Merlin Metalworks: welding

Tim Delaney struck his first welding arc in 1975, when he was studying stick-welding steel--"A lot of smoke, a lot of sparks," as he recalls it now. He joined Merlin in 1987, and perfected the puddle weld style that distinguishes our frames to this day.

How hard is it to weld titanium?
Titanium is actually easy to weld. The tricky part is weld consistency and uniformity. And preparation--the cleanliness, the gas purge, even the humidity--all those factors have to be right. There's special equipment that is cumbersome to work with, and titanium looks awful if you don't have just the right factors involved. But the actual welding is fairly easy.

What do you use to fill the joints?
We use a 6-4 titanium alloy because it is the best filler to weld 3-2.5. It flows very well and it creates very nice welds. And it is also stronger than 3-2.5.

And the two work well together?
Yes, there's no problem putting the 3-2.5 and 6-4 alloys together. Also, we use three diameters of argon-purged filler rod and each diameter is specific for some part of the bike. If the rod is too small, you run into trouble as far as necessary strength or necessary fill. Or if the rod is too large, you'll get a sloppy weld.

How do you judge a good weld?
What I look for first is uniformity in the weld bead, and also the way the tubes are welded together; you can see the weld bead integrity right off the bat. Then color; it must be silver, or slightly straw colored. And the texture is important, too; if the weld bead is dull or looks hazy, you know the temperature was too high. If it's silvery and shiny, the weld temperature and preparation were correct.

Then penetration, which is how much of the filler actually penetrates the joint. With our tubing, since we use such a thin wall, you can actually see a pattern of the weld on the inside of the tube. That's a sign of good penetration , and that all of the parts have fused into one. It has to occur for a good weld, and it is something to look for.

How does a customer judge a good weld?
I would look for a uniform puddle. If the puddles are circles, that's good. If they are ovals, or a lima bean shape, that is the start of the weld being overheated, or something else that isn't right.

Can you explain single pass and double pass welding?
Sure. We use both. A single pass weld is usually done where the weld bead does not have to be large or super strong. We use that for small parts. On the bigger joints, you may need a root pass for proper penetration and strength. Then you use a finish bead, or dress bead, to complete the weld, which is a standard welding practice whenever you have a large part that requires a high-strength weld.

The first pass is for penetration, and the second pass is the remainder of the joint fill, because you can't fill it all at once. If you try, you are going to burn through--undercut--or not get enough penetration because you have to move too fast to avoid burning through--all sorts of problems. The root pass and the finish bead are the way to go, definitely.

And there's no trouble with heating the join twice?
No, as long as all the conditions are right. If it is heated to the same temperature, and the joint is clean, and you have the argon atmosphere, the end result is a quality, uniform weld.

How long does it take to weld a frame?
There are four steps: Tacking the frame, welding the frame, tacking the parts, and welding the parts, and there are alignment checks all through there. It could take anywhere from three to seven hours. Newsboys can take seven hours, just for the welding.

It must be great to see the bikes go by at a race.
Oh, it is, it's very rewarding. It's a cool feeling. If you see someone on a Merlin in VeloNews, or at local races--it's a great feeling of pride. You know what went into it, you know the design. And when I see other makers of bikes copying our designs, such as the chainstay, it's like, you know, Rob came up with that, now everyone's doing it, what's next?

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