Do electronics soldering skills transfer to brazing bike frames?

Andre Jute wrote:

I wasn't actually thinking of a big gas cylinder with tubes running
all over the place, which has legal requirements and transport
difficulties (I haven't owned a car since 1992, in part to force me to
cycle, in part out of principle). I have a set of nozzles which can be
operated from a gas canister that also serves as a handle. Easy to
manipulate and put down. Probably more expensive in combustibles than
the big tank, but I don't think on a one-bicycle scale that will be a
big deal. This is a tool that could (according to the Little Fish
site, a real inspiration) do real brazing

I also have a big 200W soldering iron to burn teflon coating off, and
tin, the thick Cardas multistrand TC5 I use for loudspeaker cable.
It's a great big brutal soldering iron used for nothing else. I was
just wondering if 200W is enough to heat two bike-size pipes and the
lug properly.

I think you're worrying about the wrong part. The hard part of brazing,
like almost everything else, is the prep and the clean up. Brazing a
bike joint is relatively simple, the tedious part is the metal shaping
before, the jigging of the parts in precise alignment (while still
allowing free access to the joints), the clean up of all the flux and
brass dribbles, then, finally, preparing the surface for paint.

I've only brazed one bike joint, when the top tube pulled out of the lug
on my old Raleigh Grand Prix. A local garage was more than happy to let
me use their oxy-acetylene rig, but wouldn't do it for me since they had
"never fixed a bike before". Me neither, nor had I ever used an
oxy-acetylene torch, but it was pretty easy, very much like sweating a
plumbing joint. The joint never failed again after years of riding it so
I'd have to say I did a better job than the original guy at Nottingham.
Brazing lugs seems to be a pretty tolerant process, way easier than
welding or fillet brazing, which is probably why it has been so popular
for so long. An amateur can probably make an adequately strong joint
easily enough, but it's apt to be on the sloppy side.

If I were contemplating building a frame I'd make a jig, dry fit the
parts, then take it to a shop and use their torch for an hour or two.
Better yet, get someone to braze it there. My next door neighbor did
that last year when he wanted to make a new (aluminum tube)
superstructure for his fishing boat. He cut and shaped the stock and
bolted it together and brought it to a local tech school where the
instructor then welded it up. A few hours and a couple of hundred bucks
later everyone was happy.

A 200W iron wouldn't have anywhere near the heat to braze or even solder
a joint. I have brazed sheet metal with a "dual carbon torch" on an arc
welder -- basically a hand-held arc light, way fun, but for brazing a
bike frame a simple oxy-acetylene is the right tool for the job. The
only wrinkle (for an amateur) I can think of might be changing the
metallurgical properties for the worse if the joint were overheated, but
I'd think that'd be mostly a problem with exotic alloys.

Most frame failures are pretty benign. I don't think there's too much
safety at stake, just time and effort (and a paint job if you have to
re-braze). I'd go for it if you like metal working (maybe use an off the
shelf fork) -- I don't that much, so I'm happy to let the robots of
Taiwan make my frames.

Andre Jute wrote:
Jute:
I'll learn to braze (I do silver soldering of electronics all the time)

George:
Is that low temperature stuff (ie the modern replacements for leaded solder,
using an iron) or using a torch with traditional silver solder?

As you would expect by now, I don't do the expected thing simply
because everyone else does it that way. I have the usual electrical
soldering irons but rarely use them, instead preferring to use a
catalytic pencil (it literally clips into a pocket) driven by
cigarette lighter gas. It goes up to 1300 degrees and I keep it going
full blast, so one has to be quick to make the joint. But I design and
build thermionic valve (American: tube) amps, so there are no tiny
transistors, only big parts, no resistors smaller than 2W, and the
Japanese handmade Kiwame that I like for sonic reasons have wires
sticking out of them thicker than the tube rim on many everyday bikes,
never mind racing bikes.

The solder I use is 2% silver eutectic (it melts and sets at the same
temperature, so when you remove the heat, the joint is instantly set).

The process is really a sort of moderate temperature brazing, as the
solder is intended to flow between close-fitting parts, or to be
filleted around wires.

Re learning to braze - do you have a local community college who will do
courses in such things? Could well be interesting, even if you weren't
building a frame. I'd definitely want to do it on borrowed kit first.

