Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak, which
comes back to the original problem).

What do the experts do?


Cheers



Dave R


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David wrote:

A laser level might help (if I can get the level level, so to speak

They tend to be self-levelling (within sensible limits and flash if
they're outside the limits)

On 18/03/2018 14:11, David wrote:
Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Generally if you get the bubble equidistant between the lines you should
be ok.

However keep in mind that looking from an angle can shift the apparent
position a bit - so look straight on.

Also don't assume the level is actually spot on. You should test it from
time to time. (set it level and draw a line on the wall, now flip it
round left to right and repeat - the lines should be perfectly parallel
/ super imposed)

Fall back is measuring up the wall from a flat surface.

How do you know the surface is level?

(although there is an argument that if levelling something close to
another horizontal surface, it often looks better to copy any error in
it rather than fix it)

A laser level might help (if I can get the level level, so to speak, which
comes back to the original problem).

The better ones are self levelling - you just need to get them roughly
level - the do the rest. (mine flashes the laser if the base unit is
more than 4 degrees off level - that being the amount it can self level)

What do the experts do?

See above - or practice with the conventional one until you get
comfortable with it ;-)


--
Cheers,

John.

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On Sun, 18 Mar 2018 14:11:00 +0000, David wrote:

Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak,
which comes back to the original problem).

What do the experts do?

Cheapest self leveling level is
https://www.screwfix.com/p/bosch-pll1p-line-laser-level/7879g
Same price from Screwfix and Amazon.

However this seems to project a point and not a line.

Are there ones which project a line - that is set up a foot or so from the
wall on a tripod, self levels, then displays a horizontal line along the
wall so you can mark up points along the line.

I assume with the Bosch one above you mark a point then swing the level
and mark another point.

I note the flexible wall holder but I'm not sure how that fixes to a wall.

Cheers



Dave R


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On Sunday, 18 March 2018 14:11:04 UTC, David WE Roberts (Google) wrote:
Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak, which
comes back to the original problem).

What do the experts do?


Cheers



Dave R

What's the problem?

On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:

On Sunday, 18 March 2018 14:11:04 UTC, David WE Roberts (Google) wrote:
Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and
just past the line for the bubble which seems to be beyond my ability
to discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak,
which comes back to the original problem).

What do the experts do?


Cheers



Dave R

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already marked
up (fortunately) but it did remind me of failures in the past and tasks in
the future.


Cheers



Dave R


--
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On 18/03/2018 15:30, David wrote:
On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already marked
up (fortunately) but it did remind me of failures in the past and tasks in
the future.

In which case something like:

https://www.screwfix.com/p/bosch-gcl...ne-laser/9780p

(see lawson-his for them rather than SF though since they have a much
wider range of kits)

is very nice because it projects a bright clear horizontal line, a
vertical line, and a pair of straight up and straight down dots. It
makes all kinds of setting out jobs really easy.

This type I find far more useful than the type that just project a line
from the end of a conventional level.


--
Cheers,

John.

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\================================================= ================/

David has brought this to us :
Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak, which
comes back to the original problem).

What do the experts do?

The ultimate, which is always correct, is a water level. Just water
filling a clear section of pipe, but be aware that air bubbles can off
set it - always ensure any bubbles are out of the water. They work over
a short distance, or a very long distance.

On Sun, 18 Mar 2018 16:54:05 +0000, John Rumm wrote:

On 18/03/2018 15:30, David wrote:
On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already
marked up (fortunately) but it did remind me of failures in the past
and tasks in the future.

In which case something like:

https://www.screwfix.com/p/bosch-gcl...ng-cross-line-
laser/9780p

(see lawson-his for them rather than SF though since they have a much
wider range of kits)

is very nice because it projects a bright clear horizontal line, a
vertical line, and a pair of straight up and straight down dots. It
makes all kinds of setting out jobs really easy.

This type I find far more useful than the type that just project a line
from the end of a conventional level.

Erm......possibly more expensive than I was expecting.

£30 is not a big ticket item but £135 takes me into the realm of "If I was
going to spend £135 then is this top of my list".

However good tools are very rarely wasted money.

Thanks


Dave R



--
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On 18/03/18 18:01, David wrote:
On Sun, 18 Mar 2018 16:54:05 +0000, John Rumm wrote:

On 18/03/2018 15:30, David wrote:
On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already
marked up (fortunately) but it did remind me of failures in the past
and tasks in the future.

