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Re: G11 Dec Axis, How Tight to Do Up Clutch Knob

 

Dear fellows,

I have read many similar reports over the past few years, about worm to ring gear tightness being affected by clutch knob tightness.

Strictly speaking, from the design itself, if all the parts are solid and all the shafts are perpendicular, there should be no effect of the clutch knob force.? At least, I should say, I can't see a part that should be affected.

Why: let's take the DEC axis (RA is similar).? Starting from the body section, there is a flat metal section above the 1.25 inch OD cylindrical needle bearings, holding the flat needle bearing, and it's flat upper and lower race washers.? Note that (on my systems) those 2 washers are not identical, so the assembly order matters: the lower flat washer should be the thin one, then the flat needle bearing, then the thicker flat race washer.??


The top of the ring gear is the bottom surface below the clutch pad.? The flat ring gear below the clutch pad is held firmly in place by the DEC body held by the RA section below it.? The ring gear aka worm wheel cannot shift from the pull on the flat clutch surface above it.? So the worm gear, also attached to the DEC body, should never see any distortion from the clutch knob pulling down on the upper clutch plate.

But many people see something happening... what could be causing it?

Let me toss out an idea...perhaps the assembly of the upper flat needle bearing races is done wrong:

If the lower race washer were the thicker one (by mistake in assembly), the upper race washer may be too thin to stay centered on the 1.25 inch axis.? If not centered, perhaps in that case pulling down on the clutch shaft could start to tilt the ring gear with respect to the worm gear. Then the effects you notice...the clutch knob force affecting the worm gear might occur.

Anyway, that's the only easy explanation I can suggest...

Best,
Michael








On Sat, May 16, 2020, 8:05 AM Henk Aling <haling@...> wrote:
Thanks for bringing this up.? The worm gear pressure depends on the tightening of the worm gear (assuming no spring loaded ones) but also on the tightening of the clutch knob.? I finally figured out that the only way for me to achieve a consistentworm gear pressure is to shim the outer block with some foil against the frame, then pressing inwards and axially while tightening it.? That was the only way in which I could get my EQStar motors to make a full turn.?

I was happy, then I found to my surprise that the pressure depends equally on the tightening of the clutch knob.? I don't think this is right but it is what it is.? My plan is to mark the clutch knob position with a piece of tape on both sides.? The pressure itself does not matter much IMHO, what matters is that you achieve the same pressure each time.? So if you can mark it you should be good.? Find that point then adjust the worm gear using shims.?

At least, that works for me.? IMHO regulating the worm gear is a huge issue.? I thought it was good for me to upgrade from my AVX to a Losmandy, wanting to buy American.? It almost got me out of the hobby, unfortunately.? If someone would have researched and documented this, that would have helped greatly.? Just trying to do this manually as is still shown on the video, simply does not work with the Celestron or EQStar motors, and will lead to much frustration.? I can't tell you how many times I adjusted the worms, and having goto motors (not the ones with the Celestron kit) is virtually necessary to test it.
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