 | Home > Off Topic > Has anyone brazed rear dropouts? Propane or acetylene? |
 
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| ZeDefender Member Since: 15 Sep 2011 Location: Munich Posts: 4731   
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Hi all
I need some pointers for learning brass brazing 
I've got to replace the brazed-on rear dropouts on an old (75 years!) tandem bike myself: [URL=]  Click image to enlarge[/URL] Not my choice but nowhere around here is willing to do it. I understand the principles are the same as soldering (which I'm pretty good at) but are there any tricks of the trade anyone can tell me? My obvious problem is what equipment to get - most seem to use "proper" acetylene torches but propane torches are more available - do they work? Many thanks for any advice. Cheers Matt Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated  Tell someone you love them today because life is short.
But shout it at them in German because life is also terrifying and confusing... |
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31st Oct 2013 2:50pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6604  
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Have seen a Campingaz Oxypower kit used to braze with good results - not a UK product but might be available there?
1988 90 Td5 NAS soft top
2015 D90 XS SW |
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31st Oct 2013 3:30pm |
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| Orangeboy Member Since: 24 Sep 2013 Location: Uk Posts: 48 |
Might be worth asking on singletrackworld forum
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31st Oct 2013 5:30pm |
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| me@td5.org Member Since: 16 Jan 2011 Location: Warwick Posts: 856 
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Have you found replacement dropouts yet? Are you going to run it with the same (geared) hub? www.td5.org
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31st Oct 2013 5:36pm |
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| yobbie Member Since: 15 Nov 2010 Location: Isle of Wight Posts: 712 
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Make sure you build a good brick surround around it to keep the heat where you need it & make sure it's very clean.
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31st Oct 2013 8:06pm |
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| shaggydog Member Since: 12 Aug 2012 Location: Kent Posts: 3347 
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I would always go for oxy-acetaline with a blown gas flux as this is what the professional bike builders use and it makes such a difference- however that sorta set up is quite expensive and if you in the UK you can't keep ether in residential households anymore, not sure how it works in Germany.
I have used pretty much all of the "home hobby" kits and found them all to be expensive and underpowered. Personally, I'd try and source an oxy-propane kit as you can keep those at home. The set-up is very similar to oxy-acetylene except that you use propane which is readily available and much safer to use in general. I'd recommend this kit - not sure if it’s in your budget or not, but I'd rather not skimp on high pressure flammable gasses! http://www.weldequip.com/oxy-propane-brazing.htm As for the brazing, heat up until everything is a bright cherry red. First time always seems a bit like it’s all getting too hot and there is a risk of starting to panic and rush. Lightly heat the tip of the brazing rod and dip it into the flux, this will put a few globs onto your rod and will make it easier to flow. Brush the flux onto the part to be brazed (assuming you have a powder flux) and heat it until it goes clear, once it’s clear it is ready to work. Add in the brazing rod into the area and slowly almost "paint" it on. Keep the heat on the part as you work and remove the rod, then the heat and allow to cool. Heat reflective bricks help alot and conserve gas. Also make sure you degrease the parts thoroughly and give them a good going over with some wire wool and alcohol to clean the surface. Like any metal joint, 90% of it is in the preparation, make sure it’s a good fit and secure enough to work. Having don’t many brazing jobs there is nothing more irritating than trying to braze something and chase it around the workbench! Other than that usual health and safety things, goggles, gloves, leather apron. Looks like a good project be cool to see how it goes!  |
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31st Oct 2013 9:13pm |
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| Natlas Member Since: 20 Mar 2013 Location: West Sussex Posts: 460 
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Hi ZeDefender,
Not particularly disagreeing with Shaggydog but there are two differences between Acetylene and Propane. Acetylene is higher temp (higher than you need) and is a very focussed flame/heat. Propane is a lower temp (but good for brazing) and is a wider flame (assuming your nozzles are big enough. The wider spread of propane heat makes for better brazing normally because you want to heat up an area and have the braze melt flow willingly into all the cracks, (so a good and matching flux is also very important). However, at the end of the day, if you have a torch setup of either gas both should be perfectly capable of doing a good job. Note that if you are trying to braze to rust it won't work, you will need to get to clean bare metal. Cheers, John. 2.2 90 XS 88" Series One Old Norton
Minerva |
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31st Oct 2013 9:45pm |
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| ZeDefender Member Since: 15 Sep 2011 Location: Munich Posts: 4731
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Wow - great advice guys - loads of info.
