Could this ally frame be cracking ..?

[T I M]

Hi Folks,

My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser) and
has recently noticed what *could* be the beginning of a crack through the front edge of the fillet
weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins the frame). It
was spotted because the paint seems to have gone missing around the possible crack (not where or how
paint would of been chipped off)?

He is of a medium build, medium fitness 35 yr old and has done about 4k miles on it with probably
75% 'on road' use. He is unlikely to have done anything 'silly' on the thing (like 8' drops etc) and
generally looks after his stuff.

Could anyone please give us some guidance as to this sort of thing and if it is dangerous or likely
to suddenly fail etc.

All the best ...

T i m (Nth London)

 

[James Annan]

T i m wrote:
> Hi Folks,
>
> My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser)
> and has recently noticed what *could* be the beginning of a crack through the front edge of the
> fillet weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins the
> frame). It was spotted because the paint seems to have gone missing around the possible crack (not
> where or how paint would of been chipped off)?

You mean there is no sign of a _crack_ at the site of this 'possible crack'? What sort of a crack is
that then? I've got a few paint chips missing on my bikes, too.

James

 

[Huw Pritchard]

On Wed, 30 Apr 2003 22:51:39 +0100, T i m did issue forth:

> My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser)
> and has recently noticed what *could* be the beginning of a crack through the front edge of the
> fillet weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins the
> frame). It was spotted because the paint seems to have gone missing around the possible crack (not
> where or how paint would of been chipped off)?
>
> He is of a medium build, medium fitness 35 yr old and has done about 4k miles on it with probably
> 75% 'on road' use. He is unlikely to have done anything 'silly' on the thing (like 8' drops etc)
> and generally looks after his stuff.
>
> Could anyone please give us some guidance as to this sort of thing and if it is dangerous or
> likely to suddenly fail etc.

It's really difficult to judge something like this without seeing it, but my advice would be to go
and see a reputable bike shop and pick their brains as to whether it's a crack or not.

If it is a crack, then it's a problem. Cracks in welds that are big enough to be seen by the naked
eye tend to not remain that size for very long. The use that your friend has given the bike is
probably not related, cracks like this tend to start from a poor weld where there is some sort of
nice initiation point for a fatigue failure lurking deep within the weld.

--
Huw Pritchard Replace bounce with huw to reply by mail

 

[T I M]

On Thu, 01 May 2003 07:50:37 +0100, "Huw Pritchard" <[email protected]> wrote:

>On Wed, 30 Apr 2003 22:51:39 +0100, T i m did issue forth:
>
>> My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser)
>> and has recently noticed what *could* be the beginning of a crack through the front edge of the
>> fillet weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins the
>> frame). It was spotted because the paint seems to have gone missing around the possible crack
>> (not where or how paint would of been chipped off)?
>>
>> He is of a medium build, medium fitness 35 yr old and has done about 4k miles on it with probably
>> 75% 'on road' use. He is unlikely to have done anything 'silly' on the thing (like 8' drops etc)
>> and generally looks after his stuff.
>>
>> Could anyone please give us some guidance as to this sort of thing and if it is dangerous or
>> likely to suddenly fail etc.
>
>It's really difficult to judge something like this without seeing it, but my advice would be to go
>and see a reputable bike shop and pick their brains as to whether it's a crack or not.
>
>If it is a crack, then it's a problem. Cracks in welds that are big enough to be seen by the naked
>eye tend to not remain that size for very long. The use that your friend has given the bike is
>probably not related, cracks like this tend to start from a poor weld where there is some sort of
>nice initiation point for a fatigue failure lurking deep within the weld.

[T] Hi Huw,

Thanks for that.

My friend was allerted to this possible problem by the unexplained sliver of pain that suddenly went
missing in a location and manner that did not relate to chipping or an external effect in any way?

If you can imagine the (naturally bent) downtube, then a couple of inches up from the bottom bracket
are two parallel vertical plates welded to the frame to form a mount for the fwd end of the rear
swing arm.

The plates are only welded along the outside edge (and about 3" long) and an ally tube welded
between them (forming the pivot) to brace the two plates.

