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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Machine Shop
Date: Tue, 4 Mar 2025 14:07:12 -0600
Organization: Yellow Jersey, Ltd.
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On 3/4/2025 11:24 AM, Zen Cycle wrote:
> On 3/4/2025 12:44 AM, AMuzi wrote:
>> On 3/3/2025 5:30 PM, Jeff Liebermann wrote:
>>> On Sat, 22 Feb 2025 17:21:55 -0500, Frank Krygowski
>>> <frkrygow@sbcglobal.net> wrote:
>>>
>>>> On 2/22/2025 4:06 PM, Jeff Liebermann wrote:
>>>>> On Sat, 22 Feb 2025 19:58:29 GMT, cyclintom 
>>>>> <cyclintom@yahoo.com>
>>>>> wrote:
>>>>>
>>>>>> On Fri Nov 8 14:03:46 2024 Frank Krygowski  wrote:
>>>>>>> It doesn't exist, Tom. You can't pop a dent out a 
>>>>>>> bicycle frame tube by
>>>>>>> riding the bike. Thinking you can is a sign of insanity.
>>>>>>
>>>>>> If you have a slight dent in high performance steel. 
>>>>>> the tubing can revert to its natural shape under stress.
>>>>>
>>>>> Tom.  The only steel that might do that is spring steel 
>>>>> (1095, 1060,
>>>>> 1075, 1080, etc).  Bicycle frames are not made from 
>>>>> spring steel.  If
>>>>> they were made from spring steel, they would ride like 
>>>>> the proverbial
>>>>> wet noodle.
>>>>>
>>>>> So, what's the SAE/AISI number for such a spring steel 
>>>>> bicycle frame
>>>>> and who is selling such bicycles?
>>>>> <https://www.azom.com/article.aspx?ArticleID=6151>
>>>>> Since you claim that you fixed the dent on YOUR 
>>>>> bicycle, could I
>>>>> trouble you for the maker and model number of this 
>>>>> bicycle so I can
>>>>> determine steel alloy that was used?  Some photos of 
>>>>> the dent, before
>>>>> and after, would also be nice.
>>>>>
>>>>> Note that I'm not talking about shape memory metal alloys:
>>>>> <https://en.wikipedia.org/wiki/Shape-memory_alloy>
>>>>>
>>>>> I'm also not talking about hydroforming, which doesn't 
>>>>> work at
>>>>> removing dents in steel tubing without high pressure 
>>>>> hydraulic
>>>>> assistance.  It's commonly used for bending aluminum 
>>>>> frames.  You
>>>>> obviously don't have the necessary equipment in your 
>>>>> garage workshop
>>>>> because you claimed that the dent popped out after 
>>>>> simply riding the
>>>>> bicycle:
>>>>> <https://www.bikeforums.net/bicycle-mechanics/919494- 
>>>>> ding-removal.html>
>>>>>
>>>>>> Where the hell do you get off not knowing the 
>>>>>> properties of tempered steel and commenting on it?
>>>>>
>>>>> Frank, he's all yours now.
>>>
>>>> Sorry, I'm going to disagree with you about spring 
>>>> steel. AFAIK there is
>>>> _no_ steel that would spontaneously cure a dent in a 
>>>> bicycle tube from
>>>> riding stresses. If the steel is dented, it's been 
>>>> stressed in that
>>>> location beyond its yield point. There's no practical 
>>>> way for that to
>>>> spontaneously reverse itself.
>>>
>>> That's correct.  However, you're reading too much into my 
>>> mention of
>>> 1095 steel being "spring steel".
>>> <https://www.mcmaster.com/mvD/pdf/116/3630.pdf>
>>> 1095 is a steel alloy that can be used for making steel 
>>> springs.  It
>>> can also be used for making knife blades, where the a 
>>> springy steel
>>> makes the blade more durable.  The major difference is 
>>> the steel
>>> spring is fairly thin, while the knife blade is much 
>>> thicker.  Same
>>> spring effect, but very different products.
>>>
>>>> While Andrew knows much more than I about the applicable 
>>>> shop
>>>> techniques, I think you might be able to partially 
>>>> remove a dent in a
>>>> tube if, like a seat tube, you had access to an open 
>>>> end. Perhaps
>>>> forcing in a series of mandrels of increasing diameter 
>>>> could gradually
>>>> force the dent outward. (Something similar is done to 
>>>> repair dents in
>>>> the tubing of brass instruments like trumpets.) But I 
>>>> doubt it would
>>>> give a perfect result, and I think cosmetic repair 
>>>> (maybe Bondo?) would
>>>> be needed to get it really pretty.
>>>
>>> Some kind of flexible automobile body putty (usually an 
>>> epoxy) would
>>> work.  I had the left seat stay, on my Miyata 610 touring 
>>> bicycle,
>>> repaired professionally.  I didn't paint it.  I'm sure if 
>>> I had, there
>>> would be no evidence of the repair remaining.
>>> <https://www.learnbydestroying.com/jeffl/pics/bicycles/ 
>>> Miyata-610.JPG>
>>> It's the rust colored section of the left seat stay.  
>>> Unfortunately, I
>>> didn't see the work and cannot describe how it was done.
>>>
>>>> What Tom is describing is his usual mix of lying and 
>>>> fantasy and ignorance.
>>>
>>> Yep.  After so many years of cultivating Tom's fertile 
>>> imagination,
>>> all that has grown were poisonous flowers and ugly weeds.
>>>
>>>
>>
>> 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
>>
> 
>   Would you consider this type of repair on an aluminum frame?
> 

Nope.  Someone else might but it's really not my area.

-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971