Quote:
|
Originally Posted by Walrus
I am unclear on one aspect of this "bending and/or lengthening" you guys have been discussing...
Doesn't the bi-metal expand, therby lengthening, albeit at different rates? Is that not what actually causes the "bending" as the two different metals expand, therby lengthen, at different amounts/rates for the same heat input?
(The following exerpt is from an elementary text on how a bimetal thermometer works...)
...A bimetallic strip is a piece of metal made by laminating two different types of metal together. The metals that make up the strip expand and contract when they are heated or cooled. Each type of metal has its own particular rate of expansion, and the two metals that make up the strip are chosen so that the rates of expansion and contraction are different...
I would think there IS lengthening (expansion), and logically along the longitudinal axis, the amount of expansion would be greater than transverse. I agree the total amount of expansion will be minute for a small bi-metal strip such as employed on our clutches... I am sure the COE is published somewhere for different metals... I remember it from my early engineering classes...
|
. . two dissimilar metals results in "bending" by the amount of the coefficient of differential expansion (CODE). Take this picture to extremes; let say we heated the bms to a very high temp. As it bends it looks more like the letter "C".
Now, the hard part, is the C's length greater than it was before
as measured using the mounting clips on the frame of VFC? Of course not, from that perspective, it has 'shrunk'. That is precisely why there are end TABS (tits) on the bms; as the bms 'bends', the tabs serve as a safety device to ensure it doesn't 'pop' out of the mounting.
The bending of the bms allow MORE room between the mounting points. Look at the picture below to see what sizes I measured on a W140 vfc assy. When the bms is cold, there about 1/8" of slip room (back and forth) between the mounting tabs.
I will use information later in my reply to Phil regarding his experimental measurements.