Jag har en Nishiki Limited, två och ett halvt år gammal, som är helt underbar, som ett svart spjut genom rumstiden - men idag sprack bakfälgen runt ett ekerfäste. Jag har aldrig kört på annat än asfalt, aldrig kört ner i något och väger 73 kilo. Jag tycker inte det är en normal skada. Erfarenheter / kommentarer?
Fälgbrott
- Trådstartare creamwolf
- Start datum
Har ekerspänningen varit olika så är det nog där felet sitter.Under mina cykelår har många fälgar spruckit. Storgatsten som underhålls med borstmaskin är en fin grund.
go tur
go tur
Det finns alltid en orsak till fälgbrott, Köp en ny och fortsätt.
go tur
go tur
Aha, lufttrycket kan orsaka att ekern drar sig ur fälgen och spräcker den. Hur går det till? (Ursäkta kanske dum fråga, men jag förstår det inte riktigt, bara. Luften som trycker inne i däcket trycker ju åt alla håll. Hur kan den orsaka att ekern drar ur fälgen?)
Och det är klar jag fortsätter! Cyklingen håller gubben frisk, stark och dynamisk!
Fälgen har en sträckgräns. För högt lufttryck expanderar fälgen. Överallt på asfalten finns grus i olika granulationer det kan öka trycket till mer än vad fälgen tål.
Det finns en del man kan göra för att minimera risken för fälgsprickor:
1 Använda silverfärgade (icke anodiserade) alufälgar med "ögon" och "hylsor"
2 Använda tunna reducerade ekrar
3 Se till att ekrarna alltid är hårt spända.
http://www.sheldonbrown.com/brandt/anodized-rims.html
Kontentan är att det bästa sättet är att bygga sina egna hjul http://www.sheldonbrown.com/wheelbuild.html
PS! Högt däcktryck sänker ekerspänningen på kanttrådsdäck.
/Niklas
1 Använda silverfärgade (icke anodiserade) alufälgar med "ögon" och "hylsor"
2 Använda tunna reducerade ekrar
3 Se till att ekrarna alltid är hårt spända.
http://www.sheldonbrown.com/brandt/anodized-rims.html
Kontentan är att det bästa sättet är att bygga sina egna hjul http://www.sheldonbrown.com/wheelbuild.html
PS! Högt däcktryck sänker ekerspänningen på kanttrådsdäck.
/Niklas
Inte enligt Jobst Brandt i alla fall. I hans bicycle wheel http://www.amazon.com/The-Bicycle-Wheel-3rd-Edition/dp/0960723668 (eller den olagliga(?) varianten http://poehali.net/attach/Bicycle_Wheel_-_Jobst_Brandt.pdf) på sid 14-15 finns det mer förklarat. Själva ekvationen (nr 8) återfinns på sidan 130 i samma bok.
/Niklas
/Niklas
Tack Niklas för länken. Men det är väl tvärtom?
"STATIC LOADS
SPOKE TENSION
Spoke tension is the primary static load in the wheel. In a 36-spoke wheel the
force of spoke tension compresses the rim with a force of about a half ton (see
Equation 7 in Part III). Total tension depends on the number of spokes and their
individual tension. Spoke tension and the compressive force in the rim are
directly related, and changes in one affect the other.
TUBULAR TIRE PRESSURE
Although spoke tension is the principal static load on the rim, tubular tire
inflation has a similar effect. When inflated, the tire becomes fatter and shrinks
in circumference. The resulting force depends on the tire cross section, cord
angle and inflation pressure. A tubular racing tire, inflated to 0.86 MPa, for
instance, shrinks with a force of 300 N (see Equation 8 in Part III). Its effect on
spoke tension can be detected with a tensiometer.
Cords in a typical two-ply bicycle tire lie at 90 degrees to each other and at 45
degrees to the length of the tire. When the tube- shaped casing is inflated, it tries
to expand and become fatter. In expanding, the cords move scissorlike becoming
closer to parallel. As the cords try to shorten the tire, air pressure also tries to
stretch it, so that an equilibrium angle of about 3 5 degrees is reached where the
cord angle and lengthening effect are in balance. Hoses designed not to change
length with pressure have this 35 degree angle built in.
CLINCHER TIRE PRESSURE
For clincher tires (used on most bicycles), air pressure in the tube pushes inward
on the bed of the rim while the tire bead pulls outward on the hooked rim edge.
