Truss tube ideas

[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.

[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.

[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.

[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.

[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.

[FRAZ]

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.

[FRAZ]

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.

[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 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

[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.

[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.

[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.

[FRAZ]

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.

[vkx86]

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.

[FRAZ]

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!!!

[vkx86]

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

[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?

[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.

[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.

[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 ...

[banjo]

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[marktownley]

That's pretty cool Paul!

[MalVeauX]

lulu204mm.jpg

super.gif

Fantastic! I've been looking for ways to build a truss frac for solar using my existing current lens I use (150mm). This is great inspiration!

What's the total weight on that?

Very best,

[Rusted]

There is also the Porsa building system of aluminium tubes and reinforced plastic joints.
The joints are hammered into the square tubing using a rubber mallet.
The result is a very stiff construction capable of supporting aquaria.
Though not particularly lightweight.

Here is my take on the Porsa system for my folded 7"/180mm f12 R35 iStar refractor.

P1270146 rsz crop folded 7 telescope 2.JPG (259.76 KiB) Viewed 11405 times

[marktownley]

More cool scopes! Nice instrument Chris!

[Rusted]

Thanks Mark.

Collimation was a nightmare!
The folding mirrors really need remote control rods.
With collimation adjustment knobs on the back plate.
I preferred to use the simpler, straight tubed version.

[banjo]

hello.
13Kg for the trip

lunette pliée alexandros.jpg (270.57 KiB) Viewed 8532 times

no bigger than a 200/1000 Newton

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[FRAZ]

On my own journey to build something I have made steps on this looong journey.

Bought a cnc machine to learn how to make some circles or hexagons out of 10mm aluminium. This is a long journey in itself but I went for a workbee 1500 x 1500 and my learning has started. I actually had to build a room in the cellar and then a table to fit it while building it.

https://ooznest.co.uk/product/original- ... ize-colour

thumbnail_PXL_20220710_180617318.jpg (377.04 KiB) Viewed 8324 times

Sourced some reasonably priced aluminium t nut strut profile. Got the wrong size but making a smaller version while waiting for the lense for the 228. The profile does not look too dissimilar from that used to construct the workbee as pictured above.
https://www.aluminium-profile.co.uk/30x ... -kjn990720


Paid Istar £3200 for one of their excellent 228 F7.7 standard coating lenses. 7-9 month wait but that will give me the time to sort out the rest.
https://istar-optical.com/achromatic.html

Other brands and options are obviously available but this is where i am at.

Thankyou too for all of the inspiration as I have been battling through the last year. You guys are awesome.

[FRAZ]

I happened on this awesome journey while looking for some finer points and while it is a long read it was very enjoyable and thorough.


I caught a couple of points on initial read that caught my attention but this one in particular:
Connecting the mid rings to the anchor point of the equatorial (mount) source. Is there going to be an expansion problem and how can you limit that?


https://www.cloudynights.com/topic/1660 ... am-effort/

[AndiesHandyHandies]

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.

I am afraid this type are not very stiff or light.

Andrew.

[AndiesHandyHandies]

Hi

There are only two types which will be adequately stiff:

Surrier Truss as used in professional scopes.

Or for compact and quick set up a Hexapod three pole design. See Cloudy Nights thread.

Cheers. Andrew.

[FRAZ]

So I have moved a little recently after Andies post and have gone all in on two ideas.

First idea was to buy a 12 inch dob with good solid truss and modify to reach my needs but this morphed quickly into diy truss ideas that I may follow later.

Second idea was to buy an F34 aluminium truss built for dj systems that has minimal deflection over 4 metres.

I have bought a 2 metre truss of F34 and will be trying it out. I will let you know how i get on. £240 seems like a reasonable outlay considering the fing about Im otherwise thinking about.

https://www.thomann.de/gb/stairville_tr ... 12_f34.htm

[AndiesHandyHandies]

Hi

That should do as well triangulated. Looks do not matter.

The best non truss alternative is a alloy tube.

Cheers. Andrew.

[FRAZ]

I'm now thinking about the objective mount and the focuser attachment.

