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Need advice on bottom bracket repair



 
 
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  #101  
Old January 11th 17, 05:32 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,345
Default Need advice on bottom bracket repair

On Tuesday, January 10, 2017 at 4:28:53 PM UTC-8, Radey Shouman wrote:
writes:

On Tuesday, January 10, 2017 at 2:57:02 PM UTC-8, Radey Shouman wrote:
writes:

On Tuesday, January 10, 2017 at 12:23:50 PM UTC-8, Benderthe.evilrobot wrote:
wrote in message
...
On Tuesday, January 10, 2017 at 11:43:16 AM UTC-8, Benderthe.evilrobot
wrote:
"Doug Landau" wrote in message
...
On Monday, January 9, 2017 at 9:55:19 AM UTC-8, David Scheidt wrote:
Jeff Liebermann wrote:

:I want to know why it works at least twice as good as the others on
:the list.

My experience is that it doesn't. That's just one of the reasons no
one puts it in a can and sells it commercially. I read the original
article, a long time ago, and as I recall the testing method was about
as scientfic as drawing lots.

Commercial penetrating oils are far superior.


Coca-cola?


Apparently it contains phosphoric acid - which is also an ingredient of
some
rust treatments.

The rust is chemically converted into iron phosphate - the end result
bears
some resemblance to the metal equivalent of polystyrene cement.

Where did you get the idea that Coca Cola contains any sort of phosphate?
Other than phosphate salts, most phosphate compounds are poisonous.

From the ingredients label.

Citric Acid
Caffeine
Sugar
Water
Vanilla
Caramel

Which one of those is "phosphate"?

What's *your* source? I read

http://www.coca-colaproductfacts.com...cts/coca-cola/

and saw:

Carbonated water, high fructose corn syrup, caramel color,
phosphoric acid, natural flavors, caffeine.

The original allegation was that Coca Cola contains phosphoric
acid.

Buffered phosphoric acid, or "acid phosphate", was an ingredient in soda
fountain drinks for many years. Now you can buy it again:

http://prairiemoon.biz/Horsfords-Ext...oz_p_1427.html

Quaff in moderation, many claim that excessive phosphoric acid
consumption results in calcium loss from the skeleton.

--


A bottle of Coca Cola. I don't drink any softdrinks but always keep
that old bottle around to remind me why I don't. Maybe that's Mexican
though. This whole state is Hispanic now. There are sections of
Redwood City where there aren't a single sign in English. Even the bus
schedules are in Spanish.


Mexican Coca Cola uses cane sugar instead of high fructose corn syrup,
but it still contains phosphoric acid. Are you sure you don't have some
generic cola?
--


You know - it just occurred to me that the original Mexican coke had an entirely different formula and Coke got into all sorts of trouble marketing it here because the formula wasn't registered with the FDA. Maybe that's what I have. Now I don't even know where the hell I put it.
Ads
  #102  
Old January 11th 17, 07:58 PM posted to rec.bicycles.tech
Benderthe.evilrobot
external usenet poster
 
Posts: 128
Default Need advice on bottom bracket repair


"DATAKOLL MARINE RESEARCH" wrote in message
...
On Monday, January 9, 2017 at 5:17:33 PM UTC-5, Theodore Heise wrote:
On Sun, 8 Jan 2017 14:59:56 -0800 (PST),
DATAKOLL MARINE RESEARCH wrote:
On Sunday, January 8, 2017 at 12:59:14 PM UTC-5, Theodore Heise wrote:
On Sun, 8 Jan 2017 08:56:40 -0800 (PST),
wrote:


Ted, I don't quite follow. You are talking about using a
pin spanner and then say that you need to get the
adjustable cup off first. Isn't that what we were talking
about? The lock nut on the adjustable side and the fixed
cup do not use pin spanners as far as I know.

Sorry. I have the lock ring off on the left, non-drive side,
and am left with an adjustable cup that will only turn
partway. The fixed cup is still in place too (on the other
side), so the spindle is in place and blocks putting in the
bolt and nut that Sheldon describes.

