Wattsup

So I was rinsing down the bike and I noticed this. It's a titanium frame. That's the left chain stay. It's a little hard to reproduce here what I see, but along the top edge of the weld, it *appears* to have a non-flush edge, like a crack. I can't feel an edge there, and I tried to see whether the edge would catch the point of a knife or the edge of a piece of paper, but it doesn't. The right chain stay seems normal. Additionally, although I know next to nothing about welding, I did read a bit about the art of welding titanium a few months ago, and if I remember correctly, a good weld is supposed to have many overlapping lines, like the intersecting weld shown there has....not that "smear" of a weld, the one in question. So what do you think?

fietsbob

where? you want to add an arrow in that picture.. ?


I only see they smoothed bead on the end of the chainstay to dropout, a bit, before laying down the welds for the disc brake mount.

to get the 2 parts of the frame in the ideal place, perhaps ?

Wattsup

It's the top edge of that weld, the chainstay to dropout, the edge on the dropout. Maybe it's just a shadow? I don't see an edge like that in any of the other welds.

trailangel

You cannot judge welds by looking at them.

Troul 

Compare it to other like bicycles?

308jerry

It's a single pass weld.... Excellent penatration, ride it like you stole it..

jadocs

Wattsup

Why? Will it make me go faster?

Wattsup

So it's not to break on the next big hole? Good!

tagaproject6

Any professional welders here? Metallurgists, maybe?

MikeyMK

Looks like someone's pushed chewing gum into it, and then painted it silver. Id just use it to go to the shops.

CliffordK

The "smeared" weld likely has been ground.

I don't see anything concerning about the remaining material. However, one might ask why the manufacturer felt the need to grind the one weld.

It is difficult to judge things like penetration from the photo.

jadocs

FBOATSB

45 years enough? That looks like a joint between a casting, a thin wall tube, and a plate(possibly billet). The only defects I can see that weren't ground off prior to any inspection are termed "lack of fusion". Definitly not artisanal.

Koyote

Just ride.

tagaproject6

This is when we need one of those "like" buttons.

TiHabanero

Looks out of place for sure. A peanut butter weld next to a nicely stacked weld is unusual to see.

coffeesnob

..

2seven0

Aerospace industry welding has been my profession since I first qualified to the old MIL-T-5021 spec in 1982- superseded my MIL-STD-1595 now AWS D17.1. That said every Ti process spec in existence does not allow any discoloration of material beyond light amber/straw color. The brushing or sanding areas on the welds were probably done to remove discoloration indicating inadequate gas shielding (they better have argon purged the ID of those tubes) which is still evident at the very edge of the weld bead in small areas. The small crater at the tie-off (end) of the weld in Pic 2 indicates poor technique & probably would fail a fluorescent penetrant inspection but in this case is cosmetic only. Since no cracks in the weld, parent material and joint area appear to exist it will probably last your lifetime without ever failing. I wouldn't fret over it.
Just my 2 cents.
West

CliffordK

It could well be that the parts are assembled in subunits in assembly line fashion. Especially if it is a large factory operation.

So, the welder that makes the rear triangle may not be the same one that makes the forward triangle or assembles all the pieces.

The brakes may well be added in a much later step... thus different welders working on them.

It may be possible that some of the jigs get in the way if one tries to do too much at a time.

In fact, the weld for the dropout likely encircles the tube (for a strong joint), then the brake is added on top so that it actually has a weld line going under it.

It may well need a little bit of touch-up for that brake to fit properly, over the top of the previous weld. In fact, getting a clean surface with close tolerances for a second weld will be key to getting a good weld and a strong joint.

Since the brake is only on the left side of the bike, the right and left sides could be expected to be asymmetrical simply due to the second fitting the brake over the top.

Did they grind more than they needed? Probably, but it may also look funky if they just ground a very localized area.

I don't think I have any native Disc brake Titanium frames to compare to (have thought about adding some after-market).

However, I don't think @Wattsup mentioned the brand. I wouldn't be surprised if most, or all bikes from the same manufacturer looks similar.

fietsbob

Since its a bicycle not an Airplane or Spacecraft , it should be fit for purpose ..

CliffordK

Bicycles don't fall out of the sky killing all passengers onboard.

However, bicycles are often engineered with rather tight stress tolerances. I often see factory gussets added to bikes in odd places, which I wonder if they have to do more with empirical testing than engineering.

Both bikes and planes are subject to repeated stress and fatigue cycles. Open cracks tend to propagate.

And failures can be traumatic, or potentially life threatening.

But, as I suggested above, that may also be an artifact of stepwise assembly with the dropout being welded all around, then the brake mount being added later.

fietsbob

Hydroforming creates shaped tubes , but its only affordable in aluminum,,

It gets shaped & sized, to meet its foreseeable stresses..

that's why there is a lot of it out now..

Wattsup

Salsa Vaya Ti, 2016.

WizardOfBoz

This. Also, the welds look like what welders call a "stack of dimes". That is, good welding.
But I think 2seven0 is probably certainly more qualified here.