Subject: Acetylene brazing - questions

From: [email-masked] (Eric Praetzel)
Date: Fri, 23 Jul 1993 11:03:28 GMT

I am trying to braze cheap steel pipes (1" to 2", 0.065 tickness) to build
a bicycle.  I have tried to use a single tank acetylene torch but it has
barely enough heat to get the tubes upto dull red.  The brazing rod never
melts and flows.
  So how does that torch work (ie where does it get its O2?  mixed in?
from the air?)? 
  And how much better is an oxy-acetylene setup?  
  Does anyone have any experience welding such material?  It seems that the
only way I can get a brazing rig is to buy one (safety regs. prevent me from
using the one at school ....).  So that leaves welding but from what I 
remember it is quite hard to weld anything that thin.  I have no experience
welding or brazing.

  - Eric

---

From: [email-masked] (James Foster x2912)
Date: Fri, 23 Jul 1993 17:28:15 GMT

In article <[email-masked]>, [email-masked] (Eric Praetzel) writes:
|> 
|> I am trying to braze cheap steel pipes (1" to 2", 0.065 tickness) to build
|> a bicycle.  I have tried to use a single tank acetylene torch but it has
|> barely enough heat to get the tubes upto dull red.  The brazing rod never
|> melts and flows.
|>   So how does that torch work (ie where does it get its O2?  mixed in?
|> from the air?)? 
|>   And how much better is an oxy-acetylene setup?  
|>   Does anyone have any experience welding such material?  It seems that the
|> only way I can get a brazing rig is to buy one (safety regs. prevent me from
|> using the one at school ....).  So that leaves welding but from what I 
|> remember it is quite hard to weld anything that thin.  I have no experience
|> welding or brazing.
|> 
|>   - Eric 

I won't comment about the wisdom of the project, but do let us know how it
turns out. Standard Disclaimer: I'm no expert on welding, brazing, or bike
building (though I have two welders and a bike).  First, look at a real bike.
They will almost always have correctly made angled fittings for the points 
where the frame tubes meet.  These are, of course, made to match the diameter
of the tubes that are being used.  The tubes are inserted in the fittings,
aligned in a jig, and brazed in place.  If you are trying to do butt joints
of any kind they are not likely to hold in use.

Your single tank torch gets its oxygen from the air just like a propane 
torch does.  This limits the amount of heat and temperature the flame is
capable of.  It is probably capable of enough temperature to do the brazing, 
but you are not getting enough heat transfer to get the parts up to temperature.
You have to put in more heat than can be conducted away from the joint and you
want to do it quick enough so that the metal is not weakened by prolonged 
exposure to high temperature.  You could try a larger torch head for what you've
got.  You could get a torch designed for use with compressed air and acetylene
and try that.  When I worked for a company that repaired band instruments we
used compressed air and propane for brazing, silver soldering, and annealing.
Your best bet would be to go to oxy-acetylene.  Since you already have an
acetylene tank and regulator all you need is an oxygen tank and regulator, 
hoses, and torch (okay, so that's only one regulator less than a complete rig B^)).
This will be MUCH better for brazing.  And you're right, it would be difficult
to weld up such a project (for me, anyway, maybe the MIG'ers wouldn't have too
much trouble).

---

From: [email-masked] (Harry Phinney)
Date: Fri, 23 Jul 1993 20:24:25 GMT

James Foster x2912 ([email-masked]) wrote:
: In article <[email-masked]>, [email-masked] (Eric Praetzel) writes:
: |> 
: |> I am trying to braze cheap steel pipes (1" to 2", 0.065 tickness) to build
: |> a bicycle.

Yo Eric!  What, are you trying to escape the scrutiny of the
rec.bicycle'ers?  BTW - .065 is pretty heavy stuff for bikes.  It
_might_ be appropriate for the "boom" on a SWB recumbent, but even there
at least some people run .049 (seamed mild steel) tubes around 1 7/8" -
2" diameter.

: |>I have tried to use a single tank acetylene torch but it has
: |> barely enough heat to get the tubes upto dull red.  The brazing rod never
: |> melts and flows.

If you were lug brazing I'd recommend using a silver brazing material
instead of brass, as it works at a temperature low enough that your
air-acetylene torch would probably suffice.  However, I assume you're
doing this lugless, so you should probably stick with the higher
strength and easier to manipulate brass.

: |>   And how much better is an oxy-acetylene setup?  

An oxy-acetylene torch is much hotter.  It will easily weld (i.e.  melt)
steel, let alone braze.  This is what nearly all frame builders use for
brazing.

