I had not intended to publish any more blog entries on this but it’s probably worth noting a couple of things. 

First, the plans included a dial that you glue to the top that has months, days, and zodiac signs.  This looks pretty cool so after a lot of fiddling to make it print across four sheets of paper on my printer (surprisingly hard to do – for some reason the CAD program thinks the entire drawing covers 12 standard sheets of paper), I put in some cool-looking parchment patterned paper and printed it out in sections.  I cut these out and used some Type 77 spray adhesive to stick them on.  I think that if I had had the appropriate font installed, it would have come out with a vaguely Arabic look but it still looks pretty cool to me with a standard blocky font.

I then set out to put a decent coat of finish on it.  I got out whatever I had which was a can of minwax wipe-on poly.  I had previously tested this on a scrap printout to make sure that the poly did not dissolve the printing from the inkjet.  I wiped on the first coat.

Then I was annoyed to find out that the poly seemed to dissolve the spray adhesive and parts of the dial were lifting up.  After the poly dried, I thought perhaps that shellac might work better but things only got worse.  After things dried really well, the paper flattened back out at which point I took a toothpick and put some wood glue under the edges and stacked quarters, coasters, and whatever flat things I could find on the dial to hold it down.  I guess putting a finish over the dial is not in the cards.  From that point on, I just put finish on the wood.  It looks pretty good now.

Another issue is the gear trains.  This is my fault for being cautious.  The drive gear train rotates as a unit and all gears are glued to each other.  When I initially did this I was very sparing with the glue and furthermore, I only applied glue to one surface which is generally a no-no with wood glue – at least in my experience.  So twice now I’ve had the drive gear train come unglued at one of the spacer joints while cranking it.  In each case I disassemble the thing and reglued the joint with an appropriate amount of glue and with glue on both pieces.  Here’s hoping that this will hold although I’ve only repaired two – there are about 10 more similar joints. 

Also, my planet mounts are pretty lame.  As I mentioned before, I drilled these out by hand rather than letting the CNC machine do it and they just don’t fit like they should.  I have to be careful to make sure that none of these planet holders actually touch any of the others or the friction between them will cause the motion to be off. They drag on each other and usually one gets ‘coupled’ to the other.  If I was certain that I’d never have to take the thing apart again, I would squirt some thin CA glue around the shaft and lock them all into place but for now I am considering just remaking these parts and trying again.

So I can safely say that all the parts that were cut by the CNC machine have worked well; my problems have come in wherever I did some hand work.  It’s not that my hand work is sloppy although that is true in one or two places; it’s that I did something without enough forethought and testing.  In retrospect, this is not surprising. Patience is a virtue; one that I am still trying to nurture. If I had gone back to my CAD models and made them match the drawings I had and if I had waited for my friend to get back to town so that we could use the machine, some of these things would have not happened. 

But then again, there’s value in doing something by hand in order to get a full appreciation for what the machine is doing for you.  When I was in graduate school, the machinist who made our experimental apparatus would occasionally make me do some grunt work “to get my mind right” which is kind of the same thing.  So the effort isn’t wasted.  But my orrery still needs to be fixed.

This whole build is starting to remind me of having a newborn child.  The “design and build” process was super fun but now the daily maintenance has begun and that’s kind of a chore.  I hope I can get the thing running reliably and go into a crank-only mode soon.

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