From: uwe@cc.gatech.edu (Uwe Brockmann)
Subject: Re: Skates are faster than bikes! (was: ASTM Roller ...)
Reply-To: uwe@cc.gatech.edu (BROCKMANN,UWE)
Organization: Georgia Institute of Technology
Distribution: usa
Date: Sun, 24 Jan 1993 02:29:05 GMT

In article <38720@cbmvax.commodore.com> grr@cbmvax.commodore.com (George Robbins) writes:
>In article <1993Jan20.104713.8152@cc.gatech.edu> uwe@cc.gatech.edu (BROCKMANN,UWE) writes:
>> Skaters can draft each other more closely than cyclists. They can touch
>> each other and form a "train" when going downhills. This allows them to
>> go faster than cyclists.
>
>Bicylists to this in race situations.

I did not know that bicycle racers touch each other on downhills.
I assume that a cyclist who pushes another cyclist on a downhill has
to be slighly to the side of the cyclist whom he is pushing. This
increases frontal area. Skaters can be directly behind each other with
almost no gap between them.

If cyclists could form two parallel pacelines offset by half a bicycle
length in the direction of travel and if each cyclist could push the
cyclist of the other paceline who is half a bicycle length ahead of him
than they would form a "zig-zag train" and would be able to go very
fast. Can cyclists do this? If this should not be possible due to the
protruding wheels than they would be stuck with an "offset-train" in
which each additional cyclist adds to the frontal area.
	
The ASCII drawings below show cylists in a "zig-zag train" (1), cyclists
in a less efficient "offset-train" (2), and skaters in a train (3).

        (1)              (2)                (3)

         |                I                  |
          |                |                 |       
         |                  |                |
          |                  |               |
         |                    |              |
          |                    |             |

The drawings make it look as if cyclists were separated by a full
bicycle length. The separation should really be only half a bicycle
length. I just don't know how to make a better ASCII drawing.

I don't believe that cyclists would be able to go as fast as skaters on
steep downhills even if they could form "zig-zag trains". In my
experience I can go about 40 mph (clocked by cycle computers) on the
steepest downhills that I have skated with cyclists. This is without
drafting cyclists or other skaters and without pushing off (i.e. just
coasting). Cyclists can go about the same speed when coasting down the
same hills without drafting other cyclists. When coasting at 40 mph they
can still add a little bit of speed by pedalling hard.

I believe that my frontal area and my wind resistance are smaller than
theirs. Their equal speed must therefore be caused by lower
rolling resistance. On steeper downhills and at higher speeds their
higher wind resistance should be more of a disadvantage for them and
my higher rolling resistance should be less of a disadvantage for me.
Thus I should be able to go faster than them. I cannot try this because
hills aren't sufficiently steep around here. I also don't want to try
it because I already start feeling uncomfortable at 40 mph.

Even if cyclists could form zig-zag trains, a number of skaters in a
train should still be faster than the same number of cyclists because
each additional skater in the train only adds a small portion of the
wind resistance of a single skater to the train whereas each cyclist
adds a large portion of the wind resistance of a single cyclist to the
train. That's because skaters can draft each other more closely with
less wind resistance-increasing gaps between them.

Cylists have another disadvantage on steep downhills. Their large wheels
cut into the wind at up to twice the speed of the cyclists. This adds
significantly to wind resistance. For skaters with their small wheels
this is not a concern.

>> In the Athens-to-Atlanta race I observed the lead pack of skaters
>> routinely outrunning all support bicycle riders on the major downhills.
>
>I would wonder if this says more about the condition of the cycists
>relative to the skaters than the efficiency of the skates vs. cycles.

On steep downhills coasting on skates is faster than skating (pushing
off) on skates. Therefore the conditioning of skaters has no effect on
their downhill speed. I assume that hard pedalling will usually increase
the speed of cyclists even on steep downhills. However, at higher speeds
the effect of pedalling is reduced. One cyclist told me that he believes
that sitting on the top tube does more to increase speed on steep
downhills than pedalling and that hanging behind the seat is faster yet.
Is this true? On sufficiently steep downhills the conditioning of
cyclists has very little effect on their speed.

>What kind of average speed can good skaters maintain over several
>miles or tens of miles?

Haico Bouma of Holland won the 1991 Athens-to-Atlanta race in a record
time of 4:28 (hours:minutes). His average speed was about 19 mph. He
skated the last 100 km by himself because nobody else could keep up.
In Holland with no hills and more fast skaters average speed is higher.

Cyclists can of course go much faster on average.

[(Mr.) Uwe (pronounced "oova") Brockmann, (404)892-4872, uwe@cc.gatech.edu]
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