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Re: GM8 DEC Clearances

 

Nice analysis work, Alex,

Can you give some more details such as:??

Where did you buy (and what thicknesses did you buy) the shim rings for this... or did you have to just buy flat shim stock (brass?) and then cut that (exacto knife or scissors?)....

Where exactly did you install the shims... I guess it could be under or over the flat needle bearing part?

Slightly related to this... I also saw that Mark Crossley (on his WilmslowAstro.com? website) describes that he had to shim UNDER one of the worm bearing blocks in order to get his worm teeth to be level with his ring gear.? So his problem seemed opposite to yours where you had to lift the ring gear up.

(Ideally in my mind these mechanical parts are cut to be all flat and parallel, so the fact that Mark's worm was not level with his ring gear always struck me as strange... but your observation that the worm and ring are not the same center height is exactly seen on other mounts too.? The Orion Atlas/Synta EQ6 has plastic shims to get the ring and worm axis centered.? The amount of those shims is something that has to be measured and adjusted on each mount as part of its "hypertuning" process.)

Thanks again, Alex...

- Michael



On Sat, Jan 27, 2018 at 4:01 PM, a_pettit_jr@... [Losmandy_users] <Losmandy_users@...> wrote:
?

8. Strictly speaking, clutch knob force should not affect the worm to ring space, because the ring gear runs on the top large flat (incompressible) needle bearing under it, and the worm is also mounted on an immobile part.? ? ?But some people have seen this happen.? ?Eric Chesak has written about this and determined the possible mechanical causes.

I have been trying to optimize the worm / spur ring gear alignment. What is being referenced above is that
the Worm block is too high : when closely pressed to the ring it Lifts the Ring above the upper thrust bearing.

The gear cuts in the ring are very shallow .. a 0.001 of 'vertical' misalignment can cause the worm-ring to jam.

SO, when the clutch is tightened, it pulls the upper shaft downward ,presses the ring into the upper thrust bearing and jams or tightens up the worm-ring.

I found I needed to Shim Up the Ring - Thrust bearing.spacing by 0.007" on the Dec and 0.005" on RA.. I can get very tight coupling and no binding and no lockup upon adjusting the clutch.

- Alex
Winter Springs Fla




--
Michael Herman
mobile: 408 421-1239
email: mherman346@...
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