Lidl SilverCrest Satellite Dish Wall Bracket Failure

Mark#1 · 11-01-2009 01:08PM #1

Hi.

I've posted this on the specific Lidl SilverCrest satellite set thread too, but I thought it couldn't do any harm to post separately as well.

Noise from the chimney kept us awake last night. It was still there this morning, so I had a look from the ground up and could see my Lidl dish hanging pretty badly askew. Very windy last night and still is as I type, so I wasn't too keen to go up on the roof, but the consequences of me not could have been pretty bad.

This is what I found:

You can see I have the 80cm x 80cm dish. IMO, between the all-solid construction of the dish itself and its exposed position on my chimney, and the big (and not uncommonl) winds last night, the cheap-ass wall-mounting bracket couldn't cope.

I'm not going back with the product - I'm sure I'd be told I should have situated it in a less-exposed place.

But I'm posting this as a heads-up for the rest of you guys with this dish/bracket.

Personally, I'll be replacing the Lidl set with a Humax Foxsat HDR320 Freesat PVR & a perforated (like the Sky dishes) 65cm Raven dish & quad-LNB from Freesat.ie. I'll be situating the dish on the front of the house, rather than on the chimney.

Mark

Tony · 11-01-2009 02:05PM

Instead of the front of the house why not use a stand off bracket and pole at the back, looks much better and you will not fall foul of planning laws. Another issue I can see is one of the rawlbolts has been placed in the mortar and not the brick. If there is no alternative to a chimney mount a lashing kit and short pole is a much better way to go.

Gadgie · 11-01-2009 02:46PM

I suspect it had more to do with the bolts not being in the wall properly than the quality of the bracket.

pistolpetes11 · 11-01-2009 02:53PM

As you can see from the photo the bracket only gave way after the bolts slipped out of the mortar , anchor bolts dont works that well in mortar as it can become quite brittle with constant pressure ,

Ronan|Raven · 11-01-2009 03:26PM

And stop drilling into your chimneys people.

Mark#1 · 11-01-2009 07:36PM

Fair comments.

But . . .

Pistolpetes11 & Gadgie: only one bolt came out. The bolt anchor - the part that's still in the wall - is still rock solid in there: the bolt pulled out of the anchor.

And all the other bolts were still good and solid - check out how tight the bolt at top right hung on: strong enough for the bracket to fail rather than that bolt pulling out, and that bolt went in at pretty much the same horizontal position as the bolt that pulled out; ie, at the top of the brick, and not in the mortar. To be honest, I wasn't happy with the way the top left bolt went in - when I was drilling, the bit veered upwards when the tip got to maybe 50mm in, though it (and all 3 other bolts) were genuinely rock solid when I was finished. Look how much the flat backing plate bent before the bold did pull out: the top left bolt must have held on tight at least for some time.

I'm not disagreeing: you guys could well be right - what was going on in the back end of that particular anchor could have been a factor. Maybe the very back end had no real bite, so the bolt was able to pull out? Maybe the mortar did indeed eventually crumble from the stress.

This pic shows where the tubular part of the bracket had started to break away from the flat backing plate:

This must have been happening at least at the same time as the bolt pulling out, if not before, and obviously has nothing to do with the bolts. I suspect that even if all 4 bolts had remained secure, that tubular section would eventually have come away.

I'm not blaming the bracket alone for its own failure - IMO, the main factors in its failure were the solid nature of the dish and its exposed position: it's possible that even a stronger bracket might have struggled with the same load.

Ronan|Raven, is there a formal reason chimneys shouldn't be used for mounting dishes (or aerials)? Half the Sky dishes in my area are on the chimneys (that's not meant to be an argumentative question - I don't know how to word it so it doesn't seem that way).

Mark

Tony · 11-01-2009 08:04PM

Drilling a chimney can weaken the structure, I've seen dishes that I've been called to repiar actually pull the brick out.

