SG2100 shaft(s)

[wejones]

A few days ago, I was commenting on what seemed to be some variation in where the holes were and even if there were holes on the SG2100 motor shaft. Well today, I was surfing the net, and came across one dealer who sold the SG2100. This dealer was offering a replacement shaft, which had a larger diameter than the standard shaft. It was suggested that this shaft should be used on the larger dishes (I assume like the 1.2M). It showed a small picture of the shaft, and it seems to be the one which I've seen pictures of, which don't have any holes in the shaft. So it seems like apparently the smaller standard shaft has holes, and there is a larger shaft available that doesn't have holes.
While thinking about this, I thought that it wasn't necessarily the case that the replacement shaft would have the same offset angle, and/or length either, which made me think about the discussion of how heavy a dish the motor could accomodate. Ie, part of the function of the offset bend in the motor shaft, besides permitting a negative dish elevation to give the proper declination, is that with the offset angle, the center of gravity of the dish is closer to the rotation axis of the motor, meaning that there would be less torque on the motor when trying to lift the dish from a far east/west position. Also, the length of the bent portion of the shaft is important for the same reason, since the further up toward the bend you mount the dish, the greater the torque on the motor. Anyway, I wonder whether those who had a problem with this motor with the 1.2M dishes may have had the dish attached further up the shaft, and those who didn't have a problem were mounted further down the shaft??? Something else to think about.

[wildboys]

Originally Posted by wejones

A few days ago, I was commenting on what seemed to be some variation in where the holes were and even if there were holes on the SG2100 motor shaft. Well today, I was surfing the net, and came across one dealer who sold the SG2100. This dealer was offering a replacement shaft, which had a larger diameter than the standard shaft. It was suggested that this shaft should be used on the larger dishes (I assume like the 1.2M). It showed a small picture of the shaft, and it seems to be the one which I've seen pictures of, which don't have any holes in the shaft. So it seems like apparently the smaller standard shaft has holes, and there is a larger shaft available that doesn't have holes.
While thinking about this, I thought that it wasn't necessarily the case that the replacement shaft would have the same offset angle, and/or length either, which made me think about the discussion of how heavy a dish the motor could accomodate. Ie, part of the function of the offset bend in the motor shaft, besides permitting a negative dish elevation to give the proper declination, is that with the offset angle, the center of gravity of the dish is closer to the rotation axis of the motor, meaning that there would be less torque on the motor when trying to lift the dish from a far east/west position. Also, the length of the bent portion of the shaft is important for the same reason, since the further up toward the bend you mount the dish, the greater the torque on the motor. Anyway, I wonder whether those who had a problem with this motor with the 1.2M dishes may have had the dish attached further up the shaft, and those who didn't have a problem were mounted further down the shaft??? Something else to think about.

I have a fortec 120cm dish.When i move it to the bottom of the arc east or west it would not return up the arc.I had it mounted at the top of the shaft.I lowered it down toward the end of the shaft as you suggested and now it moves the motor up and down the arc from 61.5 to echostar 148 without problems.I am using sadoun SG2100 motor

[wejones]

Neat. Good to know. I guess it brought the center of gravity in closer to the rotation axis. With custom designed mounts, maybe even bigger dishes could be put on that motor.