[ESENTI]

any advice will help , someone weld this and he came to me for cure

[greasemunkey]

Cut a piece of plate in a triangle shape and make a web between the tubes?

[Toggatug]

Oh boy that looks like some fun you've got there.

Do they expect the repair to look like it never happened or are they okay with a weld bead @ the break?

Also do you have the room once assembled to have a piece of tubing slipped in between the broken bits for strength?

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[Poland308]

Looks like aluminum filler on magnesium base.

[tweake]

well i say thats had its day.
it looks like a few different repairs by different people on that (there is a nice bead in a place there should not be one).
the metal is probably screwed by now.
it looks like it was a cheap bike going by the cheap repair job done on it. so its more than likely not worth the cost of fixing it properly.

to fix it properly would be to make a whole new front piece machined from scratch and have a backing tube inside the joining tubes.
even then you could not guarantee the tube won't break further along.

[Gdarc21]

Myself, Having a bit of time and alot of love for bicycles, I agree completely with Tweake. If you repair that again its going break and its probably going to hurt someone. They are welded and treated and dont take well to repairs. You may get away with it but it wont be right.
Sorry to be a bad news bear.

[tweake]

just reading up a bit on bike frames and aluminium alloys.
i see bikes frames are often 6061 (requires heat treatment) or 7005 (no heat treating but requires aging).
one of the problems with 7005 (as with all 7 series) is they are somewhat susceptible to "hot short" cracking as shown in the pic.
you need to use the correct filler. 5356 helps with stopping the weld cracking but 4043 (or all 4 series filler) can cause it to crack.
so if someone thinks its 6061 and uses 4043, then i would expect it to crack as the pic shows. downside is it would be very difficult to remove that contaminated aluminium, so the part is basically scrap.

[ESENTI]

Thank you all for your valuable suggestions and comments , i must agree that contamination of the
basic metal is the worst thing of all . I conclude that repairs like this should be done once and very well.
The welder that weld it in the first place did not weld correctly so it end it up an almost
hopeless case. The cracks are the nightmare of all welders and i think the Si12 is the
choice i would prefer in this case .The 5356 is more hard so i believe that Si12 will work , appearance is also an issue but it is not a priority .

(this case is still open until i will talk to customer and i will inform you of how this
will end up)

[cj737]

Bin it. Regardless of the repair approach, the integrity of the tubes is shot. The ONLY possible means of a proper repair is to cut the tubes from the seat post and bottom bracket, use a new headstock, and install new tubes. Cheaper to buy a new frame.

Unless that frame is a vintage, high-end model, it will cost many hundreds to repair it properly. A new inexpensive ally frame is under $300 in most places. Or swap to a modern steel frame.

Do that customer a favor and hacksaw that into 20 pieces to save him/you from injury and liability.

[tweake]

The cracks are the nightmare of all welders and i think the Si12 is the
choice i would prefer in this case .The 5356 is more hard so i believe that Si12 will work , appearance is also an issue but it is not a priority .

i think you missed the point.
if its made from 7005 then Si12 will not work. 5356 will work and more importantly work on both 6061 and 7005.
hardness has nothing to do with it. its all about the alloy make up which makes it prone to cracking.

[Gdarc21]

Thank you all for your valuable suggestions and comments , i must agree that contamination of the
basic metal is the worst thing of all . I conclude that repairs like this should be done once and very well.
The welder that weld it in the first place did not weld correctly so it end it up an almost
hopeless case. The cracks are the nightmare of all welders and i think the Si12 is the
choice i would prefer in this case .The 5356 is more hard so i believe that Si12 will work , appearance is also an issue but it is not a priority .

(this case is still open until i will talk to customer and i will inform you of how this
will end up)

Hmmmm, repairs like that should not be done at all. The root cause is obviously harsh enough to break it in that spot from new and a repair will be much much much weaker, unless you add more bracing and then its not worth it. Its not so much a matter of how at this point, rather whether you should repair.
That is really only repairable in theory, in reality it is both too expensive (for a bicycle frame) and risky to bother with.

[ESENTI]

How can you tell what kind of aluminum is ? so you can use the appropriate rod.
The way it goes I will to weld it .

[BillE.Dee]

I'd see IF I could wake up Zanc and get his input. I can only see the rider going down the hill and have that bicycle turn into a unicycle at the most inopportune moment.

[tweake]

How can you tell what kind of aluminum is ? so you can use the appropriate rod.
The way it goes I will to weld it .

i don't know of any method to work out what grade it is.
however a quick google shows 6061 and 7005 being two common bike frame material. use a filler that works with both.

but the bigger problem is that by the time you cut out all the contaminated material, there is nothing left to weld back together.
cost of machining new parts, plus welding, treatment etc, you could probably buy a whole new bike.

