carlfogel@comcast.net
12-31-1969, 08:00 PM
On Thu, 22 May 2008 20:03:35 -0700 (PDT), Frank Krygowski
<frkrygow@gmail.com> wrote:
>I thought I read that the lowest gear of old S-A five speeds was
>extremely inefficient. IOW, that shifting to low didn't really reduce
>your workload significantly, but just gave you less speed.
>
>I rode a friend's S-A five speed a few times, and got the impression
>that the tale was true.
>
>- Frank Krygowski
Dear Frank,
Whatever the truth may be, this is a good example of the familiar RBT
controversy:
A poster heard about some effect, rode a bicycle, and things felt that
way--so was the effect real, or was it just expectation?
I couldn't find any efficiency testing of a 5-speed Sturmey-Archer,
but even a detailed test might not have settled the question.
After all, what if first gear was shown to be, say, 5.3% less
efficient than second gear? Is that increased work-load actually
noticeable while grinding up a hill at a 9.7% lower speed with [insert
imaginary number here] less wind drag?
The familiar Kyle & Berto efficiency study doesn't suggest that first
gear in hub drives is a hidden boat anchor:
http://www.ihpva.org/pubs/HP52.pdf
Sometimes that pdf downloads, sometimes it doesn't. It's worth saving
the damned file for later reference. Here's the table that compares
the efficiency, gear-by-gear, of some hub-drives at 80, 150, and 200
watts:
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Maker/Speeds
Power Efficiency Percent**
Sachs 3 80 95.0 92.9 93.6
150 94.2 95.6 94.8
200 94.1 94.9 94.1
Shimano 3 80 90.5 93.5 87.2
150 93.0 93.9 88.6
200 93.2 95.0 87.2
Sturmey 3 80 92.3 95.4 91.8
150 93.3 95.3 91.8
200 93.0 95.6 91.8
Shimano 4 80 93.6 90.1 87.1 85.8
Automatic 150 95.6 90.9 88.9 87.0
200 95.3 92.8 90.0 88.0
Sachs 7 80 88.7 — — 89.2
150 89.9 — — 92.3
200* 91.0* — — 93.0*
Shimano 7 80 90.8 90.7 87.4 89.0 83.6 90.9 88.2
150 91.8 92.9 89.9 89.0 85.6 92.8 90.4
200 92.8 94.5 90.3 91.8 86.4 93.7 91.4
Sturmey 7 80 87.3 88.7 88.4 93.0 89.3 86.0 83.0
150 89.1 89.0 91.1 93.3 90.4 88.5 85.4
200 89.7 90.3 91.3 94.7 91.0 88.6 85.3
Rohloff 14 80 89.1 90.3 87.8 90.3 87.5 87.8 86.1 89.7 90.8 87.7 89.7
87.1 87.8 86.1
150 90.6 92.5 89.9 92.2 89.6 91.0 89.9 92.6 92.7 90.4 92.3
90.4 89.7 89.1
200 91.3 92.5 90.9 93.4 90.5 90.9 90.2 92.8 92.7 91.1 93.5
90.0 91.1 90.4
*The shift mechanism was broken, and would shift to only two gears.
** All efficiencies are uncorrected for the power consumed by the
ergometer wheel drive. Although this is not large, it would increase
the indicated efficiencies by 2 to 2.5% in most cases.
------------
Here's how 1st gear efficiency compares to 2nd gear from that table:
Sachs 3 +2.1% to -1.4%
Shimano 3 -0.3% to -0.9%
Shim auto 4 -2.5% to -5.7%
Sachs 7 (broken, no data)
Shimano 7 +0.1% to -1.7%
Sturmey 7 +0.1% to -1.4%
Rohloff 14 -1.2% to -1.9%
So a typical hub-drive first gear loses less than 2% of power compared
to second gear. That's less than the drag from a light generator.
Some riders might claim that they can detect such <2% losses (<4 watts
at 200 watts) even when they shift from one gear to another, but such
sensitivity would be impressive.
But Kyle & Berto didn't test the 5-speed Sturmey-Archer. Maybe that
hub has some design quirk that makes its first gear a real dog, unlike
the 3, 4, 7, and 14 speed hubs.
