Enb,
I think that this is part of the reason that it is becoming confusing.
confusing is right! My head is spinning trying to understand what people are saying in these two threads.
Don't invert the MOTOR, invert the dish panel on its mounting bracket instead. It appears from your pictures that the mounting bracket bolt pattern for the dish reflector panel is symmetrical. So you should be inverting your dish instead of the motor.
I'm not sure that it's possible for the bolt pattern to be symmetrical, other than from left to right, because from top to bottom, the dish itself isn't symmetrical. It might be possible to flip the dish, but it also might put stress on it and warp it, because even if the spacing is the same, the angles of the surface where the bolts attach will be different.
However, I'm also trying to understand what's being suggested here compared to the OP's issue.
I guess what's confusing me is that I thought the OP had a downward facing motor, like the SG2100, etc, but that his dish requirred the shaft to come in from the bottom??? If that's the case, then inverting the dish in it's bracket alone won't help, because he'd still not be able to get the shaft into the bracket, unless either the bracket was inverted or the motor was inverted.
Putting aside for a minute the issues of getting the right angles, it seems like to even get the dish connected you have 8 options:
(1) Invert the motor, leave the dish and dish mount as is.
(2)Invert the motor, leave dish mount as is, invert dish in mount.
(3)Leave motor as is, invert dish mount, leave dish normal in mount.
(4)Leave motor as is, invert dish mount, invert dish in mount.
(5)-(8) Same as above, but invert the motor shaft (if this is possible with the specific motor), so that the bend tilts up instead of down in normal position.
Now, the actual declination needed is ~ -2.1 degrees (neg meaning down toward the southern horizon). A motor like the SG2100 has a built in declination of about -30 or -35, etc, depending upon model and shaft option, via the bent shaft. To get the proper declination, you need to use a positive dish elevation so that adding the two adds up to the proper declination. Now, if you invert the motor, the declination created by the downward sloping shaft will now be an upward, positive angle rather than down, unless you reverse the shaft coming out of the motor.
Also, the offset dish design involves an offset in the 20-30 deg range, meaning that relative to the connection points of the mount at the back of the dish, the dish is actually aiming about 25 deg higher than it appears. This angle is incorporated into the dish elevation scale if you don't invert it, however it will be aiming ~50 deg too low (relative to the scale) if you do invert it, and this 50 degrees will in effect be a fixed declination that will have to be compensated for by the dish elevation, and has to be incorporated into the calculation, which is difficult since some dish manufacturers don't have accurate specs for offset angle.
Now, the dish elevation angle. Due to the offset design, most offset dish mounts won't go below about 15 deg on the elevation scale. I'm not sure how high they go, but they can be closer to 90 than they are to zero. This dish elevation is positive if the mount is in the normal orientation, and negative if the mount is inverted.
NOW, the possible declination angles from all these options.....
motor.......dish in mount........mount.......motor shaft
1 inverted.......as is.................as is.............as is
2 inverted......inverted.............as is...............as is
3 as is............as is................inverted..............as is
4 as is...........inverted...........inverted...............as is
5 inverted.......as is.................as is................inverted
6 inverted......inverted............as is................inverted
7 as is..............as is...............inverted...........inverted
8 as is........... inverted...........inverted...........inverted
dish in mount......mount........motor shaft.........Total
1 0..............+15 to +80..............-35...............-20 to +45
2 -50............+15 to +80............ -35...............-70 to -5
3 0................-15 to -80..............-35..............-115 to -50
4 -50...............-15 to -80.............-35............-165 to -100
5 0................+15 to +80 .............35.............+50 to +115
6 -50.............+15 to +80..............35................0 to +65
7 0.................-15 to -80............... 35..............-45 to +20
8 -50...............-15 to -80..............35...............-95 to -30
Since we need -2.1 ,
1 Should work.
2 Might work if mount goes above 80
3 Will NOT work.
4 Will NOT work.
5 Will NOT work.
6 Might work if 30 deg shaft.
7 Should work.
8 Will NOT work.
So the options most likely to work would be
(1) Invert the motor, leave the dish and dish mount as is.
and
(7) Leave motor as is, invert dish mount, leave dish normal in mount reverse motor shaft so it tilts other way.
And options (2) and (6) might possibly work depending on the range of the dish elevation and/or the shaft angle on the motor.
WOW, my head is spinning..............