For what it's worth, the fixed cup also seems to be pretty
stuck. It's an aluminum frame, so presumably the shell is
aluminum too and there may be some corrosion in the interface
between the two different metals of the shell and the cups?


if you search on aluminum/steel frame/shells/cups install or
remove there should be an avalanche of umbrage.

if your system shows white material in joints then poss an
ionic binding occurred between steel and aluminum. Andy Muzi is
an expert on this.

Blaster does not dissolve the white material. Uneeda torch and
another pin tool.

expanding aluminum with torch or heat gun will remove the cup.


Okay, I will try heating too.

--
Ted Heise Bloomington, IN, USA


try utube on heating with propane torch

small flame, cone above steel, wave flame around ext of where cup is
located inside, go around around slowly at 90 degrees if poss, with all
the other tools on hand.....have a vise ? place pin tool in vise n rotate
frame...wuhwuhwuh....

heat the steel until the grease inside the BB smakes a bt...keep an eye
on that...when smokes then slowly turn in one direction just a budge then
back then forward again...you hope...then back repeating.


Hot enough to make the grease smoke has probably ruined the temper of the
steel.

It may be worth considering sacrifice the bearing cup anyway - its cheaper
and easier to replace than the frame.

  #103  
Old January 11th 17, 07:59 PM posted to rec.bicycles.tech
Radey Shouman
external usenet poster
 
Posts: 1,747
Default Need advice on bottom bracket repair

writes:

On Tuesday, January 10, 2017 at 4:28:53 PM UTC-8, Radey Shouman wrote:
writes:

On Tuesday, January 10, 2017 at 2:57:02 PM UTC-8, Radey Shouman wrote:
writes:

On Tuesday, January 10, 2017 at 12:23:50 PM UTC-8,
Benderthe.evilrobot wrote:
wrote in message
...
On Tuesday, January 10, 2017 at 11:43:16 AM UTC-8,
Benderthe.evilrobot
wrote:
"Doug Landau" wrote in message
...
On Monday, January 9, 2017 at 9:55:19 AM UTC-8, David
Scheidt wrote:
Jeff Liebermann wrote:

:I want to know why it works at least twice as good as
the others on
:the list.

My experience is that it doesn't. That's just one of
the reasons no
one puts it in a can and sells it commercially. I read
the original
article, a long time ago, and as I recall the testing
method was about
as scientfic as drawing lots.

Commercial penetrating oils are far superior.


Coca-cola?


Apparently it contains phosphoric acid - which is also an
ingredient of
some
rust treatments.

The rust is chemically converted into iron phosphate - the
end result
bears
some resemblance to the metal equivalent of polystyrene cement.

Where did you get the idea that Coca Cola contains any sort
of phosphate?
Other than phosphate salts, most phosphate compounds are poisonous.

From the ingredients label.

Citric Acid
Caffeine
Sugar
Water
Vanilla
Caramel

Which one of those is "phosphate"?

What's *your* source? I read

http://www.coca-colaproductfacts.com...cts/coca-cola/

and saw:

Carbonated water, high fructose corn syrup, caramel color,
phosphoric acid, natural flavors, caffeine.

The original allegation was that Coca Cola contains phosphoric
acid.

Buffered phosphoric acid, or "acid phosphate", was an ingredient in soda
fountain drinks for many years. Now you can buy it again:

http://prairiemoon.biz/Horsfords-Ext...oz_p_1427.html

Quaff in moderation, many claim that excessive phosphoric acid
consumption results in calcium loss from the skeleton.

--

A bottle of Coca Cola. I don't drink any softdrinks but always keep
that old bottle around to remind me why I don't. Maybe that's Mexican
though. This whole state is Hispanic now. There are sections of
Redwood City where there aren't a single sign in English. Even the bus
schedules are in Spanish.


