Re: [RBW] Re: Stem Strength
With carbon fiber, all the old standards are thrown out! James Valiensi, PE Northridge, CA H818.775.1847 M.818.585.1796 On May 7, 2011, at 7:01 AM, Bill M. wrote: > I suspect that the introduction of carbon fiber bars had something to > do with the introduction of 31.8 mm bars as well. > > Bill > > > On May 6, 10:15 pm, James Valiensi wrote: >> Hey, >> My back of the envelope calc's indicate a standard aluminum quill stem will >> deflect about ten times more than a steel stem. This is with equal >> extensions lengths and loads, and the aluminum stem has a solid 22.2mm >> diameter extension, and the steel stem is 31.8mm OD w/ 25.4mm ID extension. >> The extension into the fork vs. clamping on the outside of the fork are not >> significant here. >> By the way, neither stem deflects that much. >> If you really want a stiff stem, use a short extension, and big diameter. >> And steel too. >> And you know why they went to 31.8mm diameter handle bars? Because of the >> stinking cable grooves. The grooves make the bar section too flexible, the >> bigger diameter overcame this. >> Cheers! >> James Valiensi, PE >> Northridge, CA >> H818.775.1847 M.818.585.1796 >> >> On May 6, 2011, at 6:44 PM, Philip Williamson wrote: >> >> >> >>> When I got my Quickbeam, I tried a couple of stems, including the >>> stock Technomic Deluxe and the Nitto Dirt Drop. Both flexed noticeably >>> more than the Salsa welded stem I ended up with. The Dirt Drop not as >>> much as the Technomic Deluxe, but the quill was bottomed out in the >>> steerer. >> >>> Philip >> >>> On May 6, 9:24 am, "Bill M." wrote: Back in 1991 I bought a Cannondale (very stiff frame) that came with a standard quill stem. I swapped it out for a hollow, welded stem that had a much larger diameter extension. The first time I stood up and cranked the bike up a short steep rise I was astonished at how much stiffer the front end of the bike felt. The quill stem was allowing the bars to twist, the new one wasn't. >> That may or may not be seen as a good thing, but I have no doubt that typical threadless stems are stiffer in torsion than traditional quill stems. >> Bill >> On May 6, 3:58 am, MichaelH wrote: >> > The new RR contains an article by GP outlining his believes about > various aspects of bike strength, comfort, weight, and comfort. > There wasn't much new there for anyone who has followed him for a few > years, including why he prefers threaded headsets and stems, but it > did trigger this question from me. >> > My son, who is 39 years old and a very muscular 170 lbs claims that > he experiences stem flex while climbing with a traditional quill > stem. I am always disinclined to challenge people's subjective > experience but I have never experienced this and suspect it is in his > imagination. >> > Has anyone here felt their stem flex and has anyone ever broken a > stem? >> > michael >> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "RBW Owners Bunch" group. >>> To post to this group, send email to [email protected]. >>> To unsubscribe from this group, send email to >>> [email protected]. >>> For more options, visit this group >>> athttp://groups.google.com/group/rbw-owners-bunch?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Stem Strength
Actual, the polar moment of inertia is to the 4th power: PI()(D^4-d^4)/32. Cheers! James Valiensi, PE Northridge, CA H818.775.1847 M.818.585.1796 On May 7, 2011, at 5:29 AM, Ken Freeman wrote: > Ok, so the steel stem has a larger OD AND a stiffer modulus. Staying on the > back of an envelope, the ratio of 31.6^2 to 22.2^2 is about 2. In which case > your calc requires the ratio of moduli to be about 5. For steel it's about > 30,000 ksi and for aluminum it's about 10,000 ksi. > > Not bad, for the back of an envelope, and no finite element work!! > > On Sat, May 7, 2011 at 1:15 AM, James Valiensi wrote: > Hey, > My back of the envelope calc's indicate a standard aluminum quill stem will > deflect about ten times more than a steel stem. This is with equal extensions > lengths and loads, and the aluminum stem has a solid 22.2mm diameter > extension, and the steel stem is 31.8mm OD w/ 25.4mm ID extension. The > extension into the fork vs. clamping on the outside of the fork are not > significant here. > By