Re: Needle bearings and axial play, is this a significant performance problem and how difficult is it to fix?
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Eric ("cyclone")... Very nice work!? I love that 2 image timed video photo of the Oldham coupler end! That you show is typical of the stock gearbox play.? That's part #1 of hysteresis and you can't get rid of that unless you change gearbox model (to a McLennan type say). But I think all gearboxes have some hysteresis in the gearing.? (There is a spec in the McLennan types...see attached document.) On the Tucked motor system you'd find additional time lag #2 (seen by the worm movement delay from the motor) from the necessary gaps between the 2 transfer gears.? You must not allow those transfer gears to jam so there has to be a little gap.? You can adjust the gearbox mounting to optimize that.? (The gear driving the Oldham coupler is on a fixed shaft...) On the SLW you'd get yet another time lag #3 if the OPW that's pivoting at the left pivot point can move left to right in it's "nipple" pivot hole.? That also has to have a gap.? That affects the DEC autoguiding but not normally the RA that's always forcing the RA toward the west as the sky rotates.?? ( So I think that bolting down the SLW so it does not move (defeating the SLW action) is a good approach to try eliminating that time delay.? ) Another time delay #4 affects the DEC mostly too is any worm left to right slip along it's axis if the worm mounting blocks get loose.? I think these blocks must get pushed loose over mount temperature changes anyway, so I recommend putting in one R4 Belleville spring under the far worm bearing, and reducing that bearing OD and lubing it to slide, to get rid of that time delay. { The G11T has 3 transfer gears at the RA Titan worm drive.? I found that a 2 pulley belt drive eliminates that time delay in those gears (that thanks to Allan Ruckle who showed me his nice implementation).? } Then there is the worm to ring gear gap.? That was always the obvious place where a gap must be optimized....going back decades.? For that, we used to (and I still do) use spark plug feeler gauges to adjust that.? That's hysteresis element #5.? Many owners get rid of that gap by using a weighted cord wrapped around the axis. [On the RA axis, hang the weight to the East side to minimize chatter of the ring gear when the worm rubs it perpendicularly].? Recent emails suggest on some units there could be a gap between the 1.25 inch shaft and the needle bearing ID.? I don't find that only units but it's another thing to test for.? I guess that is potential hysteresis element #6.? Lastly, check that your dovetail mounting at the top of the DEC axis bolts are tight and that dovetail is not able to wobble.? If I left something out....I apologize. Have fun all, Michael On Fri, Jul 16, 2021, 10:10 AM Cyclone <148cyclone1@...> wrote: How do I do that?As briefly described in my previous post, I measured the backlash directly by taking pictures of the coupling. To be more specific: |
Michael Herman