Hi,

I have a Salsa Spearfish, which I absolutely love. Unfortunately, the seat tube sheared on a ride recently… right above the main suspension pivot.

I was going to get it welded from a chap that seems very good and seemed to suggest the weld would be ok. But talking to a friend, I am begging to wonder if it will hold.

Any experience of having a seat tube welded that went ok? The bike is 6066 aluminium and I don’t think the guy would be heat treating it after TIG welding.

Pictures of the frame: https://goo.gl/photos/gLqnvywxxhyPn1p48

Thanks,

Chris

😯

Warranty claim not possible? Not sure I’d be in a hurry to weld that.

How’d it happen?

I’ve seen a few similar repairs done where I work.
Looking at the crack I would probably weld the crack then wrap it a piece of tube and weld that to the weld junction below the crack and about an inch above.

Snapped my 2003 Trek liquid 30 right there and right through top tube 2″ in front of seat, I bought it second hand and Trek would not honor the lifetime warranty, only valid with the original buyer, what a load of crap, anyways I turned two 7075 Aluminium hollow inserts and lined the frame up , then got a mate to weld up burning into the insert as well as the frame. rode it hard on everything Lake District for another few years with little more than a few creaks!! I eventually stripped it and rebuilt a xs MTB for my son with the parts and scrapped the frame only because I did not want it to fail on someone else.

I would email support@salsacycles.com , it may fall within their warranty

It could be welded, but without heat treating it’ll snap again sooner or later (probably sooner). Repairing aluminium frames is a stop-gap measure, not a permanent fix.

I bought it second hand and Trek would not honor the lifetime warranty, only valid with the original buyer

Damn those horrible people not giving someone who never paid them a penny a new frame.

Thanks all.

Unfortunately it isn’t in warranty, so although Salsa have been really helpful, there isn’t much that they can do (they don’t have any Alu front triangles any more.

In terms of how it happened – no idea. There was just a bit of a banging on a ride in the Lakes, which got worse, then I realised that the seat tube was completely sheared. I guess repetitive stress…

@NorthCountryBoy – Does that type of weld generally have a “good” outcome?

@bencooper – I have heard a lot about this heat treating. Is the problem that it overstresses other areas of the tube, or the same area? Have you seen this happen yourself? I have heard lots of stories, but they have all been friend of a friend type things.

My real problem is that I cannot find another bike that is quite like the Spearfish – and I really love the Spearfish! The closest I can find is the Kona Hei Hei, which seems very good, but I am concerned about the seeming lack of rear tyre clearance :(.

Thanks!

Havnt seen a seat tube repaired. But chain stay on a rocky mountain slayer broken through and repaired as described. That went on for a long time. The repair has usually got more thickness than the original tube set.
Heat treating is usually post welding.
Heat the whole frame and let it cool slowly or quench it.

Found this on a materials site

here is one final alternative to discuss. If after welding, the structure is given a complete heat treatment (i.e., solution treat at 1000°F [540°C], quench, age at 400°F [205°C]), all of the material properties (even in the weld) will be recovered and T6 properties will be obtained. This practice is frequently followed on small structures such as bicycle frames, but it is impractical for larger structures. Furthermore, the quenching usually causes enough distortion of the structure that a straightening operation is necessary before aging.

I’m not an engineer, but it looks like it could be really difficult to repair, as it’s on an existing weld, the tube is curved, and there’s not really any room at the bottom of the tube to sleeve it.

It might be worth speaking to someone like Mike Burrows (Burrows Engineering in Rackheath, Norwich 01603 721700). He might be able to machine and bond a repair.

If you get it done properly by a decent welder it’ll be stronger than before

If you get it done properly by a decent welder it’ll be stronger than before

In that complicated weld location? Probably not….. Applying a cosmetically good weld is not the same as making a reliable fatigue resistant repair.

You’d have a new stress raiser on top of an old stress raiser, joining already fatigued adjacent material. All of which won’t have the correct heat treatment.

I work in a fatigue lab – just welding up fatigue cracks in any material is rarely successful. Reliable repairs usually involve additional patching, plugging, plating, sleeving wrapping etc.

If you read this then you would probably be convinced that 6000 series aluminium alloys need to be heat treated post-welding.

https://web.wpi.edu/Pubs/E-project/Available/E-project-042612-124752/unrestricted/Material_and_Design_Optimization_for_an_Aluminum_Bike_Frame.pdf

There is an alternative theory.
But in metallurgy meets internet fantasy forum world it is far from easy to explain ; energy of fracture, fracture toughness, yield stress etc.

The frame has failed not due to lack of ultimate tensile strength but due to fatigue fracture.
Aluminium structures that are subjected to stress reversals can and do fracture (fail) due to fatigue.

The step change in thickness from the relatively large bottom bracket and weld, to the relatively small tube does not help. High stress concentration.

Do Santa Cruz look like they rely of postweld heat treatment.
[video]https://www.youtube.com/watch?v=08ie72PcTqc[/video]

Heat treatment by precipitation hardening to the T6 condition, does increase the hardness and the UTS of the alloy, but does not solve the fracture toughness problem.

Your frame could be repaired by welding, and without precipitation hardening to T6.
As long as the weld preperation is good and clean, with no contamination of the weld then it will be acceptable.
Aluminium has poor fracture toughness, which is the resistance to fatigue from defects. Good weld prep would reduce the weld contamination / defects.