: |>   Does anyone have any experience welding such material?

Yup.

: |> It seems that the
: |> only way I can get a brazing rig is to buy one (safety regs. prevent me from
: |> using the one at school ....).

I don't get it.  The school has a welding set up that nobody can use, or
do you simply have to first take a class?  Taking a class would be an
excellent idea in any case.

: |> So that leaves welding but from what I 
: |> remember it is quite hard to weld anything that thin.  I have no experience
: |> welding or brazing.

For an inexperienced person, welding thin tubing is difficult, and would
require either an oxy-acetylene torch, a TIG welder, or a MIG welder.
(OK, some gonzo out there might be able to do .065" with a stick welder,
but not me.)

: First, look at a real bike.
: They will almost always have correctly made angled fittings for the points 
: where the frame tubes meet.

While it's true that this is a very common approach, it is not the only
joint design used on bicycles.

: If you are trying to do butt joints
: of any kind they are not likely to hold in use.

As long as the tubes are decently mitered and radiused, then "lugless"
fillet brazing will work perfectly well, as will TIG welding.  Some of
the very finest steel frames made are lugless brazed.  I haven't tried
MIG welding a frame, but particularly with that heavy a gauge tubing it
would likely work.

Harry Phinney   [email-masked]

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From: [email-masked] (Richard Engelbrecht-Wiggans)
Date: Sat, 24 Jul 1993 00:40:56 GMT

In article <[email-masked]>
[email-masked] (James Foster x2912) writes:
 
>                         ...                  First, look at a real bike.
 
HOLD IT A MINUTE.
 
Many bikes are made with lugs as you describe above.  But many have
the tubes butted and brazed without any lugs; indeed at one point,
it was felt that lugless was better than lugged.  We have several
top quality lugless bikes, including a triplet (tandem for three)
which, powered by three gorillas, once did a double century (200
miles in less than 7 hours.  It is still going strong years later,
and we now put our entire family of four (the youngest in a kid
seat on the back) on the bike.
 
Butt joints of tubes machined to match reasonably closely and then
brazed with a neat fillet will hold just fine.

---

From: [email-masked] (Eric Praetzel)
Date: Mon, 26 Jul 1993 11:33:59 GMT

In article <[email-masked]> [email-masked] (Harry Phinney) writes:
In article <[email-masked]>, [email-masked] (Eric Praetzel) writes:
|> 
|> I am trying to braze cheap steel pipes (1" to 2", 0.065 tickness) to build
|> a bicycle.
>at least some people run .049 (seamed mild steel) tubes around 1 7/8" -
  Actually it is for a LWB bent.  I made the mistake of taking two weeks
  off my upright and am looking at another month before I can build back
  upto rides > 4.5 hours.

>I don't get it.  The school has a welding set up that nobody can use, or
  They have one but it is only unlocked during normal hours (ie even the
  welders don't have a key).  Any personal work is heavily discouraged.
  A few years ago we could just roll one of the small rigs upto our dept.
  but thanks to the new safety regs. that is now out of the question.

>require either an oxy-acetylene torch, a TIG welder, or a MIG welder.
  I am leaning towards MIG.  For 'only' $700 (covers taxes, gas) I can setup
  a MIG.  That may be cheaper than paying $1200 for a built frame but is
  expensive enough to make me think about it.  I could setup an oxy torch
  for about $500 if I don't mine staying with steel and paying $110/year
  for rental on two tanks (local prices are about $55 rental, $15 fill).
  I just have to look at the other costs.  The MIG rig is supposed to be
  good for 26 ga if I ever go down to working with alumimum foil.

  It will be lots of fun cleaning up after mistakes with a MIG but they
  are supposed to be easy to use.

  Of course the next project will be a tandom 'bent  ;-)
  Actually I was looking at a pro-type bent that used square 4" by 2mm
  main boom.  That is comparable in weight to my "muffler molly" at 2"
  by 0.065

  - Eric 

//  'That man is bereft of passion and imagination. That is not who I am.
//   That Picard never had a brush with death, never realized how fragile
//   life is and each moment must be.  His life never came into focus, he
//   drifted .. never siezing the oportunities that presented themselves.
//   He learned to play it safe and he never ever got noticed by anyone.

---

From: [email-masked] (f.w.kerfoot..iii)
Date: 26 Jul 93 13:20:22 GMT

>From article <[email-masked]>, by [email-masked] (Eric Praetzel):
>   ...

