CHAPTER TS 2: Cont. from TS2.8-- Page
TS2.9 of "The Book"
ROCKS
Update Dec.18, 2001: What
used to be "illegal" brushing is now legal brushing. Every style
of brushing is now done in the Brier and World events without challenge.
Personally, I like the expertise the brushers can now bring to the game.
Now, that is, since the science of the "how/why" to do edge brushing properly has
been demonstrated.
Granite does not run on the ice! The running surface of porous granite is
"wettable" with an ice coating which runs on the pebble.
Just like an Inuit sleigh with an ice coating on the bone or wood runners, with or without
rawhide cover, the runners are wettable and an ice coating is applied to minimize
friction. Water is not generated as a lubricant under the runners. Ice shears on ice with
not enough kinetic energy from friction to melt the ice.
Granite rocks:
Tremendous energy
is lost by the rock as it travels down the sheet especially if there is a large
buildup of ice crystals/snow on the running surface leading and cup edges. Rounded
leading rock edges allow the rock to "climb over" frost rather than
totally shear/scrape it resulting in "faster" ice in the first two ends with moderate
curl. This type edge (large leading and cup radii and maybe, equal) does not shear the pebble as
fast and, thereby, maintains more uniform pebble height with minimum fudging in later
ends.
This rubbing of ice on ice rock manufacture configuration (large
radii) will result in less curl as less frost crystals are dragged
to the rock's slow side.
As compared with "old style" sharp edged rocks, initial
speed on new pebble can be 1-1/2 sec. faster. "Sharp" edged rocks are
identified by rubbing your fingers over the running surface to feel the noticeable
"sharp" break/edge. These rocks may have a large leading edge
radii and a sharp cup edge.
The large radii ground edges will not give a noticeable break/edge feel. H-H
is faster with large radii ground rocks in the first end with a gradual increase in speed
as the pebble is sheared and brushed.
With both large radii edges, radical first and second end rock speed H-H timing is reduced with a
slow increase in rock speed in the first 4 ends vs. 2 ends with "sharp" edged
rocks.
The reason why "sharp" edged rocks run slower AND CURL more
is due to a buildup of sheared snow on the edges which cause an effective increase in
surface area which has the effect of making the rock slide harder (more friction) but
contributes to curl as the snow is dragged around to the slow side of the rock with
resultant dumping out the back. So -- sharp edged rocks are slower with more curl on
any kind of ice.
Sharp edged rocks can lose granite crystals at the edges and may even
look porous with pits about the outer running surface edge. If you spin your rock with a
small forward and back motion on the ice after cleaning with the fingernail brush, your
rock will run perfectly. It will run as though there were no pits because the pits fill
with ice crystals and "become part of the rock."
Pits in rocks are grossly over rated as to the change in
curl/travel characteristics. The angle of edge grind, the porosity (especially in the case
of porcelain rock inserts) and the running surface area are the controlling factors of
curl. Contaminants on the running surface will destroy the rock's
performance!! We are disregarding other ICE curl effectors: pebble shape, size,
temperature for now).
This type of rock (granite sharp edged) will curl more on any type ice,
HOWEVER, the slightest uneven grind angle will cause different curl and different travel
distances between rocks because it "grabs" and "dumps" crystals at a
rate that is different with precision ground rocks. The friction/curl environment is
changed with non-uniform grinding of the running surface.
What you give up for "more curl," you may give up in
inconsistency of curl with the granite vs. porcelain rock and/or the high radius vs. the
low radius ground rock. The porcelain inserted rock is more dense (not heavier but smaller
pores)-- less porous and does not allow a thick crystal growth and flake-off on its
surface increasing friction on the slow side so the curl is less for porcelain rocks.
The porcelain rocks I studied have 4-5 very small grooves in the running
surface generated by the surfacing tool.
These grooves are not visible to the naked eye but
can be seen with a 10X eye loupe. I believe these very small grooves with
accompanied ridges will hold some frost to encourage curl. If these
non-visible to the naked eye grooves are removed or wear out, there will no doubt be a
loss of curl as the "natural" porosity of porcelain is too dense
to allow an adequate ice coating to adhere to the running surface similar
to natural granite and thereby promote maximum curl.
ICE
Snow, like mud, attracts more snow if it is not dumped out the
back (momentary trailing side). Water is not generated to cause curl
as the UNBC physicist has THEORIZED in E-mails messages to me but relates his
"theory" as fact in the CCN, Canadian Curling News, article of April/2000.
