10ft mast on 12" bracket
 

"Carpy" wrote in message
...
http://img392.imageshack.us/img392/3936/markyge3.jpg

I know I'm over cautious, and I'm sure that the job in your picture is just
fine, but I personally would never put that installation on one lashing
wire. I know, I know! It's me.

I also noticed the same has happened to non penetrating roof mounts. I
sometimes use the 2" version (450m slabs), and used to pay about £100 for
it. Then they changed the price down to about £45. Everything else looked
the same so I ordered one for a job, but when it arrived it wasn't great.
They have cut out lots of metal from all over, and it now weighs half of
the old one and it can't support an aerial properly now as much of the
metal has been removed from the centre part with the mast coming up.

I complained and was told the older version wasn't available and the new
one was just as good! I now have to order the "older" version (much better
version) directly from Blake UK.
I spent some time at the show talking to ISS of Leeds who make these items
for Sat Sol. The product range is VG. Have a look.

Anyway, next year I'm going to twist the arms of a few people on here to
come to the show.

Bill

10ft mast on 12" bracket
 

Bill Wright wrote:
|| "Carpy" wrote in message
|| ...
||| http://img392.imageshack.us/img392/3936/markyge3.jpg
|||
|| I know I'm over cautious, and I'm sure that the job in your picture
|| is just fine, but I personally would never put that installation on
|| one lashing wire. I know, I know! It's me.
||
||| I also noticed the same has happened to non penetrating roof
||| mounts. I sometimes use the 2" version (450m slabs), and used to
||| pay about £100 for it. Then they changed the price down to about
||| £45. Everything else looked the same so I ordered one for a job,
||| but when it arrived it wasn't great. They have cut out lots of
||| metal from all over, and it now weighs half of the old one and it
||| can't support an aerial properly now as much of the metal has been
||| removed from the centre part with the mast coming up.
|||
||| I complained and was told the older version wasn't available and
||| the new one was just as good! I now have to order the "older"
||| version (much better version) directly from Blake UK.
|| I spent some time at the show talking to ISS of Leeds who make these
|| items for Sat Sol. The product range is VG. Have a look.
||
|| Anyway, next year I'm going to twist the arms of a few people on
|| here to come to the show.
||

Provided that the lashing wire is of good quality then they're probably
won't be any reason for it to let go, I still see heavy duty galvanised
chimney brackets dating back around 50 years which were fitted by
Rediffusion to carry some pretty weighty catenaries across busy main roads,
the lashing wire on those consisted of stranded phosphorus bronze.

|| Bill

10ft mast on 12" bracket
 

Sorry I omitted to trim Bills post, so it wasn't obvious exactly what part
of it I was replying to.. error corrected.
Ivan

||
|| Bill Wright wrote:
|||| "Carpy" wrote in message
|||| ...
||||| http://img392.imageshack.us/img392/3936/markyge3.jpg
|||||
|||| I know I'm over cautious, and I'm sure that the job in your picture
|||| is just fine, but I personally would never put that installation on
|||| one lashing wire. I know, I know! It's me.
||||


|| Provided that the lashing wire is of good quality then there
|| probably won't be any reason for it to let go, I still see heavy
|| duty galvanised chimney brackets dating back around 50 years which
|| were fitted by Rediffusion to carry some pretty weighty catenaries
|| across busy main roads, the lashing wire on those consisted of
|| stranded phosphorus bronze.
||

10ft mast on 12" bracket
 

"Ivan" wrote in message
...
Provided that the lashing wire is of good quality then they're probably
won't be any reason for it to let go, I still see heavy duty galvanised
chimney brackets dating back around 50 years which were fitted by
Rediffusion to carry some pretty weighty catenaries across busy main
roads, the lashing wire on those consisted of stranded phosphorus bronze.

Yes, I've had to cut a few of them down. . .

Modern lash wire is, of course, a poor thing by comparision. My worries,
though, are usually about the stresses on the masonry than the strength of
the wire. I must say, again, that I know I'm overcautious about this.

Bill

10ft mast on 12" bracket
 

Bill Wright wrote:
|| "Ivan" wrote in message
|| ...
||| Provided that the lashing wire is of good quality then they're
||| probably won't be any reason for it to let go, I still see heavy
||| duty galvanised chimney brackets dating back around 50 years which
||| were fitted by Rediffusion to carry some pretty weighty catenaries
||| across busy main roads, the lashing wire on those consisted of
||| stranded phosphorus bronze.
||
|| Yes, I've had to cut a few of them down. . .
||
|| Modern lash wire is, of course, a poor thing by comparision. My
|| worries, though, are usually about the stresses on the masonry than
|| the strength of the wire. I must say, again, that I know I'm
|| overcautious about this.
||
|| Bill

You're right to be so Bill, there were many old neglected and bomb damaged
Victorian buildings in the postwar inner cities and those aforementioned
'weighty catenaries' usually required the efforts of a couple of blokes on
each end pulling them as taught as they could and then making off the
stainless steel support wire onto the J bolts.
In one instance I can recall despite the J bolts being tightened at both
ends no noticeable increase in tautness could be seen, the reason for this
soon became apparent when it was noticed that one of the stacks was starting
to lean forward at a precarious angle, needless to say that the J bolts were
quickly slackened and the stack eased back into its original position!

|

10ft mast on 12" bracket
 

On Wed, 2 Jul 2008 11:04:44 +0100, tony sayer
wrote:

In article , Paul D.Smith
scribeth thus
"Ivan" wrote in message
...
Marky P wrote:
|| Would this be an unstable set up:
|| || Blake SR18 element group b
|| Triax 10 element group C/D
|| 10'x2" mast
|| 12" cradle bracket
|| || I've just had a word with my friend about the replacement of his
|| aerial down in Devon and he thought a higher mast would be a good
|| idea, due to the flats being built in the line of fire. But I would
|| be dubious about using a 10' mast with a 12" bracket. Changing to an
|| 18" bracket would be loads of hassle (and extra expense) and I don't
|| think it's worth it. What d'ya reckon? Current mast is 6'x2".
||
Freesat?

|| Marky P.