In which case something like:

https://www.screwfix.com/p/bosch-gcl...ng-cross-line-
laser/9780p

(see lawson-his for them rather than SF though since they have a much
wider range of kits)

is very nice because it projects a bright clear horizontal line, a
vertical line, and a pair of straight up and straight down dots. It
makes all kinds of setting out jobs really easy.

This type I find far more useful than the type that just project a line
from the end of a conventional level.

Erm......possibly more expensive than I was expecting.

£30 is not a big ticket item but £135 takes me into the realm of "If I was
going to spend £135 then is this top of my list".



I bought a digital 'spirit level' from Lidl for ~£18. Same thing as the
usual bubble level but with a digital display added in.

Not available at lidl now but this looks much the same:

https://www.amazon.co.uk/Digital-Spi.../dp/B00A2B57AU




--
djc

(–€Ì¿Ä¹Ì¯–€Ì¿ Ì¿)
No low-hanging fruit, just a lot of small berries up a tall tree.

Well the earth is curved after all, so in reality nothing is flat or level
is it?
Brian

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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"David" wrote in message
...
Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and just
past the line for the bubble which seems to be beyond my ability to
discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak, which
comes back to the original problem).

What do the experts do?


Cheers



Dave R


--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

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https://www.avast.com/antivirus

On 18/03/2018 18:01, David wrote:
On Sun, 18 Mar 2018 16:54:05 +0000, John Rumm wrote:

On 18/03/2018 15:30, David wrote:
On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already
marked up (fortunately) but it did remind me of failures in the past
and tasks in the future.

In which case something like:

https://www.screwfix.com/p/bosch-gcl...ng-cross-line-
laser/9780p

(see lawson-his for them rather than SF though since they have a much
wider range of kits)

is very nice because it projects a bright clear horizontal line, a
vertical line, and a pair of straight up and straight down dots. It
makes all kinds of setting out jobs really easy.

This type I find far more useful than the type that just project a line
from the end of a conventional level.

Erm......possibly more expensive than I was expecting.

Probably... there are other similar ones out there that may be cheaper -
I was just showing one that I knew had the features...

£30 is not a big ticket item but £135 takes me into the realm of "If I was
going to spend £135 then is this top of my list".

However good tools are very rarely wasted money.

Yup, I know what you mean. Normally I wait until I have a job that
justifies it[1], but get something decent since I never regret buying
good tools. (and quite often have ended up buying cheap ones again!)

[1] in the case of a laser level I had about 30m^2 of tiling to do, and
that seemed like a good enough excuse! It was so much easier to get a
baton on the wall all round and know it would all line up when you got
back to the start ;-)

--
Cheers,

John.

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\================================================= ================/

On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or level
is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

--
Max Demian

On 19/03/18 11:11, Max Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level
is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

The tracks supprting the radio telecopes at Madingley - at two miles
long - were 'up' by IIRC 4 " at each end..

So not very big..





--
Climate Change: Socialism wearing a lab coat.

On Sunday, 18 March 2018 15:30:11 UTC, David WE Roberts (Google) wrote:
On Sun, 18 Mar 2018 08:24:11 -0700, tabbypurr wrote:
On Sunday, 18 March 2018 14:11:04 UTC, David WE Roberts (Google) wrote:

Am I in a minority in being unable to set an accurate horizontal level
against a vertical surface like a wall using a spirit level?

There seems to be a degree(?) of variance between just touching and
just past the line for the bubble which seems to be beyond my ability
to discriminate.

Fall back is measuring up the wall from a flat surface.

A laser level might help (if I can get the level level, so to speak,
which comes back to the original problem).

What do the experts do?


Cheers



Dave R

What's the problem?

Long term inability (decades) to set an accurate level using a spirit
level. Unlikely that learning is going to change it at this stage of my
life.

So I'm looking at alternatives.

Not pressing for today because the wall I'm working with is already marked
up (fortunately) but it did remind me of failures in the past and tasks in
the future.


Cheers



Dave R

self levelling laser job is the simple answer. Spirit levels are easy enough to learn to use though. Just place it on a probably flat surface both ways round, it should read the same each way. If not it needs adjustment.

Or if you fancied you could always make a plumb bob level
https://en.wikipedia.org/wiki/Plumb_bob


NT

On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or level
is it?

Nothing's flat or level in this house. It probably wasn't when it was
new (peasant's cottage) and now one of the upstairs floors has a 1 in 10
slope!

On the walls - I don't try to make things level. I make them parallel to
the floor or ceiling (if close) or half way between. On the walls with
exposed vertical timbers pictures are hung to line up with the timbers.