@Martin - same problem getting it here but I've E-Mailed a couple of Frenchies and hope they take pity on me @Shaggy and John - great info and I'm relieved that propane should do the job. 200 quid is in my budget so the Weldequip kit or similar will be fine. @me - dropouts may take a while to source/make and I will probably have to de-braze the existing ones to get a good design - nerve-wracking stuff 
@excossack and Orange - yeah - I guess I'll be joining even more forums on this one. Thought I'd start here though as welding and biking go together pretty well with Defenders 
@Yobbie - cheers - sort of thing I'd forget. Bit daunting to "have a go" at my wife's pride and joy (I mean the bike) but with no choice and some practice, who knows. One last question especially @ Shaggy and John: Is it simple to de-braze? Do I just heat the joint up until the brass melts and pull the dropout out of the tube? Cheers all 
Matt Tell someone you love them today because life is short. But shout it at them in German because life is also terrifying and confusing... |
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31st Oct 2013 10:26pm |
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| Green Machine Member Since: 19 Nov 2010 Location: North Yorkshire Posts: 1226 
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Is there a 'Best Forum in the World' competition? 'Cos if there is, I think we'd win, no contest! Is there any question that we collectively can't answer? I think not! Good work boys and girls! 2005 Td5 | 90 Station Wagon | Tonga Green
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31st Oct 2013 10:54pm |
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| shaggydog Member Since: 12 Aug 2012 Location: Kent Posts: 3347
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The Weld eqip kit is good as it runs off a standard calorgas style propane bottle, the oxygen bottle should be available from your local gas/welding stockist- I don't know how it works in Germany. I'd expect to pay a hire fee for the bottle as you generally hire the bottle for a flat fee and then pay for refills.
As for unbrazing a joint, it is difficult, the more braze is heated it degrades which can make it more of a pain. I would cut (deep breath) the dropper so that each tube has only one section in it so it can be pulled in line when heated to remove. Heat the tube till cherry red and pull and it should come out but be careful as it could end up distorting and bending the tube. I would also recommend removing the paint and inspecting the joint that exists as it may be welded in which case it will need to be cut. Might be worth a call to these guys http://www.thebicycleacademy.org/about/fillet-brazing/ Friend of mine went there to build his bike and he came back singing there praises. |
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31st Oct 2013 11:21pm |
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| Natlas Member Since: 20 Mar 2013 Location: West Sussex Posts: 460
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Your note about un-brazing had me re-thinking aswell.
There is a phenomenom (if that's how you spell it) called Eutectic point or something similar, look it up in wikipedia or dictionary. This means that to re-melt braze you have to use a higher temp than you had to melt it in the first place. This raises concerns that in trying to remove the old part you may soften up that area of the frame etc. Keeping things simple, I have to say that I think I would be tempted just to build up the worn area with a bit of weld, I am sure there must be a local welding shop that can build it up using a MIG welder and then all you have to do is grind/file up the welded areas after to make it all look right. I expect they would charge a lot less than the £200 mentioned you were thinking of spending and it removes all the uncertainty. This approach would heat affect the surrounding area much less and probably ensure alignment of the two sides with minimal effort. Final note, when talking about using Propane earlier I was talking about Oxygen-Propane mix, not just Propane alone which will probably not be hot enough. Good luck! John 2.2 90 XS 88" Series One Old Norton
Minerva |
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1st Nov 2013 4:53am |
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| ZeDefender Member Since: 15 Sep 2011 Location: Munich Posts: 4731
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Cheers - I'm "on it like a Puma bonnet" (although it's frequently missing...)
Matt Tell someone you love them today because life is short. But shout it at them in German because life is also terrifying and confusing... |
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1st Nov 2013 8:15am |
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| ZeDefender Member Since: 15 Sep 2011 Location: Munich Posts: 4731
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 seems I may have a problem...
Just scraped off the powdercoat around different joints and there's no sign of brass 
I'm surprised as several other brackets around there are definitely brazed on. If they're welded, then I need to take a different route - mentioned a few times in this (and another) thread. As there is plenty of axle showing, I will try to find someone to build up some weld around the tubes and reinforce with a plate outside the present dropouts. I can then reposition the slot (cut some original material away) and use the non-turn washers. Should look something like this: [URL=] Click image to enlarge[/URL] (worst photoshoping ever!) Thoughts? Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated Tell someone you love them today because life is short.
But shout it at them in German because life is also terrifying and confusing... |
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1st Nov 2013 10:36am |
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| shaggydog Member Since: 12 Aug 2012 Location: Kent Posts: 3347
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Ah, I feared that might be the case...
In that case I would cut the old plates off at good metal, buy new ones and cut at the same angle as you have previously cut and then weld on a new drop out. That way you should get a good strong repair and will cost less in time and preparation than to try building up and grinding and building up and grinding. If you take it to your local engineering works they will probably do it for less than £30 and might be able to give you further guidance. My local engineering firm are always very friendly and quite often they let me just rummage through there scrap bin for material then donation in local charity's money box and all sorted |
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1st Nov 2013 1:15pm |
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