Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old September 15th 20, 12:47 PM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

I'm thinking of making a tool to be slid up inside a bicycle frame down
tube that would expand and push out dents from the inside.

I have been thinking about two different inter-acting problems.

1. how to manipulate the tool - so far the best solution is to have it
have one part a curved shoe with two bowden cables attached; both cables
go in from one side of the BB shell if the dent is on the side, and one
from each side if the dent is top/bottom. The cables outers should be
stiff enough the push/pull and twist it. Each cable will go out to a
handlebar (what else?) with two stout brake-levers mounted.

2. how to expand and contract the other part of the tool - I am not sure
if contracting it will be a problem but want a positive method anyway,
don't want the bloody thing left up there; not sure I can trust a spring.
I can't decide whether to use a toggle, or a screw at 90 degrees to the
long axis of the tube. The tube wall will be at most 1.5mm thick, often
less, dents might be as much as 5mm deep.

A toggle might be tricky to fit inside a tube, so I'm leaning toward a
screw with a ratcheting cross-lever operated by the two bowden cables.
That'd be a bit of a bother as I think the ratcheting will be insert -
place - push - remove - advance ratchet - repeat. A toggle might allow
all the push to be done at one go, but getting positive contraction is
not a simple as with a screw - and as well I am not sure the cable would
take the strain needed to push the dent out. Toggle mechanical advantage
is best at the angle most constrained by tube diameter, there is probably
less than an inch to work inside.

I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.

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Old September 15th 20, 01:01 PM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

"charliebrown" wrote in message ...

I'm thinking of making a tool to be slid up inside a bicycle frame down
tube that would expand and push out dents from the inside.
================================
Shotgun barrel dent remover:
https://www.bevfitchett.us/repair-of...rms/a-bks.html


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Old September 15th 20, 02:29 PM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

On Tue, 15 Sep 2020 10:47:52 +0000 (UTC)
charliebrown wrote:

snip
I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


You might want to consider hydraulics too. Like a miniature
jack/expander that could slip inside. It could have its own spring
return. Maybe design for the high pressure hose to both fit and allow
you to move it around inside the tube...

--
Leon Fisk
Grand Rapids MI

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Old September 17th 20, 02:52 AM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

"Leon Fisk" wrote in message ...

On Tue, 15 Sep 2020 10:47:52 +0000 (UTC)
charliebrown wrote:

snip
I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


You might want to consider hydraulics too. Like a miniature
jack/expander that could slip inside. It could have its own spring
return. Maybe design for the high pressure hose to both fit and allow
you to move it around inside the tube...

Leon Fisk
Grand Rapids MI

=====================

Grease gun hose and copper-nickel brake line are thin, flexible tubes that
hold high pressure and connect with pipe threads. I'd start by finding a
small enough hydraulic piston seal and designing the cylinder around it.
Maybe a gas strut could be modified.

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Old September 18th 20, 10:44 AM posted to rec.crafts.metalworking
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Posts: 1,990
Default design descisions for internal tube expander

On Tuesday, September 15, 2020 at 3:48:01 AM UTC-7, charliebrown wrote:
I'm thinking of making a tool to be slid up inside a bicycle frame down
tube that would expand and push out dents from the inside.


Instead of a press, why not use an internal hammer?
Just get a heavy rod, set it into the tube, and slam the whole frame
down onto a sturdy table; the rod's inertia will hammer the dent
out.

Another popular solution is to force a large hardened BB through the tube.


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Old September 18th 20, 01:36 PM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

"Jim Wilkins" wrote in message ...

"Leon Fisk" wrote in message ...

On Tue, 15 Sep 2020 10:47:52 +0000 (UTC)
charliebrown wrote:

snip
I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


You might want to consider hydraulics too. Like a miniature
jack/expander that could slip inside. It could have its own spring
return. Maybe design for the high pressure hose to both fit and allow
you to move it around inside the tube...

Leon Fisk
Grand Rapids MI

=====================

Grease gun hose and copper-nickel brake line are thin, flexible tubes that
hold high pressure and connect with pipe threads. I'd start by finding a
small enough hydraulic piston seal and designing the cylinder around it.
Maybe a gas strut could be modified.

================================================== ===
A similar idea:
http://forums.pelicanparts.com/911-9...-expander.html

Notice that he modified parts on his metal lathe. The job may not be
possible without one.

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Old September 18th 20, 02:18 PM posted to rec.crafts.metalworking
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Default design descisions for internal tube expander

On Fri, 18 Sep 2020 07:36:17 -0400
"Jim Wilkins" wrote:

"Jim Wilkins" wrote in message ...

"Leon Fisk" wrote in message ...

On Tue, 15 Sep 2020 10:47:52 +0000 (UTC)
charliebrown wrote:

snip
I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


You might want to consider hydraulics too. Like a miniature
jack/expander that could slip inside. It could have its own spring
return. Maybe design for the high pressure hose to both fit and allow
you to move it around inside the tube...

