Quote:
Originally posted by bigben2k
I'm too worried about structural integrity, to use a clear rubber sheet in this block. Remember, the fins, in combination with the top is the only thing holding this block together. If the baseplate starts to cave in, even by a fraction of a millimiter, it's dead.
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So what does this mean? Are you planning on an o-ring (what I recall from earlier discussion)? Silicone RTV?
Anything you put in the interface will have some finite thickness. What you need to do is design a finite and tightly controlled gap between the top and base to exist when the top of the fins touches the bottom side of the top. Then you need to fill this gap with a material such that you can compress it to fill the gap while developing the right pressure to seal the interface yet not so high as to bow anything.
A solid o-ring? This can be a good choice but you need to use a relatively soft material and calculate the proper compression. Same goes for a "sheet" gasket. The most idiot-proof (no insult intended) manner is RTV because the excess will easily squeeze out if assembled right after application. It's sort of self-limiting in terms of the interface pressure it will let you develop.
This really isn't a hard problem, but isn't one that you should merely ignore, either. If statics isn't your thing, there's plenty of cookbook solutions to beam loading situations that'll help you see the orders of magnitude involved with deflection vs geometry and loading.