Andy

In article , The Natural Philosopher
scribeth thus
On 19/03/18 11:11, Max Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level
is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

The tracks supprting the radio telecopes at Madingley - at two miles
long - were 'up' by IIRC 4 " at each end..

So not very big..


Madingley?, Lords bridge Squire...


--
Tony Sayer

In article , Max Demian
wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.

--
from KT24 in Surrey, England

charles wrote:
In article , Max Demian
wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I wonder what the *smallest* man made object is that has to take account of
the earths curvature?

Tim

--
Please don't feed the trolls

On 20/03/2018 12:28, Tim+ wrote:
charles wrote:
In article , Max Demian
wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before designers
have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I wonder what the *smallest* man made object is that has to take account of
the earths curvature?

Tim

There are asian offshore airfields built on reclaimed land that have to
be jacked up to keep them level. But the length of a runway must make
that a tricky job.

On 19/03/2018 21:37, Vir Campestris wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level
is it?

Nothing's flat or level in this house. It probably wasn't when it was
new (peasant's cottage) and now one of the upstairs floors has a 1 in 10
slope!

On the walls - I don't try to make things level. I make them parallel to
the floor or ceiling (if close) or half way between. On the walls with
exposed vertical timbers pictures are hung to line up with the timbers.

Andy

There are no flat walls or completely rectangular door frames in
my 1976 semi. The lounge ceiling below the hot tank has deflected
by about 20mm because they used pairs of 50mm beams but didn't bolt
them together, just laid with a 10 cmm gap between them.

Naturally they sagged as they dried (3 inch cinder block upstairs
internal walls with sand'n'cement base coat 'plaster'.)

On Tue, 20 Mar 2018 12:28:24 +0000, Tim+ wrote:

charles wrote:
In article , Max
Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before
designers have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I tried to find out if they'd done something similar when building the
Severn suspension road bridge just over 50 years ago but the only
reference to 'tower divergence' was in relation to 388 millimetres[1] of
lean back to compensate for the weight of the suspension cables which has
nothing to do with the curvature of the earth over the one mile
separation distance.


I wonder what the *smallest* man made object is that has to take account
of the earths curvature?


I'd guess at something about a tenth of the size of the Humber Bridge
since the resulting 3.6mm 'curvature of the Earth allowance would likely
come within normal tolerances on a structure one tenth the size of the
Humber bridge but that's just a guess.

Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary on
this record breaking bridge but I've not got the time right now to spin
through the recording just to find out whether or not a figure was
actually mentioned.

[1] AFAIR, the figure was 388mm BICBW.

--
Johnny B Good

Johnny B Good wrote:
On Tue, 20 Mar 2018 12:28:24 +0000, Tim+ wrote:

charles wrote:
In article , Max
Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before
designers have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I tried to find out if they'd done something similar when building the
Severn suspension road bridge just over 50 years ago but the only
reference to 'tower divergence' was in relation to 388 millimetres[1] of
lean back to compensate for the weight of the suspension cables which has
nothing to do with the curvature of the earth over the one mile
separation distance.


I wonder what the *smallest* man made object is that has to take account
of the earths curvature?


I'd guess at something about a tenth of the size of the Humber Bridge
since the resulting 3.6mm 'curvature of the Earth allowance would likely
come within normal tolerances on a structure one tenth the size of the
Humber bridge but that's just a guess.


Thinking about it, you could argue that any structure built using plumb
bobs automatically compensates for earth curvature. I suppose the question
is, at what point does the discrepancy actively need to be compensated for?


Tim


--
Please don't feed the trolls

On Sun, 18 Mar 2018 14:32:50 +0000
John Rumm wrote:

(although there is an argument that if levelling something close to
another horizontal surface, it often looks better to copy any error
in it rather than fix it)

I fitted a mantle shelf and tiled down from there, only to find that the
tiles on one side didn't quite meet the hearth because it was "level"
with the floor. :-( Just painting the wonky grout gap made it
blend in sufficiently that the unevenness isn't noticeable, but that's
not a mistake I'll make again.

On 20/03/2018 13:18, Andrew wrote:

There are asian offshore airfields built on reclaimed land that have to
be jacked up to keep them level. But the length of a runwayÂ* must make
that a tricky job.

I wonder why they bothered to make them so precisely flat. Airfield
runways don't need to be dead level. One end of the runway at Newcastle
Airport is about 30 foot higher than the other.