I believe that you can purchase (as opposed to rent) small acetylene and
oxygen tanks. I bought mine (40 cu ft acetylene, 60 cu ft Ox.) about
15 years ago, with refill privileges. I had expected that the hydro test
every 5 years would be my problem, but the welding store I have been
dealing with has been swapping tanks with me, so I have been getting
tested tanks. I believe that I paid something like $100 per tank 15 years
ago. I am sure it is more now, but probably still compeitive with $110
per year, assuming you will keep them for multiple years. I don't believe
that purchase is available for larger size tanks.

By the way, on the subject of joining mild steel tube, I used to do
a reasonable amount of repair/modification on old British race cars,
where the frames are typically mild steel tube in the range of 1" OD
and .049-.065" wall. The joining technique was called "nickel bronze
welding", actually a brazing process with a significant fillet
build-up using a special high nickel content rod. The joints needed
to be fitted relatively well before brazing. This construction was
strong enough for a race car frame, so I would guess it is a reasonable
alternative for a bicycle frame as well.

Returning to the tanks, I would refill the tanks every few months when
I was doing a lot of this brazing, so the smaller tanks may not be
a problem unless you are planning a manufacturing operation.

Another reason to consider the Oxy-acetylene rig over a MIG is versatility.
There are a number of other heating, silver-soldering, flame-cutting
etc capabilities of a torch which are very useful.

Frank Kerfoot
[email-masked]

---

From: [email-masked] (Soren LaForce)
Date: Mon, 26 Jul 1993 16:48:00 GMT

In article <[email-masked]>, [email-masked] (Eric Praetzel) writes...
>  So how does that torch work (ie where does it get its O2?  mixed in?

O2 if from the air.

>  And how much better is an oxy-acetylene setup?  

No contest.  Much hotter flame.

You might try silver soldering the frame.  I have some hi temp (1250
deg f) solder from a welding supply outfit (not the 450 deg f stuff 
from the local hardware store) that I intend to use to install
some "braze-ons."

I think air acetelene will get this got, but I'm not sure.

If you do go the silver solder route, be warned that a lot of 
silver solder contains cadmium, which is farily toxic.

--Soren            [email-masked]

---

From: [email-masked]
Date: 26 Jul 93 16:46:04 -0400

> silver solder contains cadmium, which is farily toxic.
Harris got rid of all cadimium in all their solders quite a few years ago. 
They now call their silver solders "Safety-Silv"

Its nice stuff.  I use it almost exclusively over brass for fixes and the like.

For small stuff I use a swirl type MAPP torch instead of the big oxy/acetlylene
rig.  It works really well on most projects.

---

From: [email-masked] (James Foster x2912)
Date: Mon, 26 Jul 1993 20:49:30 GMT

In article <[email-masked]>, [email-masked] (Eric Praetzel) writes:
|> In article <[email-masked]> [email-masked] (f.w.kerfoot..iii) writes:
|> >I believe that you can purchase (as opposed to rent) small acetylene and
|> >oxygen tanks. I bought mine (40 cu ft acetylene, 60 cu ft Ox.) about
|> >15 years ago, with refill privileges. I had expected that the hydro test
|>   Tanks are $365 for a filled pair of 2' tanks (cu ft size = ???) or
|>   $160 filled for a 1 year rental. (prices are CDN, no 15% tax)
|> 
|>   So the question becomes: How long do these tanks last?  I am not doing
|>   cutting, just brazing.
|> 
|>   Thoughts of a tandom recumbent are dancing thru my head right now.  Just
|>   how do you steer a 14' long bike?
|> 
|>   - Eric

2' high?  Sounds relatively small, and expensive for the size.  I also have the
40cuft./60cuft. set of tanks.  This was recommended as a good size for home shop use.  I don't
do much welding now a days so the tanks end up lasting indefinitely B^).  Even when
I was doing a lot with them they would last a long time using smaller (000 - 2)
welding tips.  Cutting uses a lot of gas though.  I think that the casual user can
either just rent when tanks when needed and turn them back in rather quickly to avoid
the demurrage, or the better alternative is to just buy them, 'cause you can never
tell when something will break.  My supply shop offers a free refill on the 
oxygen tanks if you bring them in within two weeks when they're due for hydro testing.

---

From: [email-masked] (f.w.kerfoot..iii)
Date: 26 Jul 93 17:22:23 GMT

>From article <[email-masked]>, by [email-masked] (Eric Praetzel):
> In article <[email-masked]> [email-masked] (f.w.kerfoot..iii) writes:
>   Tanks are $365 for a filled pair of 2' tanks (cu ft size = ???) or
>   $160 filled for a 1 year rental. (prices are CDN, no 15% tax)
> 
>   So the question becomes: How long do these tanks last?  I am not doing
>   cutting, just brazing.

