wood movement - a little OT

>I've been having an email discussion with several model railroaders who
>are convinced that wood changes length with humidity. It must, because
>their track is developing kinks :-).

I wonder if they've considered the substrate the track is attached to.
Also, does the track unkink when it gets drier?

-Zz

On Fri, 4 Jun 2010 16:48:04 +0000 (UTC), Larry Blanchard
<[email protected]> wrote the following:

>I've been having an email discussion with several model railroaders who
>are convinced that wood changes length with humidity. It must, because
>their track is developing kinks :-).
>
>I've quoted websites and books that prove they're wrong, but it doesn't
>faze the true believers. Seems politics and religion aren't the only
>areas in which opinion trumps facts :-).

So, have you sold them a januwine Wood Shrinking Unit yet, LB?


>OK, it does move a little - according to the wood handbook 0.1%-0.2% from
>totally green to over dry. That's about 0.1" in 8'. And I doubt they're
>using green wood :-).
>
>OTOH, some of the same folks are convinced that Homasote (a pressed paper
>product) does not move from wet to dry.
>
>You meet the nicest people on a keyboard :-).

Say "Halelujah!" and pass the mashed potatoes.

P.S: It's nice to know that the Wreck isn't the only source of cracked
info.

--
It is not the strongest of the species that survives, nor
the most intelligent, but the one most responsive to change.
-- Charles Darwin

Larry Blanchard wrote:
> I've been having an email discussion with several model railroaders who
> are convinced that wood changes length with humidity. It must, because
> their track is developing kinks :-).
>
> I've quoted websites and books that prove they're wrong, but it doesn't
> faze the true believers. Seems politics and religion aren't the only
> areas in which opinion trumps facts :-).
>
> OK, it does move a little - according to the wood handbook 0.1%-0.2% from
> totally green to over dry. That's about 0.1" in 8'. And I doubt they're
> using green wood :-).
>
> OTOH, some of the same folks are convinced that Homasote (a pressed paper
> product) does not move from wet to dry.
...

Depending on which particular Homasote(tm) product, it's not
processed/recycled paper base but wood fiber and they're not bad wrong
on expansion properties...

> MATERIAL COMPOSITION
> Fire rated N.C.F.R.® Homasote is made with 100% recycled, all
> wood fiber material...
...
> PHYSICAL DATA
> Density, lb./ft.³ – 34-40
> Tensile parallel to surface, psi (min.) – 400-700
> Transverse M.O.R., psi (min.) – 600-950
> Hardness, lbs. (Janka Ball) (min.) – 275
> Water absorption by vol. (max.)
> (2 hrs. immers.) – 5%
> (24 hrs. immers.) – 14%
> Expansion from 50%-90% rel. hum. (max.) – 0.30%

The last is pretty much equivalent to longitudinal wood movement.

Would have to see the construction techniques, materials and know the
actual conditions to have a clue on the actual cause(s) behind reported
incidents. One would guess combination of things in most cases the most
likely being design/construction/environmental control issues w/
materials coming in there somewhere.

--

"Larry Blanchard" <[email protected]> wrote in message
news:[email protected]...
> I've been having an email discussion with several model railroaders who
> are convinced that wood changes length with humidity. It must, because
> their track is developing kinks :-).
>
> I've quoted websites and books that prove they're wrong, but it doesn't
> faze the true believers. Seems politics and religion aren't the only
> areas in which opinion trumps facts :-).
>
> OK, it does move a little - according to the wood handbook 0.1%-0.2% from
> totally green to over dry. That's about 0.1" in 8'. And I doubt they're
> using green wood :-).
>
> OTOH, some of the same folks are convinced that Homasote (a pressed paper
> product) does not move from wet to dry.
>
> You meet the nicest people on a keyboard :-).
>
> --
> Intelligence is an experiment that failed - G. B. Shaw

Have they ruled out the metal rails of the track changing length
with changing temperature? Some RR'ers solder the track section
joints for better electrical performance and some don't. Those that
don't have some expansion room in the joints to accommodate the
rails delta-L.
Art