Mexican Coca Cola uses cane sugar instead of high fructose corn syrup,
but it still contains phosphoric acid. Are you sure you don't have some
generic cola?
--


I never heard of a generic coke bottle.


https://www.google.com/search?q=generic+cola&tbm=isch


--
  #104  
Old January 11th 17, 08:27 PM posted to rec.bicycles.tech
DATAKOLL MARINE RESEARCH
external usenet poster
 
Posts: 2,011
Default Need advice on bottom bracket repair

On Wednesday, January 11, 2017 at 2:58:37 PM UTC-5, Benderthe.evilrobot wrote:
"DATAKOLL MARINE RESEARCH" wrote in message
...
On Monday, January 9, 2017 at 5:17:33 PM UTC-5, Theodore Heise wrote:
On Sun, 8 Jan 2017 14:59:56 -0800 (PST),
DATAKOLL MARINE RESEARCH wrote:
On Sunday, January 8, 2017 at 12:59:14 PM UTC-5, Theodore Heise wrote:
On Sun, 8 Jan 2017 08:56:40 -0800 (PST),
wrote:

Ted, I don't quite follow. You are talking about using a
pin spanner and then say that you need to get the
adjustable cup off first. Isn't that what we were talking
about? The lock nut on the adjustable side and the fixed
cup do not use pin spanners as far as I know.

Sorry. I have the lock ring off on the left, non-drive side,
and am left with an adjustable cup that will only turn
partway. The fixed cup is still in place too (on the other
side), so the spindle is in place and blocks putting in the
bolt and nut that Sheldon describes.

For what it's worth, the fixed cup also seems to be pretty
stuck. It's an aluminum frame, so presumably the shell is
aluminum too and there may be some corrosion in the interface
between the two different metals of the shell and the cups?

if you search on aluminum/steel frame/shells/cups install or
remove there should be an avalanche of umbrage.

if your system shows white material in joints then poss an
ionic binding occurred between steel and aluminum. Andy Muzi is
an expert on this.

Blaster does not dissolve the white material. Uneeda torch and
another pin tool.

expanding aluminum with torch or heat gun will remove the cup.

Okay, I will try heating too.

--
Ted Heise Bloomington, IN, USA


try utube on heating with propane torch

small flame, cone above steel, wave flame around ext of where cup is
located inside, go around around slowly at 90 degrees if poss, with all
the other tools on hand.....have a vise ? place pin tool in vise n rotate
frame...wuhwuhwuh....

heat the steel until the grease inside the BB smakes a bt...keep an eye
on that...when smokes then slowly turn in one direction just a budge then
back then forward again...you hope...then back repeating.


Hot enough to make the grease smoke has probably ruined the temper of the
steel.

It may be worth considering sacrifice the bearing cup anyway - its cheaper
and easier to replace than the frame.


gnaw .....800 is a warm summer's day in Steelville.

propane doesn't turn steel from everday steel color to a different heat color tho there is increased oxidation prob nearing 800.....that is very visual.

oxidation tends to double every 10 degrees.

I dunno aluminum ...thin aluminum wrinkles but the expansion rate is greater.


  #106  
Old January 11th 17, 09:00 PM posted to rec.bicycles.tech
Phil Lee
external usenet poster
 
Posts: 248
Default Need advice on bottom bracket repair

Theodore Heise considered Tue, 10 Jan 2017 20:00:09
+0000 (UTC) the perfect time to write:

On Mon, 09 Jan 2017 22:20:13 -0800,
Jeff Liebermann wrote:
On Mon, 9 Jan 2017 22:24:41 -0000, "Benderthe.evilrobot"
wrote:

"Theodore Heise" wrote in message
...
On Sun, 08 Jan 2017 17:01:01 -0800,
Jeff Liebermann wrote:
On Sun, 08 Jan 2017 16:31:15 -0800, Jeff Liebermann
wrote:
(...)

Yet another untested idea...

