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  #21  
Old February 23rd 18, 10:24 PM posted to rec.bicycles.tech
AMuzi
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Default rubber compounds

On 2/23/2018 3:41 PM, Emanuel Berg wrote:
Jeff Liebermann wrote:

To me the intuition is the other way around:
durometer = instrument, as in thermometer,
hygrometer ...


Do you measure temperature in units of
themometers? Do you measure humidity in units
of hydrometers?


I mean, "durometer" sounds like "thermometer",
"hydrometer", and so on (OK, it should be a "d"
in English), so to me, it sounds like
an instrument.

Also, one might wonder why they felt the need
to come up with a new unit for this at all!
Couldn't it be "how much power to penetrate" or
"how much power to reach a distance" or "how
long a distance for a certain power"... (I say
this without ever having used or even seen
a durometer so maybe it doesn't make sense.)


It's all Greek to me:
https://eic.rsc.org/opinion/hygromet...021051.article

and to you as well, probably. Don't mix your Twaddles with
your Brix or Oechsle or Plato ( which, in this case, is
German not Greek)

you're welcome.

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


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  #22  
Old February 24th 18, 02:33 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,015
Default rubber compounds

AMuzi wrote:

It's all Greek to me:
https://eic.rsc.org/opinion/hygromet...021051.article


Do you know the difference between
a hygrometer and a hydrometer? A hygrometer
measures humidity, the amount of water
vapour in air. A hydrometer, on the other
hand, measures the density or specific
gravity (SG) of a liquid by floating in
the liquid.

OK, so it should be "hygrometer" in this case!

(Is "vapour" English English BTW?)

you're welcome.


Thank you!

--
underground experts united
http://user.it.uu.se/~embe8573
  #23  
Old February 25th 18, 04:37 AM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,878
Default rubber compounds

On Fri, 23 Feb 2018 16:24:42 -0600, AMuzi wrote:

It's all Greek to me:
https://eic.rsc.org/opinion/hygromet...021051.article


Oops. I guessed the correct term, then during proof reading, I
changed it to the wrong term. I hate it when that happens.

Continuing with the topic drift...

Besides hygrometer, a humidity meter is also called a psychometer,
psychrometer, or various trade names (i.e. Psychron). Here's my
Bendix Psychrometer Model 566-3:
http://www.LearnbyDestroying.com/jeffl/pics/weather%20stations/Bendix%20Psychron%20566/index.html
It's a nifty little instrument and state of the art for the 1960's. It
has two mercury thermometers (wet and dry), a small electric motor
driving a fan to move air across the thermometer bulbs, and nomographs
to decode the relative humidity and dew point. The nomograph, tables,
and slide rule do not include barometric pressure compensation, but
that can be handled by an Android App:
https://play.google.com/store/apps/details?id=com.swastic.psychrometricairpropertycal culator
It's nice because it's quite accurate and responds very quickly to
changes, as opposed to the now common capacitive electronic sensors
that can take 3 days to stabilize and maybe an hour to display a
change in humdity.

you're welcome.


Well, if you insist. Thanks.
Grumble...


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #24  
Old February 26th 18, 03:12 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Default rubber compounds

Apropos the confusion over the Shore meter and the durometer:

You can measure up to 3000V with an AVOmeter if you have the military model metal-body meter with the extra resistors, which the compulsive obsessive may call "ballasts".

In the same way you can measure the durometers of a particular batch or mixture of processed rubber if you have the correct Shore meter. 20-30 would be a soft rating, 40-70 a pretty hard rating.

I've noticed recently that printmaker's ink (1) rollers are rated by "Shore durometer", which suggests to me, without any research whatsoever because it's my exercise time and my trainer is just finishing her candy bar and cigarette, that even artists are aware that the measure of the hardness is a durometer, and that there are several meters the measurements of which have not been adequately standardized -- and now Jeff comes up with the Shore A, which suggests there is at least a B model of the most trusted model as well, which gives different results, the same way two DVM's that load the circuit under measurement differently will give two different results.

