Building the Octagon Pt.43 Testing pier stability.

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This morning I screwed a length of 4x4 to the dovetail bar of my 90mm f/11 Vixen refractor. Then I simply laid it on the top plate of the pier. It made no difference whether I used 50x or 100x. The pier was perfectly stable until I hit it with my fist. Settle time was then about 2 seconds. Focusing and moving the telescope did not excite the pier into visible vibration.

I then added 6 x 2 meter lengths of 1x4 X-braces, on 3 sides, to compare the difference with bare, pier legs. The ladder would be obstructed if I braced anywhere on that side. I already have a length of larch boarding across behind the ladder to brace the pier on that side. The difference with X-bracing was not worth the effort or increased obstruction on the ground floor.

So it looks as if another sheet of plywood to reinforce the pier's bare midriff is in my stars. If that fails to please I shall have to add the big mounting to see if it changes anything for the better [or worse.]

I flattened the top of the pier posts and the crossed 4"x4" adapter ready for fitting the top plate. Then cut out and glued two sheets of 35cm x 35cm x 18mm plywood together ready to go on top of the pier.  

Rather than risk a single lift of the entire heavy mounting I dismantled it into its major components. I even managed to injure my back pulling the heavy declination assembly and 2" PA shaft out of the polar axis housing at head height. Idiot! I just hope the spasm of pain was temporary.

I was pleased with the ease with which the big mounting dismantled. The choice of stainless steel fasteners safely avoided rust in the months of sitting under a tarpaulin. Only a few minor surface spots of rust had appeared on the flange bearing journal extension collars. The [weight lifting] counterweights had also rusted lightly on the edges where I turned off the ugly casting marks. The 9"ø counterweights and smaller 8.5"ø Dec wormwheel can be seen beside the clamped-up top plate. Various spacers and the three radial screw, weight retention clamp are also visible on the right.

Friday: I seem to have been very lucky to have avoided serious back problems after yesterday's foolishness. Lifting down the heavy Dec housing and polar shaft was a very daft thing to do. I lay down for half an hour on a firm bed and that seems to have given my back muscles a chance to relax. Once bitten.. I certainly shan't be lifting anything heavy for a while in case it triggers further pain. To have escaped injury while lifting long lengths of 4x4 and 2x8 timber, and even 8x4s of 3/4" plywood, working alone suggests I am far fitter than average for my age.

Click on any image for an enlargement.

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