On Mon, Sep 30, 2019 at 1:27 PM Michael Herman <mherman346@...> wrote:
Here are two documents.? One is about GM8 PE testing.? The other is about fixing the worm lateral containment.? Perhaps there are clues in that to help you solve your GM8 issue.? ?
All the best,
Michael
On Mon, Sep 30, 2019, 7:44 AM Michael Herman via Groups.Io <mherman346=[email protected]> wrote:
Matthieu,
4 secs seems very long.
I don't think the gearbox itself is a cause, but there is an Oldham coupler that links the gearbox to the worm. Sometimes the metal ends of that coupler can work loose. Usually it's easy to tighten the tiny setscrews that hold those coupler ends to their metal shafts using an Allen hex key wrench. I think the size is 0.050 inch (and is included in sets of American size hex key wrenches by Bondhus).
The movement of the worm toward the ring gear is easy, by design of the worm blocks. ?
The difficult element is the locking of the worm between the worm blocks, but it can be done. It is easier to add in a Belleville spring washer to the place behind the far bearing (far end of the worm, away from the coupler), that will always keep pressure on the bearing and the worm.
My GM8 has essentially no backlash in either axis with these adjustments.? I leave no gap between the worm and ring gear. ?
I am surprised your RA does not have the problem, but perhaps because RA is always driven at some rate (Sidereal or solar or lunar, perhaps). ?
Let me know if you need parts like the spring washers.? I'll send you a PDF about my GM8 results.
I have a GM8 from 2006 (no upgrades) and I was looking into decreasing the DEC backlash. From my understanding, there are 3 main sources of backlash:? -Worm to gear not tight enough -Worm loose between its blocks -Gearbox.
The first two can be addressed with careful alignment. What about the gearbox? From my tests it seems I need at least 4 seconds at guide speed to clear the backlash between input and output. Does that seems right? Could this duration be decreased by doing the backlash compensation at higher speed? I don't see this option in PHD2, and I have read that it is better to leave the Gemini backlash compensation off when guiding.
--
Michael Herman mobile: 408 421-1239 email: mherman346@...
