C
Elsewhere, doubts have been cast on the accuracy of Park's modestly
priced blue bicycle spoke tension gauge.
Hmmm . . . I'd never tested my trusty (?) Park tension gauge!
It does notice whenever I add small weights or turn spoke nipples or
let the air out of a tire--what else can a simple spring do?
But what if it's been lying to me all this time and just flattering me
when I ask it whether pinching spokes together makes my spoke-tension
look fat? What if the tension is 50% higher than the calibration table
claims?
How could I enjoy visions of sugar-plums dancing through my head
tonight with this kind of uncertainty nagging me?
So I bent the ends of a helpless 2 mm straight steel spoke into
U-hooks, added some wire-rope thingies to stop the U-hooks from
straightening, hung the spoke from a ceiling rope, and dangled a crude
rope-and-2x4 swing from the spoke to allow loading a standard 195-lb
Fogel onto the spoke.
I stepped onto the swing and found . . .
That I swung so wildly on my piñata-style contraption that there was
no way to read the Park tension gauge, much less take a picture of the
festivities.
Alas, the vast stock of convenient weights at Fogel Labs totals only
about 100 real pounds on postal scales. (An inflated 110 pounds
according to the lying numbers stamped on the weights themselves.)
At first I feared that Christmas would be ruined, since I needed
something close to 200 pounds to represent a low-normal 90 kgf
spoke tension.
But then I remembered that several plastic buckets are kept around the
premises for . . . well, for important stuff like this.
Filled not too near the top, the first bucket weighed a handy 30
pounds. After filling all three buckets and checking that they weighed
30 pounds, I dangled 100 lbs of weights on a bar and three 30-pound
buckets of water from a 2 mm spoke:
http://i14.tinypic.com/4960dw3.jpg
http://i18.tinypic.com/2czqz6f.jpg
Click on the lower right for full-size images in Explorer.
The Park gauge reads about 22 on a scale of 0 to 45. (It's a little
over 22, and then the camera angle makes it look a little higher. I
steadied the camera on a handy but slightly too-high stand.)
For a 2 mm spoke, the Park calibration chart shows this to mean a
tension of 85 kgf, or 187 pounds, reasonably close to the 190 pounds
of ropes, bar, weights, buckets, and water in the picture.
Park 2.0mm spoke
mark kgf / lbs
off scale
17 51 / 112
18 56 / 123
19 62 / 136
20 68 / 150
21 76 / 167
22 85 / 187 <--~190 lbs of weights hung from spoke
23 95 / 209
24 107 / 235
25 121 / 266
26 137 / 301
27 156 / 343
28 179 / 394
off scale
I hope that this test pleases anyone who gets a blue Park tension
gauge tomorrow morning. (Or a gift certificate to places that sell
it.)
Merry Christmas!
Carl Fogel
priced blue bicycle spoke tension gauge.
Hmmm . . . I'd never tested my trusty (?) Park tension gauge!
It does notice whenever I add small weights or turn spoke nipples or
let the air out of a tire--what else can a simple spring do?
But what if it's been lying to me all this time and just flattering me
when I ask it whether pinching spokes together makes my spoke-tension
look fat? What if the tension is 50% higher than the calibration table
claims?
How could I enjoy visions of sugar-plums dancing through my head
tonight with this kind of uncertainty nagging me?
So I bent the ends of a helpless 2 mm straight steel spoke into
U-hooks, added some wire-rope thingies to stop the U-hooks from
straightening, hung the spoke from a ceiling rope, and dangled a crude
rope-and-2x4 swing from the spoke to allow loading a standard 195-lb
Fogel onto the spoke.
I stepped onto the swing and found . . .
That I swung so wildly on my piñata-style contraption that there was
no way to read the Park tension gauge, much less take a picture of the
festivities.
Alas, the vast stock of convenient weights at Fogel Labs totals only
about 100 real pounds on postal scales. (An inflated 110 pounds
according to the lying numbers stamped on the weights themselves.)
At first I feared that Christmas would be ruined, since I needed
something close to 200 pounds to represent a low-normal 90 kgf
spoke tension.
But then I remembered that several plastic buckets are kept around the
premises for . . . well, for important stuff like this.
Filled not too near the top, the first bucket weighed a handy 30
pounds. After filling all three buckets and checking that they weighed
30 pounds, I dangled 100 lbs of weights on a bar and three 30-pound
buckets of water from a 2 mm spoke:
http://i14.tinypic.com/4960dw3.jpg
http://i18.tinypic.com/2czqz6f.jpg
Click on the lower right for full-size images in Explorer.
The Park gauge reads about 22 on a scale of 0 to 45. (It's a little
over 22, and then the camera angle makes it look a little higher. I
steadied the camera on a handy but slightly too-high stand.)
For a 2 mm spoke, the Park calibration chart shows this to mean a
tension of 85 kgf, or 187 pounds, reasonably close to the 190 pounds
of ropes, bar, weights, buckets, and water in the picture.
Park 2.0mm spoke
mark kgf / lbs
off scale
17 51 / 112
18 56 / 123
19 62 / 136
20 68 / 150
21 76 / 167
22 85 / 187 <--~190 lbs of weights hung from spoke
23 95 / 209
24 107 / 235
25 121 / 266
26 137 / 301
27 156 / 343
28 179 / 394
off scale
I hope that this test pleases anyone who gets a blue Park tension
gauge tomorrow morning. (Or a gift certificate to places that sell
it.)
Merry Christmas!
Carl Fogel