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Old January 10th 17, 08:53 PM posted to rec.bicycles.tech
Theodore Heise[_2_]
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Posts: 132
Default Need advice on bottom bracket repair

On Tue, 10 Jan 2017 15:15:58 +0700,
John B wrote:
On Mon, 09 Jan 2017 19:48:48 -0600, AMuzi wrote:
On 1/9/2017 7:44 PM, John B. wrote:
On Mon, 9 Jan 2017 22:17:31 +0000 (UTC), Theodore Heise
wrote:


Okay, I will try heating too.

You might want to know that as a general statement aluminum
bike frames are heat treated after welding and heating
aluminum to approximately 300 - 400 degrees C will anneal it.

As an aside, probably because of the ability of aluminum to
rapidly transfer heat, my experience in heating cylindrical
objects to enlarge them has been spotty at best. If you heat
the cylinder in an oven so that the entire devise is an equal
temperature then it will enlarge to a rather surprising
amount. If you try the same thing with a torch it doesn't
work so well as, I suspect, while you are heating one side
the other side is merrily transferring heat to the air or
supporting structure so what you end up with isn't a circle
but an oval.


No argument with any of that, good advise.

Moderate (120~150F) heat from a heat gun seems to help
penetrants. Lighting the work on fire may have entertainment
value, but probably won't help with the actual mission.


Yes it might work but I would suggest three or four heat guns
located radially on all sides to get as even a heat as
possible. Start the heating and than go off and have a cuppa or
watch youtube and come back "after a while" and try it.


Three to four heat guns sounds logical, but not practical. I've
already invested in about as large an arsenal of equipment as I
want. Maybe more.

--
Ted Heise Bloomington, IN, USA
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