the way, neither stem deflects that much. > If you really want a stiff stem, use a short extension, and big diameter. And > steel too. > And you know why they went to 31.8mm diameter handle bars? Because of the > stinking cable grooves. The grooves make the bar section too flexible, the > bigger diameter overcame this. > Cheers! > James Valiensi, PE > Northridge, CA > H818.775.1847 M.818.585.1796 > > > > On May 6, 2011, at 6:44 PM, Philip Williamson wrote: > > > When I got my Quickbeam, I tried a couple of stems, including the > > stock Technomic Deluxe and the Nitto Dirt Drop. Both flexed noticeably > > more than the Salsa welded stem I ended up with. The Dirt Drop not as > > much as the Technomic Deluxe, but the quill was bottomed out in the > > steerer. > > > > Philip > > > > > > On May 6, 9:24 am, "Bill M." wrote: > >> Back in 1991 I bought a Cannondale (very stiff frame) that came with a > >> standard quill stem. I swapped it out for a hollow, welded stem that > >> had a much larger diameter extension. The first time I stood up and > >> cranked the bike up a short steep rise I was astonished at how much > >> stiffer the front end of the bike felt. The quill stem was allowing > >> the bars to twist, the new one wasn't. > >> > >> That may or may not be seen as a good thing, but I have no doubt that > >> typical threadless stems are stiffer in torsion than traditional quill > >> stems. > >> > >> Bill > >> > >> On May 6, 3:58 am, MichaelH wrote: > >> > >> > >> > >> > >> > >> > >> > >>> The new RR contains an article by GP outlining his believes about > >>> various aspects of bike strength, comfort, weight, and comfort. > >>> There wasn't much new there for anyone who has followed him for a few > >>> years, including why he prefers threaded headsets and stems, but it > >>> did trigger this question from me. > >> > >>> My son, who is 39 years old and a very muscular 170 lbs claims that > >>> he experiences stem flex while climbing with a traditional quill > >>> stem. I am always disinclined to challenge people's subjective > >>> experience but I have never experienced this and suspect it is in his > >>> imagination. > >> > >>> Has anyone here felt their stem flex and has anyone ever broken a > >>> stem? > >> > >>> michael > > > > -- > > You received this message because you are subscribed to the Google Groups > > "RBW Owners Bunch" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group at > > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > > > > -- > Ken Freeman > Ann Arbor, MI USA > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Stem Strength
Ok, so the steel stem has a larger OD AND a stiffer modulus. Staying on the back of an envelope, the ratio of 31.6^2 to 22.2^2 is about 2. In which case your calc requires the ratio of moduli to be about 5. For steel it's about 30,000 ksi and for aluminum it's about 10,000 ksi. Not bad, for the back of an envelope, and no finite element work!! On Sat, May 7, 2011 at 1:15 AM, James Valiensi wrote: > Hey, > My back of the envelope calc's indicate a standard aluminum quill stem will > deflect about ten times more than a steel stem. This is with equal > extensions lengths and loads, and the aluminum stem has a solid 22.2mm > diameter extension, and the steel stem is 31.8mm OD w/ 25.4mm ID extension. > The extension into the fork vs. clamping on the outside of the fork are not > significant here. > By the way, neither stem deflects that much. > If you really want a stiff stem, use a short extension, and big diameter. > And steel too. > And you know why they went to 31.8mm diameter handle bars? Because of the > stinking cable grooves. The grooves make the bar section too flexible, the > bigger diameter overcame this. > Cheers! > James Valiensi, PE > Northridge, CA > H818.775.1847 M.818.585.1796 > > > > On May 6, 2011, at 6:44 PM, Philip Williamson wrote: > > > When I got my Quickbeam, I tried a couple of stems, including the > > stock Technomic Deluxe and the Nitto Dirt Drop. Both flexed noticeably > > more than the Salsa welded stem I ended up with. The Dirt Drop not as > > much as the Technomic Deluxe, but the quill was bottomed out in the > > steerer. > > > > Philip > > > > > > On May 6, 9:24 am, "Bill M." wrote: > >> Back in 1991 I bought a Cannondale (very stiff