Weird crack ti frames

[2manyoranges]

I have never had any cracking on the Ti frames I have had. Maybe because I am a whippet and generally 'ride light'.

But I have seen a number of instances of cracking in a weird place - the RH side of the top tube-seat tube interface. Like this one (not mine):

https://www.ebay.co.uk/itm/Orange-Vit-t ... :rk:1f:0

I have seen this repair and crack location on a number of Ti frames - with some people drilling at each end of the crack, then welding, and then the crack appearing again. I can see how chain stays crack in Ti frames (and seen that many times) but I wonder if the stress forces actually concentrate at this point in a double-diamond frame? Any thoughts...?

 

[RickTheUncivil]

Re:

That one was mine. The crack was there when I bought it so don't know how it happened. The chap that sold it denied ever seeing the crack so it may have happened in transit. I figured it had taken a (sideways?) knock that had fractured the tube.

You seen the other thread going around on this topic?

 

[2manyoranges]

Re:

It’s a lovely bike and your repair seems to be settled, which is good.

Re origins, I’ve had too many instances of ‘well it was fine when I posted it...’ that I treat such claims with a bit (a lot?) of suspicion.

It seems a weird location for a crack running in that direction I think, unless you begin to think about the leverage in a frame when you really stand up and honk the frame. I have seen other instances of exactly the same location of crack, and exactly the same pattern and direction.

 

[mattr]

Probably where the two heat affected zones meet/bridge. You'll probably find another weak spot on the other side.
Welding on Ti on to thin walled structures isn't easy anyway. Then putting two welds that close......

 

[kingoffootball]

My Gary Fisher Prometheus cracked there. It had previously cracked at the same spot (viewtopic.php?f=6&t=28385) having had damage there and a weird titanium patch repair to the top tube, so it was probably inevitable it would go again eventually. Not helped by having this much seat post as leverage, I'm sure:

It was fine until a pedestrian stepped out in front of me on a cobbled street and in avoiding them I hit a huge pothole and was rewarded with a loud crack and a few hours of being a bit too sore to want to sit down at work.