--
Mike Clarke

In article ,
Vir Campestris wrote:
Nothing's flat or level in this house. It probably wasn't when it was
new (peasant's cottage) and now one of the upstairs floors has a 1 in 10
slope!

At least the dog always knows where to find his ball.

--
*Where there's a will, I want to be in it.

Dave Plowman London SW
To e-mail, change noise into sound.

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 12:28:24 +0000, Tim+ wrote:

charles wrote:
In article , Max
Demian wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level is it?

I wonder how big a thing (building? bridge?) has to be before
designers have to take into account the curvature of the earth?

It's certainly taken into account when predicting uhf tv coverage.


Humber bridge towers apparently diverge by 36mm due to curvature.

I tried to find out if they'd done something similar when building the
Severn suspension road bridge just over 50 years ago but the only
reference to 'tower divergence' was in relation to 388 millimetres[1] of
lean back to compensate for the weight of the suspension cables which has
nothing to do with the curvature of the earth over the one mile
separation distance.


I wonder what the *smallest* man made object is that has to take account
of the earth?s curvature?


I'd guess at something about a tenth of the size of the Humber Bridge
since the resulting 3.6mm 'curvature of the Earth allowance would likely
come within normal tolerances on a structure one tenth the size of the
Humber bridge but that's just a guess.

Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary on
this record breaking bridge but I've not got the time right now to spin
through the recording just to find out whether or not a figure was
actually mentioned.

Why would any bridge need to be 100% "flat"?
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On 19/03/2018 21:37, Vir Campestris wrote:
On 19/03/2018 10:26, Brian Gaff wrote:
Well the earth is curved after all, so in reality nothing is flat or
level
is it?

Nothing's flat or level in this house. It probably wasn't when it was
new (peasant's cottage) and now one of the upstairs floors has a 1 in 10
slope!

On the walls - I don't try to make things level. I make them parallel to
the floor or ceiling (if close) or half way between. On the walls with
exposed vertical timbers pictures are hung to line up with the timbers.

Andy

I think my worst is about 1 in 20. Otherwise, snap. Rotating head laser
is excellent for this, I had a cheapie which has more or less died.
Don't need to do much DIY now, trying to pluck up courage to invest £100
+ in a better one.

On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable
forces.
It might have been mentioned in the Timewatch/Timeshift documentary on
this record breaking bridge but I've not got the time right now to spin
through the recording just to find out whether or not a figure was
actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The 'lean
back' was to compensate for the final cable loading so that the towers
would become perfectly aligned to the vertical downthrust forces once
construction had been completed. I dare say the same thing applied with
the Humber bridge.

--
Johnny B Good

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable
forces.
It might have been mentioned in the Timewatch/Timeshift documentary on
this record breaking bridge but I've not got the time right now to spin
through the recording just to find out whether or not a figure was
actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The 'lean
back' was to compensate for the final cable loading so that the towers
would become perfectly aligned to the vertical downthrust forces once
construction had been completed. I dare say the same thing applied with
the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"*
figure for the slightly shorter Severn bridge (1 mile span versus the*
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?
--
Jim K


----Android NewsGroup Reader----
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On 20/03/18 21:06, Jim K wrote:
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."


WEll its a simple exercise in trigonometry, and teh accurate
appropximate answer that the difference is proprtional to the fraction
of the earths circumference, which is about 26,000 miles. So over 1 mile
the vertical 'error' is one 26000th of a mile, or around 2.5 inches.




Hence my question - why would anyone bother being*that* precise
building a mile long bridge?

Because a 2.5" step is emogh to blow a tyre going at 70 mph?

--
Those who want slavery should have the grace to name it by its proper
name. They must face the full meaning of that which they are advocating
or condoning; the full, exact, specific meaning of collectivism, of its
logical implications, of the principles upon which it is based, and of
the ultimate consequences to which these principles will lead. They must
face it, then decide whether this is what they want or not.

Ayn Rand.

On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable
forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now to
spin through the recording just to find out whether or not a figure
was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The 'lean
back' was to compensate for the final cable loading so that the towers
would become perfectly aligned to the vertical downthrust forces once
construction had been completed. I dare say the same thing applied with
the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the Severn
bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40% longer
bridge?

You have to consider that the contractors working on the shorter bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to make
sure the towers were in perfect alignment with the down thrust forces
once the cable loading was applied. Whether they were able to measure it
to such accuracy and whether the measurement matched expectations is, for
the time being, an unknown since I couldn't track down any mention of
divergence due to the curvature of the Earth.

