jasonharris
super member
Reged: 09/16/06
Posts: 137
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So I did some drilling and counterboring for the middle section. All these holes are for the adaptors to bolts the truss connectors on to the plate. I made my first mistake which has turned in to a cosmetic defect 
I picked a place to put the connectors and drilled only to find that there was an overlap between adjacent pieces.. oh well, it only happened in two spots and looks symetrical so if you didn't know it would look like it was meant to be there
Off to do some rails. I have a rail from bttechnologies that I use for my FSQ. It is pretty nice so I may just incorporate it in to the design for the top rail. I will still need a bottom one. luckily I have a bunch of 4" wide by 3/4" plate from my last set of rails.
Hmm, I wonder if I should just turn the whole lot in to dovetailed rail now... 
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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G'day Jason,
Did you get anywhere with the baffle design? I haven't heard anything yet.
guy
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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I just PM's y'all - I should have some time over the weekend to finalize your baffles. Since Paul told me your mirror sets are identical, I'll start a new thread to keep the baffle discussions separate from the rest of the construction details.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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thanks Mike.
I've been fiddling with CAD paper patterns for making conical section baffles. I am planning to use thin sheet metal with 965 solder or similar. I am not gifted in the soldering dept though. I might have to get help from an experienced friend of mine on silver soldering if I have trouble.
guy
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Well, I had a week off the project and did a bit more today. I couldn't be bothered with the losmandy rails, it was too mundane and that why I didnt do anything..
I was about to put it off again and thought I would do something else to get my motivation up.. I decided to start with the mirror cell today.. Halfway done..
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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g'day Jason - keep it up.
Motivation can be a challenge at times. My project is still waiting for delivery of 6061 plate to the CNC machine shop. I find getting high grade Al plate in Australia is a big challenge for the hobbyist, even if you are are prepared to pay a premium price. Once I have the rough machined plates for the rear cage I will start a parallel thread - maybe a couple of weeks? I'm milling a few smaller components at the moment, some basic cuts in the secondary mirror base plate in progress. We've been getting continual rainy weather over here, so no imaging either.
cheers, guy
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 799
Loc: Houston,Texas
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Jason, Looking really nice...I just wish that I had my casting setup finished...
But then it's 95 degrees F and raining,,,ugh!!!Too hot for safety gear now anyway. 
My mirror collimation tube is going to have to be machined out of a 5" diameter 9" long billet as I could not find any thick wall tubing or pipe that suited the application.
I envy your just having to clean up the castings... 
Nice!!!
Regards,
Preston
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A few I enjoy,
and a few more in the works ;<)
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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I spent last night doing the upper ring. After it was machined in to a ring it weighed 2.2 kilos or 4.8 pounds. I cold get another 1/2 kilogram off it if I tried.
I put all the pieces on a scale and so far they weigh 15.4 kg or 33 pounds.. This is without trying to take any additional weight off any components so I am happy that this is tracking for a total weight that is OK and well withing the paramount. The only additional components required are the visual back, spider, fasteners, mirrors. They may add anouther 10 kg so that still has me around 55 pounds..
I dont know how considering the rcos version has every last piece milled out to save weight and its 50 pounds. oh well, I wont complain.. Also I dont think I will be milling out pockets all over the place either.
I will post a picture when I get home as I have a question about it's inner diameter in relation to the mirrors size which I wouldnt mid comments on.
Thanks,
Jason
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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Jason,
Got your baffles optimized, for a field diameter of 1.4". Here is a graphic showing the baffle dimensions. You could make the back portion of your primary baffle cylindrical if that would help in mounting it, like I did Preston's.
The rear end of the primary baffle is arbitrarily 1/2" from the primary, just to show it as being separated.
Next I'll put up the ZEMAX design file.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
Edited by Mike I. Jones (06/25/08 12:08 AM)
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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This is the full ZEMAX prescription for your 12.5" RC, complete with optimized baffle tube dummy surfaces. The glass "ZERO_CTE_SOLID" is used to make ZEMAX draw solids like baffles, rear plates, etc. in shaded renderings. It is a glass I made up that has an index of refraction of 1.0 regardless of wavelength, and a zero CTE. It's only there to put a non-blank label in the glass column, which causes ZEMAX to draw solids.
