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Originally Posted by pberku
What I did do differently than you was to immerse a complete clutch, and a separate bms into a large pot of water, instead of just 2 stand alone bms's.
I inserted a digital thermometer into the water and started heating the water up. Well guess what? The bms that was still mounted in the clutch had bend by 73C, the stand-alone bms had bend by 97C. I repeated this test several times with the same results. The bms that was still mounted in the clutch always bend by 73C, and the stand-alone bms always bend by 97C.
Why the discrepancy? When the bms is mounted in the clutch it is FIXED at both ends, so, when heated, being fixed at both ends, it CAN NOT expand along its longitudinal axis. It can only expand upwards (bend).
The stand alone bms on the other hand, not being fixed DOES elongate along its longitudinal axis, as well as bend-up. It is the bending that causes the fan to activate, not elongation, therefore the bms that is affixed at both ends will bend faster, as no energy is wasted elongating it. Consequently, it will activate the clutch at a lower temperature.
So in real life, if you heat up a stand alone bms, the conclusions will be invalid. Now going back to your own testing, there probably was nothing wrong with the bms's themselves.
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. . is really going on! If you had said that with the bms MOUNTED on the ‘frame’ and immersed in water, it consistently ‘bent’ enough to engage the pin clutch at XX deg C, I would have said, ‘great’; it’s definitely a different Sachs (MB) part number than the my C140 vfc. No laws of thermodynamics (LoT) would have been contradicted. The world is right!
But you didn’t! You took the same strip that bent at XX deg C and put into water and now said that that very same bms bent at YY deg C. What??? Now you’ve done it! An amalgam of two pieces of metals work at TWO different temperatures??? What, that can NOT be! That means it can CHANGE is COE. Now that’s an educated piece of metal. If you had such a thing, you would be famous for being the person that showed the LoT are NOT as we have been lead to believe.
You offered a theory that said the bms is
captive in the mounting and since it can’t move, it must bend earlier than in a standalone condtion. The bms will bend whether it is captive or not; it doesn’t depend on it being captive, only the COE of each metal. And as I’ve shown, it is NOT captive. The aluminum frame that holds the bms will EXPAND also and make MORE room for the bms as it heats. Look at post #81, you will see that I used some annotated pictures to show some of the key dimensions of the bms and ‘frame’ for my C140 vfc.
Now to HELP you, there is ONE explanation that would allow your different observations to make sense: that is if the mounting ‘bracket’ itself was a bms. Then as the brass/steel bms heats and bends in one direction, the bms frame would bend in the opposite direction. The composite action of the both “bms” would lead to the pin engagement at a lower temperature than just the brass/steel bms. Again the WORLD IS RIGHT! No LoT have been broken.
But, bottom line, a bms can NOT have two (2) different COEs because each metal in the amalgam has its unique COE. It can’t change. It will always react the same to a medium that it is immersed into whether that be air or water.
This position that both you and Lea have taken may make you ‘happy’ that you could justify MBs ‘piece of paper’ but you both are like the people that thought the earth was flat, so if you sail long and far enough, you will fall off. One man (actually there were others) KNEW it wasn’t flat and but he wasn’t in the popular opinion. Just because you THINK have the valid explanation doesn’t really mean that you do. You can’t violate the LoT and be right.