I need a 300mm ring like they do on the big dobs for a focuser attachment but in this case would help hold the objective. The logic is that the truss is just too narrow to sit the objective on top and gain full aperture view. I need to hold it slightly higher in the optical path even though this will cause me issues in the focuser regions.

For the focuser I am thinking about running a plate up the truss and a newtonian focuser flattened onto the plate. I would have to modify the seating arrangement to make it flat but I have seen a Diamond steeltrack that can do that and is quality.

https://www.firstlightoptics.com/baader ... nians.html

As always, hints, tips, experience and ideas are always welcome.

[FRAZ]

In hindsight after my last post. I should have got the 1.5m version and played with both ends. I could have extended the height and expanded the optical cone beyond the truss limits and I could have brought the focuser back at the rear.

To further explain. The centre point from pole to pole is 240mm and the objective is 228mm. This cuts close with 25mm each corner and will clip the view unless the Objective is raised and that creates the need for the additional connection of a raised ring to eliminate the difference.


https://www.thomann.de/gb/stairville_tr ... 11_f34.htm

[FRAZ]

I discovered that you can buy a baseplate for the F34 Global truss system that fits a 5mm endplate.

I took this apart and after a couple of practice turns with some other aluminium I cut a 242mm hole in the endplate and fitted the Istar 227 to it. Very pleased with the results so now I am moving on to the focuser and the issues I am going to have with that.

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[marktownley]

We do like a bit of machining! Nice work, keep us updated with progress!

[FRAZ]

Focuser assembly plate next.

I have an old Skywatcher f/9 APO focuser that was on my first PST Mod and no longer used. I wanted to use this particularly because I can sandwich the two parts available between a sheet of aluminium with a hole cut out of it.

I made the hole 2mm too small despite measuring meticulously. Only thing for it was to butcher it with a file to make it fit, and it now does.

I wanted to show this because I have not seen anything anywhere about focuser assemblies on diy. My other alternative was to perhaps buy a decent short reflector focuser and bolt it on to this very plate with the hole in it.

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Now I just need to find the focus point, create a jig on the lower section of the Global Truss unit and cut the plate to size.

Thanks for looking
Fraz.

[FRAZ]

The saddle for the mount.

Due to the truss design I had to rethink my method of gripping the truss to then fit onto the mount. Again I had an item lying around which was a dual saddle. I bought a couple of dovetail bars drilled a couple of holes through the truss and bolted them on. I got lucky here in that the ADM dual saddle plate was only about 5mm off being perfect for the legs on the truss.

I know I am going to have some issues with balancing this and in the extended length perhaps being a problem when on the pier but I stole a little balance and I will put a weight on the focuser end if needed when I test it all out.

Saddle.jpg (548.98 KiB) Viewed 6565 times

Cheers,
Fraz.

[FRAZ]

Made the jig for the focuser and tried the truss on the mount.

It's heavy, too big for the observatory and ridiculous to mount but these are all good things.

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[rsfoto]

Hi,

Excellent construction. May I ask how much does the whole assembly weigh?

[FRAZ]

Hi,

Excellent construction. May I ask how much does the whole assembly weigh?

The global Truss runs at 12.5 kg
The plate and objective about 5.5 kg
The focuser assembly and saddle about 4 kg

Total about 22kg

Thanks.

5.4 kg for the objective so far out on the front is the challenging part.

[rsfoto]

Hi,

Excellent construction. May I ask how much does the whole assembly weigh?

The global Truss runs at 12.5 kg
The plate and objective about 5.5 kg
The focuser assembly and about 4 kg

Total about 22kg

Thanks.

That is reasonable for such a big lens

[Rusted]

Congratulations on the progress of your truss OTA project.

Unfortunately observatory size quickly becomes a VERY serious issue with bigger refractors.

DO NOT GET BOGGED DOWN IN CRAZY OBSERVATORY PROJECTS! SERIOUSLY!

