RE: [Frame] Brazing with Oxy-Propylene

[David Bohm]

Simon,

 

You are right.  It is practically impossible to braze with a fuel/air torch to a reasonable and safe level.  What Chimonas has done with that bit of miss information as really been a disservice to our craft.

 

Notice I said fuel/air.   Keep in mind that air only has about 21% oxygen.  It is not so much the fuel as the fact that any fuel doped with pure oxygen can work pretty well for brazing.   I could go into it quite a bit but peoples gut reaction to Acetylene is just that, just a reaction with no real basis in fact.   Many fuels can work well but they are all dangerous if mishandled and in fact carting around a cylinder of pure O2 and leaving that in a storage shed could also lead to disaster if mistreated.

 

My advice?  Go to craigslist and get a small acetylene/oxygen setup and learn with that.  If you want to try an alternate fuel give propane a try.  That is easily accessible but you will still need an oxygen tank, regs and the like so I wouldn’t count on it being any cheaper, just easier to source (go to BBQ place)

 

Good luck,

 

All the best,

 

Dave Bohm

Bohemian Bicycles

 

 

From: frameb...@googlegroups.com [mailto:frameb...@googlegroups.com] On Behalf Of Simon Newton
Sent: Monday, June 10, 2013 2:22 PM
To: frameb...@googlegroups.com
Subject: [Frame] Brazing with Oxy-Propylene

 

Hi all, forgive my ignorance but I'm looking to get into some backyard frame building (brazed lugs).  I'll Probably be sticking with silver solder for now.

 

I'm sure many of you are familiar with "Lugged Bicycle Frame Construction, A Manual for the First Time Builder" by Chimonas.  He advocates for using MAPP gas for just dipping into frame building which is certainly tempting if I want to give it a try without investing a lot into an expensive torch setup.  From what I've gathered though it sounds like a struggle to get solid, consistent joins with good penetration.

 

I went to my local welding supply store to get some advice on different entry level setups.  The dude there said to forget about MAPP and go for Oxi-Propylene.  Do any of you have experience with it?  I looked up the flame temperature and it looks like it's even lower than MAPP http://www.engineeringtoolbox.com/flame-temperatures-gases-d_422.html?

 

Any other recommendations you guys have would be hugely appreciated.  Since it's a backyard operation I'd like to stay away from acetylene if possible and preferably be entry level in price/manageability/safety.  Thanks!

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[Alex Wetmore]

JimG is playing an inexpensive setup using a medical oxygen generator and BBQ propane cylinder.  This probably won't make things too much cheaper (the medical oxygen generator is about the same cost as a small oxy cylinder and regulator), but it does make sourcing fuel really easy (oxygen comes from the atmosphere, propane comes from the neighborhood gas station).

If you aren't in a rush it might be interesting to see what he says about it after he gets to use it.  He's also done some brazing with mapp/air.

alex

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From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of David Bohm [dave...@cox.net]
Sent: Monday, June 10, 2013 3:07 PM
To: 'Simon Newton'; frameb...@googlegroups.com
Subject: RE: [Frame] Brazing with Oxy-Propylene

[Alistair Spence]

Simon,

I recommend reading through this thread over on VSalon (if you haven't already) which discusses some of the pluses and minuses of different fuel gases, 

http://www.velocipedesalon.com/forum/f10/acetylene-vs-propane-30480.html

A lot of good background info and specific tips there.

Alistair.

[Doug Fattic]

Simon,

I am in agreement that the book you reference gives false impressions of how easy (or difficult) it is to build a bicycle frame.  I don't know of any inexpensive brazing equipment that works well for brazing frames unless your are getting a deal on something used.  Besides my standard oxyacetylene outfit, I've also been using propane in a BBQ tank with an oxygen concentrator (a machine to turn air into 90 some percent oxygen to keep Grandma alive).  This is the most practical setup I know about.  The many convenience stores with long hours in my area sell propane tanks for about $50 and a refill costs under $20.  There is enough fuel in one tank to last a very, very long time.  They are also easier to transport.  A regulator for propane at my welding supply store is around $80.  

