DDDDOOOOOHH! I knew that, once upon a time! Cheers, back!
On Saturday, May 7, 2011, James Valiensi <valie...@mac.com> wrote: > Actual, the polar moment of inertia is to the 4th power: > PI()(D^4-d^4)/32.Cheers! > > James Valiensi, PENorthridge, CAH818.775.1847 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 <valie...@mac.com> 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." <bmenn...@comcast.net> 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 <mhech...@gmail.com> 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 rbw-owners-bunch@googlegroups.com. >> To unsubscribe from this group, send email to >> rbw-owners-bunch+unsubscr...@googlegroups.com. >> 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 > > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To post to this group, send email to rbw-owners-bunch@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > 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 rbw-owners-bunch@googlegroups.com. > To unsubscribe from this group, send email to > rbw-owners-bunch+unsubscr...@googlegroups.com. > 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. 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