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Equipment Discussions >> Observatories

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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5436845 - 09/23/12 07:43 PM

I finally made some progress today and got the dome ring to it's final dimensions! I have yet to cut any additional channels for shutter power but I will probably do that in the next couple of days. I doubt I'll have the shutter automated initially but I at least want to have the frame work in there and ready to do when that does come around...much easier to do now rather than later!

I didn't have enough plunge on my router bit to make it through the 1.5" of plywood (mainly because of the 3/4" of added height because of the MDF I used for the circle cutter). So I ended up having to use my jig saw to remove the excess and then used a flush trim bit to get everything evened up.

Here's a shot of the ring about half way though the cutting using the jig I quickly threw together...it worked very well too!



And here's a shot of the finished ring cut to it's final size.


I may end up getting some Formica and lining the bottom of ring with it to provide a smoother surface for the rollers...I don't know if this is really required or not or if I should just get some softer wheels. The plywood is kind of smooth...but it's not all that great. And there is some unevenness in it as well.

I'll probably pickup a couple more sheets of plywood tomorrow and get the template created for the dome forms so that I can cut them out fairly quickly and use a router to dimension them to the proper size.

Jared

Edited by averen (09/23/12 07:52 PM)


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5449474 - 10/01/12 12:38 AM

Finally had some time to work on the dome this weekend! I got the main supports and the ribs all cut out. Now I just need to size the ribs accordingly.

Here are the ribs being cut...what a mess! I even had my shop vac hooked up to the router but it couldn't keep up apparently. I cut out 8 ribs and 4 other supports with the router...it got a good workout.



After about 2 ribs I realized I was doing more work than I needed to do. I started by cutting the outside radius then I moved to cut the inside radius (also cutting the rib free). After 2 ribs like that I decided that I would just keep the radius the same and use the for the inside as well. This meant that I would really only need to do 1 cut per rib which would set it free from the sheet. Below on the left is the rib where I was making multiple cuts...the two on the right, which next better, are using the same radius.



I also cut out the main arches as well. This time I cut them with the router rather than rough cutting them with the jigsaw. This worked out much better. Here's a shot of the arches mocked up on the ring.



Hopefully I'll be able to get the ribs cut to size and the frame of the dome built this week so I can start to skin it this weekend.

Jared


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nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Pico Dome (it's that small) new [Re: averen]
      #5449610 - 10/01/12 04:28 AM

Quote:

The other option is something like this, which I'm also contemplating just scaling the outside to 6' or 5'6" rather than 8'.
http://users.csolve.net/~jilldwr/dome.html My initial plan was to use 1/8" masonite on the exterior and use a parachute gore generator to create the cutting template.


These plans show the gores curved to a partial sphere but this is not possible with sheet material which will only bend in one plane eg cylindrical - unless deformed to the spherical shape via a 'steam mould' or whatever etc

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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: nytecam]
      #5450252 - 10/01/12 02:32 PM

To cut out the gores I'm planning on using some thick paper and tracing between the ribs. Then adding on 3/8 to the sides and 1.5" to the bottom. Hopefully that will mimic the bending of the sheet material.

Thanks,
Jared


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dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5451247 - 10/02/12 01:24 AM

Neither the thick paper itself will bend between the ribs. The ribs face different azimuths so their short edges are not in line with each other.

If the ribs were parallel then the gores would meet at a butt joint.


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5459922 - 10/07/12 11:44 PM

I made a small amount of progress this weekend. I still need to cut the remainder of the bracing but figuring out how to cut those correctly is making my head hurt. I may just end up putting the dimensions of the dome in SketchUp and getting the measurements from there.

Here's the dome with the G11 inside. It's up on blocks to simulate the height that the dome will actually need to be at. It's still about 5" lower than it needs to be to put the RA axis at the middle of the dome. Since this will actually be on a pier I can make it shorter than my mount to keep things under the fence.



Someone mentioned about the sheet material only bending in a single direction. Because of this I'll be attaching the gores where the lines are in the image below and bending them up the arches.



The dome seems pretty sturdy as it is now. The main arches will hold my weight...and I'm not exactly a small guy!

