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  1. #1
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    Fillet with MAPP gas and a Hobby Torch?

    I'm about to start on my first frame. It's gonna be a pretty basic lugged frame. The plan is to use a 1 1/8" headtube though, which means i will have to TIG/Fillet the joints as there are no lugs. The problem is that i'm using a hobby torch, the Rothenberger Super Fire 2 with MAPP gas. http://www.wilstar.co.uk/productimag...157f57474c.jpgSS-image-2011-02-08-4d5157f57474c.jpg.

    I'm doing this in my tiny apartment shed so i can't use a big acetylene/oxy torch. Got to start somewhere..

    Will the MAPP gas be hot enough to heat the brass enough to lay fillets? The rest of the frame will be lugged with silver which i reckon the MAPP will do pretty well.

    Thoughts?

    Thanks
    Last edited by psee; 08-09-13 at 07:31 AM.

  2. #2
    Older I get, Better I was velonomad's Avatar
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    I did two partial fillet frames(I used a lugged bottom bracket shell) with a hobby/ Benzomatic torch. It will get hot enough if you put a piece of metal behind your work to reflect some of the wasted heat back in. Biggest issue is controlling the flow with the large uneven flame the torch puts out. The brass will want to go everywhere but where you want it. What worked for me was I held the torch in my left hand and the rod in my right hand. working from left to right I would push the rod through the puddle of brass to force it to build up the joint as it congealed. I also kept tilting the frame to the left as I progressed to take advantage of gravity . I dipped the rod in flux as I worked as opposed to fluxing the joint before hand. It will look rough at first and will take a lot filing to make it look pretty. but it will be strong. I have two frames over 20 years old that I built with this method
    Get some scrap tubing and practice.. alot! It is not easy to do with a cheap torch.

    Good Luck

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    Thanks for the reply Velonomad.

    Great to hear it's Possible, at least.

    Just came across this set.
    Turbo/Mapp+Oxy. In separate tubes. Would this be a better option? Then you'd have more control of the flame.

  4. #4
    Older I get, Better I was velonomad's Avatar
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    I bought one of those a few years ago to do some quick and dirty repairs on my son's racing go-kart while at a race. I haven't tried it on a bicycle frame. The main thing to consider is that Oxygen doesn't compress into those little bottles at the same rate as MAPP or Propane. You will go through 20-25 of those $12(USD) oxygen bottles before you use up a bottle of MAPP. The oxygen bottles lasted approximately 15-20 mins each when I used them. This torch does have a finer tip so that at least should prove better for fillet brazing.

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    Hmm. Ok.

    I've seen some different nozzles for the Rothenberger MAPP torch i originally posted. So maybe one of those with a nozzle that gives a tighter flame and then stock up on MAPP bottles is the way to go?

    The oxygen bottles were kind of expensive to that kit so if i will have to replace them twice an hour there's no point in building the frame myself to save money. Haha.

  6. #6
    Older I get, Better I was velonomad's Avatar
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    Quote Originally Posted by psee View Post
    Hmm. Ok.

    I've seen some different nozzles for the Rothenberger MAPP torch i originally posted. So maybe one of those with a nozzle that gives a tighter flame and then stock up on MAPP bottles is the way to go?

    The oxygen bottles were kind of expensive to that kit so if i will have to replace them twice an hour there's no point in building the frame myself to save money. Haha.
    I had one Mapp torch that came with a smaller tip and it was useless for anything other that small parts such as cable stops and bottle bosses. YMMV.

    Something I was not aware of (My last frame was in 2007)and just found out a few minutes ago on WIKI:

    On April 30, 2008, the Petromont Varennes plant closed its methylacetylene/propadiene plant.[2] They were the only North American plant making MAPP gas, and the only legal supplier of trademarked MAPP gas in the world. This caused a widescale shortage, and many substitutes were introduced by the companies [citation needed] who had repackaged the Dow and Varennes product(s). Most of these substitutes were propylene, like MAP//Pro [3] from BernzOmatic. Some were mixtures with higher hydrocarbons or with other ingredients like acetone [citation needed]. None get anywhere near as hot as actual MAPP gas when burned using air.

    Considering Mapp was just adequate in a hobby torch. Anything lower than Mapp's maximum temperature will be totally useless for fillet brazing and thicker frame parts such as fork crowns and drop-outs.

    It would be a good idea to confirm whether actual Mapp Gas is still be available on your side of the pond.

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    Crap. Yes it seems like the only MAP gas available is the MAP/Progas with a flame of ~2400c where Oxy/Ace has a flame of up to 3400c. May be a dead born project from the start, but im going to give it a shot. Might look into getting a smaller Oxy/Acetylen setup later on.

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    Before investing in a kit you already have doubts about, have you considered using the LP tank from your BBQ and a medical oxygen concentrator with a typical torch? That seems to the hot combo for those with space considerations or where industrial tanks are not allowed. Fuel is cheaper than acetylene, it's readily available and LP is a proven fuel for building. Store the tank with the grill and the rest of the kit doesn't take much space. Just a thought.
    Last edited by Smudgemo; 08-09-13 at 03:35 PM. Reason: minor mistake

  9. #9
    tuz
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    "Mapp" is actually propylene around here.

