A customer entrusted me with a Cosmic Carbon rim.
They want me to build a wheel with this rim and a fixed gear hub.
Yeah, that's impossible.
This rim has a low-profile aluminum rim base
with a carbon fairing on top,
but the nipples aren't at the rim peak,
so the spokes pass through holes in the rim sidewall.
↑Freewheel side hole
↑Non-freewheel side hole
The spoke incidence angle on the rim changes depending on the flange offset difference, so
the hole positions (heights) are set differently on each side to account for this.
In other words, if you build it with a single-speed hub that has little to no flange offset,
the spokes might interfere with the rim holes.
Also, while this rim has the same dimensions as the 2005 Cosmic Carbon SL,
it's technically the Cosmic Pro Carbon Exalith,
and the brake zone has a specific orientation,
so even if you're building it with a hub that has no flange offset, you have to respect this.
The hub is a Philwood (single-speed hub), but...
It actually has quite a bit of flange offset.
The rim hole issue turns out to be in our favor.
Whoever said it was impossible earlier...
There's protective tape on the Philwood logo,
but it doesn't affect the work, so I'll leave it as is.
Built it.
20 hole, black, semi-comp 4-cross lacing. I'll do the truing later.
The flange offset was large enough to require semi-comp lacing.
The way spokes enter the freewheel side holes is
like this everywhere.
But on the non-freewheel side...
At the final crossing, the spokes scissors inward and contact the rim hole.
That's unavoidable.
The different rim hole heights on each side can be explained by
the difference in spoke incidence angles when viewing the wheel from the front and back.
Next, about the spoke incidence angle difference between radial and tangential lacing when viewed from the side.
On the radial lacing side, the rim holes can be equally spaced as shown in the diagram above,
but with tangential lacing, the spokes lie back more depending on the flange diameter and lacing pattern,
causing contact like this.
So with the Cosmic Carbon rim, the rim holes on the tangential lacing side (freewheel side) are offset
in phase, positioned to match the spoke incidence angle when built with a Cosmic Carbon hub.
So anyway, I managed to build the rear wheel,
but I still have to build the front wheel.
Of course, the hub has no flange offset, so
I'll just force it to follow the Exalith direction,
but there's something else I want to investigate separately from the rim hole issue, so I'll do that later.
They want me to build a wheel with this rim and a fixed gear hub.
Yeah, that's impossible.
This rim has a low-profile aluminum rim base
with a carbon fairing on top,
but the nipples aren't at the rim peak,
so the spokes pass through holes in the rim sidewall.
↑Freewheel side hole
↑Non-freewheel side hole
The spoke incidence angle on the rim changes depending on the flange offset difference, so
the hole positions (heights) are set differently on each side to account for this.
In other words, if you build it with a single-speed hub that has little to no flange offset,
the spokes might interfere with the rim holes.
Also, while this rim has the same dimensions as the 2005 Cosmic Carbon SL,
it's technically the Cosmic Pro Carbon Exalith,
and the brake zone has a specific orientation,
so even if you're building it with a hub that has no flange offset, you have to respect this.
The hub is a Philwood (single-speed hub), but...
It actually has quite a bit of flange offset.
The rim hole issue turns out to be in our favor.
Whoever said it was impossible earlier...
There's protective tape on the Philwood logo,
but it doesn't affect the work, so I'll leave it as is.
Built it.
20 hole, black, semi-comp 4-cross lacing. I'll do the truing later.
The flange offset was large enough to require semi-comp lacing.
The way spokes enter the freewheel side holes is
like this everywhere.
But on the non-freewheel side...
At the final crossing, the spokes scissors inward and contact the rim hole.
That's unavoidable.
The different rim hole heights on each side can be explained by
the difference in spoke incidence angles when viewing the wheel from the front and back.
Next, about the spoke incidence angle difference between radial and tangential lacing when viewed from the side.
On the radial lacing side, the rim holes can be equally spaced as shown in the diagram above,
but with tangential lacing, the spokes lie back more depending on the flange diameter and lacing pattern,
causing contact like this.
So with the Cosmic Carbon rim, the rim holes on the tangential lacing side (freewheel side) are offset
in phase, positioned to match the spoke incidence angle when built with a Cosmic Carbon hub.
So anyway, I managed to build the rear wheel,
but I still have to build the front wheel.
Of course, the hub has no flange offset, so
I'll just force it to follow the Exalith direction,
but there's something else I want to investigate separately from the rim hole issue, so I'll do that later.