Post or PM with any questions.
Mike
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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Here's a shaded layout plot of your system for grins.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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Thanks Mike (apologies to Jason for butting in).
The conical secondary baffle diameter figures in your first post don't make sense to me, though the drawings look right. Shouldn't they be bigger numbers?
guy
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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DOH! Excellent catch, oh sharp-eyed Guy. I just added that code tonight to output the optimized baffle dimensions, and forgot to double the semi-apertures on the secondary baffle. They are corrected now.
Thanks!
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and a new design you'll like.
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GuyFleming
member
Reged: 01/21/08
Posts: 23
Loc: Newcastle, Australia
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Fine. Thanks for those numbers. I will plug them into my CAD sketches. The main 'unknown' for me was how wide to make the base of the primary baffle.
guy
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Thank you very much Mike! I know you have just sorted out thre people with the same set of optics. Myself, Guy and another local friend of mine who bout a set a month after I did.
I will need to spend some time looking at it and if it doesn't make sense I will ask a question, or two..
Thanks,
Jason
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Hello Mike, I do have some questions. I thought I would post rather then PM in case it helps anyone else reading..
I just posted on prestons thread how he might go about building the conical baffle, i.e. sheet metal rolled etc. I just saw some made out of carbon fiber and realised that would be quite easy to do as I could make a form to the correct shape out of wood on the lathe easily and cheaply enough.. Thats not one of the questions though
Questions are.. There is no baffling inside the primary baffle.. Is this because of the conical shape, is it essentially minimising the reflections because they dont end up going out the back of the mirror anyway?
The other is that my primary has a 3.5" hole in the back.. Some of that space is required to mount the baffle to the backplate, how much space do I have?
From your table I see that the light path is using 2.6" of this leaving .9 of an inch for the baffle to go through the primary hole. Is this 2.6" from the back of the mirror or the front? If measured from the back then obviously I have less free space but I don't know what?
And once again, thanks for our efforts so far.
Jason
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Mike I. Jones
Pooh-Bah
Reged: 07/02/06
Posts: 1093
Loc: Fort Worth TX
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No, the conical primary baffle should still be internally baffled with at least two baffle plates, similar to a refractor. These internal baffles trap stray light entering the front end of the primary baffle tube at steep angles (such as the moon at several degrees to the side) and prevent it from reaching the focal plane.
I re-did your plot to show your 3.5" primary hole, and added the minimum hole diameter required (at the front of the primary). The support sleeve coming through the primary could be 3.25" O.D. and 2.9" I.D. Or, you may want more clearance from the inside of the primary hole.
Mike
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JohnH
sage
Reged: 10/04/05
Posts: 491
Loc: vancouver near the wilds of B...
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You can make conical baffles fairly easily if you have a wood lathe.
First make a form for the inside profile of the baffles shaped like a truncated cone, then 'pin' a piece of sheet copper to flat side with a live center. Use some epoxy on the underside to glue it down to make sure it doesn't spin.
Using a metal rod with some oil to lubricate it with one end rouinded over, use that to 'push' the copper sheet onto the form while the lathe is running.
The soft copper sheet will conform well with enough pressur. Make sure the rod you use has a lot of mass. The tricky part is getting it to start over the intiial corner. As a bonus the previously soft copper will get work hardened as you press it down.
I don't know if you can do this with harder metals like sheet aluminum or steel.
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jasonharris
super member
Reged: 09/16/06
Posts: 137
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Hi Mike, thaks a lot for the additional information. Seems like I do have quite a bit of room to play with, not a tight fit at all.
Thanks for the reply John, I have seen some metal spinning done but never attempted it myself. I think aluminium is ok depending on the thickness or course..
Well it will give me something to think about! I have never worked with carbon fiber before but feel I should try it sometime as I am sure I would us it for other projects..
Thanks,
Jason
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Gert
member
Reged: 04/15/08
Posts: 19
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Hi All,
Why does the primary baffle have to be conical? It could be a straight tube with the same diameter as the front end of the cone. You can still add circular baffles into it.
Clear Skies,
Gert
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