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Path: ...!news.nobody.at!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: AMuzi <am@yellowjersey.org> Newsgroups: rec.bicycles.tech Subject: Re: tech: physics and materials Date: Fri, 30 Aug 2024 07:43:06 -0500 Organization: Yellow Jersey, Ltd. Lines: 94 Message-ID: <vaseor$fvkb$3@dont-email.me> References: <va4p2l$3s780$1@dont-email.me> <4tsbcjlcsonq1tnhproltl9kra0t3548v0@4ax.com> <va4vo7$3tfjf$1@dont-email.me> <va5amp$3v0r0$1@dont-email.me> <va5bf9$3utec$1@dont-email.me> <9kamcjdvi08cktndk1nln90um2r0pl6raj@4ax.com> <f1m2dj1dl51md67avocu0g1mcfgsj96bdd@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Fri, 30 Aug 2024 14:43:07 +0200 (CEST) Injection-Info: dont-email.me; posting-host="5057c23df029c85fdfdee10c2fe760ae"; logging-data="523915"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19MJoOJkq7WD7q/u/c9krHr" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Vj2pHv3fc7B1VZWh7ouRj4zsCFk= In-Reply-To: <f1m2dj1dl51md67avocu0g1mcfgsj96bdd@4ax.com> Content-Language: en-US Bytes: 5173 On 8/30/2024 12:27 AM, John B. wrote: > On Sun, 25 Aug 2024 20:01:15 +0700, John B. <slocombjb@gmail.com> > wrote: > >> On Wed, 21 Aug 2024 13:25:44 -0500, AMuzi <am@yellowjersey.org> wrote: >> >>> On 8/21/2024 1:12 PM, Frank Krygowski wrote: >>>> On 8/21/2024 11:05 AM, AMuzi wrote: >>>>> On 8/21/2024 9:07 AM, John B. wrote: >>>>>> On Wed, 21 Aug 2024 07:55:51 -0500, AMuzi >>>>>> <am@yellowjersey.org> wrote: >>>>>> >>>>>>> Our customer wants higher handlebars. We sold him a new >>>>>>> bike and as usual I asked for dimensions from post to >>>>>>> handlebar on centers and handlebar to ground from his old >>>>>>> bike. That's a tall riding position: >>>>>>> >>>>>>> http://www.yellowjersey.org/daily.html >>>>>>> >>>>>>> Since the new model has a carbon steerer, I swapped in an >>>>>>> aluminum column carbon blade fork of same dimensions. >>>>>>> >>>>>>> I reasoned that modern aluminum bars are farther from the >>>>>>> stem clamp (stress riser) to the bottom, where climbers >>>>>>> pull >>>>>>> forcefully, than from the top bearing to the stem. >>>>>>> Handlebars are thinner than columns with cold formed curves >>>>>>> of various radii while columns are a simple cylinder. >>>>>>> Failures in handlebars are rare now (usually >>>>>>> precipitated by >>>>>>> crash damage, corrosion or both) as are threadless column >>>>>>> failures (I have never seen one) so I can't reasonably >>>>>>> assess frequency. This was intuitive not calculated. >>>>>>> >>>>>>> The new wrinkle is that after 50 miles he says another 50mm >>>>>>> would be better. Yikes! That's a lot, and the local shop >>>>>>> refused to add an extender: >>>>>>> >>>>>>> https://www.yellowjersey.org/UPSTEM.JPG >>>>>>> >>>>>>> They also refused to run longer gear cables and brake line >>>>>>> if he installed the extender himself. >>>>>>> >>>>>>> I was OK with the bike as delivered but I'm not so sure >>>>>>> about more height. Comments? >>>>>> >>>>>> If I was in business and a similar question came up I >>>>>> believe I would >>>>>> contact the manufacturer or U.S. Distributor. >>>>> >>>>> I did, naturally. >>>>> Carbon steerers warn about maximum stem height over top >>>>> bearing (and reasonably so IMHO) but there aren't firm >>>>> limits for metal columns. >>>> >>>> That's a very tall setup, all right. I think the bike is >>>> severely undersized for the rider, and a much bigger frame >>>> would be the real solution. I'd be very wary of going any >>>> higher - not that I have your experience viewing failures. >>>> >>>> This phrasing confused me: "modern aluminum bars are farther >>>> from the stem clamp (stress riser) to the bottom, where >>>> climbers pull forcefully, than from the top bearing to the >>>> stem." >>>> >>>> But loads applied in bicycling are largely unknown and vary >>>> tremendously with the individual, which makes any attempt at >>>> calculations impossible. Will this guy really be pulling on >>>> the bars while doing steep climbs? >>>> >>>> Vaguely related: Our Bike Friday New World Tourists >>>> https://www.flickr.com/photos/16972296@N08/7410976626/in/dateposted-public/ have extremely tall gooseneck stems, made of steel. Mine flexes disconcertingly when I pull on the bars while climbing. I'm told it's also tough on the headset. >>>> >>> >>> Yes, many unknowns and that's why my decision was intuitive, >>> not calculated. >>> >>> He can't stand over a 61. This is a 59. It's not a frame >>> size problem so much as a customer who wants to ride a race >>> bike like an omafeits. >> >> Qomafeits? Theru ;look much like tjhe bocycles of my youth. Double >> tpo[ bar stromg enogh top,catryour buddy sittimhg side saddler. >> Rtneel z'i;e/ > > Good Lord, where did that come from? Good question. It displays under my header but I did not write that. -- Andrew Muzi am@yellowjersey.org Open every day since 1 April, 1971