It’s been a while since my last progress on the equatorial mounting… But I am now officially started on the “serious” work: i.e. all of the heavy assembly work. So here’s what I have so far:
Although I haven’t made any of the DEC housing parts, I needed to at least have the housing back mating plate. This part attaches to the RA shaft itself. By design, it’s retained with 6 large M8 screws only accessible before the RA shaft is installed in its housing – so it had to be done before anything.
Next, I installed the front (the larger one of the two) tapered roller bearing. Because of the tight tolerance I am working with, sliding this bearing on the shaft required to bring the shaft to sub zero temperatures (-25 C) so that it would “shrink” enough for the bearing to slide on. It actually went really well – on the picture below you can see the “frosty” shaft and its front bearing. Also note the DEC back mating plate under the shaft.
While the shaft sit there for a couple of hours under the sun (and warming up), I assembled a bunch of RA housing parts including the left panel, front block, front panel, bottom plate and worm support plate. It’s getting heavy
Figuring the details of the assembly I found out it would be easier to have the front bearing block on the shaft instead of on the housing. Something about the 15.25″ gear that I sure don’t want to damage when handling it – that way I can keep the gear on the shaft tightened with its clutch and just slide it into the housing. On the picture below I installed the front bearing block (with the bearing outer ring installed in) on the shaft. Then added the Stainless Steel and Delrin washers part of the friction clutch.
I recorded a short video showing the bearing block spinning around the shaft. Nothing super exciting there haha: http://www.youtube.com/watch?v=e4Az1otffDQ
Then is definitely the toughest step of the assembly so far: assembly of the gear and its PTFE (self lubricating nylon material) sleeve bearing. This required 4 hands. There is absolutely no play and it’s spinning well. Not hard, not easy – I’m pretty happy about it! Since this is part of the slipping clutch, the shaft will spin inside the gear ONLY when the clutch is slipping. Note the white/grey liner in between the gear and the shaft this is the sleeve bearing. Since it’s a strip that I cut to size, there is about 4-5 mm gap in between the 2 ends.
Next is the second Delrin washer and the installation of four M3x8 dowel pins. These will force the whole clutch to spin with the shaft and preventing to loosen/tighten. Since I use a “captain wheel” that screws onto the shaft to compress the clutch spring, if the friction plates were not to spin for some reason when the shaft is spinning, then there would be a chance that frictions force may cause the “captain wheel” to turn relatively to the shaft which would effectively cause the clutch to tighten or loosen (most likely loosen).
And this is pretty much where I stopped – the friction plate that mates this Delrin washer needs to slight adjustments on the CNC which I will take care of this week. Then I will be able to finalize the clutch assembly and hopefully install the shaft + 2 bearing blocks into the RA housing. At this point the assembly will already be very heavy and I will probably have to wait until the observatory is completed to install this on the pier before I can start working on the Declination assembly.