Truss tube ideas

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Re: Truss tube ideas

Post by banjo »

hello.
13Kg for the trip
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no bigger than a 200/1000 Newton
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bresser/messier 150/1200 (or 200/1800 Istar ) Mod -D-Erf 160mm intern-glasspath 1.25-etalon Pst barlow X2 ASI174
https://astropol.pagesperso-orange.fr/b ... 9/best2019
sorry for my English translators google :mrgreen:
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Re: Truss tube ideas

Post by 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
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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. :bow2


Stage 2 mod completed @ 100, 127.
Istar 228 arrived, building the frame slowly while learning cnc.
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Re: Truss tube ideas

Post by 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/


Stage 2 mod completed @ 100, 127.
Istar 228 arrived, building the frame slowly while learning cnc.
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Re: Truss tube ideas

Post by AndiesHandyHandies »

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

Andrew.


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Re: Truss tube ideas

Post by 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.


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Re: Truss tube ideas

Post by 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


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Re: Truss tube ideas

Post by AndiesHandyHandies »

Hi

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

The best non truss alternative is a alloy tube.

Cheers. Andrew.


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Re: Truss tube ideas

Post by 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.


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Re: Truss tube ideas

Post by 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


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Re: Truss tube ideas

Post by 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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Re: Truss tube ideas

Post by marktownley »

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


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Re: Truss tube ideas

Post by 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.


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Re: Truss tube ideas

Post by 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
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Cheers,
Fraz.


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Re: Truss tube ideas

Post by 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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Re: Truss tube ideas

Post by rsfoto »

Hi,

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


regards Rainer

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North 22° West 101°
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Re: Truss tube ideas

Post by FRAZ »

rsfoto wrote: Fri Mar 22, 2024 7:11 pm 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.
Last edited by FRAZ on Fri Mar 22, 2024 7:19 pm, edited 1 time in total.


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Re: Truss tube ideas

Post by rsfoto »

FRAZ wrote: Fri Mar 22, 2024 7:17 pm
rsfoto wrote: Fri Mar 22, 2024 7:11 pm 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

:bow2


regards Rainer

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Re: Truss tube ideas

Post by Rusted »

Congratulations on the progress of your truss OTA project. :bow

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! :shock:

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! :cry:
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


http://fullerscopes.blogspot.dk/

H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Truss tube ideas

Post by 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


Stage 2 mod completed @ 100, 127.
Istar 228 arrived, building the frame slowly while learning cnc.
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