I'm going to write about spoke tension and tension meters.
Without writing this, I can't get into topics like "hand-laced free-side radial lacing" or "different-diameter lacing on one flange" or "0-cross lacing that isn't radial lacing."
I should have written this back around December last year, but things kept dragging on.
Let me start with the principles and usage of tension meters.
To measure spoke deflection, the meter uses a lever action with three contact points on the spoke.
Two of these are fixed and one is movable, and it measures spoke deflection by the resistance to compression.
↑You then take that deflection measurement and apply it to the conversion chart that comes with the meter
to determine the spoke tension.
At this point, the relationship between deflection and spoke tension
follows a bow-shaped curve like the one in the image above, but
let's say this were a straight line instead.
And if you then stipulated "we only use 2.0mm plain spokes, period,"
limiting spoke types to just one,
then you could make a tension meter where the meter reading itself
displays the spoke tension directly.
(The dashed line in the figure above is drawn offset, but it's on the same line)
In reality, because the curve is bow-shaped and there's a wide variety of spoke types,
you cannot use a tension meter without a conversion chart.
This is an extremely important point:
when I simply write "spoke tension" on this blog, it can refer to any of at least three different meanings,
but I've made it a policy to not go into detail about which one I'm referring to.
I plan to basically stick with that going forward.
In my own arbitrary terminology,
the "spoke deflection as measured by the tension meter"
is what I call "first spoke tension."
When I use the term "apparent spoke tension,"
I'm usually referring to this, though looking back, sometimes I'm not.
Regarding calling spoke deflection "spoke tension" — there is a causal relationship
between low deflection and high spoke tension, so I'm calling
this "spoke-tension-like" thing "first spoke tension" as a term of my own invention.
Next, the approximate spoke tension value after converting with the conversion chart,
I call "second spoke tension."
Looking back at my past posts, I often call this "true spoke tension,"
but there are plenty of exceptions, so "second = true" isn't always the case.
This one is the conventional meaning — the ordinary sense of "spoke tension" refers to this.
Now for the third spoke tension.
This is not spoke tension itself.
It's a numerical value derived from the first and second spoke tensions,
the spoke thickness (strictly speaking, specific gravity),
and the radial angular relationship between spoke and hub,
plugged into a certain constant.
I can't write about the constant — it's my own arbitrary definition.
However, I have empirical conviction that the magnitude of third spoke tension
more accurately expresses wheel responsiveness than second spoke tension does.
Third spoke tension is broadly speaking "spoke deflection,"
but the difference from first tension is that it incorporates both
spoke specific gravity and the angle at which it's tensioned in the calculation.
Even at the same spoke tension (—now which number spoke tension is that, I wonder?),
radial and tangential lacing have different power transmission efficiency,
so the angle at which the spoke is tensioned matters greatly for responsiveness.
Think of third spoke tension as "responsiveness quantified."
It's not quite that, but roughly.
There is a "fourth spoke tension" too, but
it's a concept you don't really need for wheel building, so
I've never touched on it in this blog.
As I'll explain later, at the moment fourth tension can't be researched. Give it back.
There are some exceptions between round spokes and flat spokes, but
when you put thick and thin spokes on the same conversion chart, it looks like the image above.
Both are curves, so the relationship between meter reading and approximate spoke tension—
that is, the relationship between first and second tension—won't be the same proportion
for thick spokes versus thin spokes.
Say I'm building a rear wheel: both Champion and CX-RAY, neither is cross-diameter lacing,
but CX-RAY has less left-right spoke tension variance than Champion.
Let's say both have the free side tensioned at 1000N second tension.
Naturally, the building method, rim, and hub are all identical.
At that point, the tactile deflection feel of the non-free side spokes
will feel more taut on CX-RAY than Champion.
Even calculating this with third spoke tension, CX-RAY comes out higher.
That's because spoke specific gravity is built into the third tension formula.