[ESENTI]

Very nice weld monger thank you what about the use of 3 main categories of
magnesiun where to use them . So far I thought the best rod for cracks
was Si12 ..

[ESENTI]

There are some greeks around don't worry about them

[tweake]

Very nice weld monger thank you what about the use of 3 main categories of
magnesiun where to use them . So far I thought the best rod for cracks
was Si12 ..

its more about what parent metal it is and the application, than if its a crack repair.

eg if fixing a crack in 5 series parent metal, then use 5 series filler. especially if its something like a boat where you want best corrosion resistance.
if welding 6061 thats going to be in an engine bay, i would choose 4043 filler because 5356 doesn't handle heat well.

understanding the alloy is rather important.
that becomes a big issue for repairs when you do not know what it is.

[BillE.Dee]

tweake, i don't want to sound like a dingdong, BUT, how do ya know what it is when ya don't know what it is... I'm just pickin on ya ,, tweake. Is it just safe to assume that most bike frames are made from the same alloy?

[tweake]

tweake, i don't want to sound like a dingdong, BUT, how do ya know what it is when ya don't know what it is... I'm just pickin on ya ,, tweake. Is it just safe to assume that most bike frames are made from the same alloy?

your right on the money, you never really know what it is.
if its a generic brand name bike its probably safe to assume that its made from the standard alloys the industry uses.
i think its simply a case of using a filler that is less sensitive to "hot short" (solidification cracking) which would cover both alloys.

the hard bit is, is it safe to do that repair?
how strong is it going to be if its not heat treated? not aged?

in this case, because someone has clearly used the wrong filler (which is why the weld is cracked through the centre), its contaminated the metal and not worth repairing.

[ESENTI]

i heard the someone uses 5356 in a thick cylinder head block where cavitation from
cooling water occurs , do you think because of the heat should not be used .
I informed customer today that bike frame cannot be repaired.

[cj737]

in this case, because someone has clearly used the wrong filler (which is why the weld is cracked through the centre), its contaminated the metal and not worth repairing.

I’m not sure I would agree with your assessment that the incorrect filler was used which caused the cracking. If that were true, the weld at the headstock should also have cracked. What I believes is far more likely is the “repair” was surface level puddling only, with no penetration into an already weakened stress joint. If the underlying crack was still present, than any type of ally filler will crack through. This is the significant problem with ally repairs- cracking.

Not all ally frames are heat treated afterwards either. Some definitely are, many are not, which tends to create these stress problems. And those that are tend to be in the higher price ranges, made from 6000/7000 alloys.

[BillE.Dee]

Esenti, I believe that you will sleep better at night knowing there is no worries about that frame taking a two way split and the operator not kissing the asphalt. I WOULD try to have the owner donate that frame to you so you can work on it just for shizz and giggles.

[tweake]

in this case, because someone has clearly used the wrong filler (which is why the weld is cracked through the centre), its contaminated the metal and not worth repairing.

I’m not sure I would agree with your assessment that the incorrect filler was used which caused the cracking. If that were true, the weld at the headstock should also have cracked. What I believes is far more likely is the “repair” was surface level puddling only, with no penetration into an already weakened stress joint. If the underlying crack was still present, than any type of ally filler will crack through. This is the significant problem with ally repairs- cracking.

Not all ally frames are heat treated afterwards either. Some definitely are, many are not, which tends to create these stress problems. And those that are tend to be in the higher price ranges, made from 6000/7000 alloys.

good point.

[ESENTI]

Definitely will not be repaired , too much the risk the metal is burned and contaminated due to overwork in a form of badly "washed" technique , there is not time for shizz and giggles but you are correct it had no
penetration weld was like decorative rather than it should had been.Metal filler was also an issue .
Today
I have to weld a crankcase for a Honda motorcycle ,I will use 4043 filler rod ( as you have suggest it but i think it is better with S12 4347). This is a 2 stroke engine where the kick starting and backfiring broke the area . Deep grove
with a significant preheating before and maybe a little after with little hammering as a stress
relief. For your shake a picture before and after with a feed back if it will brake.
"every science without a virtue is evil ''Greek proverb i think.

[cj737]

You will find that welding a motorcycle engine made of unknown cast alloys will be a hair-pulling experience.

Best thing to do is: preheat, clean, clean again, gouge the crack, clean, heat and clean once more. Chemically cleaning it before and after heat cycles helps pull some of the oil and grease out of the cases. Get a brand new small stainless brush for scrubbing the weld/prep area. Set your machine for lower penetration (AC balance) and more cleaning. Frequency 50-60Hz works well.

Run the torch over the repair without filler first to help prep the surface. Scrub that clean. Then lay a pass in with fresh, clean filler. Peen that pass and every successive pass. If you get porosity, stop, grind it out and start again.

And make sure you clean your filler wire really well too. And have ample whiskey on hand and be prepared to take several long walks when things go south instead of pouring more filler at it.