Another way of putting the preceding sentence is that even with a measurement in hand, you don't know **** because your measurement is valid only for a particular model meter. Charming.

Andre Jute
I'm not confused because I anyway do this crap by analogy and comparison or work it out the slow way by reconstruction from the first principles of physics (and fervent prayer that I'll be distracted by something more urgent before long)

(1) You may think of them as very expensive paint rollers.
  #25  
Old February 26th 18, 03:31 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Posts: 8,724
Default rubber compounds

On Tuesday, February 20, 2018 at 1:30:39 AM UTC, 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?

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


The longest-lasting tyres I ever rode were Schwalbe Marathon Plus: nasty, hard and harsh.

Until I switched over to Schwalbe Big Apples. I changed my last set at 8500km, when they still had tread on them -- since they start with only cosmetic sipes rather than real tread and since Schwalbe says you can ride them until the rubber protection band starts showing, I reckoned they would probably go that far again. But I'm not poor and one of the tyres had cast its reflection band, and in my present state of health taking the wheels off and refitting them (quite a big deal on my bike as an anti-theft measure) is pretty stressful, and it was time to rotate the tyres, so I simply replaced both. Here's the punchline: the compound on the Big Apples seems not much softer than that on the Marathon Plus, yet the ride is superb, and the rolling resistance lower than on any other tyre I would consider, and the roadholding and handling at speed on rough roads are impeccable.

I think you're on a hiding to nothing here, young mater Berg: The compound has only a small influence on the impression the tyre makes on the rider, and if you buy good tyres (say Schwalbe) to start with, we're talking about tiny fractions of a penny per kilometer even if you're in the habit of throwing off half-worn tyres, so longevity is a distraction, not a real consideration. The sidewalls and the format of the tyre (I mean things like the elevated hysteresis-resistance of squirming deep treads, or on the other side the elevated compliance of soft sidewalls) have much, much more influence.

Andre Jute
Comfort isn't everything, but without comfort nothing else is worth much
  #26  
Old February 26th 18, 04:27 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,878
Default rubber compounds

On Mon, 26 Feb 2018 07:12:42 -0800 (PST), Andre Jute
wrote:

...that even artists are aware that the measure of the hardness is a
durometer, and that there are several meters the measurements of
which have not been adequately standardized


Rubbish. ASTM D2240-15e1 is the standard.
https://www.astm.org/Standards/D2240.htm

-- and now Jeff comes up with the Shore A, which suggests there
is at least a B model of the most trusted model as well, which
gives different results,


Yes, there is a Shore B.
There are 12 scales. [A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, R]
https://en.wikipedia.org/wiki/Shore_durometer#Method_of_measurement

the same way two DVM's that load
the circuit under measurement differently will give two different
results.


My DVM (digital volts guesser) will always produce the result which I
expect. If not, I'll just find another DVM that agrees with my
expectations. See Index of Conformity(tm).

Another way of putting the preceding sentence is that even with
a measurement in hand, you don't know **** because your measurement
is valid only for a particular model meter. Charming.


It's more likely that such a discrepancy is due to either using the
wrong Durometer or measuring in the extremes of its operating range.
For example, the typical Shore A Durometer is accurate from 20 - 80
Sa. If you want to measure really soft rubber, you need a Shore O or
OO. For hard plastics, Shore D.
https://www.smooth-on.com/pw/site/assets/files/30090/durometerchart.png

I'm not confused because I anyway do this crap by analogy and
comparison or work it out the slow way by reconstruction from
the first principles of physics (and fervent prayer that I'll
be distracted by something more urgent before long)


Keep your mind off the exercise physiologist and you'll probably do
better.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #27  
Old February 27th 18, 04:02 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,015
Default rubber compounds

Jeff Liebermann wrote:

Besides hygrometer, a humidity meter is also
called a psychometer, psychrometer, or
various trade names (i.e. Psychron).
Here's my Bendix Psychrometer Model 566-3:
http://www.LearnbyDestroying.com/jeffl/pics/weather%20stations/Bendix%20Psychron%20566/index.html
It's a nifty little instrument and state of
the art for the 1960's.


