284 Like the original gearbox, the two motors both mount into their own stub shafts which are supported at  both ends by ball bearings, and have integral gear pinion s. This allows for the motors to be installed or  removed from the assembly without opening the gearbo x. Also like the original gearbox, both motors  drive the same gear, but in this gearbox design, t he gear must be quite large in order to achieve an  immediate gear reduction of 3.94. This gear drives the main shaft which extends vertically down and  drives both the low and high-speed electric clutches. When high speed is required, the low speed clutch  is disengaged and the high-speed clut ch is engaged. This ca uses the main shaft to drive the output shaft,  which is located at the end of the main shaft, and gear #5. The output  shaft is support ed by its own  bearings, one on the shaft and the other on gear #5. Gear #5 includes the female hex which is the output  of the gearbox. It mates to the existing shaft hex th at protrudes above the gearbox mounting plate atop  the steering box of the wheel pod.  Conversely, when low speed is required, the low-speed clutch is  engaged and the high-speed clutch is disengaged. This causes gear  #2 on the end of the low-speed  clutch to drive the low-speed shaft via gear #3, and gear #4 then drives gear #5 on the output shaft and  with an additional 4.1 gear reduction for a total low s peed gear reduction of 16.14:1. When in high speed,  gear #2 is back-driven by gear #3 and #4 and spins relative to the main shaft on its own mini-ball  bearings.  Various gear sizes and pitches were considered unt il the final design was adopted and the exact gear  ratios were established (Fig. 7). Given these, the various low and high output speeds, torques, and power  were calculated for each of the motor characteristics of top speed, peak efficiency and peak power. This  data was then used to select the electric clutches, mainly based on their torque  capability, a maximum of  95 N-m (70 lb-ft). For high speed, this torque repr esents the gearbox output torque limit because the  clutch is acting directly on the output shaft. For low speed, the additional gear  speed reduction of 4.1  results in an output torque capability of 389 N-m (287 lb-ft).    

Figure 7.  Chariot Gearbox – Gear Ratios and Torques, Speeds, Power    Gearing lesser face lesser face low speed Gearbox Plane Gear Pitch width (mm) width (in) Gear # no. of Teeth Gear # Reduction reduction Upper 8 6.4 0.25 0 16 1 63 3.938 Center 10 6.6 0.26 2 20 3 42 2.100 2.100 Lower 10 13 0.51 4 21 5 41 1.952 x 1.952 4.100 Output Reduction High Speed 3.938  x 4.100 Low Speed 16.144no. of  Teeth Motors  and Gearing Motor: Magmotor/SatCon  Product no: 730420001 Motor Power  One Motor 2 X motor High Speed Low Speed motor High Speed Low Speed N-m N-m N-m N-m rpm rpm rpm watts Top speed0.0 (0.0 lb-ft)0.0 (0.0 lb-ft)0.0 (0.0 lb-ft)0.0 (0.0 lb-ft) 2439 619 1510 (0 hp) max efficient9.18 (6.77 lb-ft)18.34 (13.54 lb-ft)72.3 (53.3 lb-ft)296.4 (218.6 lb-ft) 2185 555 1354202 (5.63 hp) peak power28.24 (20.83 lb-ft)56.5 (41.7 lb-ft)222.4 (164.0 lb-ft)911.9 (672.5 lb-ft) 1657 421 1039805 (13.15 hp) stall88.10 (64.98 lb-ft)176.2 (130.0 lb-ft)693.8 (511.7 lb-ft)2844.6 (2098.0 lb-ft) 0 0 00 (0 hp) Clutch s tatic maximums :95 (70 lb-ft)389 (287 lb-ft) 2105.4 535 1305314.4 (7.127 hp)Torque Speeds Approx. motor speed at clutch torque maximums NASA/CP-2010-216272