Anyone tried to make BIG dish at home?

Lexzie

Lexzie

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Xtrend ET10000 DVB-C, S2, T and IPTV, VU+ Zero 4k, Xtrend ET9500
80 cm fixed dish (28.2E/23.5E/19.2E/13E)
120cm Channel Master offset dish with polarmount (42E-34.5W)
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The Netherlands
I guess my reply did not answer your question?
There is a calculation in it, so I guess that's what you're looking for.
 
I

italy2006

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starsat
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iran
IS there a simple way to curve aluminum sheet?
 
A

archive10

Guest
my question is how to make metal framwork for 180 cm.how to curve them.
In theory, dead simple.
You're showing a prime-focus dish made of mesh on a metal framework. I assume this is what you want to make.
(if you were going to mold your own dish using fibreglass and resin on a concrete mold, it would we slightly different).

The shape of the metal profile required is a parabola, so all you need is to calculate a shape that is paraboloid, and make this into a metal profile.
If you have access to CNC equipment, get someone to machine the metal profiles for you.
If not, do as in the Lexzie-posted instructions and map something out using paper and pen (and calculator).
Then, cut the metal as required.
 
A

archive10

Guest
IS there a simple way to curve aluminum sheet?
If you do not have access to a large alu-pressing machine and a suitable die, then you can do the lay-mans approach:

Make a supporting back-plane from metal profiles that are parabolic in shape.
Screw the aluminum sheets to this frame, and align things using a hammer....
 
I

italy2006

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iran
In theory, dead simple.
(if you were going to mold your own dish using fibreglass and resin on a concrete mold, it would we slightly different).

.
how much resin is needed to build 160 cm dish? one kilogram or more?
 
A

Archive4

Guest
Not sure who makes a 160cm resin dish, but I lifted a few 180cm resin dishes and they way a little more than one Kg.
 
battenfan

battenfan

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60N 18E
how much resin is needed to build 160 cm dish? one kilogram or more?
Probably a lot more, It depends on the design. You could make it thin and strengthen it with ribs and curved edges.
160 cm makes about 2 square meters. Scroll down on this link:
Code:
https://www.ecfibreglasssupplies.co.uk/t-estimating_quantities.aspx
 
RimaNTSS

RimaNTSS

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I have weighted several dishes like 1,8m Andrew and Prodelin, they weight about 35kg (no mount included). However, there are another models of same size dishes, and they can weight about 10kg. So, to answer the origuinal question, I would say, that for 1,6m dish, about 10kg of resin is needed..... depending on the design.
 
Lazarus

Lazarus

Tout Rond Bon Oeuf
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Much else.
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Mod Note: I have tidied up a few Posts in order to preserve continuity.
 
battenfan

battenfan

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60N 18E
And surface area depends on how deep the dish is:
Code:
http://www.had2know.com/academics/paraboloid-surface-area-volume-calculator.html
 
A

archive10

Guest
I have weighted several dishes like 1,8m Andrew and Prodelin, they weight about 35kg (no mount included). However, there are another models of same size dishes, and they can weight about 10kg. So, to answer the origuinal question, I would say, that for 1,6m dish, about 10kg of resin is needed..... depending on the design.
adding to what @RimaNTSS and @battenfan writes, the dishes that are around 35 kg (as my Channel Master 180) are self-carrying fibre-reinforced plastic designs where the structure of the dish keeps and carries the shape even under strong wind-loadings.
This is the commercially most efficient, as the dishes are cheaper to manufacture and especially ship than alternatives.

One of the alternatives is to made a comparatively thin reflector, and get the rigidity and shape by bolting it onto an iron frame.
There's a thread here Newbie Here - Elevation help needed for 1.8m offset dish (Malta) with pictures of a CM180 clone, which is made by molding resin (I believe it was) over a real CM180, and then fitting this onto a metal frame.

If you don't have a CM180 or similar offset dish handy as a mold, I suggest you try and make a prime focus dish instead as discussed above. This make the profile easier to obtain, as it is symmetric around the central axis. You can even make the mold from clay/soil, as demonstrated on certain African websites.

If you just want to experiment before you start pouring resin, you can even start out by making a full size test-bed with wooden parts (ribs, centre hub, edge struts), and build a surface on the clay mold using paper mache (glue, water & newspaper) and kitchen foil in a couple of layers as reflector.
This won't tolerate rain or any kind of wind, but this could get you started with geometry etc.
 
I

italy2006

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starsat
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iran
which type of resin is best for dish making?
epoxy resin or polyester resin?
epoxy is expensive but more resistant.
so can i make dish with polyester resin?

does fiberglass dish works well in summer and winter or it losses shape and form?
 
Channel Hopper

Channel Hopper

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A well designed resin dish is impervious to most things the climate throws at it. Damage really only occurs through damage (strikes/drops), continuous gusts of wind near the maximum rating, and extreme age.
 
dmaavrigdo

dmaavrigdo

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I have been wondering about making a giant straight sided feed horn disguised a shed but can't find understandable information about the required angle of the sides.
Anyone got a clue?
Might be impractical if it has to be 32ft or more long though.
 
Channel Hopper

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Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
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My Satellite Setup
A little less analogue, and a lot more crap.
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I

italy2006

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starsat
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iran
i heard that polyester resin is suitable for making fiberglass dish not epoxy resin. instead epoxy is used in industry.is that correct.
 
battenfan

battenfan

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I am not an expert on plastics. What I've read of boat repairs, epoxy doesn't like sunlight very much and is kept below the waterline but I guess there's all kinds of additives on the market for various environments. What you should think of is how much the resin shrinks as it hardens. Try investigate what the brand names are using, maybe someone here knows.
SMW OA 1600 is using abs and acrylic topcoat. SMW OA 1600 dish
What about Channel Master?
 
W

wijayak

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This is my 6ft homemade offset dish made out of steel box bar and alluminum sheet for the reflective part.
 

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