I wasn't actually thinking of a big gas cylinder with tubes running
all over the place, which has legal requirements and transport
difficulties (I haven't owned a car since 1992, in part to force me to
cycle, in part out of principle). I have a set of nozzles which can be
operated from a gas canister that also serves as a handle. Easy to
manipulate and put down. Probably more expensive in combustibles than
the big tank, but I don't think on a one-bicycle scale that will be a
big deal. This is a tool that could (according to the Little Fish
site, a real inspiration) do real brazing

I also have a big 200W soldering iron to burn teflon coating off, and
tin, the thick Cardas multistrand TC5 I use for loudspeaker cable.
It's a great big brutal soldering iron used for nothing else. I was
just wondering if 200W is enough to heat two bike-size pipes and the
lug properly.

A joint made with the electronics type eutectic silver solder would
definitely be weaker than one that is hard-brazed with gas (another
way of distinguishing between electric iron electronic soldering and
gas brazing is as "soft soldering" v "hard soldering").

But that merely raises another question or several. Is it necessary on
a bike frame to have hard brazing (either brass or silver) or is it
overkill? Would (lower temperature, soft) silver soldering with a big
iron for heating not be good enough for bicycles? If it is such a
great idea, why doesn't anyone do it?

Further questions that might cast light on the choice: What is the
normal failure mode of a steel bicycle frame? How often do joints come
apart spontaneously?

Here's a crucial test: Does a guy who regularly brazes bike parts for
a living, someone like Andrew Muzi simply by way of example, believe
that a soft-soldered bike by an amateur would be safe? I don't
actually fancy paying for being a pioneer by landing on my face on the
tarmac...

Alternatively you could try a Dave Yates framebuilding course - I've read
good things about those, and it would be an interesting way to get a custom
frame.

I visited his site a few weeks ago. Yates has so many bookings for his
course, he's just about given up building bikes to order.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review


In my small experience (fabricating auxiliary engine oil coolers) lead
solders are just not up to the requirements of frame tube joints. The
joints themselves are not strong enough under relatively small vibration
or torque.

A nickel silver is great if you have full penetration which requires
cleanliness, good fit and broad, even heating. Lower temperature than
brass/bronze, but still a lot of btus to fill a joint reliably. I like
oxy-propane for silver as the flame is clean and the temperature is
sufficient. (Oscar Wastyn used propane-air to good effect). A big torch
with such a cool flame makes the fill reliable and quick. Set up with
firebrick around the joint for even heating. I worked in a factory with
MAPP-oxygen, which was merely adequate. I prefer a big oxy-propane for
filling lugged joints. Fillet joints really need a smaller flame and a
broader eutectic range such as bronze to build up those pretty fills.

The relative bond and filler strengths, temperatures etc are all
available at your silver/bronze supplier or I'm sure online. I found
this general overview easily:
http://www.aws.org/wj/amwelder/9-00/fundamentals.html

Whichever filler you use, get the matching flux for that temperature and
don't skimp on it. Lots of translucent flux removes readily in hot water
but a small amount of burned black flux is a chore to clean and then
you're unsure about the fill rate too.

You might do practice joints and then cut them apart to check fill rate.
Target a uniform flow with even meniscus both inside and outside the
joint. Same meniscus inside and out means it was heated evenly, a smooth
outer surface with poor penetration is the mark of a cold joint. Uniform
means 'no gaps'. I like to see new guys do practice joints in tube scrap
until they no longer worry about the fill before attacking an actual
bicycle. Start your actual piece after you have no doubts about filling
the joint thoroughly.

p.s. you can always stop, think, come back to it later as long as you
haven't overheated the material, which is fatal.
--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

André Jute wrote:
[...]
I wasn't actually thinking of a big gas cylinder with tubes running
all over the place, which has legal requirements and transport
difficulties[...]

Over here in Leftpondia, all the welding supply places deliver. However,
for the casual user, the tanks are way too large.

Another alternative is to cut all the tubes and file the lugs oneself,
jig it up, and take it to a professional to braze.

--
Tom Sherman - 42.435731,-83.985007
If you are not a part of the solution, you are a part of the precipitate.

André Jute wrote:
[...]
I wasn't actually thinking of a big gas cylinder with tubes running
all over the place, which has legal requirements and transport
difficulties[...]

Tom Sherman wrote:
Over here in Leftpondia, all the welding supply places deliver. However,
for the casual user, the tanks are way too large.
Another alternative is to cut all the tubes and file the lugs oneself,
jig it up, and take it to a professional to braze.

"Too large" ?? My auto set are "bus tanks" (class X and B). Including
cart (nice first braze project by the way) about as large as an upright
vacuum cleaner. Quite small, maneuverable, transportable. Cheap too.

You'll need small brass adapters to use standard regulators. Get them
when you buy/lease/rent your tanks.
--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

On Nov 25, 1:50 am, Andre Jute wrote:
Jute:

I'll learn to braze (I do silver soldering of electronics all the time)

George:

Is that low temperature stuff (ie the modern replacements for leaded solder,
using an iron) or using a torch with traditional silver solder?

