On Wed, 21 Feb 2018 23:14:43 +0100, Emanuel Berg
wrote:

rubber compounds
Jeff Liebermann wrote:

See section under "Tread Compound": Markus
Hackmeyer, product manager at Schwalbe, feels
that hysteresis is a much more important
measure than durometer: "From our point of
view the compound hysteresis (also known as
viscoelastic properties) is much more
important than the durometer. That means the
durometer only can not define the compound
properties. That is the reason we do not
state the durometer values of our compounds."

OK, then what are the compound
hysteresis/viscoelastic properties then and how
can THEY be measured?

It's more common to measure the rolling resistance of a bicycle tire,
than to isolate the viscoelastic component of rolling resistance.

https://www.bicycling.com/bikes-gear/components/know-your-rubber-quick-start-guide-mountain-bike-tire-design
From the same paragraph as the above quote:
Hysteresis A dynamic measurement of energy loss in
the rubber compound, this can also relate to rolling
resistance or tire "grip." A 70sA compound typically
has little energy loss, while a 40sA has a large
percentage of energy loss.
So, it's a measure of energy loss in the tire and a component of
rolling resistance.

https://en.wikipedia.org/wiki/Rolling_resistance#Primary_cause
A characteristic of a deformable material such that
the energy of deformation is greater than the energy
of recovery. The rubber compound in a tire exhibits
hysteresis. As the tire rotates under the weight
of the vehicle, it experiences repeated cycles of
deformation and recovery, and it dissipates the
hysteresis energy loss as heat. Hysteresis is the
main cause of energy loss associated with rolling
resistance and is attributed to the viscoelastic
characteristics of the rubber.

There's quite a bit online found under "bicycle tire rolling
resistance" measurement. For example:
http://www.sheldonbrown.com/brandt/rolling-resistance.html

"A Direct Method of Measuring the Rolling Resistance of a Bicycle
Tire"
http://people.cst.cmich.edu/yelam1k/asee/proceedings/2015/Paper%20files/Student_Papers/2015_ASEE_NCS_Conference_submission_61.pdf

There's a section in the Bicycle Science 3rd edition book covering the
details of measuring rolling resistance:
https://books.google.com/books?id=0JJo6DlF9iMC&pg=PA225&lpg=PA225
Looks like it's difficult to isolate the viscoelastic component from
the rolling resistance. I have a guess(tm) on how it might be done,
but can't find anything definitive.

Shore Durometer, good idea. My HW store
catalogs don't have any but there is an
SI Durometer for some 50 bucks, obtainable thru
the web...

The one I bought on eBay cost me about $20. You can also get one with
a digital scale for about $40, but I don't think it's worth the added
cost. The difficult part is that it works best on a flat rubber
surface, which is rather difficult to find on most tires. The result
is that the dial will move around slightly as you roll the device
around trying to get it to stay flat with the tire surface.

I take it is a small box that ejects a pin into
the material and when motion stops the required
power/distance is an indication of
material hardness?

Exactly. It's a penetration and deformation tester.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558