actionbent part2

NYC XYZ said:

But you've got to check the gears, too, afterwards, to make sure
they're shifting right and all. I don't think they did too much of
this, though...he probably checked for half a minute!

This is fair comment, but 30 seconds should be enough in the first
instance, which still leaves us rather a lot of time. Tweaking the
gears is easy enough with the adjuster screw where the gear cable
goes into the rear mech, just needs the odd tweak to tune the shifting.

Quoted message said:

Now now, we all know about names and marketing...but I didn't know 80%
of effort expended in on behalf of air resistance!

That is, IIRC, the approximate figure on a DF, though I can't
remember if that's on the hoods, in a heavy tuck or what. But it
does show approximately the degree to which speed is dominated by
aerodynamics any time you get any sort of fast.

Quoted message said:

Still, my point is
that I should be at least as good as a DF, given my better aerodynamics
on the SMGT

They're not /that/ much better. I have my seat reclined as far as
possible and it's pretty clear that cycling with pals on DF leaned
over the drops that the frontal area catching the wind isn't all
that different. When they go into a full speed crouch it's quite
obvious they have less frontal area than me.
If you want better aero, that's what the Speedmachine is for (and
to some extent, the Grasshopper).

Quoted message said:

Yes, I knew this going in, but I figured that I'd rather have more
puncture-proof or puncture-resistance than speed, if the penalty isn't
too large and way out of proportion.

To put the dangers into perspective, I've had 2 punctures on mine
in 5 years running standard Marathons. They give very good
puncture resistance. The M+ is only really an issue if you're in
Puncture Hell, otherwise they'd be standard issue rather than the
plain Marathon.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Peter Clinch said:

NYC XYZ wrote:

[snip]

Quoted message said:

Quoted message said:

Now now, we all know about names and marketing...but I didn't know 80%
of effort expended in on behalf of air resistance!

That is, IIRC, the approximate figure on a DF, though I can't
remember if that's on the hoods, in a heavy tuck or what. But it
does show approximately the degree to which speed is dominated by
aerodynamics any time you get any sort of fast.

Quoted message said:

Still, my point is
that I should be at least as good as a DF, given my better aerodynamics
on the SMGT

They're not /that/ much better. I have my seat reclined as far as
possible and it's pretty clear that cycling with pals on DF leaned
over the drops that the frontal area catching the wind isn't all
that different. When they go into a full speed crouch it's quite
obvious they have less frontal area than me.
If you want better aero, that's what the Speedmachine is for (and
to some extent, the Grasshopper).

[snip]

Dear N & Peter,

It's common to assume that recumbents have an aerodynamic advantage
over the traditional diamond frame, but the advantage is actually
limited to fairly extreme recumbents.

You can see some of the surprising details on this speed calculator
page:

http://www.kreuzotter.de/english/espeed.htm

Hovering the mouse over the radio button for the type of recumbent will
pop up a picture that gives an idea of what a particular model looks
like. After selecting a model, clicking on calculate at the bottom will
give a predicted speed for the default values and the drag area used
for the calculation.

mph frontal type
17.1 4.3433 recumbent long wheel base
17.3 4.7889 df hands on tops
18.5 3.3781 recumbent short wheel base
19.4 3.2559 df hands on drops
20.5 2.7111 df triathlon bars
21.2 2.1748 recumbent short wheel base racer
22.3 2.0397 df superman position
23.1 1.5504 recumbent lowracer

Obviously, these are idealized guides to what a particular bike and
rider will do, with different tires and transmission efficiences
affecting things. But for the same rider and power, it takes a
recumbent that stresses speed instead of comfort to improve on the
aerodynamics of an ordinary diamond frame:

http://www.bicycleman.com/history/images/1933hour-record_lg.jpg

Cheers,

Carl Fogel

Quoted message said:

You can see some of the surprising details on this speed calculator
page:

http://www.kreuzotter.de/english/espeed.htm

Thanks for that link, Carl.

Quoted message said:

Hovering the mouse over the radio button for the type of recumbent will
pop up a picture that gives an idea of what a particular model looks
like.

Note for this discussion that a Speedmachine would probably be somewhat
better than the "ShortWheelBase, above seat steering, racing equipped"
but not as good as "Lowracer, above seat steering". That assumes it's
the ASS SpM rather than the new USS option.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

<[email hidden]> wrote in message>

Quoted message said:

It's common to assume that recumbents have an aerodynamic advantage
over the traditional diamond frame, but the advantage is actually
limited to fairly extreme recumbents.

You can see some of the surprising details on this speed calculator
page:

http://www.kreuzotter.de/english/espeed.htm

"It's not about the bike."

You're correct that the differences are not as large as people
might imagine. People who try a recumbent and think they will
automatically be 10-20% faster *will be* disappointed. It depends
on what you're comparing, but 3-7% without going"extreme"
is quite possible, however.

Note that the default tire choices on the kreuzotter website for
non-race configured recumbents are medium and wide. The df
tire choices are all high pressure, by default. Here's the list
with the high-pressure tire choices for the LWB and SWB
added**.

mph frontal type
17.1 4.3433 recumbent long wheel base (medium slick tires)
17.3 4.7889 df hands on tops
18.0 3.8777 recumbent long wheel base (high-pressure tires)**
18.5 3.3781 recumbent short wheel base (wide slick tires)
19.4 3.2559 df hands on drops
19.5 2.8408 recumbent short wheel base (high pressure tires)**
20.5 2.7111 df triathlon bars
21.2 2.1748 recumbent short wheel base racer
22.3 2.0397 df superman position
23.1 1.5504 recumbent lowracer

It's also worth noting that the two non-race configured recumbents
modeled above are under seat steering. Most recumbent bikes in
the US are above seat steering. The "recumbent short wheel base
racer" may cover many of the so-called "high racer" recumbents
(Bacchetta, Volae, RANS...) and these may not be considered
"extreme" or sacrificing of comfort.

Jon Meinecke