    The only way to make any air-fuel torch work with brass filler is with firebricks. That's what was used way back when. And then it really makes sense to do lugs, and you need to pin them, the brazing sequence is probably complicated, etc... Like Velonomad said for fillet brazing you basically have no control on the puddle and there is a good chance you'll end up with a cold braze.

    By itself air-fuel is barely adequate for silver filler and may not work for BBs and crowns. It really is a poor tool. Get the right equipment. It might seem expensive but in the long run you'll save money and time. I use propane and an oxy concentrator and it's ideal for me.

    By the way there are plenty of lugs for 1.125 steerers.
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  10. #10
    Andrew R Stewart Andrew R Stewart's Avatar
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    There are tricks to help out brazing with a small heat source. One is to limit the heat loss air flow. While you need some venting for expanding air to escape you don't need an inch plus chimney. So i loosely plug my tubes with a wad of ALU foil or a sloppy fit end cap. Another is to use two torches. A bernzamatic helping the preheat makes things go faster. A friend who understands the brazing process holding it during the actual joining can also be an aid. You might not have the best of success when the walls/masses get large. This is where practice comes in. You need to find out what works for your needs and resources. Andy.

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    Older I get, Better I was velonomad's Avatar
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    Quote Originally Posted by Andrew R Stewart View Post
    There are tricks to help out brazing with a small heat source. One is to limit the heat loss air flow. While you need some venting for expanding air to escape you don't need an inch plus chimney. So i loosely plug my tubes with a wad of ALU foil or a sloppy fit end cap. Another is to use two torches. A bernzamatic helping the preheat makes things go faster. A friend who understands the brazing process holding it during the actual joining can also be an aid. You might not have the best of success when the walls/masses get large. This is where practice comes in. You need to find out what works for your needs and resources. Andy.

    Using two torches is a great idea, I forgot that I used to do that myself. On bottom brackets I could fill the whole joint at once without having to move the torch to the other side. The even heating also helped keep the tubes in alignment.

    Andrew, Have you tried brazing with the Propylene bottles?

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    Here are some propane burner photos. You can melt the bike down with one of these. They are pretty cheap, and come in a variety of sizes, and they run off BBQ bottles which is more efficient.

    http://www.youtube.com/user/Garlaug/videos

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    Andrew R Stewart Andrew R Stewart's Avatar
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    Quote Originally Posted by velonomad View Post
    Using two torches is a great idea, I forgot that I used to do that myself. On bottom brackets I could fill the whole joint at once without having to move the torch to the other side. The even heating also helped keep the tubes in alignment.

    Andrew, Have you tried brazing with the Propylene bottles?
    velonomad- No I have not. I have watched someone else play with propane/ox. They had an ox generator too. I started with A/O, ended up getting that first torch set (still have the handle and tips). These days a run a mid size and a small size A/O set up. When I was at Cyclery North (Chicago in 1985) we played with the torch and such to see if we could help each other with heat control on the larger frame parts. We decider that with practice a second torch could be an advantage in heat up speed and maintaining the temp level on shells and crowns. But we didn't ever use this during our actual frame building. Andy.

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    I've built two frames with the MAP/Oxy set up. One lugged silver brazed and the other fillet brazed. You really burn through the oxygen and it takes a long time to get things hot enough especially fillet brazing. The silver brazed lugged frame was better suited to the Map/Oxy. The fillet brazed frame was very hard to heat and in the end some of my joints were inadequate, aka I ripped the headtube off two days ago after overshooting a jump! It hurt and now I wait until I can pony up for a small oxy/acetylene torch before tackling another fillet brazed frame. The lugged frame is still going strong after 1 1/2 years of commuting and occasional trail riding. It is a lugged 1 1/8" HT. I got the lug kit from Nova cycle supplies. I think there were more than 1 choice for 1 1/8 lugs there.

  15. #15
    Older I get, Better I was velonomad's Avatar
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    Quote Originally Posted by adrapp View Post
    I've built two frames with the MAP/Oxy set up. One lugged silver brazed and the other fillet brazed. You really burn through the oxygen and it takes a long time to get things hot enough especially fillet brazing. The silver brazed lugged frame was better suited to the Map/Oxy. The fillet brazed frame was very hard to heat and in the end some of my joints were inadequate, aka I ripped the headtube off two days ago after overshooting a jump! It hurt and now I wait until I can pony up for a small oxy/acetylene torch before tackling another fillet brazed frame. The lugged frame is still going strong after 1 1/2 years of commuting and occasional trail riding. It is a lugged 1 1/8" HT. I got the lug kit from Nova cycle supplies. I think there were more than 1 choice for 1 1/8 lugs there.
    That is interesting about your failure. it certainly sounds like this newer version of MAPP gas is not hot enough for fillet brazing. The MTB frame I fillet brazed with the old style/original formula Mapp 26 years ago is still going strong.
    Last edited by velonomad; 08-13-13 at 05:48 PM.

  16. #16
    tuz
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    Oxy-propylene (so-called mapp) is more than adequate to brass-braze bikes. So is propane and it burns cooler. If you were having trouble heating things up I suspect the torch tip size was inadequate; that's likely the case if you were using the torch that comes with the small oxy-mapp kits. Typically you'll need a range of tip sizes for braze-ons, lugs, fillets, crowns, silver and brass. The good brazers can get away in using a single, big, tip.
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