Hopefully I'll figure out how to get the rest of the supports attached this week.

Jared


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seryddwr
Innocent Bystander
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Reged: 02/19/10

Loc: La-la land.
Re: Pico Dome (it's that small) new [Re: averen]
      #5461502 - 10/09/12 12:57 AM

Makes me want to build a femto dome! (Ha, just kidding) Though this idea ain't bad at all.

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dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: seryddwr]
      #5462542 - 10/09/12 05:17 PM

any further progress on this one?

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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5464139 - 10/10/12 05:00 PM

Nope...having 3 month old takes a lot of my time these days! I can generally only work on it on the weekends and we had company last weekend...and have company this weekend too. I might see if I can sneak some time in tomorrow or Friday. I think once I get the remaining uprights figured out I'll be able to start skinning.

Thanks,
Jared


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5480735 - 10/20/12 05:34 PM

Finally made a little more progress today! Very little unfortunately as we have plans for today, but hopefully I'll be able to work on it some more tomorrow as well.

I've decided to change gears a little and rather than doing a full frame I'm going to do a "mostly frameless" dome. Getting the frame pieces cut turned out to be very difficult because of the high rate of curvature on the small dome. I think for the size of dome it's just easier to go with a frameless design and use gores.

So that's what I'm doing. I'll leave the frame as is and will attach gores to the existing frame pieces and where there is no frame the gores will just get attached to other gores and the main arches.

So the progress for today was:
1 - figuring the above out.

2 - Beveling the pieces besides the main arches to about 20 degrees so that they'll accept the gores nicely.

3 - Creating a paper template for the gores using the website I mentioned at the beginning of this post


4 - Creating a masonite template:


Tomorrow I hope to use my router with a template bit to create a big mess...er, lots of gores using the masonite template I created above. To wrap each side of the dome I should need a total of 9 complete gores and 2 half gores. Each gore is 9.6" across at the widest point.

Jared


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5482702 - 10/21/12 09:20 PM

I rough cut a whole bunch of gores today. This is enough to do one side. Each side will take 10 gores. This is 12 that are rough cut. These all came from a single sheet of 4'x8' masonite and I would have been able to get 13 out of it but I destroyed one when attempting the router.

I started to use the template and the router to cut them out...this was an epic fail. So I used the template to trace out the gores on the masonite, flipping the template over each time to get them better nested.

After I traced them out I used a skill saw to cut them into groups of 4 gores. And I took that more manageable size over to the bandsaw to cut the individual gores free.

Once they're all trimmed up I'll use a disk sander to get them to their final size and attach them to the dome.



I did a little testing with the template and found that if I pinned both of the edges of the bottom of the gore that I as able to successfully conform to the size of the dome in (roughly) both directions. I'm not sure how this will translate when multiple gores are attached but I plan to at least give it a shot.

Jared


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dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5483442 - 10/22/12 11:16 AM

well done!

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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: dobsoscope]
      #5486246 - 10/23/12 11:20 PM

I attempted to attach some of the gores to the dome today...I'm coming to the realization that small domes are fairly difficult to build! The small size of the dome means that things curve faster which means that things need to be pretty accurate. I'm planning on fiberglassing the outside so gaps don't bother me too much, but getting the gores attached and lining up fairly closely is proving difficult. I think part of this might be because of the partial frame that I'm attaching the gores to on the top.

I'll have to do some more fighting to see if I can get the gores to fit. Otherwise I may end up going to plan B...which will be a tiny roll off roof. Unfortunately I don't have a lot of spare time these days to fight with getting the dome built.

Jared


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5487139 - 10/24/12 03:00 PM

I think I have figured out a way to get the gores sized correctly. It will create some extra waste but I "think" it will get them fitting accurately. I'm going to give this a shot in the next couple of days and will post my results.

Hopefully this will work...I would much prefer to have a dome rather than RoR...especially after all the work that's already gone into the dome!

Jared


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5504112 - 11/04/12 03:30 PM

Quote:

I think I have figured out a way to get the gores sized correctly.




Ya...that was wrong.

