<VV> White pushrod tubes

[Roger Gault]

It's very difficult to say anything authoratative about this because the
needed data on "the paint" is not available.  (Well, it's actually easy to
say something, it's just hard to be sure you're right.)

At visible light wavelengths, it's a piece of cake.  Anybody that doesn't
believe that white absorbs less radiated energy than other colors at solar
frequencies is welcome to bring a convert down here to the Texas sun and sit
in it in shorts.  Then come sit in my white interior and you'll be a
believer.

Assuming our friendly exhaust tubes are running about 1000 degrees F,
they're radiating with a broad spectrum ranging from about 2 microns up to
around 5 (compared to solar radiation which is down around .5 to 1 micron.
Most non-conductive materials show a large increase in absorptivity above
2-3 microns, so there aren't many good non-conductive reflectors in
infrared.  Chances are that your random rattle can white exhaust paint is
going to have an absorptivity around .5 to .6, but we'll never know because
the data's not on the can.  It might be more like .8.  Chances are that
black paint that starts out around .9 at solar frequencies is not going to
get a bunch better and be as reflective as the white.  So, you pays your
money and takes your chances.

Interestingly, the stock "shiny" metal tubes are probably down around .2 to
.3, so they're better that any painted surface.  Until they rust and their
absorptivity goes up to maybe .8.  Metalic materials usually get more
reflective in infrared.

So, if you have nice clean, metal tubes, I'd stay away from the paint.  If
yours look like they've spent their entire life at the beach, paint them
like I did my rusty ones - you can't be any worse off.  Of course you chrome
them.  Or you can do what Finch recommended and put a barrier of .020
aluminum between the exhaust and the pushrod tubes.

Roger Gault
Home sick with a sore throat and thankful I have you guys to entertain me.
;-)


----- Original Message ----- 
From: "Ron" <ronh@owt.com>
To: <virtualVairs@corvair.org>; "Dave Morris" <BigD@davemorris.com>
Sent: Friday, February 04, 2005 2:15 PM
Subject: Re: <VV> White pushrod tubes


> Yes, there's no analytical basis using the empirical formulas available
for
> heat transfer to to say that white paint is any better than any other
paint.
> If you have any indication otherwise from a college level text, let us
know
> because that means that something new has been found in the basic heat
> transfer field.
> RonH
>
> ----- Original Message ----- 
> From: "Dave Morris" <BigD@davemorris.com>
> To: <virtualVairs@corvair.org>
> Sent: Friday, February 04, 2005 11:34 AM
> Subject: Re: <VV> White pushrod tubes
>
>
> > You have evidence that painting something with a VHT white paint will
not
> > limit its tendency to soak up heat from the exhaust pipes next to it?
> >
> > Dave Morris
> >
> >
> > At 11:17 AM 2/4/2005 -0800, you wrote:
> >
> >>On the item of using white paint, Finch was without a basis, I'm sure.
> >>Save your paint.
> >>RonH
> >>
> >>----- Original Message ----- From: "Dave Morris" <BigD@davemorris.com>
> >>To: <virtualVairs@corvair.org>
> >>Sent: Friday, February 04, 2005 9:46 AM
> >>Subject: Re: <VV> An interesting thing.....
> >>
> >>
> >>>
> >>>We paint the pushrod tubes white because Richard Finch in his book "How
> >>>to keep your Corvair alive" suggests that as a way to prevent leaks
> >>>around the o-rings.  Almost ALL of us are painting them white.
> >>>
> >>>
> >>>Dave Morris
> >>>
> >>>
> >>>
> >>>At 11:24 PM 2/3/2005 -0600, you wrote:
> >>>
> >>>>
> >>>>I note that he claims painting pushrod tubes white helps to keep heat
> >>>>away from the cylinders.  Don't know if I buy that one or not.
> >>>>
> >>>>
> >>>>Later, JR
> >>>>Of IL
> >>>>'61 Rampside Standard 4/110
> >>>>'65 Monza Convertible 4/140
> >>>>'66 beater Coupe - icemobile 4/140
> >>>>_______________________________________________
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