Help. Frame broken.

[juice]

A friend is 2k into EV 1 and near Santiago. The frame on his 2015 dawes grand tour with disc brakes has developed a 30mm split.
His options are a repair or new frame. Unfortunately they don’t seem to make the same frane anymore. Theres a new super galaxy disc frame on eBay would this be compatible. Any opinions on how safe a weld would be.

Thanks

[geocycle]

I usually leave these for Bruce, but it looks just like the braze on to me. If so I’d have it repaired or bodge it with jubilee clips or similar to get through a tour.

[willcee]

Depending on the loading he is carrying on that rack... to get home, i would fashion a steel U section bracket, very neatly tight and well fitted to the curves drill the brase on out or use a longer existant type and bolt this clip around the brase on using holes drilled in it both ends.. BUT if you can get hold of a guy who knows his steel and has good brasing skills its a simple enough repair operation but will need repaint on that stay.. imv that rust is coming from internal corrosion for some considerable while... will

[Brucey]

…. Any opinions on how safe a weld would be....

depends how good the weld is.....

However a weld repair here is liable to be difficult because the original fitting appears to be brazed on, and welding over braze metal is kind of tricky. Trying to braze up the crack is unlikely to work.

The damage itself doesn't look that recent; the rust in the crack suggests it is several weeks old at least. I've seen this kind of damage (and worse) caused many times by such things as

a) persistently carrying just one pannier (or unevenly loaded panniers) and/or
b) using a rack that isn't well triangulated at the rear and/or
c) using rack mountings which are under strain when the bolts are tightened.

Item b) causes swaying loads -which should be taken at the dropouts- to be transferred to the seat stays. In this case the stay mounts are adjustable and one of the locknuts is loose in the photo; this will cause the loads to be more like hammering (i.e. higher peak loads) and thus more likely to cause fatigue damage as the rack moves around.

To repair that damage I'd

1) remove that braze-on entirely
2) clean the surface with a file so that there is no trace of braze metal left
3) excavate the crack to remove corrosion from it
4) weld repair using whatever welding equiment is readily available locally (probably CO2 MIG)
5) dress the weld back and paint (or wrap with tape) to prevent corrosion
6) fit a P clip to the stay instead
7) make sure that the rack stay adjusting locknut is tight not loose, and that the mountings are not strained when mounted. If necessary cold-set the rack parts to suit the mountings exactly.

Provided the rack is itself stiff and properly (not unevenly) loaded I don't mind in the slightest using P clips for the upper rack mounts; if anything is going to break it is going to be a P clip and that is easily replaced; I usually carry spares and have not often needed them.

cheers

[Jamesh]

I think the rust will have damaged to stay beyond ecconomical repair and a new stay will be required.

I get you going I would get a metal worker to take a piece of 1mm thick steel and cut a 2" disc.

Measure the distance around the back of the stay from one side of the boss to the other.

Drill two holes at this distance apart with a 5mm drill bit.

Bend the plate to a u section around a piece of 12mm steel rod.
Offer up to the frame welding in place or bedding in with chemical metal or similar.

The load from a rack is then spread over a much larger area than if welded or p clipped.

Cheers James

[Brucey]

IMHO leaving the part with a crack in is not ideal; the reason is that, at the tips of the crack, stresses are highly concentrated. This means that once the crack has grown to a certain size, it will probably keep on growing even if the loads applied to the part are substantially reduced. Most strapping/reinforcing methods don't reduce the stresses seen by the cracked part to zero, leaving the crack liable to keep on growing.

The idea that the frame is damaged beyond economical repair is very far from correct. Someone who knows what they are doing could do the repair I've outlined above in less than an hour and it will probably outlast most of the rest of the bike.

cheers

[Jamesh]

Listen to Brucey....

Cheers James

[juice]

Thanks everyone.
Hopefully with this advice and a good welder he should make it to Lisbon.
He’s giving Dawes a ring on Monday hopefully they can advise on compatibility.

[Greystoke]

That's an easy repair for a welder.

[ANTONISH]

As a temporary measure a couple of decent quality rubberised (not plasticised) P clips mounted slightly above the braze on would work.
I've used them in the past for mounting a carrier on a bike without braze ons.

[Nigel]

Thanks everyone.
Hopefully with this advice and a good welder he should make it to Lisbon.
He’s giving Dawes a ring on Monday hopefully they can advise on compatibility.

I think Dawes won't know. I get the strong impression that Dawes just orders frames from Tiawan/China, puts bits on them and ships them out to shop. Not like a bike company of 30+ years ago who knew its history and who built what.

A temporary repair ought to see things through, then as Brucey said, if a proper repair is wanted, it would mean replacing the stay, which isn't a massive job for a frame builder/repairer to undertake.


- Nigel

[NATURAL ANKLING]

Hi,
First there is something going on with why it cracked?
Before remounting the rack, needs assembling loose to see where the bracket fixing is not sitting flat on the frame mounts????

I would strip the paint off.
Drill out the crack and extend say 6 mm longer with hand files.
Take off close parts like brakes cables wheel etc, likely to be affected by heat.
Pass a threaded stud through the threaded bosses and use nuts to fix the stud firm, making sure that the stud will not apply upward force on the left hand boss, clamp down onto stay with various fixings to the frame tube.
Cut a piece of steel to just over lap the dressed hole.
Tack the steel piece on with braze / clamp lightly.
Protect the boss directly from the heat source with a sheet metal, which could be clamped in place using the stud and a nut, carefully cut to fit neatly close to the stay.
Braze / brazeweld the strip on.

Braze welding sees a lower parent metal temperature.

I am not 100% sure that you can braze weld hard solder ?

[juice]

Job done. An LBS took my pal to a trusted welder. They didn't even charge him.
Many thanks for all the help. Long term i think he will get the stay swapped out. Just needs to get to Lisbon now.

[horizon]

That's amazing! Brucey: your opinion?

[Brucey]

that'll work!

cheers