Truss tube ideas

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Truss tube ideas

Post by FRAZ »

Hi all,

I am aware of a couple of people mentioning truss tube builds and have had the idea of doing my own build for some time now. I thought I'd start this thread so I can put down a couple of basics and see if anyone has any other ideas or pointers. There are going to be many outlets and ways of achieving this so sharing seems like a good idea.

I have ordered:

6 x 1metre aluminium tubes of 25mm diameter and with a 1.5mm wall. (These weigh approx 2 kg)

https://www.aluminium-online.co.uk/prod ... gth=1000mm

24 x Spring Threaded Tube Connectors that fit the tubes above with M10 bolts.

https://www.vital-parts.co.uk/spring-th ... 4629-p.asp

edit: I am going to need to double up on the poles and that will add 4kg to the overall weight)

My plan is to make either aluminium or steel circles from blanks and screw the tubes on like a truss dob. I intend to drill six holes round each support circle and use three alternately as you go up in either two or three rings. I will make a top plate / cell for each of my objectives in time but will just try to get it fixed together in the first place. (I'm thinking about an adjustable top ring that all cells would sit on)

I am planning with 250mm or so as an upper range in the future and am good for any ideas you guys may have. I think that puts my rings on the 300mm mark for future proofing.

I currently use an NEQ6 but with plans for an EQ8 if this gets too heavy.

Any thoughts or pointers would be very welcome. Please feel free to dump here any of your own initial ideas even if you do then start a post of your own. This is going to take me ages to get sorted and I will probably change my mind many times as I go along.

Thanks,
Fraz.
Last edited by FRAZ on Thu May 05, 2022 12:24 pm, edited 2 times in total.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by FRAZ »

I wondered at doing the Hexagonal build and may go there for the bigger build yet but my idea is to use the scope rings I have on my 10' reflector and turn that into a diy dob in the future.

I'm going to have to do a weight assessment but I figure that the beefy truss is going to be lighter than the 10 incher anyway.

edit: The three poles staggered will not work well and the weight is not good in total for a set of rings. I will have to go hexagonal and use a plate to attach one of the six sides.
Last edited by FRAZ on Thu May 05, 2022 12:24 pm, edited 2 times in total.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by FRAZ »

The objectives I had in mind are from Istar. When I go large I want to try and hit that 228mm.

https://www.istar-optical.com/achromatic.html#ach220f15

The aluminium I have gone with is in sheets that I will cut out myself, that will be another piece of machinery I need to buy.
I have gone for 6mm aluminium and will make probably 4 support plates out of a 600x600 sheet and a long adapted dovetail plate out of a 1 metre by 300 sheet.

https://www.ebay.co.uk/itm/401463858919 ... SwpzJaO9N5

I purchased a workbee cnc from ooznest to mill the aluminium which takes a couple of months to come and then I will have to build and learn to use the thing so it could be a while.

Please note any links are just examples and not advertising, they are just what I am thinking and would always appreciate any insights as to good or bad choices.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by marktownley »

Sounds like you're going to have fun Fraser, I've not done anything like this, but I will sit back with some popcorn and watch it develop.


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Re: Truss tube ideas

Post by rsfoto »

Hi,

Interesting project.

Maybe some sketches for a better idea what you are doing ?

I have seen many Truss tube designs and most of them have varying sizes of intermediate plates in order to avoid parallelism among the tubes.

Doing it like this perhaps saves you from using too many intermediate support plates ?

Just an idea.
Last edited by rsfoto on Thu May 05, 2022 8:19 pm, edited 1 time in total.


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Re: Truss tube ideas

Post by FRAZ »

rsfoto wrote: Thu May 05, 2022 7:36 pm Hi,

Interesting project.

Maybe some sketches for a better idea what you are doing ?

I have seen many Truss tube designs and most of them have varying sizes of intermediate plates in order to avoid paralellism among the tubes.

Doing it like this perhaps saves you from using too many intermediate support plates ?

Just an idea.
Do you mean thickness of the plates or designs of those plates?

I had only considered design as to make them narrower but your comments suggest I may be missing something here.

Thanks,
Fraz.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by FRAZ »

marktownley wrote: Thu May 05, 2022 7:31 pm Sounds like you're going to have fun Fraser, I've not done anything like this, but I will sit back with some popcorn and watch it develop.
I'm going to make lots of mistakes. I'm going to learn a lot.
:seesaw


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by rsfoto »

FRAZ wrote: Thu May 05, 2022 8:08 pm
rsfoto wrote: Thu May 05, 2022 7:36 pm Hi,

Interesting project.

Maybe some sketches for a better idea what you are doing ?

I have seen many Truss tube designs and most of them have varying sizes of intermediate plates in order to avoid paralellism among the tubes.

Doing it like this perhaps saves you from using too many intermediate support plates ?

Just an idea.
Do you mean thickness of the plates or designs of those plates?

I had only considered design as to make them narrower but your comments suggest I may be missing something here.

Thanks,
Fraz.
No, the outer perimeter.

Make a search for truss tube telescopes and you will get the idea

https://tinyurl.com/truss-tube

https://tinyurl.com/DIY-truss-tube

http://www.nfilipovic.com/astrophotogra ... -telescope


regards Rainer

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Re: Truss tube ideas

Post by FRAZ »

You know when you look at something and think, that looks more difficult, I will go for the easier option.
You just got me good and proper.

I really just wanted to make this thing, if I could do it in stages and make improvements then I would feel so good about it. It seemed the logical way to go.

