Advice wanted on Dish repair

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#1
Hi I've been given a 2.4m dish the problem being it was blown off a 4 story building having had some panel beating experiance with cars i have straightened it out i have got the basic shape more or less right what i want to know is
1, does the dish surface have to be perfectly smooth as there are hammer marks in1 area of it if it does could i use filler and sand it down.
2. the main damage was over a 2ft x 1ft area on the edge when i mount the dish would i be better having this damaged area at the bottom or top or would this make no differance
thanks in advance for all help given
 

2cvbloke

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#2
Bott said:
Hi I've been given a 2.4m dish the problem being it was blown off a 4 story building having had some panel beating experiance with cars i have straightened it out i have got the basic shape more or less right what i want to know is
1, does the dish surface have to be perfectly smooth as there are hammer marks in1 area of it if it does could i use filler and sand it down.
2. the main damage was over a 2ft x 1ft area on the edge when i mount the dish would i be better having this damaged area at the bottom or top or would this make no differance
thanks in advance for all help given
As it seems it was free, then it's a bargain, but once you get it as straight as you can, it won't perform as it used to, so wouldn't be able to pull in weak satellites as well as it used to. The metal has to be in a smooth shape, filler won't do anything aother than absorb the signals, so if you can get the dents out that would be better. Just don't expect it to be perfect once you have it in a decent shape... :)

Analoguesat has had a few bashed up dishes, and his are working well, not 100% (especially the one that was bent double!!!), but they do work, mostly!!! :D
 
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#3
at presant i'm useing a 1.5m dish but being in bulgaria i lose ch4 about 6pm would the 2.4m dish not performing at 100% be better or should i stick to the 1.5m also would sanding down the hammer marks help and a coat of paint if so what type of paint
 

2cvbloke

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#4
Bott said:
at presant i'm useing a 1.5m dish but being in bulgaria i lose ch4 about 6pm would the 2.4m dish not performing at 100% be better or should i stick to the 1.5m also would sanding down the hammer marks help and a coat of paint if so what type of paint
It really depends on the repairs as to how it performs, it may not be any better than your 1.5, but then again, it could be as good as a 2.2m, it's impossible to say...

As for the dents, it's best that you get the metal as smooth as you can, and as they tend to be thin sheet metal, sanding won't really help, so the best thing to do is try to beat out the dents and get the dish as smooth as you can, but try to keep the shape as true as you can...
 

Analoguesat

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#5
See if you can find/borrow some flatting tools as used by car panel beaters. Also see if the dish is twisted across the face by stringing it (tying several lengths of nylon fishing line across the face and seeing if they meet in the middle)

No matter how accurate your repairs are its never going to be perfect. But good luck - and let us know how you get on with the continuing repairs
 

rolfw

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#6
You can probably find a filler with a metalic content, if you can, then that will help to perfect the reflective surface.
 

johnsattuk

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#7
2cvbloke said:
As for the dents, it's best that you get the metal as smooth as you can, and as they tend to be thin sheet metal, sanding won't really help, so the best thing to do is try to beat out the dents and get the dish as smooth as you can, but try to keep the shape as true as you can...
I would second the advice above. :-worship

If you have done a bit of panel beating you will no doubt be able to get the overall shape fairly true, the hand is very good at sensing the bumps and dips, with something like a car panel the eye is generally the arbitar, but with a dish the eye is much too sensitive, a hammer mark perhaps .02mm deep might stand out like the proverbial sore thumb on a painted panel, but would have negligble effect on a dish, thats why mesh dishes work OK.

I have a dish which had several quite deep airgun pellet dimples in it which I planished out. If I get the dish in the right light I can see where they were. I have an identical undamaged dish and I am unable to see any difference in performance.

My dish was a soft ali. dish which perhaps was a bit easier to work than a thin steel one.

As long as the general shape is OK , any small holes, bumps, rivets etc affect the dish more or less relative to the area of the whole.