I said I'd start with the principles and usage of tension meters, but
I've gotten way sidetracked.
Back to spoke tension meters.
Let me start with Hozan's tension meter.
This is what I use regularly.
The list price before tax is ¥44,000. For your reference.
You press the measuring probe in the center against the spoke to measure deflection.
↑Calibration is done by adjusting the double-nut here,
but you absolutely must not touch this. It throws off the calibration.
Like a torque wrench, precision measuring tools like this
will gradually change their readings with age and use.
With Hozan's tension meter,
you can send it back to the manufacturer for recalibration.
Whether a measuring tool can or cannot be recalibrated is critically important.
Quoting from the instruction manual:
"Conversion values differ from unit to unit, so each unit undergoes individual public inspection to create a conversion chart.
Please keep your conversion chart safe.
Should you lose your conversion chart, the instrument will need to be re-certified."
That "individual" approach is what sets it apart from other manufacturers.
Next is the DT tension meter.
Without this, the Hozan meter can't be used (I'll explain why later).
The list price before tax is ¥72,380. For your reference.
↑You squeeze the spoke in here.
When you squeeze the spoke, it works like squeezing a grip trainer,
the probe gets pushed and you can measure the deflection, but
↑the probe is held with just an Allen bolt to the grip trainer.
If you mess with this, you can calibrate it.
With Hozan, I said never touch the calibration adjustment,
but with DT you can do it.
That's because DT's conversion chart is not meter-by-meter unique—there's one fixed chart.
The instruction is to adjust the meter itself so it produces values matching the conversion chart.
↑This is that conversion chart.
For reference, 2.0mm Champion.
Next, 2.0-1.5mm Revolution.
Earlier I drew a figure with a thin-spoke bow curve underneath a thick-spoke bow curve,
but looking at these two, they seem the same.
Don't be fooled. The maximum values and ranges of the graphs are completely different.
For example, Champion reaches 1000N at 2.2mm deflection,
but Revolution reaches 1000N at just under 1.3mm deflection.
Hozan supplies an individual conversion chart with each meter,
and the conversion chart from one meter isn't compatible with another identical model.
Also, the conversion chart is replaced each time the meter is recalibrated.
This conversion chart, perhaps because it was made for general-purpose bikes,
can only determine spoke tension for sizes 13, 14, and 15 plain spokes.
It explicitly states that other sizes and special spokes like aero spokes won't work.
With DT, being faithful to the single conversion chart
is considered "correct."
If you have multiple DT tension meters
and put them on the same 2.0mm Champion
and they all point to, say, exactly 2.2mm deflection—the same reading.
If you use just one continuously, it will eventually drift.
If you have another DT meter as a reference standard (seemingly reliable in accuracy),
then the user can do calibration themselves.
That's why it's better to have two or more DT meters if possible.
There's a building method I privately call "zero-in lacing"
using two or more DT meters, but
I only have one now, so I can't do it.
For my current wheel-building approach, whether zero-in lacing directly leads
to better wheel building—well, not really, so it's fine.
The DT conversion chart has the bow curves for all DT spoke models.
Strictly speaking, different butting lengths mean they're not identical, but
if I assume Sapim CX-RAY is the same as DT Aero-Lite,
Race is Competition, and Laser is Revolution,
then I can measure Sapim spokes with the DT meter.
The error should be minimal, so that's what I do.
Leader and Champion are both plain spokes, so there's barely any difference.
So what if you have only one DT meter?
Even though it's fixed that "Champion 2.0mm plain at 1000N is 2.2mm deflection,"
when you put the meter on it and it points to 2.2mm deflection,
is that really 1000N?
If you had a metronome-like standard to calibrate against—
"definitely 1000N"—that would help, but...
"Getting two DT meters like I mentioned" is like
tuning two instruments against each other.
But as long as they're new, DT meters have very little drift or unit-to-unit variation, so
buying just one is fine as long as you don't recalibrate.
