rubber compounds
 

I've heard there are different rubber compounds
in tires which makes them harder or softer.

What property is that, and how can it
be measured?

I take it in Northen Europe and Scandinavia,
one would like hard tires rather than soft?

--
underground experts united
http://user.it.uu.se/~embe8573

rubber compounds
 

On 2/19/2018 7:30 PM, Emanuel Berg wrote:
I've heard there are different rubber compounds
in tires which makes them harder or softer.

What property is that, and how can it
be measured?

I take it in Northen Europe and Scandinavia,
one would like hard tires rather than soft?


Hardness is measured with a Shore durometer:
http://blairrubber.com/determining-r...rt-or-science/

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

rubber compounds
 

"Emanuel Berg" wrote in message
...
I've heard there are different rubber compounds
in tires which makes them harder or softer.

What property is that, and how can it
be measured?

I take it in Northen Europe and Scandinavia,
one would like hard tires rather than soft?

Hard tyres last a long time but don't grip well - soft tyres have grip but
wear rapidly.

OE Bridgestone motorcycle tyres frequently outlived the machine - and
sometimes the rider.

Pirelli motorcycle tyres have plenty of grip and give "feel" to warn you of
approaching the limit - I couldn't keep up with the cost of keep replacing
them.

Last Michelins I used; stick like **** to a blanket right up to the limit -
then just let go - there was plenty of tread left when I got fed up with
that, so I sort of eeer..."donated" them to someone I didn't like much.

rubber compounds
 

Ian Field wrote:

Hard tyres last a long time but don't grip
well - soft tyres have grip but wear rapidly.

They should put the tire hardness on the tire
just like the size and intended preassure!

--
underground experts united
http://user.it.uu.se/~embe8573

rubber compounds
 

On Tue, 20 Feb 2018 23:49:48 +0100, Emanuel Berg
wrote:

Ian Field wrote:

Hard tyres last a long time but don't grip
well - soft tyres have grip but wear rapidly.

Yep.

They should put the tire hardness on the tire
just like the size and intended preassure!

https://www.bicycling.com/bikes-gear/components/know-your-rubber-quick-start-guide-mountain-bike-tire-design
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."

The rubber hardness is also not uniform over the tire surface.
For automobile tires, it would not do for customers to notice that the
hardest rubber yields the most miles per tire. Rubber tires also
become harder as they age.
"Degradation of vulcanised rubber products..."
http://www.polymerjournals.com/pdfdownload/991052.pdf

Buy one of these:
https://www.ebay.com/sch/i.html?_nkw=rubber+hardness+meter
For bicycle tires, you want a Shore A gauge:
https://en.wikipedia.org/wiki/Shore_durometer
I've been conducting some disorganized rubber hardness testing for
about 5 years. So far, I've found nothing interesting, conclusive, or
worth announcing.

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

rubber compounds
 

AMuzi wrote:

Hardness is measured with a Shore durometer:
http://blairrubber.com/determining-r...rt-or-science/

Good article!

ASTM D2240

ASTM = American Society for Testing and
Materials, 1961

--
underground experts united
http://user.it.uu.se/~embe8573

rubber compounds
 

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?

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...

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?

--
underground experts united
http://user.it.uu.se/~embe8573

rubber compounds
 

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

rubber compounds
 

Jeff Liebermann wrote:

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.

Wow, interesting!

So the viscoelastic property is what makes the
tire deform/recover as it rolls
in under/away from the weight of the
bike&rider, and this is hysteresis, and the
result is loss of energy (as heat), and this is
one component of overall loss of energy which
is bunched together as rolling resistance?

There's a section in the Bicycle Science 3rd
edition book covering the details of
measuring rolling resistance

I should get that book...

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.

Maybe disintegrate a tire and put a piece of it
in a stand or a vice? Or/and perhaps fixate the
durometer as well, like a shop drill?

BTW how do ISO/ETRTO measure the tire width?
I've heard it is from one bead, over the tread,
to the other bead, this distance divided by
2.5? Do they also disintegrate the tire before
doing this or do they use a string of some kind
to loop around?

--
underground experts united
http://user.it.uu.se/~embe8573

rubber compounds
 

Jeff Liebermann wrote:

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.

BTW what notation is 70sA and 40sA?

--
underground experts united
http://user.it.uu.se/~embe8573