Sounds to me like you have it pretty well under control, and you havn't got much too loose from trying it. :-righton
 
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#8
the dish is alluminium so i'm going to have a go at sanding it you can also get liquid metal but when it sets i'm not sure how easy it will be to sand down but will look into it. thanks for the help guys will let you know how i get on got to get some larger pipe to mount it first as bracket is way bigger than the one for the 1.5m dish
 

misterminibus

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#9
araldite would do it but just a thought people what about lead? its a conductor and a simple blow lamp melts it.
I use to make my own fishing weights with it and its a pleasure to work with would it work?
 

johnsattuk

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#10
mrminibus said:
araldite would do it but just a thought people what about lead? its a conductor and a simple blow lamp melts it.
I use to make my own fishing weights with it and its a pleasure to work with would it work?
Araldite, filler and similar are purely cosmetic in action, the lead will be a bit awkward to stick to his ali. dish. :confused

With a bit of care and persistance the ali. dish can be planished out very successfully, being ali it will be a bit thicker than a steel one and will accept some careful sanding. If lightly sanded with a shaped block any bumps/holes show up immediately, light planishing of the bumps from the appropriate side, a bit more light sanding to see what has moved where, repeat as required and bob's your uncle. :-righton

I think it is very easy to worry about minor imperfections which would have an effect that would be very difficult to measure. :D
 

misterminibus

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#11
I was thinking lead is a conductor and is contained in solder which may stick to ally ????wont it? only a thought ? if not and he cant get it super straight then just pot rivit a plate on top of the dented area? it will work but rivit it from the concave side I do have some decorum :)
 

johnsattuk

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#12
Bott said:
Hi I've been given a 2.4m dish the problem being it was blown off a 4 story building having had some panel beating experiance with cars i have straightened it out i have got the basic shape more or less right what i want to know is
1, does the dish surface have to be perfectly smooth as there are hammer marks in1 area of it if it does could i use filler and sand it down.
2. the main damage was over a 2ft x 1ft area on the edge when i mount the dish would i be better having this damaged area at the bottom or top or would this make no differance
thanks in advance for all help given
Any chance of some pics of the damaged/repaired area, we are guessing at the severity of the damaged area, might help us to advise/understand. :)
 
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#14
i now have some pics but there too big to upload and i have no programs to compress them if somebody sends me a email address i'll send them
 

Analoguesat

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#15
Send them to me - Ive pm'd you my email address. I'll put them up later when I get home.
 

Analoguesat

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#17
Heres Bott's pictures. And Ive quoted the comment that came with the email:

The jagged edge you can see is where i've had to straighten the dish lip to get the curve of the dish i'm going to get some copper pipe and useing pipe benders match the radius of the dish and put behind the dish to reform the lip unless some one has a better idea i'm really greatfull for all the help given. Regards
 

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Analoguesat

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#18
Im actually surprised its suffered so little damage considering its fallen off a building!
 

2cvbloke

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#19
Analoguesat said:
Im actually surprised its suffered so little damage considering its fallen off a building!
If it was blown off, maybe it flew like a frisbee before it hit the deck... :D
 

johnsattuk

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#20
I don't think the damage is that bad in practical terms. Only the face of the dish up to the formed radius on the edge is part of the reflecting/gathering surface. The dish is not usually illuminated right up to this point anyway, so as to avoid picking up background noise, and for the same reason the signal from the outer surface is amplified less than the central areas.

The end result being that the damage on your dish, (assuming the rest of it is OK and not warped) will have a very minimal effect.

I think that if it were my dish and I was trying to tidy the rim up, I would make a cast pattern from an undamaged part of the dish, and use this as a dolly to planish to. If required you could cast inner and outer ones.

The dish being ali. should reform quite easily. Something like reinforced car filler, or perhaps cheaper and stronger, a fine ballast concrete or floor leveling compound. The car filler would be quick but would cost more, cement type compunds would probably be better as their weight would be an advantage, but would need a few days to set properly. Could cast a nice lead block if you weren't bothered about the paint :D
 
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