You only need recalibration if you're building wheels every day, and
in this complete-wheel era, who does that?
As for how I'm measuring butted and aero spokes with the Hozan meter:
I've made my own conversion chart by comparing DT and Hozan readings
in 100N increments.
This way I can convert "CX-RAY (actually Aero-Lite)
showing ○.○mm deflection on Hozan is ○○○○N" and so on.
This amounts to "zero-in lacing between DT and Hozan,"
and as long as I keep using the current Hozan with calibrations, I can use it forever.
↑Three sets of conversion charts and such.
There are three PB 2.5mm Allen keys
for adjusting the probe set-screw
three of them.
Well, I learned the hard way that letting someone else manage tools leads to rough handling
and loss of parts, so now I only have one DT meter.
Without the conversion chart it's a useless object (though the DT chart should be obtainable),
and it's a tool beyond your station, so give it back if you haven't lost it.
Never mind that I can't do zero-in lacing,
but to verify fourth spoke tension I'd need
at least two DT meters, and man oh man do I wish I had them!
Thanks to the DT meter and conversion chart, I've been able to use
the Hozan meter with Competition and CX-RAY.
But do I consult the conversion chart every time?
No—I've just memorized "CX-RAY at 1100N, the needle is around here"
and the like, so for the DT Competition and CX-RAY I use frequently,
I don't look at the chart.
I just build using the first spoke tension reading.
Actually, some complete-wheel manufacturers
specify spoke tension this way too—
"the free side of this wheel shows this many mm deflection on a DT meter"—
using this method of designation.
This approach might be clever.
The spokes don't necessarily have to be DT brand.
It's fine to just say "we build our wheels using a DT meter."
For these reasons the DT meter is essential in shops.
It's often necessary for repairs on foreign-brand wheels.
So even if you're using it without a conversion chart for that reason, give it back.
Finally.
I figure someone will ask, "What about Park Tool's TM-1?"
so I'll address it now.
At ¥12,300 before tax, it's cheap, so I'd recommend it for home mechanics.
Just be aware—its accuracy and repeatability are somewhat questionable.
The individual variation in crimp hardness is huge, and the friction feel of moving parts differs from unit to unit.
Also, by adjusting or lubricating the crimp on a single unit,
the needle lift-off can change dramatically.
Hozan and DT have the rigidity to prevent this kind of thing, but
that shows in the price too (though I do think DT is pricey).
Structurally it's an ultra-simplified DT.
I don't think it's a shop pro tool,
but I think it's sufficient for general use.
However, as I mentioned, keeping the same conditions is important,
so pay attention to that.
It has a certain fragility—like "a ruler whose scale width changes depending on how you handle it."
Park Tool names their tools either "acronym + size number"
or "acronym + version number."
In the case of hub spanners (Park Tool calls them Shop Cone Wrenches),
the acronym for Shop Cone Wrench is SCW, with
13mm being SCW-13, 17mm being SCW-17—
this is a size number system.
For floor pumps, Professional Floor Pump
is acronymed PFP, followed by a number,
and currently existing models are PFP-5, PFP-7, and PFP-8.
This is a version number system, so there used to be 1, 2, 3, 4, and 6 at some point.
My point is: TM-1 is the first Tension Meter.
Park Tool only recently became aware of "the need to manage spoke tension"
from the catalog.
Or maybe other companies had already established trusted meters as standards,
making it hard to enter the market.
Seen that way, it looks like a masterpiece born from that tight line:
deliberate aim for "something much cheaper than what others are selling," pragmatically simple yet not cheap-looking,
keeping the assumed retail price low.
If TM-1 were the only spoke tension meter in the world,
of course I'd use it. I wouldn't rely on finger feel alone.
It's just that if price is no object, I have other options—that's all.
If someday a TM-2 comes out that's solid and trustworthy,
I wouldn't think ¥50,000 is expensive—I'm actually hoping for one.
Even Park Tool's novelty pizza cutter is up to PZT-2 now.