Use an induction heater on the steel cup.
https://www.youtube.com/watch?v=MyZEaPQinO0
https://www.youtube.com/watch?v=YJElT9xK3bk
https://www.youtube.com/watch?v=uimEZKrVNO0
https://www.youtube.com/watch?v=3u1IBgefNDs [1]
http://www.theinductor.com
You'll need various size coils for different bolts, cups, seat posts,
etc. There are induction heater kits on eBay:
http://www.ebay.com/itm/1000W-ZVS-Low-Voltage-Induction-Heating-Board-Module-Flyback-Heater-Brass-Coil-/282317713643
The steel cup gets hot and not so much the rest of the bicycle,
including the aluminum bottom bracket which sucks away much of the
heat. However, you can get the steel hot enough to melt the aluminum,
so please use an IR thermometer to keep the temperatures down.
Aluminum melts at 660C.


Yikes!


Is there a problem?


Maybe, maybe not. I read "induction heater" and just assumed it
would be pretty complex, and possibly dangerous (to me and/or
bike). Maybe I goofed by not reading the links.


An electric heat gun is safer than a blowtorch - but I think
you still have to be a bit careful.

The heavy duty paint strippers aren't too bad, but some heat
guns are designed for lighting solid fuel cooking ranges.


The problem with external heat generators is that the heat
affected zone is rather large and will surely creep into
undesirable areas, such as painted parts.


No painted parts, it's polished aluminum.


...With an induction
heater, you only heat the steel parts. Aluminum only gets hot
as far as what it conducts away from the steel.

If you happen to have an induction cooktop stove, you can
demonstrate how this works. Put a steel pot on top of the
induction heater, and only the steel will get hot. Put an
aluminum, glass, or copper pan on the stovetop, and they stay
cold. Toss a coin with stainless (magnetic stainless mostly
works, non-magnetic does not).

It's the same with using an induction heater on the bottom
bracket. The steel components get hot, while the aluminum
bottom bracket and frame do not.

I don't propose heating the cup to red hot:

http://www.hearth.com/talk/attachments/metal-color-temp-chart-png.100306/
which is why I suggested an IR thermometer be used to monitor
the temperature.


Too much complexity/equipment for me, but thanks for the thoughts.


I'm slightly surprised by the lack of reference so far (at least that
I've seen) to the relative expansion rates of aluminium (the BB shell
and the rest of the frame) and steel (the bearing cup).
As aluminium expands at a much greater rate than steel, simply heating
the whole lot by any significant amount (say by pouring boiling water
over it) should ease the grip of the shell on the cup.
I've done this exact thing on components of many different things,
ranging from fairly complex engines to assorted plumbing!
  #107  
Old January 11th 17, 09:33 PM posted to rec.bicycles.tech
Phil Lee
external usenet poster
 
Posts: 248
Default Need advice on bottom bracket repair

considered Tue, 10 Jan 2017 12:28:12 -0800 (PST)
the perfect time to write:

On Tuesday, January 10, 2017 at 12:23:50 PM UTC-8, Benderthe.evilrobot wrote:
wrote in message
...
On Tuesday, January 10, 2017 at 11:43:16 AM UTC-8, Benderthe.evilrobot
wrote:
"Doug Landau" wrote in message
...
On Monday, January 9, 2017 at 9:55:19 AM UTC-8, David Scheidt wrote:
Jeff Liebermann wrote:

:I want to know why it works at least twice as good as the others on
:the list.

My experience is that it doesn't. That's just one of the reasons no
one puts it in a can and sells it commercially. I read the original
article, a long time ago, and as I recall the testing method was about
as scientfic as drawing lots.

Commercial penetrating oils are far superior.


Coca-cola?


Apparently it contains phosphoric acid - which is also an ingredient of
some
rust treatments.

The rust is chemically converted into iron phosphate - the end result
bears
some resemblance to the metal equivalent of polystyrene cement.

Where did you get the idea that Coca Cola contains any sort of phosphate?
Other than phosphate salts, most phosphate compounds are poisonous.


From the ingredients label.


Citric Acid
Caffeine
Sugar
Water
Vanilla
Caramel

Which one of those is "phosphate"?