Mark#1 · 11-01-2009 08:18PM

Tony wrote: »

Drilling a chimney can weaken the structure, I've seen dishes that I've been called to repiar actually pull the brick out.

Thanks.

I'll consider my options before I locate the new dish.

Mark

CHW · 11-01-2009 08:47PM

Mark#1 wrote: »

I'm not disagreeing: you guys could well be right - what was going on in the back end of that particular anchor could have been a factor. Maybe the very back end had no real bite, so the bolt was able to pull out? Maybe the mortar did indeed eventually crumble from the stress.

I think this is the key to the failure - compared to a brick/block, mortar will be very variable. Could be pieces of stone or voids in there, and the bolt may seem secure tightening it up, but just one moment of excessive stress, the anchors open up enough to allow the bolt slide. You might have a bit of a job getting that anchor out too; as the bolt slid out, the sides of the anchor have have probably embedded themselves into compacting mortar inside the drilled hole. You'll probably need to hammer it in several mm's and twist it to get it out. Better to just repair over it probably.

I also read somewhere that on smaller dishes (like smaller than 1.20-1.50m) mesh dishes didn't have so much of a significant decrease in wind-loading, particularly in high, gusty wind speeds. Something about the holes being too small, and/or resulting pressure at those points. If I can dig it up, I'll post a link; I may even have seen it posted here.

EDIT: Something here on mesh/solid wind loading: http://www.afcsat.com/dual.html

Note that wind shear escalates as the reflector diameter is squared, while the overturning moment intensifies approximately as the diameter is cubed. (Mesh antennas suffer the same wind loads as solid dish antennas. Contrary to popular belief, wind does not blow through the screen mesh. When wind hits the mesh, a turbulence boundary layer is formed. This turbulence layer makes the mesh antenna behave as if it where a solid dish.)

Mark#1 · 11-01-2009 11:19PM

CHW wrote: »

Note that wind shear escalates as the reflector diameter is squared, while the overturning moment intensifies approximately as the diameter is cubed. (Mesh antennas suffer the same wind loads as solid dish antennas. Contrary to popular belief, wind does not blow through the screen mesh. When wind hits the mesh, a turbulence boundary layer is formed. This turbulence layer makes the mesh antenna behave as if it where a solid dish.)

Sh1te. I bet I'm not alone in making the mesh dish = less susceptability to wind pressure assumption. So what's the reason for the perforations then? Weight minimisation?

Even with this being the case, I think I'll still get that 65cm mesh dish from Freesat.ie. I reckon the front of the house will be a much better protected position, so whether I use the Lidl one or the mesh one - either will be safer there.

Tony, do front-of-house dishes need planning permission? There are a couple on my road on the fronts of the houses. Doesn't look great (they're dark mesh ones, so they don't look awful either), but if that's the only place suitable, what do you do?

Mark

Tony · 11-01-2009 11:42PM

Mark#1 wrote: »

Tony, do front-of-house dishes need planning permission?

Yes they do

Mark#1 wrote: »

There are a couple on my road on the fronts of the houses. Doesn't look great (they're dark mesh ones, so they don't look awful either), but if that's the only place suitable, what do you do?
Mark

You use a stand off bracket as I mentioned earlier in the thread

fat-tony · 11-01-2009 11:46PM

Mark#1 wrote: »

Sh1te. I bet I'm not alone in making the mesh dish = less susceptability to wind pressure assumption. So what's the reason for the perforations then? Weight minimisation?

Mark

Less material used in the dish makes it cheaper, lighter - but also more susceptible to rust. My understanding is that you can have one dish (less than 1 metre in diameter) on the curtilage of your property (as long as it's not the front of the house). Rental accommodation and apartments may have specific restrictions. I have a 1.1m dish on the back of my house, but it's held up with 14mm rawlbolts. I always think it's a bad idea to mount sat dishes on brick chimney stacks due to the wind load.

watty · 12-01-2009 01:16AM

Much Much cheaper to make and Ship.

