On 9/14/2019 10:24 AM, Frank Krygowski wrote:
On 9/13/2019 11:22 PM, John B. wrote:
On Fri, 13 Sep 2019 22:41:08 -0400, Joy Beeson
wrote:
On Fri, 13 Sep 2019 08:40:21 +0700, John B.
wrote:
On very steep slopes where rim heating might be a problem I use an all
on and all off braking scheme. Brake as strongly as possible to a slow
speed and than release the brakes and allow gravity to accelerate the
bike. than all on braking again, and so on.Â* On the longest and
steepest hill on Phuket, perhaps a kilometer or more of severe down
hill the rims were not hotter than I could comfortably hold my hands
on.
https://www.jamiesphuketblog.com/201...in-phuket.html
A different hill but typical of Phuket hill roads.
That was the technique I used in Albany County.Â* I would stop every
mile or so to feel my rims, and never found them hot.
If we want to be scientific maybe we can get Frank to calculate
friction heating of the rim during braking and heat dissipation when
coasting :-)
The heat input to the rims is easy to calculate. The heat dissipation
would be intensely difficult to calculate. That's why, years ago, Jobst
and others here talked about measuring rim temperatures by various
means. These were one possibility:
https://www.omega.com/en-us/sensors-...p/TL-C5-LABELS
You stick them on a surface, and as each temperature is reached, the dot
turns permanently black.
You could also use an infra-red thermometer, working quickly to use it
as soon as you stopped.
I've got one small enough to carry in a bike bag. To be really accurate,
you'd want one that adjusts for the emissivity of the surface, which
mine doesn't do.
"Most organic objects fall close to 0.95 on the emissivity scale. For
this reason, many IR thermometers are pre-set at an emissivity of 0.95.
However, objects with much lower emissivity ratings, such as polished
metal, will give false temperature readings. This will happen if the
emissivity setting is not adjusted before the temperature reading is taken."
https://ennologic.com/emissivity-inf...eter-readings/
--
- Frank Krygowski