On 4/26/21 10:26 AM, Dan Hummel wrote:
Thanks Don and Russell for
the absolute encoder issue. You save me a lot of grief,
confusion. I'm a little embarrassed that I hadn't worked
myself. If your a shoot from the hip engineer, you can end
shooting yourself in the foot. Looks like I'm committed to
encoder drive. With the limitations of the axis shaft
head clearance and bolt head access I have little wiggle
room, but I
thank I can make this work.
This brings up a new question.
using a Renishaw on the RA axis now. Without checking the
Absolute Encoders (plural) check box are we actually
its resolution? I was under the impression that you needed
encoders on both axis to have this checked.
Russell, here are a few images
What started out as a drag and
scope is now a remotely operated goto. Being a split ring
declination axis can't be directly driven. We use two 50:1
harmonic drives to get the needed reduction. Two matched
drums, one mounted on the drive output and one one the dec
linked with .010 inch by .5 inch stainless steel feeler
tensioned with modified guitar tuners. The RA drive is a
150:1 harmonic drive. The 2 inch drive wheels against the
split ring adds another 18:1 to reach the needed
reduction. It had to
be mounted outboard and back from the original drive to
clearance for the large harmonic drive. The original dec
low resolution and was driven with plastic gears. I'm
trying to mount
a pulley and cable system to drive the Renishaw encoder in
between the dec axis clamp and the dec bearing housing
original gear was mounted. These just are a few of the
modifications we've had to made over the years.
Wow that's a lot of upgrades to an NGT-18! Thanks for the
photos--other than replacing the drive system when the original died
mine is pretty much stock yet.