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My handmade 16" Truss

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#1 Manousos

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Posted 22 January 2013 - 07:09 AM

Hi there!
I have recently started the construction of a truss dob at 16". This is my second scope project. The initial guidelines were retrieved from the Krieges book, but there are a lot of modifications since I wanted a more compact and transportable design. Since I leave in Greece there are no much choices about the optics, appart from 1-2 (expensive) companies. The most value/money option was a 16" F/4.5 GSO mirror with Hilux coatings. The secondary is a 90mm Orion Optics with hilux as well. So far the constructed parts are the mirror cell, spider and uta.

Hope you enjoy it.

#2 Manousos

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Posted 22 January 2013 - 07:15 AM

The Mirror Cell
The Jig
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The triangles and bars
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The strip
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Supports
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The fan
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Testing with the mockup mirror
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#3 starman345

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Posted 22 January 2013 - 08:07 AM

Hi, great to see you post your project here. From what I"ve read there is nothing wrong with those GSO mirrors, good choice. How thick is it? Mirror cell frame is steel, the rest is aluminum? I"m interested to see your ideas on making it more compact. Thanks for the pictures and hope to see more.

#4 Manousos

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Posted 22 January 2013 - 10:12 AM

Thank you!
The thickness of the mirror is 45,3mm (1.8"). The mirror cell frame is steel and the triangles and bars are alouminum.

#5 Manousos

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Posted 22 January 2013 - 10:18 AM

Next part the spider and secondary holder.
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#6 rboe

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Posted 22 January 2013 - 10:28 AM

Are you using a thread locking compound on the threads of the screws in the spider? Loctite in the name brand over here but there are others. Fingernail polish makes for a poor mans thread lock if you can't source a commercial version.

I love the details on the spider; well done! :bow:

#7 Achernar

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Posted 22 January 2013 - 11:56 AM

You've made your tailgate and mirror cell the same way I did, namely welded mild steel for the tailgate, 6061 T6 aluminum alloy for the bars and triangles. I used stainless steel allthread, screws and nuts for the rest. For collimation knobs, I used disks of aluminum alloy cut out with a hole saw. The sidepins were made from hardwood dowels I drilled lengthwise, a difficult opperation at that. The mirror clips I made from short left over pieces of the stock used for the bars to which the triangles are attached, with rubber padding between them and the mirror. You did a very nice job on your mirror cell and tailgate. :waytogo: You'll see the payoff evertime you look into the eyepiece.

Taras

#8 Manousos

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Posted 23 January 2013 - 06:24 AM

Well regarding the collimation knobs, at the beginning I was forced to use metal disks because the maximum width for full threads with embedded plastic knobs I found, was not enough. Although later on I realised that using metal disks is better because I could use these knobs as foots putting on the ground the mirror box without putting extra foot for that. Moreover using plastic knobs was a risk to broken them when I put the mirror box on the ground. At the other side plastic knobs are more aesthetic when view the back of the mirror cell.

Regarding the locking compound, no I'm not using something. I have just tighten the bolts with the nuts. But its a good idea to put fingernail polish to secure the nuts :applause:

Follows the UTA photos. The UTA ID is 17" and the width of the ring is 2"

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#9 Achernar

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Posted 23 January 2013 - 07:22 AM

I was thinking the same thing, plastic knobs tend to get broken off sooner or later. I would have rather welded a stainless steel disk to the collimation bolts, but I simply used a pair of stainless steel hex nuts to hold the disks in place, then dogged them tight. So far, they haven't a problem.

Taras

#10 Víctor Martínez

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Posted 23 January 2013 - 11:43 AM

Be careful with the weight of the upper or you will have to put a lot of wood and weight in the rocker box for counterbalance

#11 Achernar

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Posted 23 January 2013 - 05:47 PM

There is a way around that problem. Once he has the mirror cell and the UTA finished, he can calculate how much torque each part of the telescope has. With that information, he will know how long to make the mirror box so he won't be adding ballast to either end to balance it. When I built mine, it was to my immense relief that I calculated everything correctly.

Taras

#12 Víctor Martínez

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Posted 23 January 2013 - 06:21 PM

Yes, but that does not mean that he can saves an unnnecessary excessive weight in the rocker box if he controls a little the excess upper weight.

#13 Achernar

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Posted 23 January 2013 - 06:30 PM

True, that is why he can run the numbers before he builds the mirror box, so there won't be any surprises.

Taras

#14 starman345

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Posted 23 January 2013 - 06:56 PM

Its also easy to calculate the weight of the secondary cage before building it, maybe Manousos has already done that since he is trying for a compact and easily transportable scope. Am I right in guessing you are making a single ring secondary cage?

#15 Manousos

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Posted 24 January 2013 - 05:43 AM

Actually becuase my theoretic calculations was not very precise in the real world and because of the reason that I want a compact design my approach has changed. No calculations for balancing at all. I just need to make the proper diameter of the altitude bearings by finding the center of gravity of the fully assemble scope. Assemble the main body of the scope and put weights on secondary cage in order to simulate finder scope, focuser, the heaviest eyepiece and telrad. The same weight of the primary mirror needs to be putted on the mirror cell. Then put horizontaly the scope and find the center of gravity by lifting from the trusses. The altitude bearings needs to be cutted in the radius from the cog to the place that will contact with the teflon pads. A cresent shape helps to keep light the bearings and if possible to be removable from the mirror box.

I found this approach very precise at my first scope I built and my scope was the lightest possible without heavy counter weights at the back of the mirror or tall mirror box. Only some light weights in the front in order to counter balance the altitude bearings weight.

#16 Manousos

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Posted 21 March 2013 - 11:22 AM

Hello again!!
I have finished the scope but I didn't have the time to upload the photos. So Im sending you the remaining photos!!

Have fun...


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#17 zjc26138

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Posted 21 March 2013 - 11:55 AM

Dimitris,
Simply Beautiful!

#18 Bill Kocken

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Posted 21 March 2013 - 01:48 PM

That's a beautiful job. I'm almost inspired enough to rebuild my own 16"!

#19 David Castillo

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Posted 21 March 2013 - 01:56 PM

That is a thing of beauty :waytogo:
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#20 richard7

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Posted 21 March 2013 - 04:55 PM

Absolutely beautiful.
You've got something to be proud of.

#21 sn1987a

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Posted 21 March 2013 - 07:12 PM

You Sir, are a god to me!. :bow: :bow: :bow:

#22 starman345

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Posted 21 March 2013 - 07:31 PM

Beautiful, you did a great job!

#23 cpr1

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Posted 21 March 2013 - 07:35 PM

+1 Great job. Nice scope.

#24 Víctor Martínez

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Posted 22 March 2013 - 03:21 AM

Well built!

#25 Manousos

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Posted 22 March 2013 - 05:16 AM

Thank you all you guys! I'm glad you like it. This is my second DIY scope. This time the construction and plans was much better than my first attempt. I'm going to start building another one, this time with motor drives.

Thanks again for watching.






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