--
Johnny B Good

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable
forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now to
spin through the recording just to find out whether or not a figure
was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The 'lean
back' was to compensate for the final cable loading so that the towers
would become perfectly aligned to the vertical downthrust forces once
construction had been completed. I dare say the same thing applied with
the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the Severn
bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40% longer
bridge?

You have to consider that the contractors working on the shorter bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to make
sure the towers were in perfect alignment with the down thrust forces
once the cable loading was applied. Whether they were able to measure it
to such accuracy and whether the measurement matched expectations is, for
the time being, an unknown since I couldn't track down any mention of
divergence due to the curvature of the Earth.

--
Johnny B Good


As is obvious, I'm not talking about tower divergences.
I'm merely pointing out (again) that your basic assumptions about
bridges needing to be "flat" (and so obsessional adjustments of
tower verticality by mm over miles to adjust for earths
curvature) appear erroneous ...
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

On Wed, 21 Mar 2018 17:48:30 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus
the Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back'
on the towers during construction to compensate for the suspension
cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now
to spin through the recording just to find out whether or not a
figure was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The
'lean
back' was to compensate for the final cable loading so that the
towers would become perfectly aligned to the vertical downthrust
forces once construction had been completed. I dare say the same
thing applied with the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the
Severn bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40%
longer bridge?

You have to consider that the contractors working on the shorter
bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to
make sure the towers were in perfect alignment with the down thrust
forces once the cable loading was applied. Whether they were able to
measure it to such accuracy and whether the measurement matched
expectations is, for the time being, an unknown since I couldn't track
down any mention of divergence due to the curvature of the Earth.

--
Johnny B Good


As is obvious, I'm not talking about tower divergences.

True, you seemed to have an obsession with 'flatness' in spite of my
only wondering why I couldn't find a divergence figure to compare with
the one for the Humber Bridge which Tim+ had managed to find.

I'm merely pointing out (again) that your basic assumptions about
bridges needing to be "flat" (and so obsessional adjustments of tower
verticality by mm over miles to adjust for earths curvature) appear
erroneous ...

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good

Johnny B Good Wrote in message:
On Wed, 21 Mar 2018 17:48:30 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus
the Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back'
on the towers during construction to compensate for the suspension
cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now
to spin through the recording just to find out whether or not a
figure was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The
'lean
back' was to compensate for the final cable loading so that the
towers would become perfectly aligned to the vertical downthrust
forces once construction had been completed. I dare say the same
thing applied with the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the
Severn bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40%
longer bridge?

You have to consider that the contractors working on the shorter
bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to
make sure the towers were in perfect alignment with the down thrust
forces once the cable loading was applied. Whether they were able to
measure it to such accuracy and whether the measurement matched
expectations is, for the time being, an unknown since I couldn't track
down any mention of divergence due to the curvature of the Earth.

--
Johnny B Good


As is obvious, I'm not talking about tower divergences.

True, you seemed to have an obsession with 'flatness' in spite of my
only wondering why I couldn't find a divergence figure to compare with
the one for the Humber Bridge which Tim+ had managed to find.

I'm merely pointing out (again) that your basic assumptions about
bridges needing to be "flat" (and so obsessional adjustments of tower
verticality by mm over miles to adjust for earths curvature) appear
erroneous ...

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good


Oh dear. Put very simply, if one wasn't trying to build
something flat, why would one be bothered with calculations to
the mm to allow for curvature of the earth ? !
--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

Jim K wrote:
Johnny B Good Wrote in message:
On Wed, 21 Mar 2018 17:48:30 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus
the Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back'
on the towers during construction to compensate for the suspension
cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now
to spin through the recording just to find out whether or not a
figure was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The
'lean
back' was to compensate for the final cable loading so that the
towers would become perfectly aligned to the vertical downthrust
forces once construction had been completed. I dare say the same
thing applied with the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the
Severn bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40%
longer bridge?

You have to consider that the contractors working on the shorter
bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to
make sure the towers were in perfect alignment with the down thrust
forces once the cable loading was applied. Whether they were able to
measure it to such accuracy and whether the measurement matched
expectations is, for the time being, an unknown since I couldn't track
down any mention of divergence due to the curvature of the Earth.

--
Johnny B Good


As is obvious, I'm not talking about tower divergences.

True, you seemed to have an obsession with 'flatness' in spite of my
only wondering why I couldn't find a divergence figure to compare with
the one for the Humber Bridge which Tim+ had managed to find.

