What happens to cheap chinese mesh dishes under moderate wind

[BombedOne]

I've installed this baby (2.4m primefocus C band mesh dish) couple of days ago. Performance in C band was spectacular, I did some DXing using it, but whole construction (except polar mount) was wery fragile and flimsy. For the several days, we had moterate northen wind here (no emergency, no broken glasses, no damage to trees, just typical wind of this period of the year). On the pictures you can see what was, and what remains now.

Sorry for terrible quality pics - my camera is quite old, and focus performs badly at negative ambient temperature.

So, if you live in moderately windy area, think twice, before investing your money into such dish.

 

[guest]

OMG!

A salutary lesson for us all - many thanks.

 

[guest poster]

Very sorry to see that happen BombedOne...

........it was very difficult to see how weak the build of the dish was on your previous photos.....

........you could rebuild it for C Band use... but make it much stronger .. a project/ challenge..

not sure if you could get it all the way to use KU band mesh ...



We work on some high roofs and on the ground it can be very calm all the way up to the top... but when you get up over the top of the roof it can be very different

 

[BombedOne]

Luckily no one was injured, as while petals broke off from polar mount, LNB support legs still remain on them, and whole construction was saved from falling down from the roof by LNB cable, which is broadcast grade cable with AMPHENOL crimp on connectors.

I don't think that there's any capability of repairing this dish, just one 1/4 section is relatively intact, and may be used as primer, if building a newer one.

Currently, I'm estimating approximate budget for building large, 3.6 meter sized mesh dish. Unlike this one, it will be made from steel tubes and steel mesh (and very custom adjustment system). By 1st calculations, I should be able to fit under $300 budget. Let's see what will be tomorrow, after I get quote from metal tube supplier. (by my drawings, I may need them up to 100 meter!)

 

[guest poster]

I am surprised they offer a KU mesh option for that dish then.... maybe low down in a sheltered yard it had a better chance. If you don't mind.. how much was the dish.

best of luck with the 3.6m then

 

[wod]

are you going to use the polar mount for the 1.5m dish now ?

looks like the dish could have done with some support bars welded on the back of it as maybe that would have stopped it breaking up like that

how bad do the winds get in your area 50mph + ?

 

[BombedOne]

There's nothing to be surprised - china offers everything you want, for price you want, but not with quality you want

Whole dish price, including polar mount was US $180

I don't know much about wind MPH, since we use different measuring system - meters per second. Heaviest wind, acccording to forecast, was about 15-20 meters per second, which converts to 33-45mph?

 

[LAURO2008]

Buongiorno Bombedone,

I feel so sorry to see that...you didn't deserve it!

but I know also that you never give up...so wish you all the best with the new project. And thanks in advance for sharing it with us.

Ciao

 

[BombedOne]

Thanks everyone for support. I'm currently thinking about various ideas for such high windy roofs, including building of wind deflector.

If anyone else wants to install big dish on high building, check this document:

_ttp://www.cadfem.ru/data/62M.pdf

It is in russian, but pictures and numbers speak for themselves.

In short - this is example calculation of load received by 3.75m primefocus antenna, mounted on building roof with height of 40 meters, and wind speed of 35 meters/sec. You can skip directly to page #8, where's table of wind loads received by dish, during various directions of wind and dish location, are given. Numbers are in newtons.

 

[kwp58]

So, if you live in moderately windy area, think once.
About Archimedes did not hear, about a difference of shoulders, about concepts - the lever. It was necessary to do the support area much more.
Variant of wall fastening:
So professionals in Russia establish the aerial.View attachment 20651

 

[BombedOne]

I don't see polar mount anywhere on that pic and also dish size is nowhere close to 2.4m

 

[RedDevil_UK]

well you have certainly BombedOne

sorry couldnt resist

not being one to call your DIY skills, but when this came as 4 petals to be built.... did you build it properly making sure it was secure?

or are you not being honest about the wind strength?

not having a go.... but im amazed it would fall apart so easily!

