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Topic Date User

Rapping with a Gri Gri - Danger? 18-Mar-2011 At 2:27:30 AM Jim Titt

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The guys at DMM do laugh about that occasionally!
The reality is that the V-Twin as a whole is cooler but the bits that touch the rope are a lot hotter. Sadly because it was a bit of weak plate anyway more heat ended up in your hands anyway!

Anecdotal evidence is to be taken with a pinch of salt anyway because what people mean is that it felt cooler, what they are really testing is the thermal conductivity of stainless steel and thus the ability of heat to transfer into the skin. You have to transfer a not-inconsiderable amount of energy from the object into the skin before you feel a temperature difference as the nerves are underneath layers of skin and fat which conduct the energy away. In the days of development of the space shuttle the engineers used to take great pleasure in demonstrating the amazingly low thermal conductivity of the insulating tiles by picking them up at over 1200° with their bare hands. There is another nerve system which detects radiant heat and as stainless radiates poorly this is also fooled.

We spent quite a long time working out the cooling curves for plates and the V-Twin was always interesting, straight out of boiling water it measures about 49°C using a thermal imager and can easily be held in the hand whereas the aluminium plates are hot!

Sadly we haven´t yet found a material with the thermal properties of aluminium but the wear resistance of stainless, at least not an affordable and useful one.

Jim