It is better to carry out the OTA and mount it than NEVER to use it while you build a suitable housing!
Buy an industrial quality stepladder, like JUMBO, to help you reach the mounting height safely.
A handrail or two may save your life AND your OTA! Be warned! I have been doing this for years!

Full observatory? I would recommend Peter Drew's half cylinder observatories to house your project.
MUCH more practical than a hemispherical dome for a DIY builder.
Or perhaps a roll-off roof housing only large enough to cover the instrument.
Not easy given the height when horizontal! It could easily end up as a spinnaker in a storm!

Like an idiot, I built a 4.3m [14'] diameter dome out of a fiberglass agricultural unit but it needed a crane to lift it.
So I am currently trying to give it away. Over 3000 hits on Facebook and still nobody wants it!
Be warned that the scale of such a dome is unbelievable! As is the cost! Even for DIY. $6500+US or £5000+GBP.

https://fullerscopes.blogspot.com/2023/ ... y-43m.html

[FRAZ]

I hear you on the projects Chris, I just last year built the missus a fully insulated summerhouse 3.6 x 2.4 with a hot tub in and a roll off roof. Would look nice with a telescope in it and after reading your blog I can see you jump in with both feet (right up to the neck in it).

I hope you are keeping well and I really appreciate your experience and help here.

Fraz

[FRAZ]

Focuser help needed!!!

I have found the terrestrial focus point, I have measured the 1756-1800 zone for the specs of the lens. I can't find focus with the quark attached to my jig for finding the focuser position.

How far from the narrowest point of convergence should I be looking?
If I can get out and find the focus point for the moon is that going to be similar?

I don't want to commit to a position until I know it will work which makes the whole positioning process a bit rocky to say the least.

Thanks,
Fraz.

[AndiesHandyHandies]

Hi

Are you using a standard 4.2x Quark with 9mm blocker or one from the Combo for off axis Catadioptrics with a 20mm blocking filter and your own choice of Tele-extender Barlows?

Ignore the elitist crap about only Baaders or more exotic stuff being 'truly' tele-centric.

I have a 2" ES TE which visually gives identical views to the more expensive 2x T2 Baader TE.

I use a 3x Vision King 1.25" for F20 on my F6.7 90mm triplet, and either DS with a PST mod and 20mm apature or a 2x ES 1.25" added for F40.

I use a 1.25" T2 Baader prism as short. It has bad scatter so I put a stop right by the input and output faces and much better haze rejection.

Good luck.

[FRAZ]

Hi Andrew,

I'm using a standard 4.2x Quark. Soon to be replaced with a Sundancer II but I can't find the focus point and time and weather are making testing rare.

Thanks,
Fraz.

[FRAZ]

Finding the focus point.

This has been really difficult for me and I have been running up and down the length of the tube and beyond on any rare opportunities. I am pleased to report that I have found focus!!!!!

PXL_20240519_125044435.jpg (334.45 KiB) Viewed 5558 times

The image is so soft and bouncing all over the place. I've got a couple more issues to deal with. It seems the frame bounces so much on a standard movement of the mount that i will have to reconsider the mounting solution I have. The soft focus will put down to aperture and seeing.

We are moving onwards though and I feel confident enough to buy a decent focuser and fasten it in. I am overjoyed that the image train is almost exactly the length of the protection of the truss. I should be able to add a mini scope ring to help stabilise the unit.

Very tricky stage this was and in the image it looks like the erf is at strange angles but it isn't.

Best
Fraser.

[Michelo]

Hi Fraz,

Your truss tube build sounds exciting! Here are a few pointers:

Material Choice: Aluminium is a good choice for weight saving. Ensure all connections are secure and consider reinforcement where needed.
Tube Connectors: Make sure the M10 bolts and connectors are strong enough to handle the additional weight when you double up on poles.
Support Circles: Using steel or aluminium circles is a solid plan. Ensure accurate drilling for stability.
Top Plate/Cell: An adjustable top ring is a great idea for flexibility with different objectives.
Weight Management: Keep an eye on the total weight, especially if you plan to upgrade to an EQ8 mount.
Looking forward to seeing your progress!