Having thought about it for a short while I think that a bracket could be made in the same position and rods used at different angles, it complicates things mostly in my machining capabilities I will need to look into this. Thankyou.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by Rusted »

Back in the early 80s [?] I made a truss tube 8.5" f/3.8 Newtonian using rubber "expansion bolts".
As the central screw is tightened a cone expands the hollow rubber "plug" into a very solid fixing.
This reduces the need for precision angle brackets. The rubber can allow some misalignment before it is fully tightened.
Such "expansion bolt" systems are easily made from "borrowed" cones and rubber bushes. Skateboard trucks?
They also exist in many different commercial forms for fixing items to walls.
This idea works well with aluminium tubing but might split carbon fibre tubing.
The other advantage is that the system can be dismantled repeatedly. Just by loosening a few screws.


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Re: Truss tube ideas

Post by vkx86 »

Lunt has one very nice truss design - I think you can get some ideas from it.
There is very cool truss design from one of the forum's members - really good one IMHO.


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Re: Truss tube ideas

Post by FRAZ »

vkx86 wrote: Sat May 07, 2022 4:51 am Lunt has one very nice truss design - I think you can get some ideas from it.
There is very cool truss design from one of the forum's members - really good one IMHO.
Thankyou very much.

That first Lunt design, did you catch the price of that telescope!

The second is absolutely where I was aiming for and I couldn't have a better example.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by vkx86 »

FRAZ wrote: Sat May 07, 2022 1:52 pm Thankyou very much.

That first Lunt design, did you catch the price of that telescope!

The second is absolutely where I was aiming for and I couldn't have a better example.
It's my pleasure to offer some help in such an endeavor of yours :)
Lunt 300mm price is indeed astronomical - I have no idea what contributes to such a price.
Regarding Alessandro's truss design - it's ticks all boxes in very best ATM design I'd ever saw.


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Re: Truss tube ideas

Post by FRAZ »

vkx86 wrote: Sat May 07, 2022 2:12 pm Lunt 300mm price is indeed astronomical - I have no idea what contributes to such a price.
I guess it is a combination of etalon size and 'research grade'
I wonder how much more it is for the double stack!!!

:o


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by vkx86 »

FRAZ wrote: Sat May 07, 2022 2:30 pm I guess it is a combination of etalon size and 'research grade'
I wonder how much more it is for the double stack!!!
Their largest PT etalon is one used in their 230mm, it's 80mm CA un-obstructed etalon.
Off 230mm USD 33K price I would wildly guess that the tube, focuser and achro lens (using istar prices) costs 500+500+3700 = 4700 USD, let's round that to 5K.
That lefts us with 2 x 80 mm etalons at 28K, so 14K for one etalon.
I think they use same etalons in their 305mm, so we can speculate if applying research grade polishing to etalons is a main driver to two-fold price increase and not the fancy truss-tube and 70mm bigger lens ;)


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Re: Truss tube ideas

Post by FRAZ »

I know I have called this thread Truss tube ideas (but) and I want to talk about lenses.

It seems to me that after exhaustive research I came back only to Istar, the mod by Allesandro used the exact same objective I found! I am going to assume that there is not a glut of quality objective producers outside of china? I appreciate that this could be a thread of its own and will cut this short.

Are there any others I have missed that are in the realistic price range. Not more than 3 or 4 k?


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by Rusted »

Just as a side note: Parallel tubes are not a true truss design. [Not a Serrurier]
Parallel tubing OTAs have been used and called "skeleton" tubes for over a hundred years.
Parallel tubes do offer much easier linear adjustment of all the components.

The tubing used must be stiff in a parallel tube design.
Or the whole OTA will bend like a banana under its own weight!
Even before you add any optical components.

A full length brace to fit on the mounting saddle is a very good idea.
It brings its own inherent stiffness to the design [due to its beam dimensions].
You could use multiples of these rectangular beams to form your "tube."

I have used "builder's straight edges" for this purpose. Look up SWALK straight edges.
These are used for levelling screed and plaster work.
Very light and inexpensive for the quality and proportions they provide.
Available in lengths to match any likely amateur OTA. 3.6m? They have an internal rib for extra stiffness.
Most builders merchants sell them over here. Sometimes with a bubble level fitted at far higher prices.

This design has a sturdy beam.

viewtopic.php?f=11&t=26691

iStar objectives have a good reputation and have been used by some "world class" imagers.


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3, PST etalon, Lunt B1200S2, Assorted T-S GPCs, ZWO ASI174.
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Re: Truss tube ideas

Post by FRAZ »

I was speaking to a workmate today who recommended that I make the rods out of single longer rod of thicker aluminium instead of trying to connect multiple rods to either side of the plate, instead use connectors that attach the plates to the rod.

I can't see very well how Ale had his attached but I am keen to try that design. It just means I have wasted all that money on shorter poles and spring loaded connectors. I'll have to make something else out of that :)

I think the base plate is a t strut system and the aluminium is thick enough to bolt through and this is also how the rings are bolted to the tubes. RS Pro do this base plate and bolts. That may be worth looking into.


Coronado 60 DS BF15 - EQ6 Pier mounted - Stage 2 mod completed @ 100, 127, and working on a coronado 60 to 150 mod. Working on a Pst Etalon DS Quark.

When I first went dark sky I took the advice to get the best mount I could. I give you the advice to get the best erf you can.
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Re: Truss tube ideas

Post by rsfoto »

... instead of trying to connect multiple rods to either side of the plate, instead use connectors that attach the plates to the rod ...
Hi,

Not necessarily. Take a good look at those huge truss tube constructions of the Ritchey Chretien or whatever mirror telescopes.

Make some sketches and look at them ...

Thicker walls not always bring more rigidity but increase the weight of the construction and so other problems will arise ...


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