Welding Question....

Discussion in 'Cycling Equipment' started by Xandre, Oct 2, 2003.

  1. Xandre

    Xandre New Member

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    Hey guys, just wondering I've heard of Tig welding, I think there's like "silk" welding??? and I know there's another type of weld....Just wondering what are the differences? Also what are butted tubes? Thanks guys..
     
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  2. dabac

    dabac Well-Known Member

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    TIG stands for Tungsten Inert Gas. Basically you have a Tungsten electrode surrounded by a flow of inert gas. The welder creates an arc (sort of a sustained spark) with the electrode and uses the heat from the arc to heat/melt materials together. Sometimes material is added to the weld in the form of a thin rod and sometimes it's enough merely to melt the original material where the pieces meets up. The gas flow is needed to keep the molten material from oxidizing in contact with the air, which can prevent the weld from reaching its full strength.
    What? TIG welds can be very smooth due to how they're done, but so can most types of welds if the operator is skilled enough.

    There are a number of other welds. Oxyacetylene for instance, where you use a mixture of oxygen and acetylene to get a flame that's hot enough to melt metals together. There are MIG/MAG welds where you have a wire electrode surrounded by a protective gas. The electrode carrries the current to the spot to be welded and simultaneously acts as the additive material as it's being fed out by the welding machine. There are "stick" welds, much like MIG/MAG with a wire electrode that both carries the current and melts into the weld. Biggest difference is that a stick weld hasn't got any protective gas flow but instead relies on a thick coating of flux material on the electrode (the stick) to keep the weld from oxidizing.
    Butted means that the tube walls are thicker at the end (where the joints are) than at the middle. Makes frames lighter by putting the material where it's most needed. Joints and seams always acts as force concentrators and can often benefit from being reinforced.
     
  3. jon

    jon New Member

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    Tig welding always uses a rod to join the metals together. You never just melt the existing metals. For instance if you are welding stainless steel 316 grade, you would use stainless steel 316 rod to joint the two objects into one fused weld.
    All bike welds that I have ever seen are TIG or Heli Arc as old time welders sometimes call this type of weld.
    Double butting is always referred to as being superior to make the bike stronger,which is true, but in reality Aluminum is very difficult to weld and the material has to be double butted or thicker at the joints to insure enough thickiness to keep the the heat from blowing a hole through the thin tubing in the welding process. BTW,contrary to what one popular bikes company says, grinding the weld down and presenting a smooth and aerodymatic finish, which is pleasing to the eye, does not strenthen the bike in that joint of the welded material. It actually creates a weaker joint if anything. I always get a kick out the salepeople telling me that this is a stronger weld. A properly formed tig weld will as strong or stronger, than any other part of the tube of the frame. You should be able to bend the material at the joint at a 180 degree angle without the weld breaking. If it breaks during the bending process, the weld was not properly done, which could be caused by several reasons.
    The Tig weld should be very smooth and symetrical, and is created by the welder, moving his wrist and hand in a back and forth manner, which is referred to as "walking the cup" by welders. The tig torch has a ceramic cup, and the welder shapens the tungsten to a very sharp point on the welding end, and insterts the blunt end into the cup. The inert gas passes through the hose and torch, going through the cup and surronding the tungsten rod during the welding process.
    I have not idea who does the welding on the Olympus bikes, but the few I have seen, have a quality weld from someone who obviously is a excellent welder. Most bike welds look very good, but some are better than others.
    Most high quality Tig welders are very well paid, consider themselves as artist, and have a big ego to match!
     
  4. dabac

    dabac Well-Known Member

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    You're wrong here. If you have a good fit between the pieces, and if the pieces are thin enough to get good penetration of the heat zone and if the load case is right it is fully possible to do a TIG weld without adding any material, although I admit that adding material is the more common way of doing things.
     
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