Sunday, March 25, 2007

My EQ6 mount improvement - Part 1

This is the first part of I don't how many to describe the improvements being done to my EQ6 mount right now. The mount is currently getting worked on and I hope to have it back in the next week or so. In the meantime I have some pictures of the process that were sent to me by Tom at Astro Motion Technologies. This process is currently in beta test mode and I am one of the lucky beta testers.
The point of this process is to even out all the inaccuracies in the mounts internal gears and make them all mesh together much better. This will reduce periodic error and increase the load bearing ability of the gears. The secret of the process is the application of WS2, also known as Tungsten Disulphide. This is a compound developed by NASA as a lubricant for spacecraft. WS2 forms a molecular bond with whatever it is coating, but does not stick to itself so it won't build up where you don't want it. It has a very low coefficient of friction and can withstand pressures of over 300,000 psi. The coating is applied with high-velocity and is very thin - about 0.5 microns thick.

My EQ6, like other mounts of this type, move and track objects in two axis - right ascension (RA) and declination (DEC). Each axis has a worm gear, as shown in the worm block above. Each worm gear drives a larger gear along the axis of motion. The worm gears are driven by stepper motors controlled by the mounts internal electronics. The larger shaft gear, shown to the right of the mount, and the worm gear are the surfaces to be coated with WS2. The shaft gear has bearings inside that are friction-fit. They are pressed out using a hand press with even pressure, as shown below.

Once the gears and bearings have been completely removed, they are given a good cleaning in an ultrasonic cleaner. Thankfully Synta has stopped using the super-thick black grease that has always caused sticky operation in cold weather. They put that thick grease in there to make up for less-than-accurate gear tolerances. Back to the process - the gears come out of the ultrasonic cleaner all nice and shiny:

The worm gear is then measured on a machine gauge to check run out, radial run out, and gear tooth spacing. My gears checked out pretty good, with accuracies down to around a thousandth of an inch variance. Looks like Synta is doing pretty good with their gears. After the gears are measured, they are closely inspected on an optical comparator. But, more on that next time.

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