frame) that came with a > >> standard quill stem. I swapped it out for a hollow, welded stem that > >> had a much larger diameter extension. The first time I stood up and > >> cranked the bike up a short steep rise I was astonished at how much > >> stiffer the front end of the bike felt. The quill stem was allowing > >> the bars to twist, the new one wasn't. > >> > >> That may or may not be seen as a good thing, but I have no doubt that > >> typical threadless stems are stiffer in torsion than traditional quill > >> stems. > >> > >> Bill > >> > >> On May 6, 3:58 am, MichaelH wrote: > >> > >> > >> > >> > >> > >> > >> > >>> The new RR contains an article by GP outlining his believes about > >>> various aspects of bike strength, comfort, weight, and comfort. > >>> There wasn't much new there for anyone who has followed him for a few > >>> years, including why he prefers threaded headsets and stems, but it > >>> did trigger this question from me. > >> > >>> My son, who is 39 years old and a very muscular 170 lbs claims that > >>> he experiences stem flex while climbing with a traditional quill > >>> stem. I am always disinclined to challenge people's subjective > >>> experience but I have never experienced this and suspect it is in his > >>> imagination. > >> > >>> Has anyone here felt their stem flex and has anyone ever broken a > >>> stem? > >> > >>> michael > > > > -- > > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > [email protected]. > > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > > -- Ken Freeman Ann Arbor, MI USA -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Stem Strength
Hey, My back of the envelope calc's indicate a standard aluminum quill stem will deflect about ten times more than a steel stem. This is with equal extensions lengths and loads, and the aluminum stem has a solid 22.2mm diameter extension, and the steel stem is 31.8mm OD w/ 25.4mm ID extension. The extension into the fork vs. clamping on the outside of the fork are not significant here. By the way, neither stem deflects that much. If you really want a stiff stem, use a short extension, and big diameter. And steel too. And you know why they went to 31.8mm diameter handle bars? Because of the stinking cable grooves. The grooves make the bar section too flexible, the bigger diameter overcame this. Cheers! James Valiensi, PE Northridge, CA H818.775.1847 M.818.585.1796 On May 6, 2011, at 6:44 PM, Philip Williamson wrote: > When I got my Quickbeam, I tried a couple of stems, including the > stock Technomic Deluxe and the Nitto Dirt Drop. Both flexed noticeably > more than the Salsa welded stem I ended up with. The Dirt Drop not as > much as the Technomic Deluxe, but the quill was bottomed out in the > steerer. > > Philip > > > On May 6, 9:24 am, "Bill M." wrote: >> Back in 1991 I bought a Cannondale (very stiff frame) that came with a >> standard quill stem. I swapped it out for a hollow, welded stem that >> had a much larger diameter extension. The first time I stood up and >> cranked the bike up a short steep rise I was astonished at how much >> stiffer the front end of the bike felt. The quill stem was allowing >> the bars to twist, the new one wasn't. >> >> That may or may not be seen as a good thing, but I have no doubt that >> typical threadless stems are stiffer in torsion than traditional quill >> stems. >> >> Bill >> >> On May 6, 3:58 am, MichaelH wrote: >> >> >> >> >> >> >> >>> The new RR contains an article by GP outlining his believes about >>> various aspects of bike strength, comfort, weight, and comfort. >>> There wasn't much new there for anyone who has followed him for a few >>> years, including why he prefers threaded headsets and stems, but it >>> did trigger this question from me. >> >>> My son, who is 39 years old and a very muscular 170 lbs claims that >>> he experiences stem flex while climbing with a traditional quill >>> stem. I am always disinclined to challenge people's subjective >>> experience but I have never experienced this and suspect it is in his >>> imagination. >> >>> Has anyone here felt their stem flex and has anyone ever broken a >>> stem? >> >>> michael > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rbw-owners-bunch?hl=en. > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
