GM-8 Oldham coupler alignment
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Greg, That's an interesting puzzle: a glitch at 1022 sec....and you say it is repeating at the time period?? ?That is like 4.26 x as slow as the G11 worm period. Nothing in the front section (motor, gearbox, Oldham coupler) of the RA drive train is that slow.?? The Oldham revolves exactly at the same ~240 sec as the worm. Since it can wobble in the front and back slots where the metal rods insert, I think it could cause a speedup or slowdown either 2x or 4x per period.?? Even if one of the metal rods "slips" or gets "caught" in the plastic center part, it would happen at some period matching the RA drive rate. The gearbox gears revolve faster than 240 sec, and only the output gear rotates at that speed. So cannot be the gearbox.? The motor is 25x as fast...can't be that (it's a 25:1 gearbox).?? That leaves something at the back end of the drive: it's possible that you have a ball bearing getting pinched in one of the worm bearings.? There were 8 balls in the bearing I disassembled once.? I can't tell what rate those balls pass a certain position in the race, but if you have maybe one bad ball bearing that is slightly larger than the others, perhaps it takes many center axis rotations for that bad ball bearing to get to the pinch point.?? So my guess is: If the 1022 sec is repeating, I think you should replace your two R4ZZ worm bearings with new ones.? I prefer the ABEC-7 quality rated R4ZZ ones.? Get a bunch like 5 and hand test them each yourself for smoothness...pick the two best and put them in the RA worm drive, closest to the worm teeth.? (Some older G11 OPWs have 3 R4ZZ bearings.)?? The Worm Blocks are required to be lined up to prevent pinching a ball bearing.? Getting an OPW will ensure the worm blocks are lined up by the OPW case.? Lining the blocks up by hand requires using a metal straightedge and very hard to do for one person alone without an OPW.?? If the 1022 second is not repeating....say it's a sporadic glitch...I'd suspect some speck of dirt on the Ring gear.? I'd take out the ring gear, and scrub the teeth clean with an abandoned toothbrush.? Same with the RA worm teeth...make sure there is no hard particle stuck in the grease.?? Best of luck, Greg!!! Michael On Sun, Jul 26, 2020, 8:24 AM Gregory Latiak <glatiak@...> wrote: Question... is there any decent way one can check if the oldham coupler is actually properly aligned when reassembling the drive? Not a lot of clearance between the worm block and the gear housing. When looking at my PEC data there are a number of anomalous peaks, like a big one at 1022 sec that bothers me. ANy thoughts or suggestions? |
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Hi Greg, Ok...you have an RA OPW, so the blocks are supposed to be well aligned.?? You must then determine if the 1022 sec glitch really does repeat at that same period.? If it does....I think it has to be a bad worm bearing.? They are not very expensive...about $12 each from Boca bearings. (If non repeating,...any chance something bumped the mount?? ) If non repeating, points to some burr or a speck of dirt...maybe a damaged gear thread on the ring gear (if an abrasive hard particle got ground in).? I guess clean, inspect and relube.? You can generally swap the RA and DEC components to try too...worm and ring gears maybe.?? Best of luck on unraveling this puzzle... Michael On Sun, Jul 26, 2020, 9:24 AM Gregory Latiak <glatiak@...> wrote: Thanks, Michael. |
Michael Herman