Without writing this, I can't get into topics like "hand-laced free-side radial lacing" or "different-diameter lacing on one flange" or "0-cross lacing that isn't radial lacing."
I should have written this back around December last year, but things kept dragging on.
Let me start with the principles and usage of tension meters.
To measure spoke deflection, the meter uses a lever action with three contact points on the spoke.
Two of these are fixed and one is movable, and it measures spoke deflection by the resistance to compression.
↑You then take that deflection measurement and apply it to the conversion chart that comes with the meter
to determine the spoke tension.
At this point, the relationship between deflection and spoke tension
follows a bow-shaped curve like the one in the image above, but
let's say this were a straight line instead.
And if you then stipulated "we only use 2.0mm plain spokes, period,"
limiting spoke types to just one,
then you could make a tension meter where the meter reading itself
displays the spoke tension directly.
(The dashed line in the figure above is drawn offset, but it's on the same line)
In reality, because the curve is bow-shaped and there's a wide variety of spoke types,
you cannot use a tension meter without a conversion chart.
This is an extremely important point:
when I simply write "spoke tension" on this blog, it can refer to any of at least three different meanings,
but I've made it a policy to not go into detail about which one I'm referring to.
I plan to basically stick with that going forward.
In my own arbitrary terminology,
the "spoke deflection as measured by the tension meter"
is what I call "first spoke tension."
When I use the term "apparent spoke tension,"
I'm usually referring to this, though looking back, sometimes I'm not.
Regarding calling spoke deflection "spoke tension" — there is a causal relationship
between low deflection and high spoke tension, so I'm calling
this "spoke-tension-like" thing "first spoke tension" as a term of my own invention.
Next, the approximate spoke tension value after converting with the conversion chart,
I call "second spoke tension."
Looking back at my past posts, I often call this "true spoke tension,"
but there are plenty of exceptions, so "second = true" isn't always the case.
This one is the conventional meaning — the ordinary sense of "spoke tension" refers to this.
Now for the third spoke tension.
This is not spoke tension itself.
It's a numerical value derived from the first and second spoke tensions,
the spoke thickness (strictly speaking, specific gravity),
and the radial angular relationship between spoke and hub,
plugged into a certain constant.
I can't write about the constant — it's my own arbitrary definition.
However, I have empirical conviction that the magnitude of third spoke tension
more accurately expresses wheel responsiveness than second spoke tension does.
Third spoke tension is broadly speaking "spoke deflection,"
but the difference from first tension is that it incorporates both
spoke specific gravity and the angle at which it's tensioned in the calculation.
Even at the same spoke tension (—now which number spoke tension is that, I wonder?),
radial and tangential lacing have different power transmission efficiency,
so the angle at which the spoke is tensioned matters greatly for responsiveness.
Think of third spoke tension as "responsiveness quantified."
It's not quite that, but roughly.
There is a "fourth spoke tension" too, but
it's a concept you don't really need for wheel building, so
I've never touched on it in this blog.
As I'll explain later, at the moment fourth tension can't be researched. Give it back.
There are some exceptions between round spokes and flat spokes, but
when you put thick and thin spokes on the same conversion chart, it looks like the image above.
Both are curves, so the relationship between meter reading and approximate spoke tension—
that is, the relationship between first and second tension—won't be the same proportion
for thick spokes versus thin spokes.
Say I'm building a rear wheel: both Champion and CX-RAY, neither is cross-diameter lacing,
but CX-RAY has less left-right spoke tension variance than Champion.
Let's say both have the free side tensioned at 1000N second tension.
Naturally, the building method, rim, and hub are all identical.
At that point, the tactile deflection feel of the non-free side spokes
will feel more taut on CX-RAY than Champion.
Even calculating this with third spoke tension, CX-RAY comes out higher.
That's because spoke specific gravity is built into the third tension formula.
I said I'd start with the principles and usage of tension meters, but
I've gotten way sidetracked.
