Re: *Exact* method for minimizing backlash with spring loaded worm
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Hi Paul, That "out of round" observation sounds like something could be damaged or mis-assembled., or just a bad component.? There is virtually no way a new component would be "out of round", but... it?could be one of three low probability causes.? My suspicions are: a) a bad worm bearing. These are R4 size (R4ZZ or others that size).? These are used in roller skates and rollerblades, etc. so a huge market volume.? you can buy super quality listed as "ABEC-7" for about $13 each.? I recommend you replace the ones in your RA and if the DEC is the problem, replace those too.? These are small bearings, and not all that strong.? Still,?I've never heard of?them getting broken except when I try to remove a stuck one.? However the center rotating part can become?loose if the bearings are not strongly held in place by?the bearing blocks, or if a bearing block is off kilter.??See the possible bearing block trouble that Mark Crossley identified in his website .? b) damaged Worm axle (that is 1/4 inch diameter). The modern worm is made of brass, and the older version was made of?stainless steel.? I suppose it might be possible to bend the worm shaft if the mount was severely dropped.?But I've never seen a bent worm on any of my mounts.? Brass is softer than stainless steel, but still very strong stuff.?? Solution: switch the RA and DEC worms.? Does the problem move with the worm (if so, it is definitely a damaged worm), or does it stay with the axis (bearing or ring gear problem)? c) off center axis ring gear?? The ring gear is not really precisely centered but instead is mounted on top of the upper flat "thrust bearing" that is a flat needle bearing.? The center of that bearing rides on a brass cylinder up the middle of the axis.?The assembly order of the parts matters: the upper flat thrust bearing has a thin "race washer" under the bearing, and a thicker race on top of the bearing.? The
thinner?race must be the lower?one, else the ring gear won't be able to touch and be centered by the low brass cylinder.? If the upper thrust bearing is not centered right, then I think?the ring gear could rotate?off center.? That assembly must be correct.? It wouldn't go wrong by itself.? Anyway, that's the way you diagnose a bad part...by swapping RA and DEC components, and keeping track of the results.?? Best of luck with this effort, Michael On Sun, Dec 20, 2020, 1:55 PM Paul Goelz <pgoelz@...> wrote: On 12/20/2020 4:24 PM, Brian Valente wrote: |
Michael Herman