easy/safe to weld exhaust pipe with propane torch?

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by motor_bike_fanatic, Apr 3, 2012.

  1. motor_bike_fanatic

    motor_bike_fanatic New Member

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    I have a modded pocketbike expansion chamber that fell apart because I previously had it put together with fiberglass. I decided welding it is a lot cheaper than getting a new one. I got a decent quote from a local shop, but the shop is about 5 miles from me, and my only way of getting there is pedaling my bike, a beach cruiser, up some steep hills. Home depot is right down the street, and they have a propane torch for about 13 bucks, a stainless steel brush for 2.50, and copper pipe couplings are really cheap too. so for about the same price as the welding shop, I can do this at home myself. I was thinking of using copper pipe couplings because that might make it easier for me. Or should I use some type of flux and solder, like how they weld plumbing pipes together? I was actually even thinking of buying a length of copper tubing so that I could extend my head pipe a little for a wider powerband. Also, can I cool the parts in water after welding them? I have multiple spots to weld, and speeding up cooling time would make the whole process a lot easier. Thoughts?
     
  2. halfevil333

    halfevil333 New Member

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    Nothing applied with a propane torch is going to last. The pipe itself will reach temperature hot enough to weaken whatever solder used, then vibrations will do the rest...
    If you get MAPgas (a lil hotter than propane) and a brass brazing rod, you may have a better chance. Although, I don't believe the copper will stay all that strong after the constant heat/cool cycle of running bike, stop somewhere, run bike....
    Would be my suggestion just to lug it on down to the welding shop. -bribe a buddy to bring you!
     
  3. Al.Fisherman

    Al.Fisherman New Member

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    Brass brazing rod will work fine. I made a exhaust pipe (copper tube) for both my son's choppers and to date (3+ years) I haven't had a break. NOTE: I use a oxygen/propane torch.
    [​IMG] [​IMG]
     
    #3 Al.Fisherman, Apr 3, 2012
    Last edited: Apr 3, 2012
  4. halfevil333

    halfevil333 New Member

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    Ok, so perhaps I was wrong about it becoming brittle from the heat/cool/heat/cool cycle.
     
  5. motor_bike_fanatic

    motor_bike_fanatic New Member

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    So Al, my budget is about 20 to 25 bucks. The shop quoted me a price of ten to twenty dollars. the torch I will be getting is propane, not propane/oxy. the pipe has an entire section missing, so that section will need brazed in in two places. is the torch and the brazing rod all I need, or do I need the pipe couplings as well? do i need flux or solder? or can i just heat the pipe with the torch and use the brazing rod to make a joint between the sections of pipe? can I cool the pieces in water?
     
  6. Bicycle Motor Fun

    Bicycle Motor Fun New Member

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    Large sections of metal, copper especially, will "sink" a lot of heat. As mentioned earlier, I would use a MAP gas torch, available at HD, Lowes, etc. I would use Silver Solder, it will take a little less heat than brazing rod-check a local welding supply for the Silver Solder, it is extremely strong. BMF
     
  7. silverbear

    silverbear The Boy Who Never Grew Up

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    I don't think you will be successful using a regular propane torch even with a Map tank. Map plus Oxygen makes a lot more heat. I attempted a copper pipe with silver solder and within a few minutes several of the joints melted from the heat of the exhaust. I wasted a good bit of money between the copper joints and silver solder with nothing to show for it.

    If you need to stay in budget and also want to be sure of success, have the shop do it. If you are willing to invest more for the right stuff then do it yourself, especially if you think you will be doing this again on another build.
    SB
     
  8. Al.Fisherman

    Al.Fisherman New Member

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    Propane torch won't cut it, although I've never used it, MAP and oxygen should do the trick.
    Silver solder is good for water pipes and A/C, but it is too brittle to use on anything that will move. Anytime I join 2 pieces of copper tube, I use a coupling, unless one tube can be inserted into the other.
     
    #8 Al.Fisherman, Apr 3, 2012
    Last edited: Apr 3, 2012
  9. dragray

    dragray New Member

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    doing anything with propane is not welding...it would be soldering at best.
    Propane just doesn't get hot enough to melt anything more than silver solder. it will not melt brazing rod.
    map gas might, but i'm afraid that you may end up with a cold joint which will eventually fail (but i could be wrong because i've never used map gas)
    if you want to "weld" you need to get a wire feed welder to do the job right, and use steel pipe.
     

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