fused rollers or the inefficient output bushing. Figure Legend:

8. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Comparison of planetary, wolfrom, and cycloid drive efficiency. Theoretical cycloid efficiencies are overlaid on Fig. 3(c). These include the case when the cycloid uses rollers housed in ball bearings (η = 0.9992), when the cycloid uses free rollers (η = 0.993), and when the cycloid rollers are fused to the grounded annulus (in this case η is a function of the circumference, governed by the geometry, but a representative value of η = 0.985 was chosen based off the designs reported in this paper). Planetary and wolfrom efficiencies are shown for gear-teeth permutations within a 1–30 tooth range. Figure Legend:

9. Date of download: 6/28/2016 Copyright © ASME. All rights reserved. From: Efficiency of High-Sensitivity Gear Trains, Such as Cycloid Drives J. Mech. Des. 2013;135(7):071006-071006-9. doi:10.1115/1.4024370 Tuttle's model of harmonic drive gear meshing, modified from Ref. [33] Figure Legend: