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Newsgroups: rec.sport.skating.inline
From: uwe@netcom.com (Uwe Brockmann)
Subject: Re: steep hills?
Date: Wed, 9 Jun 1999 06:20:56 GMT
In article <slrn7lg4vn.4tb.ese002@spica.exile.org>
Eric Edwards <ese002@news9.exile.org> wrote:
>No, one brake can stop just as quickly as two, but you need to lift the
>non-braking skate off the ground. Going to two brakes simply
>distributes the weight and the stopping power between the two brakes.
>There is no net gain. Two brakes should, however, be more stable.
I have previously wavered on agreeing and disagreeing with you based on
theoretical arguments :-). I felt that it was time to do a practical
experiment. Therefore I skated down a hill multiple times to compare
different heel braking techniques. I was surprised by some of the
results.
I picked a relatively steep downhill for my brake tests in order to
amplify any differences in stopping power between different braking
methods. The hill is about 300' (91 m) long. I measured the downgrade
in various locations with a small level and a ruler. I was looking for
the steepest and flattest sections. I found a maximum drop of 31 mm
and a minimum drop of 10 mm over the 210 mm length of the level. This
makes for a maximum downgrade of 15% (31 mm divided by 210 mm) and a
minimum downgrade of 5% (10 mm divided by 210 mm). About two thirds
down the hill there is a right turn of almost 90 degrees. At the end of
the hill there is a 90 degree left turn.
I used a pair of Roces Paris (hinged plastic shell, rec 5-wheel, citizen
racer style) boots mounted onto 13.0" low profile Mogema frames with
two Mogema heel brakes using Rollerblade Lightning brake pads and two
"brake leverage devices" mentioned earlier in this thread. I used 80 mm
78 A Labeda MDI race wheels that were already worn down to slightly
less than 77 mm and Twincam bearings lubricated with Twincam TK Racing
Gel. The brake pads were almost new. The front overhang (horizontal
distance from the front of the boot to the front of the front wheel) was
about 55 mm. The rear overhang was about 12 mm. I have previously
found that I can skate fastest on 5-wheel skates if the rear and front
overhang are about the same. However, the mounting system on this
particular combination of boots and frames does not allow me to trade
any more of the front overhang for rear overhang. Holding the skates
next to a pair of (long wheelbase 4-wheel) 1999 Salomon TR9 skates of
the same size showed about equal rear overhang. Thus one could
reasonably expect about the same stopping power from the heel brakes on
both skates (if the brake pads were made from the same material which
they are not).
I picked these skates for my tests because they are the only ones
available to me that allow me to use all three of the following leverage
methods to apply pressure to the heel brake pad(s):
(1) pulling up the front of the foot (feet)
(2) pushing back against the cuff(s)
(3) pulling up on the rope(s) of the brake leverage device(s)
attached to the front of the frame(s)
First I tried to apply one heel brake while pushing back against the
cuff of the braking skate and lifting the other skate off the ground
while coasting down the hill from the top at low speed (about 5 mph).
I noticed that I was unable to lift the non-braking skate off the ground
for more than a few seconds at a time. Then I had to put it back down
to prevent falling over backward. I noticed that I had to straighten
the braking leg in the knee joint in order to maximize pressure against
the cuff. I noticed that it was easier to press back against the cuff
when the laces and the buckle above the laces were as tight as possible.
To reduce my tendency to fall over backward without reducing pressure on
the cuff I tried to shift my center of gravity forward by bending
forward in the hip as much as possible, stretching both arms out
straight forward and holding the non-braking skate in the air above
and forward of the braking skate. Bending forward in the hip appeared
to be essential to prevent falling over backward. Stretching out both
arms did not make a noticeable difference. Holding the non-braking
skate forward negatively affected stability while perhaps reducing my
tendency to fall over backward slightly. In particular it seemed to
help throw off my balance when I rolled over minor road irregularities.
Stopping power was much less than I had expected. Even during the brief
moments that my non-braking skate was off the ground stopping power was
not sufficient to prevent acceleration from the downhill. Eventually
I tried to increase stopping power by pulling up with the front of my
braking foot in addition to pressing back against the cuff. This helped
and almost allowed me to prevent acceleration on the flattest (5%
downgrade) sections of the downhill. When I came closest to
neutralizing acceleration I was unable to steer effectively. In fact I
was unable to go in a straight line.
I tried using the single heel brake method with the other foot off the
ground at higher speed (about 15 mph) but it did not work any better,
i.e. it did not prevent further acceleration.
I also tried this method on a flat section (0% grade) at the end of the
downhill at low speed. It worked much better there. I was able to keep
the non-braking foot off the ground much longer and there was noticeable
deceleration. However, even on a flat surface I was not very stable.
Even slight road imperfections threw off my balance and forced me to put
the non-braking foot back down. I was also unable to stand at a
standstill with the heel brake applied and the other foot off the
ground. I also noticed that while the brake was applied I had little if
any control over the stopping power. With the other skate off the
ground applying the brake was like operating an on/off switch with no
middle ground.
Why did the single-foot heel brake method with the other foot off the
ground work better on a flat surface than on a downhill? My explanation
is that the (limited) stopping power that can be exerted with this
method resulted in significant deceleration on the flat surface only.
The deceleration threw my body forward thus reducing the problem of
falling over backward. Thus the brake could be applied longer which
resulted in a further increase in stopping power.
Once, just after putting the non-braking foot down on one of my downhill
runs, I inadvertently pushed the braking foot out further to the front.
Stopping power improved significantly. I had no trouble coming to a
full stop (from about 10 mph at a downgrade of perhaps 8% or 9%). This
is a surprising result as it suggests that stopping power is better with
the non-braking foot on the ground than with the non-braking foot off
the ground. I believe that the explanation is that pushing the braking
foot further in the front allowed me to put more pressure on the cuff
and thus improve stopping power.
Next I tried skating downhill with both brakes applied simultaneously.
I had a lot of stopping power and no trouble stopping even on the
steepest (15% downgrade) sections of the hill. I had good steering
control and no trouble maneuvering around both turns with both brakes
applied. I also had a lot of control over the amount of stopping power.
At any point I was able to increase or decrease stopping power gradually
as much or as little as I wanted to without taking either brake off the
ground. I was also able to ride out the full length of the downhill
>from the top of the hill to the bottom with both brakes applied without
any balance problems. Minor road imperfections had no effect on my
balance. Applying the brakes did not require me to bend forward in the
hip. I was also able to stand at a standstill on a flat surface with
both brakes applied for as long as I wanted to but I had to bend far
forward in the hip in order to do so.
To my surprise I had no trouble whatsoever pressing back on both cuffs
simultaneously. However, I had to straighten my legs in the knee joints
to do so. Pressing back against the cuffs increased stopping power
significantly.
Finally I employed both brake leverage devices in addition to both heel
brakes. This appeared to further increase stopping power, stability
and control over the amount of stopping power. It did require me to
bend forward in the hip in order to reach the handles that are located
below my knees. However, this was not a problem.
Summary:
The simultaneous use of two heel brakes resulted in vastly improved
stopping power, stability and control compared to the use of a single
heel brake even when the single heel brake method was combined with
pressure on the rear of the cuff of the braking skate and/or the
non-braking foot was taken off the ground. Several people's theories
(including my own) had predicted either no difference or only a small
difference in stopping power. Therefore, it is surprising to see such
a large difference in my experiments.
Other people have reported better results with the single-foot heel
brake method with the other foot off the ground than I did here.
Conceivably this could be caused by insufficient braking skill on my
part. However, I do not see what I could have done wrong.
Technical differences between their skates and mine are therefore a more
likely explanation. Most 4-wheel skates, excluding some long wheelbase
4-wheel skates such as Salomon TR9, have less rear overhang than the
skates that I used. Thus all heel brake stopping methods, including the
method with one foot off the ground, should work better with them.
Also, all skates that allow skaters to put more pressure on the back of
the cuff, without leaning back as far as I had to do in my skates,
should provide more single heel brake stopping power. This might
include skates with a higher heel lift, with a non-hinged, higher or
more rigid cuff as well as skates that force skaters' lower legs into a
more forward-leaning stance. Undoubtedly such skates exist. However,
all such skates would, through their very design, also improve dual heel
brake stopping power proportionately.
Thus I do not see how stopping power with a single heel brake could be
as good on any in-line skates as it is with dual heel brakes used
simultaneously.
Conclusion:
Two heel brakes used simultaneously provide far more stopping power
than a single heel brake.
Uwe Brockmann, uwe@netcom.com
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Newsgroups: rec.sport.skating.inline
From: uwe@netcom.com (Uwe Brockmann)
Subject: Re: steep hills?
Date: Mon, 14 Jun 1999 04:32:06 GMT
In article <uweFD1qyw.367@netcom.com> Uwe Brockmann <uwe@netcom.com> wrote:
>I plan on redoing my test with Rollerblade Aeroblade or Lightning
>skates.
I did some more tests. I used the following skates:
(1) 1994 Rollerblade Aeroblade skates converted to Rollerblade
Lightning brakes, brake pads about 20% worn
(2) 1988 Rollerblade Lightning skates, brake pads about 50%
worn
(3) 1999 Salomon TR9 Custom Fit skates, brake pads about 20%
worn
(4) 13" low-profile Mogema frames with Roces Paris boots (the
same skates as used in the previous tests), brake pads about
20% worn
(5) 12.8" high-profile Mogema frames with custom Harper boots,
brake pads about 90% worn
I used the following braking methods to the best of my ability:
(a) single heel brake with the other skate on the ground
(b) single heel brake with the other skate off the ground
(c) dual heel brakes applied simultaneously
(d) single heel brake with the other skate off the ground in
combination with a brake leverage device
(e) dual heel brakes and dual brake leverage devices, all
applied simultaneously
I checked for braking performance on the flattest section (5% downgrade)
and on the steepest section (15% downgrade) of my local hill. I gave
each braking method a rating for each pair of skates for each of the two
downgrades as follows (higher numbers imply better braking):
(-) braking method cannot be used with these skates, because
they are not equipped with brake leverage devices
(1) braking method could not prevent significant downhill
acceleration
(2) braking method almost, but not completely, prevented
downhill acceleration
(3) braking method caused some, but very limited, deceleration
(4) braking method caused significant deceleration
Here are the results:
5% downgrade:
|skates 1|skates 2|skates 3|skates 4|skates 5
--------+--------+--------+--------+--------+--------
method a| 4 | 4 | 4 | 4 | 4
method b| 4 | 4 | 2 | 2 | 1
method c| 4 | 4 | 4 | 4 | 4
method d| - | - | - | 4 | 4
method e| - | - | - | 4 | 4
15% downgrade:
|skates 1|skates 2|skates 3|skates 4|skates 5
--------+--------+--------+--------+--------+--------
method a| 4 | 4 | 3 | 3 | 3
method b| 4 | 4 | 1 | 1 | 1
method c| 4 | 4 | 4 | 4 | 4
method d| - | - | - | 4 | 4
method e| - | - | - | 4 | 4
Comparison of skates
--------------------
Unsurprisingly the 4-wheel Rollerblade skates (Aeroblade and Lightning)
with small rear overhang (i.e. the brake pad does not stick out far to
the rear) performed best. The 4-wheel Salomon TR9 skates and the
5-wheel Mogema frames with Roces Paris boots both have about the same
(medium) amount of rear overhang and, accordingly, performed worse. The
5-wheel Mogema frames with custom leather racing boots have the most
rear overhang and performed worst.
The Mogema/Harper racing skates were also hurt by their lack of a cuff
that could otherwise have been used for leverage. The Rollerblade
skates may have been helped by a cuff that is more effective for braking
purposes than that of either the Roces Paris boots or the Salomon TR9
skates.
It is somewhat surprising that the Mogema/Harper racing skates performed
as well as the Mogema/Rocis Paris combination on the 15% downgrade.
This can probably be explained by their greater brake pad wear (90% vs.
20%).
Comparison of braking methods
-----------------------------
There are large differences in braking performance between different
skates and braking methods that all resulted in a score of 4. To find
out what these differences are with the methodology that I used, I would
need steeper hills. However, searching out steeper hills for further
tests was beyond the scope of my tests.
My tests suggest the following:
(1) Using a single heel brake with the other skate on the ground
works better than using a single heel brake with the other
skate off the ground.
(2) All of the following methods work better than using just a
single heel brake:
- using a single heel brake and a brake leverage device
- using two heel brakes simultaneously
- using two heel brakes and two brake leverage devices
simultaneously
It is surprising that a single heel brake with the other skate off the
ground performed significantly worse than two heel brakes used
simultaneously since other skaters have claimed otherwise. It should
be noted that in all cases where the single heel brake method with the
other skate off the ground did not score a 4, the failure mode was
falling over backward rather than just a lack of deceleration. Thus it
could be said that the method only fails on skates on which it cannot be
performed.
In my tests heel braking with the other skate off the ground only
performed well on the Rollerblade skates which feature a small rear
overhang and high and effective cuffs. These features also improve the
performance of other heel braking methods. Therefore I suspect that
this method would not improve its rank among heel braking methods if it
was tested on steeper downgrades.
Uwe Brockmann, uwe@netcom.com
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Newsgroups: rec.sport.skating.inline
From: uwe@netcom.com (Uwe Brockmann)
Subject: Re: steep hills?
Date: Mon, 14 Jun 1999 18:31:58 GMT
In article <7k3a23$g$1@bgtnsc03.worldnet.att.net>
Elliott Suckow <elliott.suckow@worldnet.att.net> wrote:
>I suspect that the two-brake approach isn't as effective because of our
>body's biomechanics and geometry. Whatever gain there is from using the two
>sets of muscles to raise the feet is probably offset by the additional
>effort required to keep upright since both skates (and legs) are now
>involved in braking and balancing.
>
>My theory: With the one-brake approach, the trailing leg does most of the
>stabilizing assuming a fairly stable position to start, that is, only small
>balancing adjustments are necessary. This is effective in part because it is
>easier to make small balancing adjustments with muscles which don't have a
>heavy load on them. In the two-brake approach, both legs are actively
>involved in braking, and each leg therefore requires a greater effort to be
>used for balance.
>
>In addition, with the two-brake approach, either you keep one skate trailing
>or you balance "behind both skates". With one skate trailing, because of our
>biomechanics and geometry, you can not generate the same stopping force on
>the trailing skate as you can on the leading skate. With the "behind both
>skates" approach, a substantially greater effort is needed to maintain
>balance since your "base" is much smaller (much like the greater effort
>required to stay balanced on your toes versus on the entire length of both
>feet).
Your theory makes sense to me. However, my practical experience largely
contradicts your theory. When I use two heel brakes simultaneously I
do not keep one skate trailing. Instead I balance, as you call it,
"behind both skates". I have tried to keep one skate trailing, as you
call it, but that did not seem to make balancing any easier or harder.
On four-wheel skates and even on five-wheels skates with little rear
overhang I find it easy to balance while using two heel brakes
simultaneously. For me balancing when using two heel brakes only
becomes difficult when I use 5-wheel skates with a lot of rear overhang.
However, on such skates I use dual brake leverage devices in conjunction
with the heel brakes. When the brake leverage devices are used
balancing on two heel brakes on 5-wheel skates with a lot of rear
overhang becomes as easy or easier than it is on 4-wheel skates with
little rear overhang and no brake leverage devices.
Before I started using two heel brakes simultaneously I also thought
that balancing would be difficult and that stopping power would not
increase. It is only after I tried it that I realised that it was not
difficult at all while being much more effective than I had thought.
I suggest that you give dual heel brakes a try, compare your practical
observations to your theory, and report your results back to this
newsgroup.
If practical observations contradict your theory, there must be a flaw
in your theory. I suspect that there are three flaws:
(1) The balancing adjustments that need to be made while using
two heel brakes simultaneously are much smaller than you
think.
(2) I suspect that the muscles used for balancing adjustment are
not the same as those used for braking or are not heavily
loaded while braking.
(3) While it is true that the supporting "base" is short when
two heel brakes are used simultaneously, this does not seem
to result in as much instability as one would expect. I
suspect that the reason for this is a "self-stabilizing"
effect: If you brake too hard, you will start to fall over
forward, which will take pressure off the brake pads, reduce
braking power, reduce deceleration and prevent you from
falling over forward. If you brake too little, you will
start to fall over backward which will increase pressure on
the brake pads, increase braking power, increase deceleration
and prevent you from falling over backward.
The two most important lessons that I have learned about braking with
heel brakes on in-line skates are:
(1) Using two heel brakes simultaneously works much better than
using a single heel brake.
(2) Using brake leverage devices in addition to heel brakes
vastly improves stopping power, control and balance,
especially on 5-wheel skates.
I was very reluctant to believe either lesson. I had to try both
techniques for myself before I believed that they worked as well as I
now claim they do. I was so convinced that these techniques would not
work that it took me years from the time I first heard about their
effectiveness until I got around to trying them out myself. Now I
regret not having started to use them earlier.
Uwe Brockmann, uwe@netcom.com
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Uwe Brockmann, uwe@pobox.com, http://www.panix.com/~uwe/brakelev/