Rusts aboput x4 quicker

At certain angles to side it has higher wind load. Straight on it's about the same wind load.

You need a large open mesh like for L-band or C-Band for mesh to have lower wind load.

Also with Chimney, corrosion from smoke, lack of access for replacing LNB or cable as well as wind load. Though not much worse than a very tall 3m MMDS pole.

I have got and had strange Chimney items. I used 2 sets of angle brackets at opposite corners and THREE lashing kits. One at top and bottom of bracket instead of single middle kit and metal corners under cable. 3rd kit twice over top of chimney. Just a few aerials though. I'd not mount a dish.

I have the serious Aerial on two sets of K T with bolts entirely through the gable end into attic.

My dish mount poles on end wall of an outhouse also use long stud bolts with big washers and nuts inside the shed too.

85/90cm elliptical dish for 28.2E, 23.5, 19.2 and 13E. Pole on end wall.

Rear view of same dish and two others to extreme right:
http://www.irishwattystuff.com/images/aerials/aerials.jpg

Mark#1 · 12-01-2009 01:24AM

fat-tony wrote: »

I always think it's a bad idea to mount sat dishes on brick chimney stacks due to the wind load.

So do I now . . . :rolleyes:

Tony/Watty (or anyone who can answer), what if my roof is exactly in the way of the direction my dish needs to point for Astra2? For me, unless I'm mising something, the pole I'd need to get the dish to clear my roof would be so long that wind blowing the dish around would probably ruin any chance of the dish receiving anything, let alone being pulled out of the wall.

BTW, what do you guys suggest I do to repair the holes left in the chimney? Remove anchors or knock them in further? Fill with mortar? Fill with silicone?

Thanks,

Mark

homer911 · 12-01-2009 10:55AM

Mark#1 wrote: »

Hi.

I'm not going back with the product - I'm sure I'd be told I should have situated it in a less-exposed place.

Mark

My Lidl dish didnt last a month. The mounting bracket broke where the mounting arm was spot welded to the face plate. The face plate had also torn from around the mounting bolts, but had not sheared.

I replaced it with a sky mesh dish. Never had a problem since, despite the winds over the last few nights (Which is more than can be said for my shed, which had its felt roof torn off!)

Dish was and is mounted on rear wall of house, very exposed to SW wind

Tony · 12-01-2009 04:06PM

You need to bear in mind that these are "offset" dishes which means the angle to the satellite is much higher than it appears to be from looking at the dish. From the pitch of the roof in your pics you could mount a dish on a pole just above the gutter and it will work fine. I'd leave the anchors in and cover with silicone. I think Byte has some nice diagrams to help explain the "offset" principle

Mark#1 wrote: »

So do I now . . . :rolleyes:

Tony/Watty (or anyone who can answer), what if my roof is exactly in the way of the direction my dish needs to point for Astra2? For me, unless I'm mising something, the pole I'd need to get the dish to clear my roof would be so long that wind blowing the dish around would probably ruin any chance of the dish receiving anything, let alone being pulled out of the wall.

BTW, what do you guys suggest I do to repair the holes left in the chimney? Remove anchors or knock them in further? Fill with mortar? Fill with silicone?

Thanks,

Mark

watty · 12-01-2009 06:34PM

If you look at ICDG wiki,

Or my photo imagine
(<

( is dish
< is signal getting recieved at elevation of about 21 degrees and bouncing off dish (it's a curved radio mirror) down to LNBs on bracket.
That's why most western LNB of the four on the arm picks up the most Eastern satellite too.

stylers · 13-01-2009 12:27AM

haven't seen too many of those LIDL dish brackets survive too long, the pole rips away from the center of the very thin steel plate, or the plate just buckles.

KonstanDKAY · 04-09-2009 03:01PM

hey where do i pick up one of those off set mounts to attach to the back of my house? are they reasonably easy to install?

Lidl SilverCrest Satellite Dish Wall Bracket Failure

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