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After automating the dome on my Pulsar Obsy which has been a revelation, I have spent a considerable time researching how I could automate on what is a very basic manual shutter. The existing shutter slides on the aperture side of the dome and supported by two curved aluminium rods at the rear. What I will require is to create a runner system to allow the shutter to open & close smoothly, be aligned & contained to enable attaching a motor and drive system, thus allowing software automation.
The rollers are 30 mm dia nylon roller bearings, four per side of the shutter opening. This will allow the shutter to slide smoothly over the open aperture.
The rear side of the dome needed to be built up so I could affix tracks to enable the shutter to slide smoothly to the rear of the dome. This was relatively tricky as I had to build rear track support blocks to line up with the existing shutter. I plumped for wooden supports as I had to mount the on a sloping curved dome and as they had to be mounted vertically, creating some rather complex compound angles and curves. These were bonded in place and further secured with stainless screws from within the dome. Then having formed the arc in which the shutter will run I attached UPVC strips to complete the assembly. The sides will be cladded with UPVC.
The calculations had to be quite precise as I didn't have much breathing space
To be continued...........
I have already earlier written an article about the old observatory at Stockholm in Sweden where I live. Only 30 minutes away from my home by the subway. A friend to me, Nippe, told me that he had written an article about that observatory's history. I got permission to use it on my homepage. I have translated it to english (not perfect but I hope you understand the information) and implemented it among my earlier photos from the observatory.
Nippe's history article is very interesting, a lot of information about the observatory that I wasn't aware about.
Enjoy reading !
I am finally getting to the point of having a working dome and shutter driver from an electronics point of view:
I have alpaca controllers and drivers for both, sensor switches in place for the shutter travel, encoder for the dome rotation, relay latch for unlocking the shutter, motor drivers for the opening motor.
I've also put in place a bicycle-wire based winch system to raise and lower the lower shutter on an endless rope system.
What's missing is this:
When winching, the lower shutter rises on the rails up the slot and under the lower shutter to a certain point and then brings the upper shutter with it by virtue of pressing under the bottom edge.
When the lower shutter raises to a certain point on the cycle, gravity takes over, the top part of the shutter unhooks from the lower part and slides down the back of the dome with a a crash into the buffers.
I'd really rather that didn't happen, since the buffers and the dome they are attached to wont last long doing that regularly.
I tried putting shock cord elastic between the two so the larger upper part couldnt run away but the lengths are wrong and wouldnt allow the shutters to close properly with the right length to prevent or at least dampen runaway.
What I am looking for is ideas to prevent this happening in a reliable way so the dome automation can do its job, night after night.
What I find is writing about the problem also helps me think about it, so hope this is useful.
The winch system:
The bicycle wire system has rollers on the inside of the shutter rail that guide the wire that is pulling the shutter up , which is fastened to the lower edge of the lower shutter. The wire goes up to the top of the dome, round a pulley and then back again, this time inside bicycle wire guide tube which mean I can more or less run it where I like with a small amount of give. In this case it runs back along the rail down to the winch. The wire wraps around the winch about 3 or 4 times and then fastens on the shutter again.
Something to make the upper shutter stick to the driven lower shutter on the way up and come apart on the way down ...
Something to dampen the crashing of the shutter into the buffer...
hope this stirs your creative engineering juices.
Just a quickie, I've moved and am relocating my steel pier. So, would postcrete do a decent job for the footing of my steel pier in conjunction with rebar and 14mm threaded bolts? I'd make the hole big enough to cater for the size of the pier base and threads, I'm just purely asking if it will be strong enough as it is designed to hold concrete fence posts up with fence panels in the wind. The alternative is to mix concrete but if postcrete in the right quantity will do the job satisfactorily I'd choose that for convenience.
Thoughts please 🙂