Instead of building and studying his own model with appropriate sensors, he just
takes another professors theory as fact and proceeds on with the water theory.
I would like to see and measure the amount of water created by kinetic friction when the
ice sheet -40F as it used to be with outdoor rinks and there was still rock curl. much
less yes, but curl and with the rock and ice temperature, I'm sure without water present.
Efforts to get the professor to put up pictures of generated water have not
been addressed. He has refused to answer my many questions which challenge his
mathematical theory of water friction causing curl. If you read the article, you note his
pictured "model rock" has a net force sideways to cause curl. Any damn fool
knows that IF a net lateral force sideways worked on the ass end of the rock, IT WOULD
SOON STOP TURNING in the direction of normal turn/curl. The rock does turn and turn with
only 5grams of force applied to the turn. WHY? Because the transverse/longitudinal
friction on the slow side is higher than the fast side which causes the rock to not only
curl but continue to rotate as if in perpetual motion. Actually, the rock continues to
rotate and may even INCREASE rotational/angular velocity because it is bleeding off
longitudinal force.
Kinetic friction is minor to the restraining forces holding the rock back/slowing it. It
is not only rubbing friction but the larger component of resistance is shearing
force, i.e.
first ends rocks need more push! Now that shouldn't be too hard for a professor to
understand. So, there is not enough kinetic friction to generate water AS A FRICTION
COMPONENT TO CAUSE CURL!!
The spaces between pebble causing rock vibration (up and down and
rocking) facilitate this cleaning action and are an important part of maintaining curl
because snow is not dragged to the forward spin or fast side of the rock which would
neutralize friction making the rock run straighter. Occasionally, an ice lump will bond on
the running surface causing an ice "pick" and the rock will deviate to the side
with more friction. There will be more "ice picks" as the pebble wears down with
MANY picks as the rock comes in more and more contact with sheet ice especially
if the water is not treated with a Jet Ice treatment.
Open flat space between LARGE (gravity made with medium
beavertail holes) pebble of approximately 1/2"-1&1/2cm. minimum spacing is THE
essential characteristic which makes keen uniform curl ice without slowing and erratic
curling by the 6'th+ ends.
As more pebble is applied to the ice, you can figure it will slow by
1/4 second per pebbling application. Double shaved ice with a pebble base and one
pebble application before the draw (maybe two light coatings) (clipped)
is the fastest ice possible for a particular pebble size, shape, temperature and SPACING!
More pebbling (causes built up pebble - one pebble on top or side of the original pebble),
less space between pebble - more friction!
Too big a pebble space -- more friction. Too little pebble space -- more
friction. The pebbler machine manufactured by Thomps'on
Products eliminates much guess work allowing a novice pebbler to apply
uniform pebble with their new Master Pebbler machine.
Weedsprayer pebble by its very nature of
application (high vertical fall) and usual "fine" or "extra fine" hole
sizes makes faster ice initially-- first 4 ends because the pebble is smaller and taller
with a small upper area in contact with the rock running surface.
There will be an early rock slowing/fudging and the curl can go crazy
(up to 6') in the eighth end as the rock comes in contact with sheet ice because the small
pebble has sheared to a point where partial contact is made with the sheet.
This is because:
Small diameter "pointee" pebble shears faster than "flatter/
fat and low" gravity pebble. It will shear and shear until the pebble surface area is
sufficient to hold up the approx. 40lb. rock on a 3-4square inch running surface which is
in partial contact with pebble. You start out at 10+PSI on perfectly flat ice and without
any pebble present. When small pebble is present, the rock will readily crush and shear
the small area points until the ice can hold up the rock with its, (ice), 1,000psi crushing
limit. ON small scattered pebble, the rock to ice pressure can momentarily (instantaneously -not measurable) exceed 2,000psi (as the rock crushes the ice); thereby,
the rock crushes while it shears the pebble immediately reducing the pressure to that
maximum allowable for the ice present.
Crushing strength of ice can vary greatly due to prior cracking/crushing
(look at the slide out area) and entrained amount of air. It is white because light is
refracted from millions of small crush cracks. Air entrainment affects ice
strength/density. Warm water used to make ice will have less air entrained. Treated water,
Jet Gloss type product will minimize air but may change the surface tension affecting
pebble. Don't use any chemical additive in the water when making pebble.
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Remember, cold ice is slower but harder ice.
Cold ice generates more frost per unit time and the lattice structure crystals of cold ice
is very stiff / "grabby."
