My 16" f7.2 Newt project code named "Grace"
Posted 04 June 2013 - 09:57 PM
Posted 04 June 2013 - 10:01 PM
Posted 04 June 2013 - 10:06 PM
Posted 04 June 2013 - 10:12 PM
My last step of the night was to add some trim to the top. I'll use the coping saw to rough the corners and finish up with the belt sander.
Posted 28 July 2013 - 07:51 PM
Once the box was put together I took a fair amount of time working on the altitude bearings. I thought maybe I should use some cast aluminum tube caps from a 60's fiberglass newt tube I had salvaged. The rings are 11" dia but I was having fitting and mounting issues. The rings were no more than 1/2" wide and tapered immediately to 1/4". The problem that I couldn't get my head around was how to drill through the sides of the box and hit the rings to an accuracy of 1/16" inch or so. After a week or so I went back to my original idea of a 24" wooden disk cut in half and glued directly to the sides.
Then I got tricky. I figured with a scope this big, at some point I'd like to have both axis driven. Also, if it's on an eq platform, I would need to be able to lock things down to change eyepieces(that is going to be a process!) or check out the charts. When thinking about movements and big things, the magic of materials gets kinda hard to figure out ahead of time. One thing I learned building my Eq mount is that you have to build things to move nice and easy, then you build a brake. Thinking about materials that will do both can be a roll of the dice and when things get big and heavy, everything moves nice and easy!
Posted 28 July 2013 - 07:56 PM
Posted 28 July 2013 - 08:15 PM
I used a hole saw to cut out some disks of UHMW Polyethylene and mounted three on the inside of the oak chair side as well as 3 in a piece of strong ply. I had to cut out some material and countersink the UHMW pads for clearance.
Posted 28 July 2013 - 08:21 PM
Posted 28 July 2013 - 08:34 PM
Next up is a little bit of beautification. I glued up the UTA out of my plywood rings and some plywood planks...
I picked up some red oak iron-on veneer tape and spent a night taping over all of the exposed ply on the UTA. It's a nice light assembly and kinda purty too...
Posted 28 July 2013 - 08:35 PM
Posted 28 July 2013 - 10:44 PM
Here is where I'm at now: a mocked up LTA. I will have to figure out a way to ensure the side bearings are parallel before gluing...
Thanks for the update Sean!
As for the parallelisms:
1) Not too critical for non-DSC scopes. In understand well it is a point of pride, but don't go crazy on it.
2) Parallelism starts from the Inside Out. If you have not already glued the mirror box, cut a series of spacers to maintain equal widths of the mirror box interior. Clamp it tight until the walls meet the spacers and do not use the edge cuts of the mirror box for guidance! Any excess edge(s) on the mirror box can be sanded down.
If the MB is already glued, you can use a spacer cut to the same width as the back edge of the mirror box and place it at the front edge of the alt bearings, shimming as needed any gaps in the mirror box.
Posted 18 August 2013 - 11:11 PM
I have spent most of the last 2 weeks figuring out how I was going to attach the poles. So what did I do? something else.
First, the mundane. I glued up some oak floor board scraps and glued them to a sheet of 3/4 birch ply for a stiff base. Another problem had been working on was how to brake the azimuth axis. I was very please with my alt-brake and was looking for the same magic for the az-axis. The complication was I did not have the space on the bottom as I did on the sides. I needed a brake that was going to fit in 3/4 of space. I also wanted to use a lazy-susan bearing for easy movement. After digging through my parts pile I settled on a train-wheel style brake. I guess one of the benefits of building a bunch of scopes is that I have assorted circles and arcs left over from other builds and sure enough, this time my parts bin came through!
I started by finding a nice round and centered 12" disk of plywood left over from the interior of routing out disks for the UTA.
I spent some time truing the circle and sanding it smooth. I then centered it on the base board via center screw and after lots of careful measurement, attached the lazy susan bearing:
Posted 18 August 2013 - 11:24 PM
So here is what I came up with: a clamping shoe actuated by a simple lever:
Posted 18 August 2013 - 11:34 PM
Posted 19 August 2013 - 11:16 AM
I would think that humidity changes will raise the grain on the wood parts, changing the feel the of action. Are you going to attempt to seal that, or just retune with each observing session?
Posted 19 August 2013 - 12:09 PM
I've contemplated gluing a bit of sandpaper to facilitate everything wearing down. After a while, a bit of clearance will wear in and I can line each with a bit of plastic or aluminum strip. Or asbestos, whatever...
Posted 19 August 2013 - 12:41 PM
May I ask where your lazy susan bearing came from, its weight limit, and dimensions?
Posted 22 August 2013 - 11:22 AM
Posted 22 September 2013 - 07:58 PM
I began this project with lofty ambitions about how to handle the tube connections. I considered buying ball-connectors but I had second thoughts about having so much visible machinery, this being mostly wooden construction. I then talked to another ATM who had made wooden clamping blocks and was telling me about how expensive they were, since they had to be cut from one piece of wood. I must have gone back to the drawing board a dozen times!
I finally decided on a simple bolt at either end. For that I needed 6' tubes(technically 5'-6"L) So I went to my local box store and the only conduit lengths were 5' or 12'! Oh brother. Nothing like a mid-aisle redesign. So I could spend $8.60 and figure out something new or $120 on proper sized aluminum. Guess which direction I picked? Yep. $10.45 total with the bag of M&Ms.
That's okay, trying to figure out how to stretch 5' of tubing to 5'-6" of tube ended up fixing another issue, that of inevitable trimming of tubes. Having 8 tubes, I was not looking forward to that part. I have found ways with my other builds to have some adjustability for accessories like filter slides, binoviewers, etc.
Posted 22 September 2013 - 08:07 PM
Construction is simple, I routed a channel for 5" down a 7"l block. I then cut a back-plate that will clamp down on the tube end via screws.
Easy, huh. Now make 8 of them. Still have 10 fingers (whew!)
Posted 22 September 2013 - 08:15 PM
Posted 22 September 2013 - 08:19 PM
Posted 22 September 2013 - 08:22 PM