On one of the plates, the paint has vanished in a 1/2" long thin strip over the middle of the fillet
weld and from one end of the plate (ie, not in the middle). As the plates are olny welded on the
outside one can visualise the unwelded inside edge and bottom of the plate just sitting on the frame
and possibly aligning with the line of any 'crack' that may be forming?

I suppose he could remove more of the paint, clean the area and examine it with a strong magnifying
glass or small microcope?

I hope this describes the problem a bit better. I'm not sure we have any decent bike shops around
here to get the frame examined?

All the best .. and thanks again ..

T i m

 

[T I M]

On Thu, 01 May 2003 07:42:26 +0900, James Annan <[email protected]> wrote:

>T i m wrote:
>> Hi Folks,
>>
>> My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser)
>> and has recently noticed what *could* be the beginning of a crack through the front edge of the
>> fillet weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins the
>> frame). It was spotted because the paint seems to have gone missing around the possible crack
>> (not where or how paint would of been chipped off)?
>
>You mean there is no sign of a _crack_ at the site of this 'possible crack'? What sort of a crack
>is that then? I've got a few paint chips missing on my bikes, too.
>
>James

Hi James,

It's a 'strip' of paint missing (10mm x 1mm, rather than a 'chip') over the middle of a fillet weld,
just where it might crack if it was going to do so?

One can 'visualise' a crack due to the shape of the missing paint but can't actually see one as such
(with the naked eye that is)

The trigger for the question was why the paint would suddenly 'fall off' at what is obviously a
high stress point over a single sided weld and if slight movement was happening, suggesting summat
was wrong?

All the best ..

T i m

 

[M-Gineering Imp]

T i m wrote:
>
> On Thu, 01 May 2003 07:42:26 +0900, James Annan <[email protected]> wrote:
>
> >T i m wrote:
> >> Hi Folks,
> >>
> >> My non internetted mate has a bought-from-new 99 Ridgeback "Mr Black" (ally framed full susser)
> >> and has recently noticed what *could* be the beginning of a crack through the front edge of the
> >> fillet weld at the forward 1/2" of the rhs rear swinging arm mounting gusset (where it joins
> >> the frame). It was spotted because the paint seems to have gone missing around the possible
> >> crack (not where or how paint would of been chipped off)?
> >
> >You mean there is no sign of a _crack_ at the site of this 'possible crack'? What sort of a crack
> >is that then? I've got a few paint chips missing on my bikes, too.
> >
> >James
>
> Hi James,
>
> It's a 'strip' of paint missing (10mm x 1mm, rather than a 'chip') over the middle of a fillet
> weld, just where it might crack if it was going to do so?
>
> One can 'visualise' a crack due to the shape of the missing paint but can't actually see one as
> such (with the naked eye that is)
>
> The trigger for the question was why the paint would suddenly 'fall off' at what is obviously a
> high stress point over a single sided weld and if slight movement was happening, suggesting summat
> was wrong?
>
> All the best ..
>
> T i m

some pictures of cracks might help: www.m-gineering.nl/oopsg.htm

--
Marten

 

[Tony Raven]

In news:[email protected], T i m <[email protected]> typed:
>
> Could anyone please give us some guidance as to this sort of thing and if it is dangerous or
> likely to suddenly fail etc.
>

If it is a crack then you should stop riding it. The best way to see if its a crack is to find a
local engineering shop. They will have a dye and UV lamp which will very quickly show if there is a
crack there or not.

Tony

--
http://www.raven-family.com

"All truth goes through three steps: First, it is ridiculed. Second, it is violently opposed.
Finally, it is accepted as self-evident." Arthur Schopenhauer

 

[T I M]

On Thu, 1 May 2003 11:57:24 +0100, "Tony Raven" <[email protected]> wrote:

>In news:[email protected], T i m <[email protected]> typed:
>>
>> Could anyone please give us some guidance as to this sort of thing and if it is dangerous or
>> likely to suddenly fail etc.
>>
>
>If it is a crack then you should stop riding it. The best way to see if its a crack is to find a
>local engineering shop. They will have a dye and UV lamp which will very quickly show if there is a
>crack there or not.
>
>Tony

[T] Hi Tony,

Thanks for that .. I'll tell him.

I believe there is a highg tech engineering Co near him that may have such stuff.

All the best ..

T i m