[T3] Flaps Closed for Business
Jim Adney
jadney at vwtype3.org
Tue Nov 18 21:30:50 PST 2014
On 18 Nov 2014 at 19:15, Keith Park wrote:
> Keep in mind, the thermostat bellows either works or it doesnt, no in
> between. THey are meant to CLOSE the flaps only, not open them, the spring
> is there to do that.
Gotta disagree with you here, Keith. The bellows is capable of
exerting LOTs of force in both directions, actually more in expansion
than in contraction. The spring just takes the play out of the
linkage. The thermostats are filled with a liquid that boils at the
operating temp. The change of phase creates lots of pressure. That's
why the thermostat holder constrains the upper limit of how far the
bellows can expand. If there was no limit, the bellows would expand
and tear itself apart. Same reason that you don't want to test them
in hot water without installing them in one of those holders.
Think about what it would be like if they were filled with water and
water vapor. The operating temp would be 212 F and the internal
pressure would go from negative to huge when the water boiled.
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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