His experiment was just that . . a "BENCH" experiment. It does NOT prove that it will work in the car. Some basic question still remain . .
1) is the vfc the same as the vfc in W140 - - probably not,
2) and fundamentallly, will it work on his car - - still to be proved.
Phil's theory/explanation is NOT correct and he's fit the measurements by using a non-real explanation. If the bms bends at 90C in water, it should bend the same when mounted on the 'frame'. No difference! I personally think that when the bms was mounted, it was MUCH easier to see a bend because you have a point of reference for the 'eyes'. With just a bms in the pot of boiling water you have no frame of reference to see a bend. Remember you don't need a lot of bend to engage the clutch. It HAS to bend the same.

Anyway I will do the same test and report.

My aux fans always come on low (draw total of 12 amps). but if it's a hot day, done fast freeway driving, exit into stop/go traffic and then shut-off the car. If it's started 10 mins or so later, the aux fans come for about 30-45sec in Stage 3; you should hear them roar! But the temp drops from 100 to 95 in that short time.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

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Jim,

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...

This is not to say you or anyone here is wrong, or right... Just a matter of perspective, I guess. 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...

The attached picture is from the MB manual for a 1988 560sl... Others, I'm sure, are gonna differ...

One other important thing to realize... When the clutch is disengaged, heat is going to be generated within the vcf due to friction in the fluid from the differenting operating speed of the components. This is why the vcf has "fins" on it... to radiate the heat generated. Of course, when the vcf clutch is engaged, all the internal parts of the vcf are moving at the same speed, thereby no extra heat generated.

Your thoughts...

Attached Thumbnails

 

Hi Lea, Jim, and the others.

I have to leave this debate for awhile. My 14 year old step daughter was just admitted to childrens hospital with a serious infection.

Will get back to this facinating debate when she is released.


Phil

__________________
'95 E300 Diesel, 264,000 Miles. [Sold it]

I hope all goes well for her... My thoughts will be with you.

. . 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.

Attached Thumbnails

 

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

out to her and the family for a quick recovery.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

We agree 100% that expansion is the cause for bending... And, if the bms expands, its physical length increases. This there can be no dispute. Geometrically, however, the length from the ends of the bms, relative to the mtg bracket very well may appear to have shrunk. I can see this and agree with you. Using your analogy, the ends of the "C" are closer together, even though the measured distance along the arc of the "C" will be longer than before the expansion which caused the bms to bend into your "C" shape (in the hypothetical extreme case).

Perfectly clear! Now that thats all settled, why not just remove the bms and seal the pinhole... Your fan would then be turning engine rpm until the centrifugal weight closes off the port, disengaging the fan at or above 300rpm (I think that is the speed reported by MB in my manual)? Of course, your engine would be mighty noisy, but that could be tolerated if heating could be cured by this plan. Perhaps a more flexible fan could also minimize noise as it would flatten out as engine rpm increased (and vehicle speed and air speed thru the radiator as well).

Nice discussion... I have enjoyed following this topic. Good Show!

BTW, Nice website, Jim. I am still unclear if your cool harness is applicable to my 1988 560SL...

. . 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.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Rats... You've done it again and confused me. Perhaps the 140 is 180degrees opposed to the 107 in operation. You state above the ...bms bends, then engages the pin... when on a 107, the pin IS engaged until the bms heats up, bends away from the pin, releasing the pressure on the pin and therefore spring plate to uncover the hole allowing fluid to flow thru...(reference pic posted above ).

As I posted earlier, why not just remove the bms, seal the pin hole, and let it ride?
What a topic!

but all VFCs operate the same: When I said "engage", I mean the operation where the clutch engages and it becomes a "locked" up fan. To 'engage' you must release the pressure on the pin clutch.

The hypothetical 'frame' that I presented DOESN'T exist but if it did, the bms in the vfc would bend UP and the 'frame' bms would bend DOWN; together that operation would make the clutch engage earlier. Clear????

If you remove the bms and make it a FULL time operation: it roars pretty loud and is always in operation. We want it to work ONLY when it gets to 100C as measured on the temp gauge in the IC.

And YES, my Cool Harness will work nicely on your 560SEL. .

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Firstly and more importantly, Phil, I'm so sorry to hear your news and feel for you and your family. Hope your daughter recovers soon.

Jim

Whilst I respect your comments, apparent education and view, I occasional find your tone most patronising - sometimes a little arrogant even. Perhaps it's just my perception - and communication via the keyboard can sometimes be misinterpreted - so I apologise if it's me.

Please don't be offended that others challenge thinking, testing or comments made by anyone here. It's natural to be inquisitive and not to accept that the 'world is flat' or even if someone else 'proves it is' if you're an engineer!


Lea

__________________
'93 R129 500SL-32
'89 190E 2.6 - sold in 2002

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117.961 and earlier engines use a vfc WITHOUT temp controls, is why I was asking... What I do NOT know is if the earlier engines have a fan constructed differently as to limit or lower the noise, and if so, would the fan be as efficient. All this is moot, of course, for highway driving; however,is very apres po for 'round town puttering.

This thread ranks as one of the best discourses I have had read or had a part in... Amazing that it went 6+ pages without Flaming!!! Kudos guys!

Oh, and my engine is a 117.967 in a 560sl (107.048)... not sel. I guess the CH will still work? I may just have to call you for one, if I can just figure out where the correct sensor is...

Thanks!

And to answer the original post... The MB manual I have sez to listen to the engine noise for changes in pitch to determine if the clutch is functioning properly or not. Of course, the engine must be at or above lock-in temp for any change as if cooler, the fan will be un-coupled the whole time. Dumb test, in my opinion. I can guarantee you one thing... sticking anything into a rotating fan would not be a course of action that I would choose!

. . I'm here to help us all 'stay-on-track'. My writing style is not intended to be arrogant but to 'teach'. If I didn't make these corrections, I not sure where we might be at this juncture.

Well, Lea, if somebody does prove it's flat. . there's a lot of re-writing needed for all of the world's books, both techical and otherwise. And then just maybe the bms does have dual COE.... just kidding.

And I'm a Physicist too . . .

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

. . Exclusive Motors, has the older 'always-on' clutch. And I think that you are correct; don't seem to make as much "roar" as these do.

I believe that MB wanted to increase gas milage, lower engine noise so they designed the VFC. Nice device but they do seem to be problematic, since the W140 versions don't work as advertised.

It's HAS been a good thread; Lea, Phil, jbaj007's contribution, Marshall's comments, all adding to this body of knowledge.

As far as a CH for you, send me an email from my web page, and we'll go from there. Tnx for your comments.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page

Jim

I knew I could dig a sense or humour out of you....

BTW - I found a 'laser' temperature measuring device today and experimented. But unfortunately have found the measuring technique fraught with difficulties and error.

Firstly the emissivity of materials plays havoc with the accuracy and although the 'laser' measuring device sounds ideal, of course it has a multitude of problems. It's 'real' IR measuring beam is subjective, distance, obstruction and a multitude of effects cause inaccurate results and so even using a 'branded' unit, I still failed to attain an accurate and stable reading. Better off mounting several thermocouples with glass tape to be honest, apart from the revolving bms itself of course!

I'm still not 'taught' yet, I have to say, or understand why we all have such differing results, but I do believe the world is round so at least we all agree on something - I think!?

Mind you - we also have seem to have attracted a reasonable following as shown by the number of views -but just wish a couple of others would join in.

Lea

__________________
'93 R129 500SL-32
'89 190E 2.6 - sold in 2002

http://antron.pwp.blueyonder.co.uk/i...nature/Sig.jpg