Re: Snow load evaluation

[Beamer Smith <beamer@xxxxxxxxxxxxxx>]

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>"Beamer Smith" <beamer@xxxxxxxxxxxxxx> wrote in message
>news:qqspt2pmuqqthjqnvpv2374e3v10r8gdrg@xxxxxxxxxx
>> Beamer Smith <beamer@xxxxxxxxxxxxxx> wrote:
>>
>> >
>> >"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:
>> >
>> >>Anybody doing anything automated in terms of detecting an excessive snow
>> >>load on a structure's roof?   I saw a news report about upstate NY where
>a
>> >>guy said "when your doors begin to stick, that's when it's time to clear
>the
>> >>snow off the roof.  It's good to know one of the warning signs but
>surely
>> >>there's got to be a better way!
>> >
>> >Less tech than the others but you hang a length of steel pipe inside a
>> >slightly larger plastic pipe... (use wire so it doesn't stretch) a
>> >quarter of an inch above a pair of contacts... when the roof sinks
>> >that quarter of an inch the contacts are closed and what ever you
>> >attached them to responds... low tech = light... high tech = sensor
>> >that alerts a computer that dials a phone number that alerts the
>> >media.. or whom ever.
>> >n'est pas?
>> >
>> >Beamer Smith
>> >Yes *that* Beamer Smith
>>
>> Oh and do it in the attic where the wifes visitors won't see it... ;)
>
>That sounds like it might work but I'd be worried that time would eventually
>cause enough of a sag to activate the detector without any snow load
>present.

Wouldn't you want to know that too? I suspect that Any load that would
bend the roof would require the owner to take action.
I'd actually thought of doing this myself.. placing a steel rod in the
center beam and having it protrude the plaster  flush with the
ceiling.  If the roof sinks it becomes unsightly and I act.  I might
even put some sort of lever in line so that a half inch deflection
would show as a one inch protrusion.

Which could press a button which would ignite a fuse that would drop
dog food into a bowl which would then drop a bowling ball at the top
of the stairs which after bouncing down the stairs, runs over the dogs
tail causing him (or her) to howel and alert everyone to the load on
the roof...

And you wanted to use lasers...


>
>I've been fooling around with lasers and my video cam trying to see if I can
>detect joist deflection.  I thought whatever worked for the basement and
>first floor would also work for the attic and roof.   I was surprised to
>discover that the laser beam diverged quite a bit more than I expected.  I
>was also surprised at how little activity on the floor above was detectable.
>
>I mounted the laser on the most unsupported joist I could find.  I trained
>it on a piece of graph paper across the basement and then trained a videocam
>on the paper.  My thought was that if there was deflection of the joist from
>rolling a heavy power wheelchair over that spot, I should be able to see the
>laser dot jump around on the video.  Nada.  About the only thing that made
>the laser dot jump was jumping up and down on the floor above.  I need a
>better way of amplifying the very slight movements involved.  I suppose it's
>going to have to be the Pulsor sensors and some epoxy!

Certainly an interesting way to determine deflection but it requires
someone to monitor it.