Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Frank Krygowski Newsgroups: rec.bicycles.tech Subject: Re: Machine Shop Date: Tue, 4 Mar 2025 23:04:14 -0500 Organization: A noiseless patient Spider Lines: 58 Message-ID: References: <4edkrj13v11bkgfpmgcr58psf6v64j906f@4ax.com> Reply-To: frkrygow@gmail.com MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Wed, 05 Mar 2025 05:04:16 +0100 (CET) Injection-Info: dont-email.me; posting-host="e45c4557a9a8cc0980efe60bc42cb36a"; logging-data="2397547"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/oRCXCKriTrKMxoOQTwQNgodDaKJ8NYK0=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:1xTcdIq3UWAbp+AG3hTSxzIWtLM= In-Reply-To: Content-Language: en-US Bytes: 3824 On 3/4/2025 3:06 PM, AMuzi wrote: > On 3/4/2025 11:03 AM, Frank Krygowski wrote: >> On 3/4/2025 12:44 AM, AMuzi wrote: >>> >>> For a typical dent, this Waterford for example: >>> http://www.yellowjersey.org/wfd12a.jpg >>> >>> the tube is rolled to reform the greater part of the deformation: >>> >>> http://www.yellowjersey.org/wfd12b.jpg >>> >>> then the remaining low spots are filled with polyester bondo or with >>> metal (brass, silver, lead. I use lead): >>> >>> http://www.yellowjersey.org/wfd12c.jpg >>> >>> and finished: >>> >>> http://www.yellowjersey.org/wfd12e.jpg >> >> Could you explain what's meant by "the tube is rolled"? As I said >> earlier, I'd thought the first step would be pushing a mandrel through >> (if the dent was in the seatpost) to partially push out the dent. Of >> course, that wouldn't work except on a seat tube, and I suppose would >> still require filling. Are you skipping that step entirely? >> >> BTW, my antique BMW has a slight dent in the top of the gas tank, >> apparently from something falling onto it. I've heard of "paintless >> dent repair" for car bodies and wondered about it, but never looked >> deeply into it. I gather that some skilled body workers can do pretty >> well at pushing dents back out from the underside. >> > > Can't generally fit anything inside a bicycle frame tube in any > reasonable time. Taking a frame apart is more than a magnitude of labor > greater than the cost of a tube. Once apart, you'd just replace it > rather than repair. > > Here's one set of steel blocks for rolling dents. > > http://www.yellowjersey.org/photosfromthepast/den24a.jpg So how exactly are the blocks used? Are the blocks tightened in place and rotated around the tube? > > I have various diameters. On oval tube of course there are limited > options. I generally don't take those jobs except where the dent is > minimal: > > https://www.yellowjersey.org/photosfromthepast/denw25a.jpg It occurred to me after posting that forcing a mandrel inside the tube might cause some of the metal around the dent to bulge outward. I can see why you wouldn't want that to happen. -- - Frank Krygowski