The whole point of the Atlantis is that it is meant for loaded
touring. The second tube goes on the bikes for taller riders who are
presumably heavier. That along with a heavy touring load makes the
extra tube a good idea.
On Tuesday, August 4, 2020 at 6:58:58 AM UTC-7 Patrick Moore wrote:
You are right that a second top tube will do something
structurally; there's no avoiding that, and I overstated my own
case. But my point is that for anything but a very large frame, or
for a frame to be ridden by someone exceptionally heavy, there's
no **practical** purposes served by the added tube.
Still, that Atlantis frame does look very pretty; far nicer IMO
than the other models with 2 top tubes; they got the mix of
straight and curved just right.
On Tue, Aug 4, 2020 at 12:07 AM S <sbl...@gmail.com> wrote:
As is my habit, I overstated my case. What I said is
technically true, because of physics, but I can believe the
real world effect might be negligible.
In the back of my mind was the side discussion on here or iBob
about the supposed deadness of the Surly Cross Check frame.
Some forum members -- me included -- insisted the frame was a
dog, no question, while others disagreed. As it turned out,
those in the former camp had the 56 and those in the latter
camp larger sizes. The theory was floated that maybe the frame
"opens up," that is, flexes more, in a good way, in the larger
sizes -- and with generally heavier riders -- and that
accounted for the difference. To me, this seems plausible. And
if it's plausible that a frame could improve in this way, then
it also seems plausible that, conversely, some frames could
open up *too much* and become too flexy, in larger sizes, thus
necessitating some modification to maintain the same relative
stiffness as in the smaller sizes.
Also in the back of my mind was the experience of my larger
cycling friends who seem to break more frames than I ever
have. But then, that's anecdotal.
I don't know if Grant ran any numbers or did any testing
before deciding to add the second tube to some bikes. Could
just be for looks, or could be a belt and suspenders kind of
thing. Or a mix. But I wouldn't say it's totally off base from
an engineering point of view.
Anyway, you've ridden more 60 (and maybe 60 plus?) size frames
than I have, and if you say you don't feel a difference, then
I can't argue.
On Monday, August 3, 2020 at 8:27:15 PM UTC-7 Patrick Moore wrote:
Not true at all, unless -- perhaps -- you are well over
200 lb and carry heavy loads. I owned and rode a 60 c-c
frame extensively -- my best level top tube size is 60 c-c
-- and there was no more flex notiher 6- X 56 c-cceable
than with an 18" mountain bike frame. And this frame was
made from standard gauge, and not OS, tubes.
I currently have another 60 X 56 c-c frame being
refurbished; this is also standard gauge, and it is
/very/ light: 5.9 lb for frame + fork + steel Campy
headset; I /do not/ expect to need a second top tube. I'm 175.
And my best load carrier of all time, that happily and
securely carried 40+ in back (on an 11 oz rack!) was made
from standard gauge, lightweight 531 and was noticeably
lighter than my 2003, 58 c-c Riv frame that weighed 7 lb
for frame + fork and Ultegra headset. This frame was a 58
c-c, IIRC.
For anyone under say 250 lb who does not carry camping
loads, a second top tube is ornamental, not structural. Amen.
Back when I lived in India and Pakistan and Kenya, you'd
often see heavy duty models of the stereotypical rod brake
roadster wtih a second top tube (and with heavy
aftermarket fork braces), but these were bikes cheaply
made from cheap, weak tubing that carried 100 lb loads of
firewood or 200 lb loads of charcoal in gunny sacks, or a
family of 4; even so, most Indian and Pakistani made r b
roadsters have single top tubes.
Upshot: they look cool, but their benefit is purely aesthetic.
On Mon, Aug 3, 2020 at 8:19 PM S <sbl...@gmail.com> wrote:
Yes, the extra tube strengthens the frame. Otherwise
you would be left with a wobblier triangle and have to
use thicker tubes and there goes at least some of your
weight savings. I think it's a good solution and looks
cool, so a double win.
On Monday, August 3, 2020 at 11:42:08 AM UTC-7 Jason
Fuller wrote:
I can imagine it's useful once you get into the
60cm range, since the average rider weight is
going up while the structural triangulation of the
frame is going down. But I can't deny that I love
the totally unnecessary extra tube on the Hunq so
who am I to judge.
The "unnecessary tube" I want, and would put on a
Riv custom if I ever got one, would be the lift
handle from the Rosco's. I keep hoping for it on
new models.
On Monday, 3 August 2020 at 09:00:02 UTC-7 Patrick
Moore wrote:
I don't want a second top tube on any bike I
own because it would serve no real purpose and
add needless weight (and also, perhaps,
rigidity where I don't want it), but I do have
to say that the curved second tube on those
Atlantises looks wonderful *as sculpture.* In
fact, merely aesthetically, I think that
edition of the Atlantis is one of the
prettiest bikes, if not the prettiest bike
that Rivendell has made.
In other, and very unrelated news -- but I
opened the window at the same time as I opened
the Blug window -- fenders are going
road-mainstream:
https://www.bikeradar.com/features/bikes-with-fender-mounts/
Patrick Moore, who would indeed install
fenders on his Atlantis if he had an Atlantis.
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