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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: RE: Re: Machine Shop
Date: Tue, 4 Mar 2025 23:31:31 -0500
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On 3/4/2025 4:43 PM, cyclintom wrote:
> On Sun Feb 23 08:52:41 2025 AMuzi  wrote:
>> On 2/22/2025 4:21 PM, Frank Krygowski 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.
>>>
>>> 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.
>>>
>>> What Tom is describing is his usual mix of lying and fantasy
>>> and ignorance.
>>>
>>
>> Methods to form, or re form, steel are irrelevant here.
>>
>> The principle is that once you're beyond the elastic limit,
>> the piece will have measurable deformation. That's a crystal
>> slip, i.e., the structure of the material has changed.
>>
>> Regardless of human decisions after that (re form,
>> cosmetically cover such as lead fill or bondo, replace the
>> damaged piece, throw out the unit) the material has changed;
>> it's not going to spontaneously pop back to pre-strain shape.
> 
> 
> 
> Andrew, if you look at a framed house after it has sat there for awhile you will not see most of the hammer marks on the wood because there is a wide space betweed yield strength ad ellastic limit and in the cases of good framers, those limits are not exceeded. while the distance between those points is narrower with steel, they still exist. Don't be fooled into thinking that any deformation means the elastic limits have been exceeded or that if it doesn't rebound immediately yield strength has not been exceeded.

Yup. Like talking to a wall.

-- 
- Frank Krygowski