1960s? Sounds like an 1880s Jule Verne novel...

--
underground experts united
http://user.it.uu.se/~embe8573
  #28  
Old February 27th 18, 06:01 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 2,878
Default rubber compounds

On Tue, 27 Feb 2018 05:02:57 +0100, Emanuel Berg
wrote:

Jeff Liebermann wrote:

Besides hygrometer, a humidity meter is also
called a psychometer, psychrometer, or
various trade names (i.e. Psychron).
Here's my Bendix Psychrometer Model 566-3:
http://www.LearnbyDestroying.com/jeffl/pics/weather%20stations/Bendix%20Psychron%20566/index.html
It's a nifty little instrument and state of
the art for the 1960's.


1960s? Sounds like an 1880s Jule Verne novel...


Hardly.
https://en.wikipedia.org/wiki/Hygrometer
The early hygrometers used a human or horse hair, which changed length
with the RH. The wet/dry bulb (psychrometer) was invented in the
early 19th century. That morphed into the sling psychrometer:
https://www.google.com/search?q=sling+psychrometer&tbm=isch
which earned me an afternoon at the local police station while they
attempted to identify the type of weapon I was swinging around. Todays
motorized and electronic wet/dry bulb contraptions are improvements on
the basic design. Capt Nemo probably had one aboard the Nautilus as
too much or too little humidity in a closed environment tends to do
bad things to men and machines.
https://books.google.com/books?id=vicCAAAAYAAJ&pg=PA703&lpg=PA703
Where an accurate psychrometer comes in handy is demonstrating to
buyers of elaborate electronic weather stations that their humidity
measurements are very slow to change, and rather inaccurate.

Make one for about $10 or a wall hanger type for $15.
https://www.teachersupplysource.com/product/61246/scott-resources-hubbard-scientific-sling-psychrometer-kit/
http://www.spectrum-scientifics.com/ProductDetails.asp?ProductCode=3619
http://www.spectrum-scientifics.com/Wall-Thermometer-Wet-and-Dry-Bulb-p/6213.htm

Topic drift at its best...


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #29  
Old February 27th 18, 08:39 PM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,015
Default rubber compounds

Jeff Liebermann wrote:

Capt Nemo probably had one aboard the
Nautilus as too much or too little humidity
in a closed environment tends to do bad
things to men and machines.


What humidity is that? Here in the
studio/office right now is 18.3C/22% and in the
workshop is -3.6C/56%. With a heat fan, I can
get that up to ~4.5C tho. Outside is -11C and
a heat fan won't help

But I don't need data to know that -3.6C is too
cold to work with tools, one needs to go inside
in between every individual part just a second
to get back warm hands.

Where an accurate psychrometer comes in handy
is demonstrating to buyers of elaborate
electronic weather stations that their
humidity measurements are very slow to
change, and rather inaccurate.


I tested my analogous German-made hygrometer
after a hot shower, but not in the actual
shower of course, and it had changed a lot.
So how slow is "slow"?

--
underground experts united
http://user.it.uu.se/~embe8573
  #30  
Old February 27th 18, 09:35 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 6,271
Default rubber compounds

On 2/27/2018 1:01 PM, Jeff Liebermann wrote:
The wet/dry bulb (psychrometer) was invented in the
early 19th century. That morphed into the sling psychrometer:
https://www.google.com/search?q=sling+psychrometer&tbm=isch
which earned me an afternoon at the local police station while they
attempted to identify the type of weapon I was swinging around.


I'm betting you and I are the only ones here who have used a sling
psychrometer.

I never got arrested for doing it, though.

(I can't even remember where my psychrometric chart is now.)

--
- Frank Krygowski
 




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