Phosphoric Acid, which you somehow left out.
It appears on the label of (at least) Classic Coke, Cherry Coke, and
Vanilla Coke, which are all the varieties I have in reach at the
moment. I rather doubt that it would be absent from the rest of the
range.

As regards your "most phosphate compounds are poisonous" - so are many
things if taken in quantity, but almost all poisons have a safe dose,
below which they may be consumed (never mind used in a process like
the one proposed here).
Alcohol is a classic example of this, along with most other drugs
(legal or otherwise). To know if it is poisonous in the application
proposed, you would need to know the safe dosage levels.
I'm on several prescribed drugs which are potentially lethal, but as
long as I don't overdose, they do more good than harm.

Phosphorus is in fact a vital component of the human body, and
therefore, diet - you cannot generate any energy in any cell of your
body without adenosine triphosphate (ATP), and phosphorus (mostly in
the form of phosphates) makes up 1% of the human body (or 2% if you
ignore the water content) - the 6th most abundant element. As a
component of both DNA and RNA, it is actually essential for all known
life, and the average human body contains about a pound and a half of
it!
  #108  
Old January 11th 17, 09:36 PM posted to rec.bicycles.tech
[email protected]
external usenet poster
 
Posts: 3,345
Default Need advice on bottom bracket repair

On Wednesday, January 11, 2017 at 1:00:16 PM UTC-8, Phil Lee wrote:
Theodore Heise considered Tue, 10 Jan 2017 20:00:09
+0000 (UTC) the perfect time to write:

On Mon, 09 Jan 2017 22:20:13 -0800,
Jeff Liebermann wrote:
On Mon, 9 Jan 2017 22:24:41 -0000, "Benderthe.evilrobot"
wrote:

"Theodore Heise" wrote in message
...
On Sun, 08 Jan 2017 17:01:01 -0800,
Jeff Liebermann wrote:
On Sun, 08 Jan 2017 16:31:15 -0800, Jeff Liebermann
wrote:
(...)

Yet another untested idea...

Use an induction heater on the steel cup.
https://www.youtube.com/watch?v=MyZEaPQinO0
https://www.youtube.com/watch?v=YJElT9xK3bk
https://www.youtube.com/watch?v=uimEZKrVNO0
https://www.youtube.com/watch?v=3u1IBgefNDs [1]
http://www.theinductor.com
You'll need various size coils for different bolts, cups, seat posts,
etc. There are induction heater kits on eBay:
http://www.ebay.com/itm/1000W-ZVS-Low-Voltage-Induction-Heating-Board-Module-Flyback-Heater-Brass-Coil-/282317713643
The steel cup gets hot and not so much the rest of the bicycle,
including the aluminum bottom bracket which sucks away much of the
heat. However, you can get the steel hot enough to melt the aluminum,
so please use an IR thermometer to keep the temperatures down.
Aluminum melts at 660C.

Yikes!

Is there a problem?


Maybe, maybe not. I read "induction heater" and just assumed it
would be pretty complex, and possibly dangerous (to me and/or
bike). Maybe I goofed by not reading the links.


An electric heat gun is safer than a blowtorch - but I think
you still have to be a bit careful.

The heavy duty paint strippers aren't too bad, but some heat
guns are designed for lighting solid fuel cooking ranges.

The problem with external heat generators is that the heat
affected zone is rather large and will surely creep into
undesirable areas, such as painted parts.


No painted parts, it's polished aluminum.


...With an induction
heater, you only heat the steel parts. Aluminum only gets hot
as far as what it conducts away from the steel.

If you happen to have an induction cooktop stove, you can
demonstrate how this works. Put a steel pot on top of the
induction heater, and only the steel will get hot. Put an
aluminum, glass, or copper pan on the stovetop, and they stay
cold. Toss a coin with stainless (magnetic stainless mostly
works, non-magnetic does not).

It's the same with using an induction heater on the bottom
bracket. The steel components get hot, while the aluminum
bottom bracket and frame do not.