As you would expect by now, I don't do the expected thing simply
because everyone else does it that way.

I took my very first bike (a 1960's department store "sting ray" type
thing) into the Junior High School metal shop at age 13, chopped it
up, added some bits for mono-shock rear suspension (this in the early
1970's!), brazed it all together, repainted, and rode it very hard and
extensively thereafter.

The only subsequently failed joint was where I'd cut up the high-rise
handlebar and brazed pieces together to achieve a sort of early "BMX"
type bend. (I'm not sure, but think this may have pre-dated the term
"BMX".) The handlebar broke in two while I was riding a wheelie
across a State Highway - yet I didn't crash, but instead set the front
wheel down somehow and rode on :-)

At age 14, I refined the design and built a new bike by cutting my own
steel tubes and welding to a salvaged BB, headshell, and rear
dropouts.

I would like to become a good wheel builder, but have no ambition to
build frames.

Thanks to all who replied. Soft soldering is clearly not on, but,
though you've convinced me I could learn hard-brazing with some time
invested, I don't think I'll be doing it. As Peter pointed out, the
difficult bit is the preparation of the tubes, and I would find that
too time-consuming while I waited for the blisters on my hands to heal
before filing the next tube...

Still, an excellent thread, from which I for one have learned much
(including some stuff I'd forgotten I knew already).

Andre Jute
Not the boy genius of metalwork class

On Nov 25, 9:50 am, Andre Jute wrote:
Jute:

I'll learn to braze (I do silver soldering of electronics all the time)

George:

Is that low temperature stuff (ie the modern replacements for leaded solder,
using an iron) or using a torch with traditional silver solder?

As you would expect by now, I don't do the expected thing simply
because everyone else does it that way. I have the usual electrical
soldering irons but rarely use them, instead preferring to use a
catalytic pencil (it literally clips into a pocket) driven by
cigarette lighter gas. It goes up to 1300 degrees and I keep it going
full blast, so one has to be quick to make the joint. But I design and
build thermionic valve (American: tube) amps, so there are no tiny
transistors, only big parts, no resistors smaller than 2W, and the
Japanese handmade Kiwame that I like for sonic reasons have wires
sticking out of them thicker than the tube rim on many everyday bikes,
never mind racing bikes.

The solder I use is 2% silver eutectic (it melts and sets at the same
temperature, so when you remove the heat, the joint is instantly set).

The process is really a sort of moderate temperature brazing, as the
solder is intended to flow between close-fitting parts, or to be
filleted around wires.

Re learning to braze - do you have a local community college who will do
courses in such things? Could well be interesting, even if you weren't
building a frame. I'd definitely want to do it on borrowed kit first.

I wasn't actually thinking of a big gas cylinder with tubes running
all over the place, which has legal requirements and transport
difficulties (I haven't owned a car since 1992, in part to force me to
cycle, in part out of principle). I have a set of nozzles which can be
operated from a gas canister that also serves as a handle. Easy to
manipulate and put down. Probably more expensive in combustibles than
the big tank, but I don't think on a one-bicycle scale that will be a
big deal. This is a tool that could (according to the Little Fish
site, a real inspiration) do real brazing

I also have a big 200W soldering iron to burn teflon coating off, and
tin, the thick Cardas multistrand TC5 I use for loudspeaker cable.
It's a great big brutal soldering iron used for nothing else. I was
just wondering if 200W is enough to heat two bike-size pipes and the
lug properly.

A joint made with the electronics type eutectic silver solder would
definitely be weaker than one that is hard-brazed with gas (another
way of distinguishing between electric iron electronic soldering and
gas brazing is as "soft soldering" v "hard soldering").

But that merely raises another question or several. Is it necessary on
a bike frame to have hard brazing (either brass or silver) or is it
overkill? Would (lower temperature, soft) silver soldering with a big
iron for heating not be good enough for bicycles? If it is such a
great idea, why doesn't anyone do it?

Further questions that might cast light on the choice: What is the
normal failure mode of a steel bicycle frame? How often do joints come
apart spontaneously?

Here's a crucial test: Does a guy who regularly brazes bike parts for
a living, someone like Andrew Muzi simply by way of example, believe
that a soft-soldered bike by an amateur would be safe? I don't
actually fancy paying for being a pioneer by landing on my face on the
tarmac...

Alternatively you could try a Dave Yates framebuilding course - I've read
good things about those, and it would be an interesting way to get a custom
frame.

I visited his site a few weeks ago. Yates has so many bookings for his
course, he's just about given up building bikes to order.

Andre Jute
Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review