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robdotcalm
Aug 25, 2009, 3:22 AM
Post #101 of 104
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Registered: Oct 31, 2002
Posts: 1027
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If we're getting this precise, maybe the heat loss due to Stefan-Bolzmann radiation should be taken into account.
Cheers,
Rob.calm
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FriendOfMonoPockets
Aug 25, 2009, 3:31 AM
Post #102 of 104
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Registered: Aug 23, 2009
Posts: 36
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jt512 wrote: RockLimbaugh wrote: [image]http://media.rei.com/media/606102.jpg[/image] That was completely predictable. Jay |
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petsfed
Aug 25, 2009, 6:40 PM
Post #103 of 104
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Registered: Sep 25, 2002
Posts: 8599
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patto wrote: Exposed surface area of ATC ~ 36cm^2 or 0.0036m^2
This was the other thing that was bugging me. We're talking about a pyramid, which is half again as long as an ATC, and has all of those extra cooling fins. Now, I'm not going to claim that that in and of itself is enough, just that if you go up to 50cm^2 for the unfinned pyramid and probably 2-3 times that for a finned pyramid, you'll be getting close to 10% of the heat generated by a rappel could, in principle, be radiated from the device during a moderately paced rappel (say 2 minutes for a 50m rappel, which still seems ludicrously fast on a 10.5, but possible on a 9.4mm or something smaller). Of course, this is back of the envelope type stuff. I think it would be more useful to actually run the tests with a variety of different devices and if there's a noticeable difference between them, then go the extra step and build a pyramid that has the extra mass but with a minimized exposed surface area.
Also, point A. from the same post is technically accurate but not what we're concerned about. To generate an analogy, we don't care that the earth absorbs a very tiny fraction of what the sun radiates. We're just concerned with what the earth does with the energy it absorbs. Dig?
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zeke_sf
Aug 25, 2009, 6:56 PM
Post #104 of 104
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Registered: Apr 28, 2006
Posts: 18730
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shoo wrote: Stop hijacking my thread, and get back to the topic at hand? Mad Lock - Mad Rock  There was a reason Petzl discontinued this design. Though some may appreciate the versatility of a belay device that can magically turn into a knife, I think I'll stay away. And what's with this removable pin crap? I say hell no to the frankenreverso.
Look, if you want things back on topic, why the hell are you posting pics of sex toys?
For me, the worst device is the B-52 by Trango. I love the device -- smoothest ATC I've used -- but, damn, does that thing sharpen up. 'Course, I never owned the old Petzl Reverso, so I never really developed an affinity for the "sharp end".
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