I'm not entirely sure which way you meant the the question. If you mean
"how many years before I have to buy new tanks", the answer is dependent
on their care. The tanks require an internal inspection and a hydrostatic
perssure test every 5 years. As I understand it, the dominant failure
mode is corrosion. If no moisture (or other corrosive elements) are
introduced, I would expect many 5 year cycles. I believe that some of
the swapped tanks (with current hydro dates) have been 20-25 years
old, based on the sequence of hydro test dates, which are stamped into
the outside of the tanks.

Your comment about just brazing, not cutting, makes me wonder if your
question is about low long a single fill lasts. My 40 cu ft. acetylene
bottle is about 2' high. My 60 cu ft oxygen bottle is more like 2 1/2',
but a 40 cu ft oxygen tank is a common combination, and it is about
2' high. It is hard to relate gas usage. Most of my work is on small
parts, with tips in the 00-2 range (Airco 400 torch). Occasionally
I will do something larger with a #3 tip (my largest). With occasional
use (every week or 2) I would say I refill them once a year. I have
a cutting torch, but I very seldom use it. As you seem to suggest,
cutting uses oxygen much faster than welding, and my small tanks
would probably not be a good choice if you plan to do much cutting
(in case others are interested).

Frank Kerfoot
[email-masked]

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From: [email-masked] (Harry Phinney)
Date: Tue, 27 Jul 1993 01:18:54 GMT

Eric Praetzel ([email-masked]) wrote:
:   I am leaning towards MIG.  For 'only' $700 (covers taxes, gas) I can setup
:   a MIG.
:   ...
:   The MIG rig is supposed to be
:   good for 26 ga if I ever go down to working with alumimum foil.

MIG might work OK, but I've never tried it on a frame.  Maneuvering the
gun around some of the joints might be less than fun.  Be warned that if
you think you're going to do aluminum with it you may need a bigger
machine (i.e.  more amps) because Al is a _good_ heat sink, and you'll
likely need a spool gun, because small diameter Al wire has a tendency
to "birds nest" if you try to push it through a normal MIG cable and
gun.

:   Of course the next project will be a tandom 'bent  ;-)
:   Actually I was looking at a pro-type bent that used square 4" by 2mm
:   main boom.  That is comparable in weight to my "muffler molly" at 2"
:   by 0.065

I was recently looking at a tandem recumbent vehicle (a kinetic sculpture 
titled "Red Hot") which consists primarily of .049" wall 2" square tubing.

---

From: [email-masked] (Dave Uebele)
Date: 26 Jul 1993 23:37:35 GMT

I also have the 40 and 60 cu foot tank size which is nice size to have around.
If I was doing it again, I would probably purchase the next size smaller and 
when I know I have a big project comming rent larger tanks.
The local welding supply basicly gives free rental (cost of refill
only) if you return the tanks within about a week.
So if I know I have a big project coming up, like chopping a car
into recyclable pieces, I rent a big set of tanks for the weekend.
I keep the smaller set around for short notice projects.
They get refilled/swapped often enough to not worry about the
testing.

dave
-- 
Dave Uebele        [email-masked]
DoD# 1717	'92 R100R

---

From: [email-masked] (Bart Smaalders)
Date: 26 Jul 1993 18:58:55 GMT

> from the local hardware store) that I intend to use to install

Note that a normal silver-brazed joint needs a very tight clearance (.001"
-> .003" )and significant surface area to get proper strength.  Hence this
works well for attaching braze-ons, etc, that have enough surface area wrt
the load they are asked to carry.  For lugless construction, large fillets
are essential to achieve proper strength, since the joint itself has very
little surface area .  Use regular brazing rod for the frame; you really
don't want to pay for the amount of silver "solder" needed to build up
proper fillets.  Since a significant amount of material must be applied,
this is much slower than silver soldering where capillary action wets
the joint very quickly.

Either a air acetylene or oxy acetylene torch gets plenty hot enough to
do silver brazing; the question is whether they produce enough heat.
I have done very satisfactory silver brazing with a propane torch, but
the part was the size of a quarter.  Oxy-acetylene torches can accept
very large tips (aka "rosebud") that produce enough heat that it is 
difficult to use w/o full leathers.  The gas consumption, however,
is pretty fierce as well.  Friends that have silver-brazed 1.5" scale
copper model locomotive boilers (50+ lbs Cu) have mentioned building
fire-brick enclosures and using multiple propane weed-burners as
pre-heaters.  

- Bart ([email-masked])