1.1.17

2" shaft mounting Pt.61 Polar altitude adjuster.

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A simple, fencing turnbuckle between two stainless steel U-bolts provides fine adjustment in Polar altitude. The large hole allows my hand to reach in to adjust the turnbuckle. No strength is required.

The balance of the Declination housing around the 16mm pivot stud is just right. When the pivot nuts are slackened off the Dec housing drops straight down. However, it requires only a little effort to lift it back up again. This nice balance avoids placing heavy loads on the turnbuckle. Which might make Polar altitude adjustment more difficult.

I still need to provide a stop or fixing for the fork front plate. Though I don't want to spoil the "cleanliness" and unity of the fork blades by making holes or adding nuts and bolts. I may replace the stainless steel nuts with furniture flange nuts to carry the theme through to the base. Which I duly did. I also screwed two stainless steel screws into the inside edge of the fork blades to act as stops for the 10mm front plate.

The second image show the mounting without the Declination shaft or saddle.

The overall balance of the mounting, as shown, is offset by an inch or two towards the hammer lying on the bench. I dropped a plumbline down from the center of the housing where the axes cross. I don't think the balance will change much with the OTA and counterweights added.  These will add weight but these items will inevitably be balanced perfectly around the Polar Axis.

The 7" diameter cylinder still makes the mounting look a little top heavy. The cylinder cannot be shortened in height because it houses the Tollok bush. So there is nothing I can do about this. I deliberately chose the Tollok 110 50-65 to have the maximum flange size and clamping bush length along the shaft. This was to ensure maximum grip and rigidity at the vital junctions between the shafts and attached components.


Click on any image for an enlargement.
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