I don't propose heating the cup to red hot:

http://www.hearth.com/talk/attachments/metal-color-temp-chart-png.100306/
which is why I suggested an IR thermometer be used to monitor
the temperature.


Too much complexity/equipment for me, but thanks for the thoughts.


I'm slightly surprised by the lack of reference so far (at least that
I've seen) to the relative expansion rates of aluminium (the BB shell
and the rest of the frame) and steel (the bearing cup).
As aluminium expands at a much greater rate than steel, simply heating
the whole lot by any significant amount (say by pouring boiling water
over it) should ease the grip of the shell on the cup.
I've done this exact thing on components of many different things,
ranging from fairly complex engines to assorted plumbing!


I'm really surprised that Kragowsky hasn't simply showed his mechanical engineering prowess by giving the actual growth rate differentials over the size of a BB and the expected temperature differentials.

The expansion rates of aluminum ia .0000231 per degree C and hardened steel is .0000173 or even a little more. IF you could get an 80 degree total temperature increase in the frame/bottom bracket area (very unlikely with the coefficient of heat transmission of aluminum) which is an inch and a half wide, the total difference in diameter change would be nil.

What normally jams a bottom bracket cup is a piece of cutting from the threading of the area. This will even happen when chasing the threads if you don't VERY carefully clean the area. A cutting is a great deal larger than the difference in expansion of the metals that you're heating.

DAMN SCIENCE.
  #109  
Old January 11th 17, 09:39 PM posted to rec.bicycles.tech
Phil Lee
external usenet poster
 
Posts: 248
Default Need advice on bottom bracket repair

Radey Shouman considered Tue, 10 Jan 2017
19:28:51 -0500 the perfect time to write:

writes:

On Tuesday, January 10, 2017 at 2:57:02 PM UTC-8, Radey Shouman wrote:
writes:

On Tuesday, January 10, 2017 at 12:23:50 PM UTC-8, Benderthe.evilrobot wrote:
wrote in message
...
On Tuesday, January 10, 2017 at 11:43:16 AM UTC-8, Benderthe.evilrobot
wrote:
"Doug Landau" wrote in message
...
On Monday, January 9, 2017 at 9:55:19 AM UTC-8, David Scheidt wrote:
Jeff Liebermann wrote:

:I want to know why it works at least twice as good as the others on
:the list.

My experience is that it doesn't. That's just one of the reasons no
one puts it in a can and sells it commercially. I read the original
article, a long time ago, and as I recall the testing method was about
as scientfic as drawing lots.

Commercial penetrating oils are far superior.


Coca-cola?


Apparently it contains phosphoric acid - which is also an ingredient of
some
rust treatments.

The rust is chemically converted into iron phosphate - the end result
bears
some resemblance to the metal equivalent of polystyrene cement.

Where did you get the idea that Coca Cola contains any sort of phosphate?
Other than phosphate salts, most phosphate compounds are poisonous.

From the ingredients label.

Citric Acid
Caffeine
Sugar
Water
Vanilla
Caramel

Which one of those is "phosphate"?

What's *your* source? I read

http://www.coca-colaproductfacts.com...cts/coca-cola/

and saw:

Carbonated water, high fructose corn syrup, caramel color,
phosphoric acid, natural flavors, caffeine.

The original allegation was that Coca Cola contains phosphoric
acid.

Buffered phosphoric acid, or "acid phosphate", was an ingredient in soda
fountain drinks for many years. Now you can buy it again:

http://prairiemoon.biz/Horsfords-Ext...oz_p_1427.html

Quaff in moderation, many claim that excessive phosphoric acid
consumption results in calcium loss from the skeleton.

--


A bottle of Coca Cola. I don't drink any softdrinks but always keep
that old bottle around to remind me why I don't. Maybe that's Mexican
though. This whole state is Hispanic now. There are sections of
Redwood City where there aren't a single sign in English. Even the bus
schedules are in Spanish.