Because propane is heavier than air it makes me even more cautious with safety procedures than acetylene which will disperse more into the atmosphere.  The ABC sports announcer Hannah Storm almost blew off her face lighting her BBQ last fall.  An oxygen concentrator of course is not a missile or a bomb waiting to go off and never has to go back to the store to be refilled.  The government regulates their use for medical purposes but used ones can be sold for non-medical purposes (like lampworking - which is really glass working) more cheaply.  These can be regularly found for $200.  I've had students pay as little as $50.  DotMed is a classified website that has hundreds of them for sale.  They don't require a regulator to operate (so you save that expense) that would be a necessity on an oxygen tank.  They have a knob on the front of the machine that controls the oxygen flow.  Their disadvantage is that they have to be turned on a few minutes before use otherwise the not-pure-oxygen–yet will blow out your flame.  Of course they can be used with acetylene too.  And they make a small amount of background noise.  I love not having the bother of transporting for an exchange or the annoyance of running out after store hours.  

Other observations about using propane is that it doesn't give off a soot shower if you don't turn the oxygen up fast enough.  However they are definitely fussier to light.  Propane is not as hot as acetylene which is both good and bad news.  That gives beginners more time to assess and correct what is going on at the joint but of course takes a bit longer.  In reality I can switch back and forth between acetylene and propane without much thought or adjustment.  The only place where I give acetylene a clear edge is doing fillet brazing although I can fillet braze just fine with propane.  Most students that take my class prefer using propane.       

I covered torch, tip and hose options in that Velocepede subject thread Alistair mentioned.

Doug Fattic

Niles, Michigan                          

[Olivier Alonzo]

I also use the propane/concentrator combo. I fashioned an adapter to try a disposable 1 lb propylene bottle since in theory it burns hotter with more heat in the inner cone. In practice I found it was quite similar to propane, and still far from acetylene. I thus favour the bigger propane tank.
Olivier

[Doug Fattic]

Oliver,

I'm curious how long one of those small disposable bottles roughly lasts while brazing?  I know that there are some that need to braze in less than ideal circumstances  and a small container would be more acceptable (because of building regulations or safety concerns or whatever) than a larger BBQ tank.  If it can go for an hour or more it might be an option for some.

Thanks,

Doug  

[Olivier Alonzo]

I only ran the small bottle for about 15-20 mins with a no. 3 Victor tip. At this point the tank was running low from previous usage and the pressure was dropping. I think it would likely last 1 hour. Roughly speaking there is 8.6 cuft of gas per pound of liquid propane. So 1 lb is about the same as a MC acet tank.
olivier

[Alex Wetmore]

About one hour sounds about right.  I used a few disposable MAPP cylinders with my setup to see if I liked fillet brazing with it better than propane.  I did, so I switched my big cylinder over to Chemtane from propane.  It's a bit harder to source (you have to go to a welding supplier), but lasts so long that it's really not a concern.  I think I'm on year 3 of my first Chemtane tank and it's still quite full.  Admittedly I haven't been brazing much this last year.

The oxygen concentrators are quite interesting.  I'm tempted to switch over.

alex

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From: frameb...@googlegroups.com [frameb...@googlegroups.com] on behalf of Olivier Alonzo [olivier...@gmail.com]
Sent: Thursday, June 13, 2013 6:51 AM
To: frameb...@googlegroups.com
Subject: [Frame] Re: Brazing with Oxy-Propylene

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[VeryRedBike]

Newbie here. Got a concentrator and made a camp bottle propane adaptor. Got a lot of advice from the vs thread. Works great!

Those 1lb bottles last a long time. I haven't completed a bike with this setup (bunch of practice and most of a fork so far), but I'd guess three bottles max including fork and suiting a bit early to prevent running out mid braze. The propane being stored mostly as a liquid means long run times... And that the pressure in the bottle doesn't tell you jack about how much is left.