Leon Fisk
Grand Rapids MI

=====================

Grease gun hose and copper-nickel brake line are thin, flexible tubes that
hold high pressure and connect with pipe threads. I'd start by finding a
small enough hydraulic piston seal and designing the cylinder around it.
Maybe a gas strut could be modified.

================================================= ====
A similar idea:
http://forums.pelicanparts.com/911-9...-expander.html

Notice that he modified parts on his metal lathe. The job may not be
possible without one.


That's a nice article. Both the failures and solutions to what he was
trying to do

I'd hazard a guess that if I was to poke around in the Patent database
I'd find some interesting items that pertain to this subject. Seeing
how Charlie Brown hasn't been back to comment I don't think it's worth
my time. I'm not that interested in making such an item ;-)

--
Leon Fisk
Grand Rapids MI

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Old September 18th 20, 05:53 PM posted to rec.crafts.metalworking
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First recorded activity by DIYBanter: Jun 2011
Posts: 5,744
Default design descisions for internal tube expander

"Leon Fisk" wrote in message ...

On Fri, 18 Sep 2020 07:36:17 -0400
"Jim Wilkins" wrote:

"Jim Wilkins" wrote in message ...

"Leon Fisk" wrote in message ...

On Tue, 15 Sep 2020 10:47:52 +0000 (UTC)
charliebrown wrote:

snip
I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


You might want to consider hydraulics too. Like a miniature
jack/expander that could slip inside. It could have its own spring
return. Maybe design for the high pressure hose to both fit and allow
you to move it around inside the tube...

Leon Fisk
Grand Rapids MI

=====================

Grease gun hose and copper-nickel brake line are thin, flexible tubes that
hold high pressure and connect with pipe threads. I'd start by finding a
small enough hydraulic piston seal and designing the cylinder around it.
Maybe a gas strut could be modified.

================================================= ====
A similar idea:
http://forums.pelicanparts.com/911-9...-expander.html

Notice that he modified parts on his metal lathe. The job may not be
possible without one.


That's a nice article. Both the failures and solutions to what he was
trying to do

I'd hazard a guess that if I was to poke around in the Patent database
I'd find some interesting items that pertain to this subject. Seeing
how Charlie Brown hasn't been back to comment I don't think it's worth
my time. I'm not that interested in making such an item ;-)

Leon Fisk
Grand Rapids MI

=====================================

I am, mildly, to tighten the excessively loose fit of the slip joints in the
chain link fence top rail I use for my antenna mast. The exhaust pipe tool
might work if I can find it. Also I acquired a collapsed tube-framed tarp
garage that could be rearranged into a smaller snow blower shelter if I
could swage the tube ends to join them. I re-roofed it twice for the owner
by attaching a new tarp to PT wood strips screwed to the tubes.

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Old September 18th 20, 09:25 PM posted to rec.crafts.metalworking
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First recorded activity by DIYBanter: Aug 2008
Posts: 2,104
Default design descisions for internal tube expander

On Tuesday, September 15, 2020 at 6:48:01 AM UTC-4, charliebrown wrote:
I'm thinking of making a tool to be slid up inside a bicycle frame down
tube that would expand and push out dents from the inside.

I have been thinking about two different inter-acting problems.

1. how to manipulate the tool - so far the best solution is to have it
have one part a curved shoe with two bowden cables attached; both cables
go in from one side of the BB shell if the dent is on the side, and one
from each side if the dent is top/bottom. The cables outers should be
stiff enough the push/pull and twist it. Each cable will go out to a
handlebar (what else?) with two stout brake-levers mounted.

2. how to expand and contract the other part of the tool - I am not sure
if contracting it will be a problem but want a positive method anyway,
don't want the bloody thing left up there; not sure I can trust a spring.
I can't decide whether to use a toggle, or a screw at 90 degrees to the
long axis of the tube. The tube wall will be at most 1.5mm thick, often
less, dents might be as much as 5mm deep.

A toggle might be tricky to fit inside a tube, so I'm leaning toward a
screw with a ratcheting cross-lever operated by the two bowden cables.
That'd be a bit of a bother as I think the ratcheting will be insert -
place - push - remove - advance ratchet - repeat. A toggle might allow
all the push to be done at one go, but getting positive contraction is
not a simple as with a screw - and as well I am not sure the cable would
take the strain needed to push the dent out. Toggle mechanical advantage
is best at the angle most constrained by tube diameter, there is probably
less than an inch to work inside.

I also thought about a screw-operated pair of wedges - but the
manipulation arm would have to be able to take torque as well, yet be
flexible enough to bend through the 90 degrees of the bb shell/tube
joint. A pair of wedges could be operated by cables, but again would the
advantage be sufficient given the limit of the cable.


Don't know whether this is going to help, but this:
https://youtu.be/zEL-qJuaMN8 is how they get dents out of brass musical instrument tubes. Of course you'd have to scale up the sturdiness of the tools and use a hammer on the outside, but it ought to work.


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