 

[kwp58]

I don't see polar mount anywhere on that pic and also dish size is nowhere close to 2.4m

Respected, BombedOne, on my support it is possible to establish больший\The big\, than 2.4m the size. It is the polar aerial. It is made, the same in China. Safety factor of an arm - 10 times. The installation site is closed from the main wind. This most important thing + calculation and intuition.
It is told perfectly: "A Wise Man can see more from the bottom of a well than a Fool can see from the top of a mountain."

 

[divibi]

So professionals in Russia establish the aerial.View attachment 20651

Hi Kwp58

Welcome to the forum! Thanks for the pic. It's great that you can receive AsiaSat- the Astra of Asia.
I have always wanted to ask someone from Russia about what dishes are manufactured there. And since you are probably the first person from Russia, here do you know how many dish manufacturers there are in Russia? I only ever heard of SUPRAL (cynpal???) dishes, which are said to be of absolutely phenomenal quality, as if they were made for Space Stations. Are any dishes produced in Russia nowadays? Is it still possible to buy a new SUPRAL dish, let's say 2.4m or more, preferably Prime Focus? About a year ago I found an online Russian shop that had a picture of a Supral offset 375cm X 405cm- is it one piece or segments? Does Supral make Prime Focus dishes? Thank you in advance.

 

[kwp58]

Hi Kwp58

I only ever heard of SUPRAL (cynpal???) dishes, which are said to be of absolutely phenomenal quality, as if they were made for Space Stations. Are any dishes produced in Russia nowadays? Is it still possible to buy a new SUPRAL dish, let's say 2.4m or more, preferably Prime Focus? About a year ago I found an online Russian shop that had a picture of a Supral offset 375cm X 405cm- is it one piece or segments? Does Supral make Prime Focus dishes? Thank you in advance.

Respected, Divibi, SUPRAL dishes have high quality, at us much, in the beginning, became for army, and then for people. Supral offset 375cm X 405cm\СТВ-3,7-4/6 2,5 AL АУМ\expensive also it is applied to professional installation. The manufacturer - _http://www.supral.ru/p0213.html Инструкция по сборкеА3700 лепест.АУМ\. I learn later.

 

[divibi]

SUPRAL dishes have high quality, at us much, in the beginning, became for army, and then for people.

Thank You, Walentin, Much appreciated!
Yes, it must be high quality, because it was designed by the army. I believe it is expensive, as such dishes cost thousands of dollars. But how much is it? From the Russian forums - do you know what the 1.65m prime focus dish costs? Thanks in advance.

 

[kwp58]

Thank You, Walentin, Much appreciated!
Yes, it must be high quality, because it was designed by the army. I believe it is expensive, as such dishes cost thousands of dollars. But how much is it? From the Russian forums - do you know what the 1.65m prime focus dish costs? Thanks in advance.

Manufacturer Supral yet has not answered mine Е-mail about price СТВ 3,7-4/6 2,5 AL АУМ in Moscow. There is data about the price of this product for Urale\Ekaterinburg\- nearby 6000$.

 

[kwp58]

Thank You, Walentin, Much appreciated!
Yes, it must be high quality, because it was designed by the army. I believe it is expensive, as such dishes cost thousands of dollars. But how much is it? From the Russian forums - do you know what the 1.65m prime focus dish costs? Thanks in advance.

Respected, Divibi,Manufacturer Supral yet has not answered my letter on price СТВ-3,7-4/6 2,5 AL АУМ. There is data about the price in the city of Ekaterinburge\Ural\- nearby 6000$.

 

[kwp58]

Thank You, Walentin, Much appreciated!
Yes, it must be high quality, because it was designed by the army. I believe it is expensive, as such dishes cost thousands of dollars. But how much is it? From the Russian forums - do you know what the 1.65m prime focus dish costs? Thanks in advance.

Respected, divibi, price СТВ 3,7-4/6 2,5 AL АУМ on 17.03.2009 at the manufacturer \the city of Ulyanovsk, 1000 km.to the city of Moscow\. - 280000 rub. or 8000$

 

[zeadesmawa]

many thanks