These two forces cancel each other exactly; only the effect of the cord angle, as
in tubular tires, causes a net inward force. That is, the bead does not pull out as
much as it would if the cord angle force were absent, so the inflation force is not
entirely cancelled by the bead pulling outward. For a specific tire cross section
and cord angle, the constriction of clinchers can be computed by treating them
as tubular tires and subtracting the open part of the tire casing.
Because measured spoke tension changes from tire pressure only to the extent
of cord angle effects, it is apparent that the steel or Kevlar beads of clincher tires
are not what support radial forces on hooked bead rims. The primary holding
force comes from the clinching effect by which the bead of the tire is locked into
the hooked rim by inflation pressure. To verify this, the steel bead wires of a
high-performance tire were cut. After inflating this tire to operating pressure,
it remained on the rim. This test was prompted by the observation that even tires
that require great force to be stretched onto a rim, will lift off it and their tubes
will explode if their beads are not properly seated in the hook on the rim."
Thure
"STATIC LOADS
SPOKE TENSION
Spoke tension is the primary static load in the wheel. In a 36-spoke wheel the
force of spoke tension compresses the rim with a force of about a half ton (see
Equation 7 in Part III). Total tension depends on the number of spokes and their
individual tension. Spoke tension and the compressive force in the rim are
directly related, and changes in one affect the other.
TUBULAR TIRE PRESSURE
Although spoke tension is the principal static load on the rim, tubular tire
inflation has a similar effect. When inflated, the tire becomes fatter and shrinks
in circumference. The resulting force depends on the tire cross section, cord
angle and inflation pressure. A tubular racing tire, inflated to 0.86 MPa, for
instance, shrinks with a force of 300 N (see Equation 8 in Part III). Its effect on
spoke tension can be detected with a tensiometer.
Cords in a typical two-ply bicycle tire lie at 90 degrees to each other and at 45
degrees to the length of the tire. When the tube- shaped casing is inflated, it tries
to expand and become fatter. In expanding, the cords move scissorlike becoming
closer to parallel. As the cords try to shorten the tire, air pressure also tries to
stretch it, so that an equilibrium angle of about 3 5 degrees is reached where the
cord angle and lengthening effect are in balance. Hoses designed not to change
length with pressure have this 35 degree angle built in.
CLINCHER TIRE PRESSURE
For clincher tires (used on most bicycles), air pressure in the tube pushes inward
on the bed of the rim while the tire bead pulls outward on the hooked rim edge.
These two forces cancel each other exactly; only the effect of the cord angle, as
in tubular tires, causes a net inward force. That is, the bead does not pull out as
much as it would if the cord angle force were absent, so the inflation force is not
entirely cancelled by the bead pulling outward. For a specific tire cross section
and cord angle, the constriction of clinchers can be computed by treating them
as tubular tires and subtracting the open part of the tire casing.
Because measured spoke tension changes from tire pressure only to the extent
of cord angle effects, it is apparent that the steel or Kevlar beads of clincher tires
are not what support radial forces on hooked bead rims. The primary holding
force comes from the clinching effect by which the bead of the tire is locked into
the hooked rim by inflation pressure. To verify this, the steel bead wires of a
high-performance tire were cut. After inflating this tire to operating pressure,
it remained on the rim. This test was prompted by the observation that even tires
that require great force to be stretched onto a rim, will lift off it and their tubes
will explode if their beads are not properly seated in the hook on the rim."
Thure
Jag vet inte dina fälg och däcksmått men igår mätte jag sprickor och djup på Stortorget i Ystad, storgatsten som underhålls med borstmaskin.
Gap mellan stenarna 8-17mm djup ner till gruset 12-17mm. Perfekta fälgförstörarmått i min bok.
S änden på Södergatan i Lund har tagit minst 5 fälgar för mig.
go tur
Gap mellan stenarna 8-17mm djup ner till gruset 12-17mm. Perfekta fälgförstörarmått i min bok.
S änden på Södergatan i Lund har tagit minst 5 fälgar för mig.
go tur
Vandrat på ett platåberg? Upptäck Billingens unika landskap!
Njutvandra året om i fantastisk natur med böljande sluttningar och dramatiska klippavsatser – bara ett stenkast från Skövdes centrum.
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