aluminum welds finish

[isaak]

Would be interesting to hear if somebody has facts why welds on Trek aluminum road bikes are very rough and unfinished and other makes, for example Cannondale, finish is very smooth and welding non visible.
Does it has to do with labour cost of finishing welds or different process of welding ,or leaving large rough welds gives more welding contact area and strength to frame joints ?

[mtbbmet]

double pass welding vs single pass. Also bondo and filing

[ultraman6970]

I remember i read time ago that the welds are basically polished "in hot" per say, and thats the reason they get them smooth. The issue i see is that the costs of manufacturing a cheap a$$ trek would go to the roof if they add an extra step.

Bondo is a pretty bad filler, maybe aluminum/metal filler? there are many fillers now a days in the market but in a bike to use bondo is a pretty bad idea, it will start cranking maybe after a year maybe soon. There are fillers now a days that bond with the metal no problems forever.

[isaak]

besides estetics, which weld and finish is better for strength of frame ,rough like on Trek or smooth finished ?

[terbennett]

Not sure which is better strength wise but if you look at late 80s- mid 90s Treks, they had smooth welds too. Thinking it is to cut costs. Besides a CAAD frame is a much better frame than the Trek's Alpha frame. You should be able to see it in the cost as well. That's probably why you don't see Trek building a $2600 Dura Ace-equipped aluminum framed bike

[isaak]

i could be wrong but think the same, to save cost.
if Cannondale welding and finish of welds would not be as strong as Treks their frames would fall apart and they would not stay in business to long.

[rx-79g]

Not sure which is better strength wise but if you look at late 80s- mid 90s Treks, they had smooth welds too. Thinking it is to cut costs. Besides a CAAD frame is a much better frame than the Trek's Alpha frame. You should be able to see it in the cost as well. That's probably why you don't see Trek building a $2600 Dura Ace-equipped aluminum framed bike

The original Trek aluminum frames weren't welded. They had cast lugs bonded to tubes.

Cannondales and Kleins were over-welded and ground smooth. I have an '89 Cannondale with the paint stripped and polished - no filler needed or used. Who knows how crazy they looked before they were ground down.

Treks have big thick normal aluminum TIG welds that are only surface finished. Other brands look very similar, though some companies welds are a little smoother due to either better technique or different robot welder setting. Due to the thickness of aluminum TIG welds, they are pretty hard to get pretty.

[ewitz]

Before carbon was a mainsteam frame choice quality aluminum welds were a selling feature. Good welds looked like a nice stacked roll of dimes across the welded surface. Smooth and evenly distributed.

The smooth welds seen on Crack'n'Fails are a cosmetic cover up.

[rx-79g]

Before carbon was a mainsteam frame choice quality aluminum welds were a selling feature. Good welds looked like a nice stacked roll of dimes across the welded surface. Smooth and evenly distributed.

The smooth welds seen on Crack'n'Fails are a cosmetic cover up.

Cannondales were copies of Kleins. Both predate almost every other welded aluminum frame you could name, so this comment really doesn't make much sense.

[laffeaux]

Cannondales were copies of Kleins. Both predate almost every other welded aluminum frame you could name, so this comment really doesn't make much sense.

Agreed. In the 80's (at least in the US) Cannondale, Klein, Cunningham, and American were the first producers of welded aluminum frames - as pointed out by others (Trek, Raleigh, etc) used aluminum tubes bonded to lugs. American and Cunningham frames had "stack of dimes" welds (Cunningham's welds were a bit less uniform), while Cannondale and Klein came with a weld that was ground smooth. Aesthetically they're different, but I don't think that either is stronger. Smooth welds can hide imperfections, but a smooth weld does not mean that it was done to hide imperfections - it's most often done because people like the way it looks.

[PlatyPius]

Agreed. In the 80's (at least in the US) Cannondale, Klein, Cunningham, and American were the first producers of welded aluminum frames - as pointed out by others (Trek, Raleigh, etc) used aluminum tubes bonded to lugs. American and Cunningham frames had "stack of dimes" welds (Cunningham's welds were a bit less uniform), while Cannondale and Klein came with a weld that was ground smooth. Aesthetically they're different, but I don't think that either is stronger. Smooth welds can hide imperfections, but a smooth weld does not mean that it was done to hide imperfections - it's most often done because people like the way it looks.

Exactly. It gave the smooth, flowing-lines look of modern carbon before anyone even knew what that was.

[terbennett]

The original Trek aluminum frames weren't welded. They had cast lugs bonded to tubes.

Thanks for the info. I always liked the look and thought that they were welded. I was wrong but now I know why they looked that way,

[rx-79g]

I'll just throw this bit of history out:

Klein probably ground his welds for both aesthetics and because some of his tube miters weren't going to look right, since down tubes were thicker than headtubes and toptubes bigger than seat tubes. So those joins had to be over welded to bridge the gaps, and the extra ground off to keep the weight reasonable. The aesthetic is taken from filet brazing.

Klein had a patent on the level of stiffness he achieved over a steel frame of the time. Cannondale violated that patent and had to pay Klein (not sure how that worked out, exactly). Everybody else had to avoid using the really large tube diameters Klein did, so their miters were more appropriate for glued lugs or more normal looking welds. If you look at the old Treks, Litage, Diamond Back or other aluminum frames of the time you'll see that their tubing is always smaller than a Kleins. This difference became most noticeable with the '89 3.0 Cannondales that had 2" downtubes.

So ground welds were a necessity on the Klein/Cannondale design, and pointless on all the other aluminum frames.

[mike.]

Also depends on the quality of aluminum material being welded.

[rx-79g]

Also depends on the quality of aluminum material being welded.

It's not usually a "quality" difference. 6061 is better tubing for welding and can take more heating than 7000 series, but both are high quality aerospace grade tubing. They are just built for different uses, and neither makes for a "better" frame.

I do remember that Schwinn had a welded frame in the late '80s that was 5000 series - never saw that anywhere else.

[laffeaux]

Klein probably ground his welds for both aesthetics and because some of his tube miters weren't going to look right, since down tubes were thicker than headtubes and toptubes bigger than seat tubes. So those joins had to be over welded to bridge the gaps, and the extra ground off to keep the weight reasonable. The aesthetic is taken from filet brazing.

That makes a lot of sense.

American used small-diameter thicker-walled tubing and didn't run into the same issues. This pic is of 1985 frame made from 6061. The welds are about all that lets you know that it's aluminum.

[doogiepa]

I'll just throw this bit of history out:

Klein probably ground his welds for both aesthetics and because some of his tube miters weren't going to look right, since down tubes were thicker than headtubes and toptubes bigger than seat tubes. So those joins had to be over welded to bridge the gaps, and the extra ground off to keep the weight reasonable. The aesthetic is taken from filet brazing.

Klein had a patent on the level of stiffness he achieved over a steel frame of the time. Cannondale violated that patent and had to pay Klein (not sure how that worked out, exactly). Everybody else had to avoid using the really large tube diameters Klein did, so their miters were more appropriate for glued lugs or more normal looking welds. If you look at the old Treks, Litage, Diamond Back or other aluminum frames of the time you'll see that their tubing is always smaller than a Kleins. This difference became most noticeable with the '89 3.0 Cannondales that had 2" downtubes.

So ground welds were a necessity on the Klein/Cannondale design, and pointless on all the other aluminum frames.

I will never understand how Klein got a patent on frame stiffness...

[rx-79g]

I will never understand how Klein got a patent on frame stiffness...

He patented the method of making an oversized aluminum tube frame and defined the performance of the design via stiffness. Bicycles had a pretty narrow standard of perfermance back then.