In an earlier post I referred to some work I did measuring temperature rise in a STOP.
I just dug out the results, from January 2013.
I glued 2 thermocouples to the inside of the hollow bottom bobbin of an old STOP, drilling a hole in the back for the wires.
One was on the lower curve, close to the hole that can be used for a krab to remove the autolock function, the other was directly opposite that, inside the pointy bit that nips the rope on autolock.
The temperatures were read off on a 2-input digital thermometer.
I have a photo, but no clue about how to post it here.
I was given an old, stiff, retired 50m length of 10.5mm Mammut and used it on the 45m surface pitch of Titan.
The pitch was dry (as it almost always is) and the rope had been kept knitted up in our living room for days so it was also dry. I had considered using the TSG drying room, which has a dehumidifier, but decided against it.
The rope went through a braking krab, which was never used.
I think each drop took less than a minute, but I didn't time them.
I could read one channel of the thermometer on the way down.
On the first drop I pressed the handle fully in the prescribed manner and easily controlled the descent by hand.
At the start both temperatures were 4C and at the end the lower thermocouple read 110C, the upper one 65C.
Half a minute later both read 65C.
On the second drop I controlled the descent using the handle, as this seemed likely to generate most heat at the site of the upper thermocouple.
At the start both read 16C, and at the end they read 82C (lower) and 86C (upper).
Half a minute later both were down to 55 - 60C.
Neither the body of the STOP nor the handle were anything like too hot to touch at the end of either drop.
The rope was not glazed at all.
The mass of the bottom bobbin plus backplate and handle is 110 grams, so the bobbin itself (steel) would make up most of that. The rest is aluminium alloy.
My mass of about 70kg means that about 30,000J of heat would be produced on each drop.
A very simple and simplistic calculation, using 100g as the mass of the bobbin, says the temperature rise that would produce in the bobbin is 600C.
That's daft because some will be taken by the top bobbin and some will escape via convection, forced or otherwise, but to my mind it would take some extreme assumptions to believe that all (or even most) of the heat goes into the descender.
Apart from the odd occasion, of course.
