Current Motors

Of course to replace the motors on the LX200 Classic, we need to know how things are currently setup - after all the scope can not know that anything has been changed or it will not work correctly.

As has been described by several others on the Internet, the motor that drives either axis on the LX200 is best described as a "toy motor". Which is sort of funny when Meade has on the LX200 base "DC Servo Motor". But in all fairness, it is acting as a closed loop servo. The motor has a 2.0 mm diameter shaft, 10 mm long, that is splined on the end for 4.5 mm. All gears in the housing appear to be 48 pitch. Attached to the shaft is a 8 tooth gear (4.93 mm diax .485 mm face width) and the encoder mask holder. The encoder mask is 23.50 mm in diameter and has 90 slots. The 8 tooth gear on the motor drives a 30 tooth gear (16.11 mm dia. x 2.56 mm face width), for a reduction of 3.75:1. On the same shaft with the 30 tooth gear is a 9 tooth gear (5.75 mm x 4.00 mm face width). The 9 tooth gear drives a 36 tooth gear (20.11 mm dia. x 3.15 mm face width) for a reduction of 4:1. This gear is mounted on the shaft that allows manual movement of the declination axis. On the same shaft with the 36 tooth gear is an 11 tooth gear (6.98 mm dia. x 3.40 mm face width). The 11 tooth gear drives a 44 tooth gear (24.43 mm dia. x ? mm face width) for a reduction of 4:1. The 44 tooth gear is on the same shaft as the worm for the declination axis. The reduction of the gear train from the motor to the worm is 3.75 x 4 x 4 = 60:1. For every 60 turns of the motor shaft, the worm turns once.

Examining the output of the opto sensors for the declination encoder wheel, at Slew speed there pulses occurring every 60 us which for a 90 slot encoder gives a motor revolution of 5.4 ms per revolution or 185 rps or 11,111 rpm.

Speed       Pulse Width      Time/Rev       Motor RPS     Motor RPM
Slew           60 us                5.4 ms              185             11.1k
Find           186 us              16.7 ms              59.7           3.58k
Center       2.82 ms          253.8 ms               3.9            236
Guide         86 ms                7.74 s              .129            7.75

Examining the output of the opto sensors for the right ascension encoder wheel while set for 60.1 Hz Quartz Clock:

Speed       Pulse Width      Time/Rev       Motor RPS     Motor RPM
Slew E           67 us             6.1 ms              164            9.8k
Slew W          68 us             6.1 ms              164            9.8k
Find E           185 us           16.7 ms              59.7           3.58k
Find W          182 us           16.4 ms              61.1           3.66k
Center E       2.71 ms          243.9 ms             4.1            246
Center W     2.58 ms          232.2 ms             4.3           258
Guide E       motor stops          0                     0             0
Guide W         46 ms             4.14 s               .24           14.5
Sidereal       89.6 ms             8.06s              .124          7.44

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