Wednesday, October 15, 2014

Post-Calstar 2014 Wrapup: Thursday

My Thursday at Calstar was ... a bit challenging.

While it was great to learn to use the bow that Carl brought (no pictures of me doing this as far as I know) and having the clouds meant little heat from the late summer sun, there was not a lot going on.  The day was overcast in the morning and didn't break up until later in the afternoon.

The challenging bit was that I didn't power up the mounts until after dark.  Had I done a bit of testing beforehand, I would have been aware that the Dec motor on the G11 was experiencing an encoder failure.  The symptom was a jerky, incomplete slew that stalled prematurely.  Originally, I thought it might have been due to a tight gear, so I loosened the mesh a bit and that didn't solve things.  I recognized that this was an encoder issue and tried cleaning the optical discs with the puffer bulb and checking clearance.  Nothing worked.  By about 10 pm, I knew that the G11 was dead in the water.  Luckily, the GM8 was plugging away, going through a roll of E200, so there wasn't a total loss of progress.
Prior to failure!

I talked with Rich and Carl about the problem.  I knew that Casey's G11 was a push-to style, so he wouldn't have a spare motor.  Marek's G11 was sitting unused under its tarp.  I was tempted to "borrow" a motor.  We joked about how his gear could be stripped like a car at a chop shop, leaving it up on cinderblocks.  The only thing left would be some cut-rate parts, hanging forlornly at the end of a frayed cable.

It was getting late and the night was pressing on.  I finally made the decision to field strip the GM8, back convert it to the push-to motors, and cannibalize the spare Gemini motors and gear boxes for the G11.  In the dark, I spread out a sheet to catch small parts, and tore apart the mounts.  Surprisingly, the whole job only needed about 90 minutes to complete.  Everything was back to running a little before 1 am.

There seems to be a link between the failed gearboxes and the encoders going bad.  I think there's something about how the old gearboxes split open that allow the motor shaft to move and possibly collide with the encoders.  With all the cannibalism of stealing parts back and forth between mounts, the G11 currently has 2 good boxes and 2 good motors.  I dropped the slew rate on the G11 down to 500 as well, reducing the overall speed at the benefit of a lower noise and possibly a better chance to avoid stalls or gearbox breakage.

I did miss the luxury of using TheSky to point the GM8 to the part of the sky where I wanted the film shot to be.  I found that if I was patient, I could use the red dot finder well enough.

The rest of Thursday night into the wee hours of Friday morning was pretty much uneventful.  The camp got very quiet after 3 am.  At 5 am, the morning twilight was starting and thus I wrapped up the efforts.