Back to spoke tension meters.
Let me start with Hozan's tension meter.
This is what I use regularly.
The list price before tax is ¥44,000. For your reference.
You press the measuring probe in the center against the spoke to measure deflection.
↑Calibration is done by adjusting the double-nut here,
but you absolutely must not touch this. It throws off the calibration.
Like a torque wrench, precision measuring tools like this
will gradually change their readings with age and use.
With Hozan's tension meter,
you can send it back to the manufacturer for recalibration.
Whether a measuring tool can or cannot be recalibrated is critically important.
Quoting from the instruction manual:
"Conversion values differ from unit to unit, so each unit undergoes individual public inspection to create a conversion chart.
Please keep your conversion chart safe.
Should you lose your conversion chart, the instrument will need to be re-certified."
That "individual" approach is what sets it apart from other manufacturers.
Next is the DT tension meter.
Without this, the Hozan meter can't be used (I'll explain why later).
The list price before tax is ¥72,380. For your reference.
↑You squeeze the spoke in here.
When you squeeze the spoke, it works like squeezing a grip trainer,
the probe gets pushed and you can measure the deflection, but
↑the probe is held with just an Allen bolt to the grip trainer.
If you mess with this, you can calibrate it.
With Hozan, I said never touch the calibration adjustment,
but with DT you can do it.
That's because DT's conversion chart is not meter-by-meter unique—there's one fixed chart.
The instruction is to adjust the meter itself so it produces values matching the conversion chart.
↑This is that conversion chart.
For reference, 2.0mm Champion.
Next, 2.0-1.5mm Revolution.
Earlier I drew a figure with a thin-spoke bow curve underneath a thick-spoke bow curve,
but looking at these two, they seem the same.
Don't be fooled. The maximum values and ranges of the graphs are completely different.
For example, Champion reaches 1000N at 2.2mm deflection,
but Revolution reaches 1000N at just under 1.3mm deflection.
Hozan supplies an individual conversion chart with each meter,
and the conversion chart from one meter isn't compatible with another identical model.
Also, the conversion chart is replaced each time the meter is recalibrated.
This conversion chart, perhaps because it was made for general-purpose bikes,
can only determine spoke tension for sizes 13, 14, and 15 plain spokes.
It explicitly states that other sizes and special spokes like aero spokes won't work.
With DT, being faithful to the single conversion chart
is considered "correct."
If you have multiple DT tension meters
and put them on the same 2.0mm Champion
and they all point to, say, exactly 2.2mm deflection—the same reading.
If you use just one continuously, it will eventually drift.
If you have another DT meter as a reference standard (seemingly reliable in accuracy),
then the user can do calibration themselves.
That's why it's better to have two or more DT meters if possible.
There's a building method I privately call "zero-in lacing"
using two or more DT meters, but
I only have one now, so I can't do it.
For my current wheel-building approach, whether zero-in lacing directly leads
to better wheel building—well, not really, so it's fine.
The DT conversion chart has the bow curves for all DT spoke models.
Strictly speaking, different butting lengths mean they're not identical, but
if I assume Sapim CX-RAY is the same as DT Aero-Lite,
Race is Competition, and Laser is Revolution,
then I can measure Sapim spokes with the DT meter.
The error should be minimal, so that's what I do.
Leader and Champion are both plain spokes, so there's barely any difference.
So what if you have only one DT meter?
Even though it's fixed that "Champion 2.0mm plain at 1000N is 2.2mm deflection,"
when you put the meter on it and it points to 2.2mm deflection,
is that really 1000N?
If you had a metronome-like standard to calibrate against—
"definitely 1000N"—that would help, but...
"Getting two DT meters like I mentioned" is like
tuning two instruments against each other.
But as long as they're new, DT meters have very little drift or unit-to-unit variation, so
buying just one is fine as long as you don't recalibrate.
You only need recalibration if you're building wheels every day, and
in this complete-wheel era, who does that?
