Another day working on wheels (and so on...).
A customer left me with a rear wheel using a Cosmic Carbon tubular rim.
It's a 20H Mavic hub built 4130-equivalent style.
They want me to build a fixed gear rear wheel using this rim.
On the freewheel side the spokes are at a steeper angle in tangential lacing,
while on the non-freewheel side the spokes are at a shallower angle in radial lacing,
so relative to each incident angle against the rim's carbon hood
the freewheel side holes are positioned right at the inner edge of the rim,
while the non-freewheel side holes are positioned slightly toward the outer edge.
Additionally, the holes are positioned specifically for tangential and radial lacing respectively.
In building a fixed gear wheel with this rim, I started to tell the customer
"You'll need a 20H fixed gear hub with a single-threaded axle and some dish,
for example something like..." but it turned out to be
the same customer from a previous similar job (→here),
so the explanation wasn't necessary.
By the way, there's also another past case with an Exalith rim (→here).
I disassembled the wheel.
Just to be clear, this is the weight of the rim alone, not the complete rear wheel.
Built it.
Fillwood single-threaded fixed gear hub, 20H,
all-black CX Sprint 4430 Italian lacing.
I'll do the spoke wrapping later.
Looking at the final spoke crossing on the right side
The holes are for tangential lacing, so
the spokes pass through pretty much straight,
but with the left side spokes
those are radial lacing holes, so
they end up right at the edge.
Something I noticed just now—
with the tubular version, this rim
was single-eyelet specification.
It's hard to see because it's hidden behind the
nipple engagement flats that can be turned from the outside,
but the double-wall rim has eyelets only on the inner edge holes.
In contrast, the WO (wired-on) Cosmic Carbon
has double-eyelet specification,
with eyelets on the outer edge holes too to support spoke tension.
By the way, according to Mavic's official site,
the double-eyelet rim was patented in 1934 by Mario Rongi, an Italian,
and Mavic manufactured it under license until 1947.
However, another Italian rim maker, Fiamme, also
received a license to manufacture them.
According to different sources, Mario Rongi was associated with Fiamme,
and Fiamme granted the license to Mavic.
↑This is a much later Fiamme rim
(though still from the late 1980s),
model Iride 191.
Well, this one's single-eyelet anyway.
Mavic makes double-eyelet rims their selling point,
and even their lightweight 280g GEL280 rim,
which is weight-disadvantaged by double-eyelets, uses that specification.
The WO super-bestseller Open Pro also has double-eyelets,
but the Open Pro Disc Rim has poor compatibility with tubeless-ready,
so it finally switched to single-eyelet spec.
Back to the Cosmic Carbon rim.
The Cosmic Carbon SL rim is
single-eyelet spec.
Besides that change, the reason for the SL designation is that
like the Ksilium SL,
the material between rim holes is machined away to pursue lightness.
↑Here are X-ray images of
the WO Cosmic Carbon and Cosmic Carbon SL rims.
I was going to throw in a joke about cancer rays showing up,
but I couldn't be bothered.
↑This is the Cosmic Carbon.
You can faintly see the carbon hood as well.
↑This is the Cosmic Carbon SL.
You can see the machining between holes and the single-eyelet design.
This is a non-destructive testing technique, but
↑Here's an example using destructive methodology.
A customer left me with a rear wheel using a Cosmic Carbon tubular rim.
It's a 20H Mavic hub built 4130-equivalent style.
They want me to build a fixed gear rear wheel using this rim.
On the freewheel side the spokes are at a steeper angle in tangential lacing,
while on the non-freewheel side the spokes are at a shallower angle in radial lacing,
so relative to each incident angle against the rim's carbon hood
the freewheel side holes are positioned right at the inner edge of the rim,
while the non-freewheel side holes are positioned slightly toward the outer edge.
Additionally, the holes are positioned specifically for tangential and radial lacing respectively.
In building a fixed gear wheel with this rim, I started to tell the customer
"You'll need a 20H fixed gear hub with a single-threaded axle and some dish,
for example something like..." but it turned out to be
the same customer from a previous similar job (→here),
so the explanation wasn't necessary.
By the way, there's also another past case with an Exalith rim (→here).
I disassembled the wheel.
Just to be clear, this is the weight of the rim alone, not the complete rear wheel.
Built it.
Fillwood single-threaded fixed gear hub, 20H,
all-black CX Sprint 4430 Italian lacing.
I'll do the spoke wrapping later.
Looking at the final spoke crossing on the right side
The holes are for tangential lacing, so
the spokes pass through pretty much straight,
but with the left side spokes
those are radial lacing holes, so
they end up right at the edge.
Something I noticed just now—
with the tubular version, this rim
was single-eyelet specification.
It's hard to see because it's hidden behind the
nipple engagement flats that can be turned from the outside,
but the double-wall rim has eyelets only on the inner edge holes.
In contrast, the WO (wired-on) Cosmic Carbon
has double-eyelet specification,
with eyelets on the outer edge holes too to support spoke tension.
By the way, according to Mavic's official site,
the double-eyelet rim was patented in 1934 by Mario Rongi, an Italian,
and Mavic manufactured it under license until 1947.
However, another Italian rim maker, Fiamme, also
received a license to manufacture them.
According to different sources, Mario Rongi was associated with Fiamme,
and Fiamme granted the license to Mavic.
↑This is a much later Fiamme rim
(though still from the late 1980s),
model Iride 191.
Well, this one's single-eyelet anyway.
Mavic makes double-eyelet rims their selling point,
and even their lightweight 280g GEL280 rim,
which is weight-disadvantaged by double-eyelets, uses that specification.
The WO super-bestseller Open Pro also has double-eyelets,
but the Open Pro Disc Rim has poor compatibility with tubeless-ready,
so it finally switched to single-eyelet spec.
Back to the Cosmic Carbon rim.
The Cosmic Carbon SL rim is
single-eyelet spec.
Besides that change, the reason for the SL designation is that
like the Ksilium SL,
the material between rim holes is machined away to pursue lightness.
↑Here are X-ray images of
the WO Cosmic Carbon and Cosmic Carbon SL rims.
but I couldn't be bothered.
↑This is the Cosmic Carbon.
You can faintly see the carbon hood as well.
↑This is the Cosmic Carbon SL.
You can see the machining between holes and the single-eyelet design.
This is a non-destructive testing technique, but
↑Here's an example using destructive methodology.