I've gone back to the frame design. And I'm positive I can get this to work! The semi-frameless design was not working. As the gores approached the uprights the angles got all crazy and I couldn't get things to work out. I even removed the uprights and planned on trimming everything to fit but this didn't work either. I think if I would have gone completely frameless this would have worked fine, but the "hybrid" method just did not work.

So...back to the frame. I managed to figure out how to cut the remaining frame elements...after I accepted the fact that they're not carrying any weight so they don't have to be perfect. The frame is just there to help the hard board contour to the dome shape.

Here's the current state of the frame:



After getting the frame constructed I then used some thick paper stapled to the frame to size the gores. This worked extremely well.



I was actually surprised by how close all the gores are to the same size. They're all within about 1/2" of each other so I can use the same template for all of them and just size each of the gores individually.

Here's a shot of one of the gores clamped on to the dome. I still have all 4 of the small ones to cut...I have a template cut for the small pieces but haven't cut any of them out yet. Since I ended up wasting a piece of hard board on the frameless gores I'll have to go pick up another sheet to make the small gores. Thankfully 1/8" hard board is only $8 a sheet!



Jared


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averen
Vendor Main Sequence Software
*****

Reged: 01/20/09

Loc: Austin TX
Re: Pico Dome (it's that small) new [Re: averen]
      #5504545 - 11/04/12 08:50 PM

After my minor success today with getting everything figured out I just couldn't leave it alone. I worked a couple more hours out in the garage and have the dome nearly half way sheeted!

Here's a shot of the exterior. Each half has 4 gores. Here 3 of them are sheeted. The area opposite of the shutter should be fairly easy (I'm hoping...what could be difficult about a rectangle??)



The gores are held on with a couple of screws and a washer on the frame. At the top each gore has a couple of screws holding it in place as well.

Here's a shot of the interior of the gores:



I need to pickup another couple of piece of hard board tomorrow. Hopefully that will be enough for the rest of the dome structure.

Jared


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Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5507829 - 11/07/12 01:35 AM

The stainless is what gets eroded. Look at the screws.

-Rich

Quote:

Amateur radio antennas are typically aluminum with stainless fasteners. I have never noticed any corrosion when taken down for cleaning/tune up.




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Mary B
Vendor - Echo Astronomy and Electronics
*****

Reged: 05/21/10

Loc: Minnesota
Re: Pico Dome (it's that small) new [Re: Starhawk]
      #5508622 - 11/07/12 04:03 PM

Just serviced my 43 foot vertical that is all aluminum/stainless. No corrosion I can see. The stainless hose clamps look like new yet. All the screws look new too.

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CMacD
super member


Reged: 01/23/12

Loc: Ontario, Canada
Re: Pico Dome (it's that small) new [Re: Mary B]
      #5509713 - 11/08/12 10:51 AM

Quote:

Amateur radio antennas are typically aluminum with stainless fasteners. I have never noticed any corrosion when taken down for cleaning/tune up.




I am at the point of skinning my trailer in aluminum and decided to research this topic. Funny - when I look at the theory it would seem to suggest that aluminum and stainless are not the best match. In practice, however, it seems that many people use them. And to my surprise the aluminum boat and plane people say that they work great together. Apparently the water test is really the true test of robustness as the water normally leads to the galvanic reaction. Needless to say I have started to skin the trailer with aluminum held down with stainless screws. I guess I will find out


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dobsoscope
sage
*****

Reged: 05/24/06

Re: Pico Dome (it's that small) new [Re: averen]
      #5510212 - 11/08/12 04:29 PM

well done!!

Quote:

After my minor success today with getting everything figured out I just couldn't leave it alone. I worked a couple more hours out in the garage and have the dome nearly half way sheeted!

Here's a shot of the exterior. Each half has 4 gores. Here 3 of them are sheeted. The area opposite of the shutter should be fairly easy (I'm hoping...what could be difficult about a rectangle??)



The gores are held on with a couple of screws and a washer on the frame. At the top each gore has a couple of screws holding it in place as well.

Here's a shot of the interior of the gores:



I need to pickup another couple of piece of hard board tomorrow. Hopefully that will be enough for the rest of the dome structure.

Jared




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