WHY is weed sprayer pebble smaller?
If you use the same temperature water for the gravity sprayer as the
weed sprayer pebbler, the weed sprayer water is super cooled and freezes at impact with
the sheet (if not freezing before it hits) because of more air-time cooling.
The water falling may not be frozen but can be super cooled below 32F.
The water is squirted up to 15 feet in the air. It is cooled by a loss of pressure at the
nozzle (at one of my clubs, the ice technician pumps the weed sprayer bottle 48 times and
then sprinkles a sheet in 23 seconds applying; maybe, 1 liter of water per sheet). It is
cooled by the 38degree upper air environment. It is cooled by evaporation. Small drops
with more surface area per unit volume cool faster yet. You have watched the experiment
where warm water freezes faster (at the surface) than colder water.
Evaporation will drop the droplet surface temperature
faster. You end up with a "tall/skinny & scattered" pebble that will give
faster (but straighter) early end results but will slow and curl crazily as the game
progresses. The pebble diameter is small even with the higher sheet striking velocity from
dropping 12-15feet because of super cooling. If you want wider pebble from a weed sprayer,
do not pump up the pressure beyond 3 psi and hold the nozzle low to the
ice.
At one point in the 4-15foot upward squirt, the water will not cool enough and the droplet
"splat" area will be much larger with a useless totally flat
pebble because there is no water volume in the droplet.
Droplets falling without super cooling will have an area of impact
directly proportional to the fall distance due to the velocity squared function caused by
the acceleration of gravity. So too hot a water and you have flat sequin pebble because it
did not cool enough much less super cool.
The small thin "sequin size" pebble will still flatten/crush if
they are more than 1/2" apart because they can not sustain the high rock downward
pressure which exceeds 1,000psi in the first ends if pebble is spread too thinly.
A walk speed covering the sheet of at least 60 seconds is
necessary to apply enough water/pebble (2-3 liters). I have seen ice technicians spray at
a rate from 23- 45 seconds and on different sheets at the same club and with different
weed sprayer pressures per sheet!
While the droplet size is still small when the "fine" head is
used, you get a wider/flatter pebble with more water/ice in the upper half of the pebble
that is better able to support the rock with minimum initial crushing. This type pebble
will last longer because the supporting area is higher off the sheet minimizing frost
"grab" from frost and aluminum sulfate (Grey sludge) between pebble.
A gravity pack solves this height of spray variable and will
provide a repeatable droplet size IF the water temperature is constant and
the water surface tension is consisitant -- carbon filtered water. Jet ice
treated water produces a pebble with less mass in the upper portion of pebble
Small pebble:
The rock shears the tops of small pebble to the tiniest bump on the
ice,1/4inch, so the high friction Frosted SHEET SURFACE must help support the rock.
If there is no "BASE Pebble" from previous draws or
applied after shaving, you will have the rock sitting on the frosted sheet surface
resulting in no curling or speed consistency for each rock and rock path.
SOFT PICK vs. HARD PICK
After the small pebble is sheared (with no pebble base present), you will notice an
unusual event:
THE SOFT PICK.
Definition: The soft pick is a pick in which the rock will deviate from its natural course
by as little as 2" and as much as 12" depending on how far it slides. The SOFT
pick is now more evident when ice is weed sprayer pebbled and in the 6'th-10'th ends.
A typical draw may have 10-15 soft picks if mineral free water is not
used (Jet Ice type of treatment solves many of these problems). Most soft picks will
go UN-noticed or be in the "I don't know why the rock did that?" category.
Why? The rock settles onto the sheet surface. The water used to
make curling ice is normally VERY "hard" with minerals. The Grey sludge that
accumulates on your brush is the turbidity flocculent aluminum sulfate WITH bonded
minerals from the water source (even with de-ionization if not done completely -- change
the bottles!
This sludge makes a SOFT pick. It is the 1-3" arched
"mark" on the ice that looks like a duct tape Grey created glob mark. This mark
of accumulated crud is formed by sliding on the sheet, stopping with a foot twist, leaving
a Grey soon to be soft - pick. It can also be a "spot" Grey glob that will not
sweep off and is embedded in the sheet waiting for that tiny pebble to shear/crush and
then it grabs onto your rock and collects frost and then makes you miss a perfect delivery
a few inches with a SOFT pick.
Great for the opposing team until it is their turn! And for those who
do not initially clean the rock with the finger nail brush, great soft picking and missing
your shots!