The stress concentration problem would possible be reduced, definately not eliminated though, by the additional weld material in the weld repair.

Bottom line is that your frame could be repaired by welding, only if the inside and outside of the tubes (a couple of inches either side minimum) etc at the welds are as clean as possible before welding. If they are not clean then it is pointless trying to repair it. All corrosion etc has to be removed from near the weld.

Hi I have tried to post a picture of that crack but cant seem to save it to generate a link.
Anyway it looks as it is so low that it may have started to corrode from inside the tube, possibly from water / mud etc getting in down the seat post etc.
The corroded metal becomes weak and thin and easily fatigue fails.
i have seen a similar failure around the front mech band on an ally frame where the mech had broken the paint and caused corrosion only that time it propagated from the outside.

However it still may be possible to get a good weld onto the BB shell using a split tube as a wrap and make a repair.

Are you anywhere near cumbria?

Aluminium does corrode

http://www.pardo.net/bike/pic/fail-001/FAIL-174.html

Nice post paton

If you do can you buy a helmet cam an strap it to the the seat tube so we can see when it goes again 🙁

Personally where that is would make me very dubious of any fix just due to the proximity to the original weld and BB, the shape makes supporting it difficult an a sleeve would be out of the question.

Got to be a bike somewhere, don’t just go by numbers go take a look and a ride of some, may not be the same, might be better!!

Sorry to hear your troubles – I love my ‘fish too. What size is yours?

Some on ebay http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xsalsa+spearfish.TRS0&_nkw=salsa+spearfish&_sacat=0

The frame is wrecked, so you can’t make it any worse.

So why not fix it by wrapping the area with carbon fibre? Do it thick enough and it won’t break. It’ll look ugly (unless you’re really good) but your bike will still work.

So why not fix it by wrapping the area with carbon fibre? Do it thick enough and it won’t break. It’ll look ugly (unless you’re really good) but your bike will still work.

Made me think of this!

[video]https://m.youtube.com/watch?v=niQr5Nh4vzk[/video]

I used to build all my prototype frames at my University from Alcan HE30 (6082) this always required me to apply a heat treatment to T6 after welding

I have fond memories of T6 heat treatment using a huge oven, and a huge water bath, and having a successful outcome on many frames.

Paton :- the stress concentration would only be reduced with the increase in weld metal if all the material had similar properties, i.e. after heat treatment

What about the residual stresses your putting into the area due to welding? How will that affect fatigue life.

As welded T6 Al. will have a yield of about half that of T6

Chuck it in the bin is my advice.

What about having a new front end fabricated? Surely one of the custom shops can do it?

Yeah there are a number of things to consider.
The frame probably is scrap.
But if no post heat treatment is used it does simplify things. eg the choice of filler wire etc. If the frame is to be heat treated / precipitation hardened then you are limited possibly to 4643 filler. But if not using post weld heat treatment then 4043, 5356, 5183, and 5556 filler would do the job.

It is a repair so its not going to be pretty and it is not going to be the optimal design solution. But it would possibly make the frame usable again, with some not too expensive welding.

New triangle IMO

There is a guarenteed way to fix it.

Buy a carbon ‘fish frame and store it in case your weld fix breaks. Get the ally frame welded and ride. Having spend £1600 on the spare the alloy frame will never break.

Heat treatment doesn’t really help the stress concentration – you’d need other processes like weld profiling etc. to help with that (and even then you might have some internal stress concentrations in the weld).

What heat treating will do is remove residual stresses from the heating/cooling during the weld – this will make the joint much better in terms of fatigue resistance (although it won’t make much difference in terms of strength). It can do other funky things with grain structure, but as far as I’m aware that’s not usually the aim with post weld heat treatments.

Google TWI and you might find some info – I’m not sure how much they give out for free though.

Phil Junior – You have described a stress relief post weld HT. That’s more typical of Carbon steel and the like. Its a Different process when it comes to what they define as HT of aluminium, where they Solution anneal – quench – then age harden. Its not a process to remove residual stresses but to completely change the microstructure from its as welded condition

Weld profiling does increase fatigue life in certain cases. But definitely not here. Not when the HAZ will have the properties of cheese.

Epicyclo, perfect the frame is wrecked try what you can , Ive fixed all sorts that people think is shot, might not look perfect but works fine, as for Wiggles what is wrong for someone offering a lifetime guarantee on their frame and not honouring it on a second owner? They are blatently saying our frames last a lifetime , surely this is regardless of how many owners!!Ive bought four Treks brand new , and they`ve been fine but kept any receipts to pass on.

They are blatently saying our frames last a lifetime , surely this is regardless of how many owners!!

Not really. Its all down to interpretation. “Lasts a lifetime” can mean “when the frame snaps we’ll send someone round to kill you”. Luckily for you as the second owner this isn’t the case, but if I was the guy who sold the frame I wouldn’t bother starting any long books. Trek’s ‘cleaners’ will be on their way.

smiththemainman – Member
Epicyclo, perfect the frame is wrecked try what you can , Ive fixed all sorts that people think is shot, might not look perfect but works fine…

On an mtb repairs don’t need to be perfect looking because a light covering of mud hides all. If there isn’t a light covering of mud, the bike will in the shed. 🙂