For the altitude bearing, wooden disks made by George Gourko were pressed into the ends of the 4" diameter aluminum tube. These were drilled off-center (left) to allow a vertical adjustment for balancing the scope. But the off-center holes means there will be some torque on the tube, so sandpaper disks were glued to the disks (right) for better friction when the bearing is mounted between the side plates in the box frame. To allow for horizontal adjustments, slots rather than holes were cut in the side plates for mounting the bearing.
Finally, to finish the project, the inter-ocular adjustment system was added.
The following parts make up the bearings: At left is a section of 4" PVC pipe that slides into the pier. Two snug wooden spacer rings made by George Gourko provide a tight fit (only one is shown-the other is already in the pier). At the top of the pipe is a threaded adapter. In the center of the picture is a 4" PVC "T", sliced in half, that forms the heart of the mount (Jim Sattler's idea). The third ("stem of the T") opening is threaded, and screws on top of the pipe to form the azimuth bearing. Heavy grease is applied for smooth movement. At right is a 4" diameter aluminum tube that will be cradled in the top of the "T" to form the altitude bearing. This tube will be mounted in the box frame between the optical tubes, so it will be sort of an "inside out" version of a standard Dob mount.
Teflon pads were added to the T, and a stop was added to make sure the mount wasn't accidentally "unscrewed".
The nearly completed pier and bearings.
The handle in the middle rotates a part (below) that moves two struts attached to the upper mounting rings of the optical tubes, at a point roughly opposite their pivot points, so that the tubes swing apart.
Last, the pier was constructed.