HARD PICK:
Definition: A pick in which the rock veers at a high rate and angle and usually leaves a
scratch trail on the ice from a brush hair or piece of gravel.ROCKS
Thomps'on's Tilesert non-granite, porcelean, inserted rocks, while made very accurately (they all
"run" precisely the same) may have an inherent "low-curl" limiting
problem. New Tilesert rocks were put in play at Grande Prairie, Alberta in
Oct., 1999. They
had an initial curl of 2-- 2-1/2 feet with the prevailing ("heavier" weed
sprayer pebble technique on a base) also used when the "old style" granite
rocks where in play. After 4 months use, the
rocks now curl 9 inches with draw weight using 1-1/2 handle
turns!! At season end, the curl was 9inches - yes, "9 inches!"
A loss of 24" of curl. Hack weight hits affords 3" curl and board
weight; maybe, 1". This "curl" scenario is great for "hitting"
strategy but takes away the fun of curling and burying a rock is out of the question.
I have been advised that an "in-place" fix has been applied to
the Tilesert rocks under the supervision of Mr. Thompson. I will report on
the type of "fix" used and the longevity in terms of the amount
curl that the "fix" generated.
THESE ROCKS WILL CURL a little more however by:
1.Pebble made from a gravity can pebbler using medium holes in the beavertail sprinkler!!
2. Scrubbing the running surface with a nail brush and then spinning the rock to re-coat
with ice.
Back to the "why rocks curl discussion."
BIG pebble slows the ice/rock while maintaining curl with no
significant fudging in later ends. On newly shaved ice, double base pebbled and
dragged/clipped, you can still get 14secs. H-H for one draw. Additional draws
can be 1/4
sec. slower. If you look at the running surface of these rocks, Tilesert, you can note, visually,
that the "grain" is small and tight/dense. I'm starting to think that the
mineral in the water may have further accumulated in the small Tilesert pores causing them
to be very smooth with less curl because there is minimum bonding of an ice
coating.
These rocks were transferred to another club and (without
instruments) I "felt" they were 1/2 second faster than the clubs original
granite rocks under the same ice pebbling gravity system. This club's rocks were garnered
for the Alberta Women's Provincials because of the reduced curl scenario with Tilesert
rocks. The tilesert rocks on gravity pebble curled 24 inches so
pebble most definitely affects curl.
I HAVE CHANGED MY ICE SPEED PHILOSOPHY I WAS WRONG in advocating very fast 14+sec. ice.
I have modified my judgment with personal experience, observation and
discussions with the people who make our ice TO a more realistic, attainable by most
clubs, "ideal" speed of 13-1/2 sec. after brushing.
Why? Because local clubs can not afford manpower and equipment to shave
after every 1-2 draws. In a local spiel, the ice must last the day without shaving. And 13-1/2 second ice curls, will run fairly straight for the board+ hit
and in general is more fun for the curling public.
Will the "CCA," change their ever increasing tendency to laud
"fast" ice at major media events! Fast-straight ice detracts from TV viewing
interest and the "fun" of curling.
Participating curlers from local clubs find it very difficult to adjust
to fast straight ice at "money and Briar" level competitions.
TV commentators regularly, now, note runs and falls and many more picks
in the straight/fast ice scenario while offering excuses for the pro curler's missed
shot. As the ice becomes more keen (shaved after each draw), the rock "finds"
the .1-.2mm. error in the blade and blade "float" and angle. In short, the
slightest "mistake" (mechanical or operator) in shaver operation makes a minute
ridge or fall that the rock is highly sensitized too in the 14-1/2++ sec.
H-H speed
scenario.
Have you ever placed your hand on the shaver blade back as your ice
technician is shaving? It is vibrating irregularly making those previously mention ridges.
No fault of the operator but the inherent design of hanging a blade 3' out over a single
set of wheels. (This rock vibration forming ice ridges
does contribute to fast ice with curl by making pebble tops of an irregular
height which causes the rock to vibrate breaking the ice on ice bond for
faster ice ( less friction means the rock slides easier) AND dumping friction
causing crystals to exit the momentary back side-- with straight blade shaving and
not angled).
Let us go back to reasonableness in the "ice speed
scenario" that most clubs can adhere to and make
up a new curl and speed guideline ideal approximating 13-1/2secs H-H and 3 feet of curl.
The game will be more fun to play and TV watching will be more
enjoyable as the viewing curler will better relate skills and conditions at their clubs to
those on "TV" ice.
Nitty Gritty Illegal Brushing page2
JKR: The Curling Doctor |