*
Another hot and sunny day reaching 79F at 15.00 and still climbing.
I spent the morning tidying up the projecting 2x8 at the bottom of the slit which was bumping into the steering wheels. A jigsaw made quick work of cutting the curve to match the inner radius of the dome. Followed by the angle grinder. The carbide faced disks are amazingly fast at cutting. Though a bit rough on the material, they haven't clogged. Nor shown the least sign of wearing out. I smoothed things off afterwards with the orbital sander.
I spent the morning tidying up the projecting 2x8 at the bottom of the slit which was bumping into the steering wheels. A jigsaw made quick work of cutting the curve to match the inner radius of the dome. Followed by the angle grinder. The carbide faced disks are amazingly fast at cutting. Though a bit rough on the material, they haven't clogged. Nor shown the least sign of wearing out. I smoothed things off afterwards with the orbital sander.
Some of the [skateboard] steering wheels were slightly tight across some dome diameters. So I re-sited the bolt axles inwards and outwards [as appropriate] on the heavy duty [ss] shelf brackets to equal the clearances all round.
The dome almost seems to self steer itself without obvious interaction from the steering wheels. Not that anyone should ever dare to try it without the steering wheels! It is obviously an illusion that they don't do much. Because one can't be watching all of them all of the time.
The dome almost seems to self steer itself without obvious interaction from the steering wheels. Not that anyone should ever dare to try it without the steering wheels! It is obviously an illusion that they don't do much. Because one can't be watching all of them all of the time.
Some screw points were slightly projecting downwards into the wheel track of the base ring. It took only moments to rub the offending points away with a coarse, flat file. The points tended to bump noisily over the supporting wheels/rollers as if there were a large step in the base ring track.
I decided to drill the outer shelf bracket holes and re-site the ratchet strap hooks to clear the large supporting wheels. Everything rotated much more easily after that, without the straps rubbing.
A test with digital, luggage scales showed the dome needed 5-8lbs to get going from a standstill. It varies slightly because the ring isn't dead flat. So some of the time it is climbing uphill and at others is sinking relative to the supporting rollers. Anybody else building a dome should pay attention to base ring flatness and use a good glue for laminating plywood together.
The cheap, construction adhesive I used has delaminated in places. I shall have to find a way of squirting better glue into the visible gaps. Or, I could use a lot of bolts, with countersunk heads underneath. With nuts and oversized washers on top of the horizontal struts.
I uncovered the big GEM mounting and measured the clearance from the center of the horizontal Declination shaft to the underside of the dome overhead. Say about 120cm total at the zenith with probably, 115cm safe clearance overall.
The stepladders are getting in the way at the moment. So I shan't be certain of the true clearance until I can swing the telescope freely [but slowly and carefully] to all possible sky positions. I shall have to slide the [7" f/12] refractor's huge, 10" diameter dewshield in and out until I am absolutely certain of safe clearance. I always feel a refractor should have a "proper" dewshield or it just doesn't look right.
A refractor OTA can also be slid through the tube rings to adjust its height in use. Though this will obviously effect the eyepiece height when pointing near the zenith. Lower it too much and the tail end could strike the inside of the dome. Or make head clearance a serious problem when viewing objects lower down. A star diagonal is normally used with a refractor. So this allows a sideways head position in an emergency.
It was good fun to sit on the top crossbars of the big stepladders so high above the ground. It is quite a view from up there! I can even see over the neighbour's old barn. I have ordered a scaffolding hook to improve my safety while working on the exterior of the dome from a tall ladder. The price in Denmark for the identical hook was three times higher than in the UK. Or about double with postage included.
A test with digital, luggage scales showed the dome needed 5-8lbs to get going from a standstill. It varies slightly because the ring isn't dead flat. So some of the time it is climbing uphill and at others is sinking relative to the supporting rollers. Anybody else building a dome should pay attention to base ring flatness and use a good glue for laminating plywood together.
The cheap, construction adhesive I used has delaminated in places. I shall have to find a way of squirting better glue into the visible gaps. Or, I could use a lot of bolts, with countersunk heads underneath. With nuts and oversized washers on top of the horizontal struts.
I uncovered the big GEM mounting and measured the clearance from the center of the horizontal Declination shaft to the underside of the dome overhead. Say about 120cm total at the zenith with probably, 115cm safe clearance overall.
The stepladders are getting in the way at the moment. So I shan't be certain of the true clearance until I can swing the telescope freely [but slowly and carefully] to all possible sky positions. I shall have to slide the [7" f/12] refractor's huge, 10" diameter dewshield in and out until I am absolutely certain of safe clearance. I always feel a refractor should have a "proper" dewshield or it just doesn't look right.
A refractor OTA can also be slid through the tube rings to adjust its height in use. Though this will obviously effect the eyepiece height when pointing near the zenith. Lower it too much and the tail end could strike the inside of the dome. Or make head clearance a serious problem when viewing objects lower down. A star diagonal is normally used with a refractor. So this allows a sideways head position in an emergency.
It was good fun to sit on the top crossbars of the big stepladders so high above the ground. It is quite a view from up there! I can even see over the neighbour's old barn. I have ordered a scaffolding hook to improve my safety while working on the exterior of the dome from a tall ladder. The price in Denmark for the identical hook was three times higher than in the UK. Or about double with postage included.
Click on any image for an enlargement.
*
No comments:
Post a Comment