As for how I'm measuring butted and aero spokes with the Hozan meter:
I've made my own conversion chart by comparing DT and Hozan readings
in 100N increments.
This way I can convert "CX-RAY (actually Aero-Lite)
showing ○.○mm deflection on Hozan is ○○○○N" and so on.
This amounts to "zero-in lacing between DT and Hozan,"
and as long as I keep using the current Hozan with calibrations, I can use it forever.
↑Three sets of conversion charts and such.
There are three PB 2.5mm Allen keys
for adjusting the probe set-screw
three of them.
Well, I learned the hard way that letting someone else manage tools leads to rough handling
and loss of parts, so now I only have one DT meter.
Without the conversion chart it's a useless object (though the DT chart should be obtainable),
and it's a tool beyond your station, so give it back if you haven't lost it.
Never mind that I can't do zero-in lacing,
but to verify fourth spoke tension I'd need
at least two DT meters, and man oh man do I wish I had them!
Thanks to the DT meter and conversion chart, I've been able to use
the Hozan meter with Competition and CX-RAY.
But do I consult the conversion chart every time?
No—I've just memorized "CX-RAY at 1100N, the needle is around here"
and the like, so for the DT Competition and CX-RAY I use frequently,
I don't look at the chart.
I just build using the first spoke tension reading.
Actually, some complete-wheel manufacturers
specify spoke tension this way too—
"the free side of this wheel shows this many mm deflection on a DT meter"—
using this method of designation.
This approach might be clever.
The spokes don't necessarily have to be DT brand.
It's fine to just say "we build our wheels using a DT meter."
For these reasons the DT meter is essential in shops.
It's often necessary for repairs on foreign-brand wheels.
So even if you're using it without a conversion chart for that reason, give it back.
Finally.
I figure someone will ask, "What about Park Tool's TM-1?"
so I'll address it now.
At ¥12,300 before tax, it's cheap, so I'd recommend it for home mechanics.
Just be aware—its accuracy and repeatability are somewhat questionable.
The individual variation in crimp hardness is huge, and the friction feel of moving parts differs from unit to unit.
Also, by adjusting or lubricating the crimp on a single unit,
the needle lift-off can change dramatically.
Hozan and DT have the rigidity to prevent this kind of thing, but
that shows in the price too (though I do think DT is pricey).
Structurally it's an ultra-simplified DT.
I don't think it's a shop pro tool,
but I think it's sufficient for general use.
However, as I mentioned, keeping the same conditions is important,
so pay attention to that.
It has a certain fragility—like "a ruler whose scale width changes depending on how you handle it."
Park Tool names their tools either "acronym + size number"
or "acronym + version number."
In the case of hub spanners (Park Tool calls them Shop Cone Wrenches),
the acronym for Shop Cone Wrench is SCW, with
13mm being SCW-13, 17mm being SCW-17—
this is a size number system.
For floor pumps, Professional Floor Pump
is acronymed PFP, followed by a number,
and currently existing models are PFP-5, PFP-7, and PFP-8.
This is a version number system, so there used to be 1, 2, 3, 4, and 6 at some point.
My point is: TM-1 is the first Tension Meter.
Park Tool only recently became aware of "the need to manage spoke tension"
from the catalog.
Or maybe other companies had already established trusted meters as standards,
making it hard to enter the market.
Seen that way, it looks like a masterpiece born from that tight line:
deliberate aim for "something much cheaper than what others are selling," pragmatically simple yet not cheap-looking,
keeping the assumed retail price low.
If TM-1 were the only spoke tension meter in the world,
of course I'd use it. I wouldn't rely on finger feel alone.
It's just that if price is no object, I have other options—that's all.
If someday a TM-2 comes out that's solid and trustworthy,
I wouldn't think ¥50,000 is expensive—I'm actually hoping for one.
Even Park Tool's novelty pizza cutter is up to PZT-2 now.