I'm merely pointing out (again) that your basic assumptions about
bridges needing to be "flat" (and so obsessional adjustments of tower
verticality by mm over miles to adjust for earths curvature) appear
erroneous ...

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good


Oh dear. Put very simply, if one wasn't trying to build
something flat, why would one be bothered with calculations to
the mm to allow for curvature of the earth ? !

To ensure perpendicular loading of the towers maybe?

Tim

--
Please don't feed the trolls

Tim+ Wrote in message:
Jim K wrote:
Johnny B Good Wrote in message:
On Wed, 21 Mar 2018 17:48:30 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 21:06:43 +0000, Jim K wrote:

Johnny B Good Wrote in message:
On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature
compensation"
figure for the slightly shorter Severn bridge (1 mile span versus
the Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back'
on the towers during construction to compensate for the suspension
cable forces.
It might have been mentioned in the Timewatch/Timeshift documentary
on this record breaking bridge but I've not got the time right now
to spin through the recording just to find out whether or not a
figure was actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The
'lean
back' was to compensate for the final cable loading so that the
towers would become perfectly aligned to the vertical downthrust
forces once construction had been completed. I dare say the same
thing applied with the Humber bridge.

--
Johnny B Good


I know.

You said,
"Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span),..."

Hence my question - why would anyone bother being *that* precise
building a mile long bridge?

The precision will be a consequence of making sure the towers were
precisely aligned to the downthrust forces in both cases. Assuming the
Humber bridge's vital stats were a factor of 1.4 scale up of the Severn
bridge design, my best guess for the divergence at the top of the
Severn bridge's support towers would approximate to a figure of 18mm.

Are you trying to suggest that a mere 30% shortening of bridge length
compared to its successor, the Humber Bridge justifies a disregard for
the same level of precision that was deemed necessary for the 40%
longer bridge?

You have to consider that the contractors working on the shorter
bridge
weren't just 'anyone'. I'd expect they were aiming to achieve a
divergence that matched the theoretical divergence due to the curvature
of the Earth as a consequence of taking the 'lean back' measures to
make sure the towers were in perfect alignment with the down thrust
forces once the cable loading was applied. Whether they were able to
measure it to such accuracy and whether the measurement matched
expectations is, for the time being, an unknown since I couldn't track
down any mention of divergence due to the curvature of the Earth.

--
Johnny B Good


As is obvious, I'm not talking about tower divergences.

True, you seemed to have an obsession with 'flatness' in spite of my
only wondering why I couldn't find a divergence figure to compare with
the one for the Humber Bridge which Tim+ had managed to find.

I'm merely pointing out (again) that your basic assumptions about
bridges needing to be "flat" (and so obsessional adjustments of tower
verticality by mm over miles to adjust for earths curvature) appear
erroneous ...

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good


Oh dear. Put very simply, if one wasn't trying to build
something flat, why would one be bothered with calculations to
the mm to allow for curvature of the earth ? !

To ensure perpendicular loading of the towers maybe?

Tim

--
Please don't feed the trolls


Plumb bob?
Perpendicular to the centre of the earth?

--
Jim K


----Android NewsGroup Reader----
http://usenet.sinaapp.com/

I've got one of these which works really well and is reasonably priced - suspect you can get it for less than £60

It projects a massive cross onto the wall and finds its own level once you've positioned it nearly right

https://www.clasohlson.com/uk/Bosch-...xoCv88QAvD_BwE

On 21/03/2018 20:22, Jim K wrote:
Johnny B Good Wrote in message:

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good


Oh dear. Put very simply, if one wasn't trying to build
something flat, why would one be bothered with calculations to
the mm to allow for curvature of the earth ? !

To ensure that it's curved to the right degree?

--
Max Demian

Max Demian Wrote in message:
On 21/03/2018 20:22, Jim K wrote:
Johnny B Good Wrote in message:

It was not I who was obsessed with bridges needing to be "flat", it was
you. I think you are conflating Brian's mention about 'flatness' and
curvature of the Earth corrections with my not being able to find a
curvature of the earth divergence figure for the Severn bridge to compare
against the figure that Tim+ had found for the Humber bridge. I made no
mention of 'flatness' until you introduced it into this sub-thread.

--
Johnny B Good


Oh dear. Put very simply, if one wasn't trying to build
something flat, why would one be bothered with calculations to
the mm to allow for curvature of the earth ? !

To ensure that it's curved to the right degree?

--
Max

Such as a.........?
(not a bridge shurely, if anything they are more likely to be hump
backed...)

--
Jim K


----Android NewsGroup Reader----
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