Cheers,
Carl Fogel
<frkrygow@gmail.com> wrote:
>I thought I read that the lowest gear of old S-A five speeds was
>extremely inefficient. IOW, that shifting to low didn't really reduce
>your workload significantly, but just gave you less speed.
>
>I rode a friend's S-A five speed a few times, and got the impression
>that the tale was true.
>
>- Frank Krygowski
Dear Frank,
Whatever the truth may be, this is a good example of the familiar RBT
controversy:
A poster heard about some effect, rode a bicycle, and things felt that
way--so was the effect real, or was it just expectation?
I couldn't find any efficiency testing of a 5-speed Sturmey-Archer,
but even a detailed test might not have settled the question.
After all, what if first gear was shown to be, say, 5.3% less
efficient than second gear? Is that increased work-load actually
noticeable while grinding up a hill at a 9.7% lower speed with [insert
imaginary number here] less wind drag?
The familiar Kyle & Berto efficiency study doesn't suggest that first
gear in hub drives is a hidden boat anchor:
http://www.ihpva.org/pubs/HP52.pdf
Sometimes that pdf downloads, sometimes it doesn't. It's worth saving
the damned file for later reference. Here's the table that compares
the efficiency, gear-by-gear, of some hub-drives at 80, 150, and 200
watts:
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Maker/Speeds
Power Efficiency Percent**
Sachs 3 80 95.0 92.9 93.6
150 94.2 95.6 94.8
200 94.1 94.9 94.1
Shimano 3 80 90.5 93.5 87.2
150 93.0 93.9 88.6
200 93.2 95.0 87.2
Sturmey 3 80 92.3 95.4 91.8
150 93.3 95.3 91.8
200 93.0 95.6 91.8
Shimano 4 80 93.6 90.1 87.1 85.8
Automatic 150 95.6 90.9 88.9 87.0
200 95.3 92.8 90.0 88.0
Sachs 7 80 88.7 — — 89.2
150 89.9 — — 92.3
200* 91.0* — — 93.0*
Shimano 7 80 90.8 90.7 87.4 89.0 83.6 90.9 88.2
150 91.8 92.9 89.9 89.0 85.6 92.8 90.4
200 92.8 94.5 90.3 91.8 86.4 93.7 91.4
Sturmey 7 80 87.3 88.7 88.4 93.0 89.3 86.0 83.0
150 89.1 89.0 91.1 93.3 90.4 88.5 85.4
200 89.7 90.3 91.3 94.7 91.0 88.6 85.3
Rohloff 14 80 89.1 90.3 87.8 90.3 87.5 87.8 86.1 89.7 90.8 87.7 89.7
87.1 87.8 86.1
150 90.6 92.5 89.9 92.2 89.6 91.0 89.9 92.6 92.7 90.4 92.3
90.4 89.7 89.1
200 91.3 92.5 90.9 93.4 90.5 90.9 90.2 92.8 92.7 91.1 93.5
90.0 91.1 90.4
*The shift mechanism was broken, and would shift to only two gears.
** All efficiencies are uncorrected for the power consumed by the
ergometer wheel drive. Although this is not large, it would increase
the indicated efficiencies by 2 to 2.5% in most cases.
------------
Here's how 1st gear efficiency compares to 2nd gear from that table:
Sachs 3 +2.1% to -1.4%
Shimano 3 -0.3% to -0.9%
Shim auto 4 -2.5% to -5.7%
Sachs 7 (broken, no data)
Shimano 7 +0.1% to -1.7%
Sturmey 7 +0.1% to -1.4%
Rohloff 14 -1.2% to -1.9%
So a typical hub-drive first gear loses less than 2% of power compared
to second gear. That's less than the drag from a light generator.
Some riders might claim that they can detect such <2% losses (<4 watts
at 200 watts) even when they shift from one gear to another, but such
sensitivity would be impressive.
But Kyle & Berto didn't test the 5-speed Sturmey-Archer. Maybe that
hub has some design quirk that makes its first gear a real dog, unlike
the 3, 4, 7, and 14 speed hubs.
Cheers,
Carl Fogel