SMC roof differences
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SMC roof differences
Since eventually I assume that we will all get one, I was wondering just what the actual differences are between the SMC roof and the original painted roof. I have seen that it is heavier, but I was wondering what it is made of, is the frame different and why will this top not separate? On the original, I understand that it it was the coefficient of expansion that caused the problem. Why isn't that an issue with the SMC? Also, what does SMC stand for? Just wondering, thanks.
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St. Jude Donor '05-'06-'07-'10
Originally Posted by SDCEB
Since eventually I assume that we will all get one, I was wondering just what the actual differences are between the SMC roof and the original painted roof. I have seen that it is heavier, but I was wondering what it is made of, is the frame different and why will this top not separate? On the original, I understand that it it was the coefficient of expansion that caused the problem. Why isn't that an issue with the SMC? Also, what does SMC stand for? Just wondering, thanks.
(In physics, shear stress is a stress state in which the shape of a material tends to change (usually by "sliding" forces) without particular volume change. The shape change is evaluated by measuring the relative change in the angle between initially perpendicular sides of a differential element of material (shear strain). A simple definition of shear stress is the components of stress at a point that act parallel to the plane in which they lie.)
Paul
Last edited by talon90; Sep 9, 2006 at 02:15 PM.
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St. Jude '03-'04-'05-'06
Originally Posted by talon90
An SMC roof is made of well, you guessed it, SMC. Sheet molded composite is the material that the C5 roof is made of. For the C6 the roof material was changed from SMC to a polycarbonate material. This change was designed to be a weight savings of about 3 pounds. The frame is magnesium. The frame will continue to be magnesium. The problem as you indicated is that the frame and the roof panel had a difference of coefficient of thermal expansion that was greater than what the adhesive could overcome. This expansion puts the two materials in shear.
Once this happens if the forces are great enough the structural integrity of the adhesive becomes violated and the roof can separate.
Paul
Once this happens if the forces are great enough the structural integrity of the adhesive becomes violated and the roof can separate.
Paul
)Frank
Last edited by Another Yellow; Sep 9, 2006 at 03:01 PM.
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St. Jude Donor '05-'06-'07-'10
Originally Posted by Another Yellow
Paul, you explained it perfectly, exactly the explaination given at the NCM Labor Day event by Tom Hill. It should be repeated every time this question comes up. (Which is often
)Frank
Frank,How's it going? I figure we can back it up with a little photo proof from Tom's seminar. I spent some time talking with him afterward. He did such a fantastic job. Not to mention. He stayed, on station for about 7 hours that day just to talk to people and address issues and concerns.
All I can say is anyone not attending NCM events are really missing out on the big picture.
Paul
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Once this happens if the forces are great enough the structural integrity of the adhesive becomes violated and the roof can separate.
Paul[/QUOTE]
Thanks, I know that there have been a lot of threads about the top, but I wasn't able to find an explanation of just what they were using to replace it. I have an engineer friend who suggested that they could instead use a carbon fiber top and tune it so the the coefficient of expansion is the same as the magnesium alloy frame. Guess that would cost too much.
Paul
[/QUOTE]Thanks, I know that there have been a lot of threads about the top, but I wasn't able to find an explanation of just what they were using to replace it. I have an engineer friend who suggested that they could instead use a carbon fiber top and tune it so the the coefficient of expansion is the same as the magnesium alloy frame. Guess that would cost too much.
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St. Jude Donor '05-'06-'07-'10
Originally Posted by SDCEB
Once this happens if the forces are great enough the structural integrity of the adhesive becomes violated and the roof can separate.
Paul
Paul
[/QUOTE]My pleasure
Tell your friend he's right. That would be a perfect roof but it would probably cost $4,000 or more dollars.
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My pleasure
Tell your friend he's right. That would be a perfect roof but it would probably cost $4,000 or more dollars.[/QUOTE]
Cost is of no concern to him, it is all about meeting an engineering objective!
Tell your friend he's right. That would be a perfect roof but it would probably cost $4,000 or more dollars.
[/QUOTE] Cost is of no concern to him, it is all about meeting an engineering objective!