Soldering iron to patch tubes?

Phil Lee said:

The idea is just as it seems... melt the rubber to seal the hole.

Anyone done this before? Success?

Won't work. If you have a spare tube that you don't want to repair,
try it and see. There are several issues involved, but the bottom
line is that trying to heat-weld a butyl tube using a soldering iron
is not going to produce the required result.
--
Typoes are a feature, not a bug.
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"Phil Lee" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

The idea is just as it seems... melt the rubber to seal the hole.

Anyone done this before? Success?

No.

Try it if you light, but butyl rubber won't melt. It's molecules are
cross linked during manufacture and can't be separated again without
supplying enough energy to char the rubber.

In short you will end up creating a stink and burning a bigger hole
than you had before.

Andrew Webster

Hmmm, what kind of flux do you use?

Carapace Completed Umber
Leadville, Colorado
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"Phil Lee" wrote: (clip) Anyone done this before? Success?
^^^^^^^^^^^^^How many of you are old enough to remember when car tires had
tubes, and "hot patches" were routine? What was the theory there?

Leo Lichtman said:

"Phil Lee" wrote: (clip) Anyone done this before? Success?
^^^^^^^^^^^^^How many of you are old enough to remember when car tires had
tubes, and "hot patches" were routine? What was the theory there?

Those are for the old, natural rubber tubes. Today's are synthetic butyl and work fine with rubber cement.

I remember seeing the hot patch kit. It had little patches with tins of some pyrotechic compound on the back. You would rought the patch area like today but you would place one of these "burners" over it and light. It sputtered like a firework for a few minutes. After cooling, the patch was complete.

It doesn't work on modern tubes because butyl rubber pyrolyzes before it melts. To "melt" rubber, you must break the bonds with cold work in a calandering mill. Significant heat is developed and the rollers are cooled to prevent premature vulcanization. The rubber can then be plastically formed to whatever shape and then it is baked to vulcanize the rubber into the final form.

Leo Lichtman said:

"Phil Lee" wrote: (clip) Anyone done this before? Success?
^^^^^^^^^^^^^How many of you are old enough to remember when car tires had
tubes, and "hot patches" were routine? What was the theory there?

Essentially the heat is applied to cure the glue to hold the patch.
This will give maximum strength much more quickly than cold patching
where you might need to wait a day or two for full curing to occur
(hence the oft-quoted recomendation to use a spare tube rather than
re-insert a freshly patched one if you have a puncture).

"Hot patches" are still used for tubeless tyre repairs in automotive
applications, applied to the inside of the tyre rather than the
outside of the tube so they are not as visible.

Andrew Webster

Sheldon Brown said:

Hmmm, what kind of flux do you use?

Carapace Completed Umber
Leadville, Colorado

That is a silly question. Everyone knows inner tubes are TIG welded.

--
Tom Sherman – Earth

"Tom Sherman" wrote: That is a silly question. Everyone knows inner tubes
are TIG welded.
^^^^^^^^^^^^^^^
Do you have to fill the tube with inert gas?

"Leo Lichtman" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Tom Sherman" wrote: That is a silly question. Everyone knows inner tubes
are TIG welded.
^^^^^^^^^^^^^^^
Do you have to fill the tube with inert gas?

Unfortunately we're starting with a punctured tube. We have to patch
it conventionally first so it will hold the inert gas.

--
Dave...

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Hmmm, what kind of flux do you use?

None needed. The soldering iron flux the tube all by itself.

--
Dave...

Leo Lichtman said:

"Phil Lee" wrote: (clip) Anyone done this before? Success?
^^^^^^^^^^^^^How many of you are old enough to remember when car tires had
tubes, and "hot patches" were routine? What was the theory there?

Vulcanizing patches were made from *partially cured* rubber, and the
heat both bonded them in place *and* cured the patch material. They
didn't use glue; the rubber itself bonded with the tube.

Hot patches for tubeless tires existed for a while, but they were a
real hassle to use. I think that the shift away from hot patches for
tubes began when it was found that the "chemical patches" for tubeless
tires worked just fine on tubes as well. When those became widely
available at a reasonable price, there was no longer any justification
for putting up with the hassles of applying a vulcanizing patch. I
used my last hot patch sometime around 1967, though I didn't toss the
clamp into the steel recycling bin until a couple of years ago.

Vulcanizing patches had several inherent problems. In damp climates,
if the cellophane bag was torn, the combustible charge would hydrate;
after that, it wouldn't burn hot enough to cure the patch, though it
often would still burn hot enough to make it *appear* that the patch
had set. They also had a very definitely limited shelf life in damp
climates, even if the cello bag was intact. And, if you were the
least bit incautious in using a hot patch, you could burn a hole in
the tube just beyond the margin of the patch.

I'm told that there are still vulcanizing patches available, but I
haven't used one for nearly 40 years now.
--
Typoes are a feature, not a bug.
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Werehatrack said:

Hot patches for tubeless tires existed for a while, but they were a
real hassle to use. I think that the shift away from hot patches for
tubes began when it was found that the "chemical patches" for tubeless
tires worked just fine on tubes as well. When those became widely
available at a reasonable price, there was no longer any justification
for putting up with the hassles of applying a vulcanizing patch.

Except maybe the really impressive show the hot patches made. Well,
impressive at least if you were 10 years old at the time.

Mark "I saw 'the show' when I was 10" Janeba

Andrew Webster said:

"Phil Lee" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

The idea is just as it seems... melt the rubber to seal the hole.

Anyone done this before? Success?

No.

Try it if you light, but butyl rubber won't melt. It's molecules are
cross linked during manufacture and can't be separated again without
supplying enough energy to char the rubber.

In short you will end up creating a stink and burning a bigger hole
than you had before.

Andrew Webster

I can empirically confirm Andrew's allegation.

Phil Lee said:

The idea is just as it seems... melt the rubber to seal the hole.

Anyone done this before? Success?

Won't work.

Butyl won't melt in any useful way.

Once a upon a time there were vulcanizing patches that consisted of a "raw"
rubber patch that was stuck to the bottom of a drawn steel pan that held a
flammable fiber. You'd clamp the patch against the tube, burn the stuff in the
pan the heat would vulcanize the rubber and bond it to the tube. As I recall
those worked very well, if a bit more involved than the rubber cement approach.

Ron