Saturday, December 13, 2014

Up to Date on Construction!

In the last post, you saw the walls and siding of the back yard observatory going up in a day's work.  It was a few days later till we got back to it with John's schedule, and my task was to work out the final pivot dimensions for the roof. I made another larger-scale model and found there were so many variables that it was tough to finalize.  Generally, some notes are shown at left.  The outer pivots attach near the roof Center of Gravity (CG), and will be counterweighted to assist in lifting the roof off the walls as well as starting the roof closed.  The inner struts, attached to the center roof pivots, are mostly for guiding the roof, perhaps partially counterweighted.   As far as the roof pivots were concerned, they could be attached, so after an aborted attempt to install the door, construction resumed on 5 December.

The original door installation was complicated by the 6 foot wall height.  That meant a good foot was chopped off the door, including the lower hinge.  That reduced the stability of the door to the point that John had difficulty getting it to hang properly.  After an hour's effort, without the right tools with him and with me still uncertain about pivot locations, he left to go paint houses to return another day.  This day with the right tools, he remounted the previously sawn-off hinge and it then behaved normally in its installation.  Now, with the gentlest of swings, it closes and latches nicely!

After that old business, it was on to
installing the pivots on the roof sections.  I had made the pivots out of 1" diameter solid steel shafts, welded into 3" angle iron to facilitate attachment to wooden frame or welded to the roof frame.  There is also a tapped hole in the shaft to hold on the expected struts that will be mounted.  I marked out where I wanted them and John made good use of his welder to attach them permanently.  At left, he welds one at the center of the roof section that faces outwards (another already mounted above his helmet), and at right he welds one on the inside of the roof section.

Note in the previous image that the inner pivots are not well supported, welded only on the inside 2" of their 6" length on the roof tubing.  I had gotten some 2X3" steel tubing to reinforce them, and at left John again uses his handy grinder with the cutting blade to chop them to 6" lengths to weld on for reinforcing.  In addition, I fabricated some hefty hold-down brackets from 3.5" heavy-duty angle iron.  Particularly with a mostly counterweighted roof, I didn't want roof sections flying off in inclement weather!  With these brackets welded on (shown at right), with the six 3/4" bolts holding the roof on to the observatory frame, it won't be going anywhere!

Finally it was time for a roof!  Using
galvanized steel roofing, after deciding on how long to overhang, he chopped them off (again that grinder/cutting wheel) to the right length before hoisting them to the roof frame for attachment.  Starting on the top, on one end, he went along and fastened them down with self-tapping screws into the metal frame.  There is a little washer with rubber grommet that seals out weather from future storms... 

As you can imagine, with pretty large sections, it went up pretty fast, with a couple ribs overlap between sections.  Battery-powered tools are wonderful for working over a large surface without running an electrical line.  The hex-head socket is also great to get in the screws without stripping-out the normal Phillips head screws...  Before I knew it, he had all the roof sections on, and attached a center span to seal against weather (attached only on one side for roof removal). 

Since this was our last work day until after the holidays, I had asked him for a "bill-to-date".  Interestingly, his labor was pretty much exactly the same as the materials used!  I'll likely provide a final cost when we're finished.  The only work remaining is electrical (which I'll likely do with friend's volunteer effort), finish sealing the roof with siding, and building trim.  I'm sure he wants to see how well my plan for the removable roof works, which I'll attack over the holiday as well.  Then it will be finished 'cept for the telescope part - a whole 'nother story. 

After my van collision and the anticipated totaling-payoff, I've moved all the astro and camping stuff into the now-weathertight observatory.  Lots of room to spare, so there was more room in there than it seemed!

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