Chainstay frame crack on a steel Woodrup frame: advice please

[Illaveago]

That looks like the result of dropping the chain a few times and not being careful about unjamming it. The crack has spread from the weakened area. Any decent frame-builder should be able to give you an opinion as to whether the rest of the frame is sound and is worth repairing.

I thought I would just let you know of my discovery of why the chainstay was worn through having dismantled it prior to having it repaired. It looks like whoever built the frame last put the BB in the wrong way round bringing the chainring closer to the frame. A slight buckle in the chainring meant that it would cut into the stay. Why it wasn't heard or noticed I don't know but it must have continued for quite a while to cause that amount of damage.
A new stay was fitted by Woodrup. When the weather improves I will get round to spraying it.

 

[rogerzilla]

That must have made a huge noise. I've built bikes where the chainring is a hair's breadth from the stay (135mm rear ends and fixed gear are problematic in this regard) but it never made contact, since the flex caused by pedalling tends to only be at the top and bottom of the ring. If the ring made contact on your frame, it was doing it on every single rotation.

 

[gbb]

A moot point really but also possible a larger chainring has been fitted that was designed ?
I 'upgraded' a mtb once, the idea I could simply fit a larger chainring to get better suited gearing for me. The second I fitted it, I could see now the chainring is rubbing the stay. Oh well, back to the drawing board..

 

[Illaveago]

Wheels can cause similar damage if they slip to one side. Wet muddy tyres make nice grinding paste.

 

[rogerzilla]

A moot point really but also possible a larger chainring has been fitted that was designed ?
I 'upgraded' a mtb once, the idea I could simply fit a larger chainring to get better suited gearing for me. The second I fitted it, I could see now the chainring is rubbing the stay. Oh well, back to the drawing board..

I had to run 39/13 when I converted a Cannondale MTB to fixed - that's a 70" gear with 26" road tyres. The chain tension with that small ring was too high, really, and the ENO eccentric hub kept creeping around and losing tension.