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Topic: 2009/10 Fox 180mm single?? (Read 1308 times)
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mxlemming
Junior
 
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Posts: 56
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25mm, or one inch, added to a fork with an axle to crown length of 550mm (is that typical, I haven't looked it up, but since it's in the denominator it makes little difference...) gives a percentage length change: 25/550*100 = 4.55%. This means a moment increase of.... 4.55%, plus whatever stupid big stunts that extra inch makes you do...... It isn't likely to cause it to snap, if the structure (tubes, crown etc) remains the same Deflection is proportional to the third power of length for a given beam stiffness, thus for a 4.55% increase in length, deflection increases by (1.0455)^3 = 1.143, or a 14.3% increase in flexure, or 1/1.143 = 0.8752, a 12.5% decrease in stiffness.
That's a pretty rough calculation, not even meritting the 3sf I quoted, it's not FEA tailored to a specific fork, and I haven't even looked up the length of a Fox 36, since it doesn't really matter. It also assumes the head angle doesn't change, i.e. you are using it on an appropriate frame. It does suggest it wouldn't be hard to beef it up a bit to make it strong enough though.
Another point, when manufacturers only say the frame is suitable/warrantable for a certain length of fork, this SHOULD be acknowledged, since the effect is multifold - longer=more leverage and slackens the head angle, which increases moment on the head tube quite a lot.
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Looking for: xc frame, light xc wheels, offers?
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mtballtheway
Full Member
  
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Posts: 115

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25mm, or one inch, added to a fork with an axle to crown length of 550mm (is that typical, I haven't looked it up, but since it's in the denominator it makes little difference...) gives a percentage length change: 25/550*100 = 4.55%. This means a moment increase of.... 4.55%, plus whatever stupid big stunts that extra inch makes you do...... It isn't likely to cause it to snap, if the structure (tubes, crown etc) remains the same Deflection is proportional to the third power of length for a given beam stiffness, thus for a 4.55% increase in length, deflection increases by (1.0455)^3 = 1.143, or a 14.3% increase in flexure, or 1/1.143 = 0.8752, a 12.5% decrease in stiffness.
That's a pretty rough calculation, not even meritting the 3sf I quoted, it's not FEA tailored to a specific fork, and I haven't even looked up the length of a Fox 36, since it doesn't really matter. It also assumes the head angle doesn't change, i.e. you are using it on an appropriate frame. It does suggest it wouldn't be hard to beef it up a bit to make it strong enough though.
Another point, when manufacturers only say the frame is suitable/warrantable for a certain length of fork, this SHOULD be acknowledged, since the effect is multifold - longer=more leverage and slackens the head angle, which increases moment on the head tube quite a lot.
yer... you beat me to it, was going to say exactly that  i do agree though that they should have like a Fox 38 in 180mm
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kitebits
Full Member
  
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Posts: 184
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25mm, or one inch, added to a fork with an axle to crown length of 550mm (is that typical, I haven't looked it up, but since it's in the denominator it makes little difference...) gives a percentage length change: 25/550*100 = 4.55%. This means a moment increase of.... 4.55%, plus whatever stupid big stunts that extra inch makes you do...... It isn't likely to cause it to snap, if the structure (tubes, crown etc) remains the same Deflection is proportional to the third power of length for a given beam stiffness, thus for a 4.55% increase in length, deflection increases by (1.0455)^3 = 1.143, or a 14.3% increase in flexure, or 1/1.143 = 0.8752, a 12.5% decrease in stiffness.
That's a pretty rough calculation, not even meritting the 3sf I quoted, it's not FEA tailored to a specific fork, and I haven't even looked up the length of a Fox 36, since it doesn't really matter. It also assumes the head angle doesn't change, i.e. you are using it on an appropriate frame. It does suggest it wouldn't be hard to beef it up a bit to make it strong enough though.
Another point, when manufacturers only say the frame is suitable/warrantable for a certain length of fork, this SHOULD be acknowledged, since the effect is multifold - longer=more leverage and slackens the head angle, which increases moment on the head tube quite a lot.
Been revising your A Level maths recently??  The fact is, travel lengths on single crowns are getting longer and Fox is getting overtaken (IMO) by Marzocchi and Rockshox in terms of travel and performance. I just wondered if anyone had heard if there was anything in the pipeline as Fox are generally very good at setting market trends rather than following them. Thanks for the "information" though!
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kitebits
Full Member
  
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Posts: 184
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The fact is, travel lengths on single crowns are getting longer and Fox is getting overtaken (IMO) by Marzocchi and Rockshox in terms of travel and performance. I just wondered if anyone had heard if there was anything in the pipeline as Fox are generally very good at setting market trends rather than following them. Thanks for the "information" though!
I don't think RS and especially Marzocchi are even close to the performance of Fox yet with regards to single crowns. I've owned both Totem Solo Airs, Rockshox' top of the line long travel freeride fork, and Fox 36 Floats...the RS forks weren't even a patch on the Fox forks. Marzocchi's quality control isn't good enough and neither is RS really. The only reason for Fox possibly thinking about introducing longer travel forks is to make forks physically longer to suit a different type of fork...this doesn't seem likely. Fox have gone for XC, All Mountain and DH race...not freeride or slopestyle. That seems to be a marketing choice from them. They have forks to suit the types of riding they want to cater for. Rootes Try a Totem Coil - way nicer than the 36 Talas or Van. And yes i ve ridden all three and now run the Totem on my ASX 2. Air forks and long travel - no thanks.
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