Freesat is an interesting thought as the expense of your components must be
starting to get up to the cost of a Freesat setup. Or even, perhaps, the
Sky FTA offering i.e. getting someone else to put the dish up for him ;-).
I did hear of cheap deals from Currys/Dixons. If you make sure the dish is
in a good place, and he gets one of the multi-head LNBs, then next time
you're down there you can wire up some extra cables for him and he gets 4
output (2 for PVR plus two bedrooms perhaps?).

Paul DS


Theres no fun in that;).

Waaay too sensible....

Freesat is an option for the main telly, but still need Freeview for
the other 3 tellies.

Marky P.

10ft mast on 12" bracket
 

As far as I'm aware Mr P, there's no readily available 12" cradle bracket.
It's either 8" or 13.5".


Actually you're right. It is a 13.5" bracket. Got it from CPC. At
the time, I didn't know if the chimney was tall enough for an 18"
bracket, so I went for the next size down.

Marky P.

10ft mast on 12" bracket
 

"Bill Wright" wrote in message
...

"Ivan" wrote in message
...
Provided that the lashing wire is of good quality then they're probably
won't be any reason for it to let go, I still see heavy duty galvanised
chimney brackets dating back around 50 years which were fitted by
Rediffusion to carry some pretty weighty catenaries across busy main
roads, the lashing wire on those consisted of stranded phosphorus bronze.

Yes, I've had to cut a few of them down. . .

Modern lash wire is, of course, a poor thing by comparision. My worries,
though, are usually about the stresses on the masonry than the strength of
the wire. I must say, again, that I know I'm overcautious about this.

Bill


The way I see it is that if the same bracket / lashing was only supporting a
small 10 element aerial on the same 10ft mast, then I wouldn't do the
lashing kit any looser, so really the compressional stress (which I believe
is the more relevant one) on the chimney is the same for either rig.

If you look at the bracket as a kind of dual cantilever beam with virtually
no deflection, then having 3 smallish aerials instead of 1 adds so little to
the imposed load that it won't have any worthwhile bearing on the moment
applied to the bracket (beam).

The wind loading will be increased a fair bit, but it could never really
impose enough force on the chimney to matter. The mast will always be the
weakest link and must resist constantly going from tension to compression,
so a nice lightweight aerial such as a log is a good choice if possible.
Obviously the higher up the pole the aerial goes the more magnified the
force becomes as force = load x distance..

The Sky dish adds a small load but in that position relative to the bracket
it's irrelevant.

So really for me, with a bracket like this, the only relevant things are the
horizontal compression stresses on the chimney, and a mast that is plenty
strong enough yet will flex sufficiently to prevent transferring too much to
the chimney, and not be so thick that it becomes overly heavy and places a
much larger load on the bracket.

We always used to design structures with a safety factor of 3. That is, work
out the maximum theoretical load that could ever possibly be imposed and
design the building / structure to take three times that load. I'm confident
that a bracket / chimney like the one above has a much much larger safety
factor.

All this could of course be complete ********, as it's been quite a few
years since I've done anything remotely useful in the Civil / Structural
engineering scene, but I still maintain a good "eye" for what's acceptable
and what's not, although these days it's more down to judgement than
calculation.

10ft mast on 12" bracket
 

In article ,
Bill Wright wrote:

"Ivan" wrote in message
...
You're right to be so Bill, there were many old neglected and bomb damaged
Victorian buildings in the postwar inner cities and those aforementioned

with it. This was a fortunate because the damage caused by a hundredweight
of soot landing in the living room was considerable.

We forget these days about soot. I used to come home covered in the stuff,
and I could never get it out of my pores.

Good detoxing agent? ..or early toner refill
as it's mostly carbon. With white lips and a
banjo fashioned from aerial wires, you must
have been made around the clubs.. ;'))

Bill ZFC

--
Adoption InterLink UK with -=- http://www.billsimpson.com/
Domain Host Orpheus Internet -=- http://www.orpheusinternet.co.uk/

10ft mast on 12" bracket
 

....snip...

Freesat is an interesting thought as the expense of your components must
be
starting to get up to the cost of a Freesat setup. Or even, perhaps, the
Sky FTA offering i.e. getting someone else to put the dish up for him
;-).
I did hear of cheap deals from Currys/Dixons. If you make sure the dish
is
in a good place, and he gets one of the multi-head LNBs, then next time
you're down there you can wire up some extra cables for him and he gets 4
output (2 for PVR plus two bedrooms perhaps?).

Paul DS


Theres no fun in that;).

Waaay too sensible....

Freesat is an option for the main telly, but still need Freeview for
the other 3 tellies.

Marky P.


I suppose the cost does go up for each Freesat box purchased, which I hadn't
allowed for. Question is will your friend wait until SD Freesat boxes are
10-a-penny or does he want all his TVs NOW! But then I add up "PVR + 3
others = 5" - bother, one more than a quad LNB can handle.

How often does your friend have multiple TVs on watching multiple things?
What about somehow driving the other TVs from the Freesat box? Or perhaps
he needs a full blown "hotel" like distribution system.

All getting too complicated now ;-) Good luck with the aerial.

Paul DS.