Mexican Coca Cola uses cane sugar instead of high fructose corn syrup,
but it still contains phosphoric acid. Are you sure you don't have some
generic cola?


Or completely fake Coke, which is far from unheard of.
Many popular brands suffer from faking, and some fakes are fairly
difficult to detect - especially in places where container recycling
is commonplace, and the fakers can get hold or genuine containers,
complete with label.
  #110  
Old January 11th 17, 09:44 PM posted to rec.bicycles.tech
Benderthe.evilrobot
external usenet poster
 
Posts: 128
Default Need advice on bottom bracket repair


"Phil Lee" wrote in message
...
Theodore Heise considered Tue, 10 Jan 2017 20:00:09
+0000 (UTC) the perfect time to write:

On Mon, 09 Jan 2017 22:20:13 -0800,
Jeff Liebermann wrote:
On Mon, 9 Jan 2017 22:24:41 -0000, "Benderthe.evilrobot"
wrote:

"Theodore Heise" wrote in message
...
On Sun, 08 Jan 2017 17:01:01 -0800,
Jeff Liebermann wrote:
On Sun, 08 Jan 2017 16:31:15 -0800, Jeff Liebermann

wrote:
(...)

Yet another untested idea...

Use an induction heater on the steel cup.
https://www.youtube.com/watch?v=MyZEaPQinO0
https://www.youtube.com/watch?v=YJElT9xK3bk
https://www.youtube.com/watch?v=uimEZKrVNO0
https://www.youtube.com/watch?v=3u1IBgefNDs [1]
http://www.theinductor.com
You'll need various size coils for different bolts, cups, seat
posts,
etc. There are induction heater kits on eBay:
http://www.ebay.com/itm/1000W-ZVS-Low-Voltage-Induction-Heating-Board-Module-Flyback-Heater-Brass-Coil-/282317713643
The steel cup gets hot and not so much the rest of the bicycle,
including the aluminum bottom bracket which sucks away much of the
heat. However, you can get the steel hot enough to melt the
aluminum,
so please use an IR thermometer to keep the temperatures down.
Aluminum melts at 660C.

Yikes!

Is there a problem?


Maybe, maybe not. I read "induction heater" and just assumed it
would be pretty complex, and possibly dangerous (to me and/or
bike). Maybe I goofed by not reading the links.


An electric heat gun is safer than a blowtorch - but I think
you still have to be a bit careful.

The heavy duty paint strippers aren't too bad, but some heat
guns are designed for lighting solid fuel cooking ranges.

The problem with external heat generators is that the heat
affected zone is rather large and will surely creep into
undesirable areas, such as painted parts.


No painted parts, it's polished aluminum.


...With an induction
heater, you only heat the steel parts. Aluminum only gets hot
as far as what it conducts away from the steel.

If you happen to have an induction cooktop stove, you can
demonstrate how this works. Put a steel pot on top of the
induction heater, and only the steel will get hot. Put an
aluminum, glass, or copper pan on the stovetop, and they stay
cold. Toss a coin with stainless (magnetic stainless mostly
works, non-magnetic does not).

It's the same with using an induction heater on the bottom
bracket. The steel components get hot, while the aluminum
bottom bracket and frame do not.

I don't propose heating the cup to red hot:

http://www.hearth.com/talk/attachments/metal-color-temp-chart-png.100306/
which is why I suggested an IR thermometer be used to monitor
the temperature.


Too much complexity/equipment for me, but thanks for the thoughts.


I'm slightly surprised by the lack of reference so far (at least that
I've seen) to the relative expansion rates of aluminium (the BB shell
and the rest of the frame) and steel (the bearing cup).
As aluminium expands at a much greater rate than steel, simply heating
the whole lot by any significant amount (say by pouring boiling water
over it) should ease the grip of the shell on the cup.
I've done this exact thing on components of many different things,
ranging from fairly complex engines to assorted plumbing!


Boiling water frequently doesn't get the job done - and its guaranteed not
to if someone previously used thread-lock.

 




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