Welding Question

Anything is possible - but IME that is particularly fucking difficult.
The difference in melting points would make it impossible to get the
stainless steel hot enough to be welded before the Al has turned
liquid and run away.

TIG might, but it would be more of a solder job than weld.

There you have your two options.

 

Is it possible to weld a bit of stainless steel onto a bit of aluminium?

There is a bodge on my bike which has broken and the bit of ali left
over isn't big enough to weld it all back together again. The guys my
dad uses [2] say you can't just weld the 2 bits together although TIG
(?} might work.

The alternative is to bolt the bit of steel onto the ali bracket, which
I guess could work. Or bite the bullet and see how much Suzuki want for
a new bracket

[1] They make aircraft undercarriage so if they can't do it, I've got no
chance.

 

As both Keelworm and PIP have said you can not weld dissimilar metals. You
can braze, solder or bond them but not weld them. Bolting together will make
one corrode faster than normal. So bite the bullet and get a new part / get
one from a breakers

AJ

 

I though both those bits you were trying to do were aluminium.

! Bodge! That's precision engineering, that.

 

I've often seen aluminium welded to steel. I'm thinking of (ally) cabins
of small ships/boats welded to a steel hull.
Steel is prolly "grade A" wot they normally make boats out of, I don't
know what sort of ally it is though.
Seems to work OK.

 

Ask Ernie at sci.engr.joining.welding.
Ernie's fucking brilliant, a walking welding encyclopaedia.

 

It's something called electrolytic effect. Happens a lot with
aluminium bicycle seatposts going into steel frames. It forms a
cathode when wet and basically welds itself to the steel I think.

 

Nope the bit Andy B made is steel. Dad thought he could do it because he
thought the bracket was also steel but it's not.

Okay! Actually it's obviously stood the test of time considering
there are supposed to be 4 points where the fairing joins on to the
bracket and it's actually been held by 1 for however long it is.

 

Time to stop being a pikey then and get on the blower to Suzuki. The
likelihood of one coming up on Ebay I'd say is fairly slim I'd say!

 

What he said. Lack of fusion on one side of the joint is likely and even
if successful, the composition of the weld (being the product of the two
parent materials and the filler) is likely to be the material from hell.
You can weld anything with the right kit and technique, it's just a
question of whether the end product has useable properties and is free
from cracks.

A brazed/soldered joint woundn't have much strength, so you'd need large
surface areas and careful joint design.

Could you get it rivetted in place or bolt it? Make sure you apply some
sort of non condutive 'isolating' compound between the two otherwise
it'll be likely to suffer from galvanic corrosion of the aluminium.

I had a look on the welding institute's website and all I can find is
laser and solid state diffusion joining techniques, both of which I
imagine are outside of your budget/capabilities.

TBH I've never come across a requirement to do this before, but then I
don't work in the Automotive industries.

 

For real? The only reason I ask is that there are other steel bits
bolted on to the bracket anyway, the steering damper for example.

I may just do that anyway.

Cheers

 

Oh, yes, indeedy.

Anybody got any tips for getting the remains of an Al seatpost out of an
Fe frame?

(And don't tell me about Sheldon Brown's tip - it didn't work. Hence why
I have the "remains" of an Al seatpost.)

 

if there's a stub to grab onto - Blowtorch and molegrips?

 

Cut off what remains to about 1" above the seat tube.Get a hacksaw blade
in the inside,sweat like mad with aching arms for 10 minutes or until it
has cut through the alli, then get some stillsons, and twist it round.It
should now be loose enough to get out.
Or,before trying the above, put the seatpost in a good bench vice (still
attached to the bike obviously) and twist the frame around.This gives a
lot more leverage compared to using stillsons/mole grips.
Alan.

 

Ha!

 

I should have been more explicit when I said "don't tell me about
Sheldon Brown's tip", shouldn't I?

 

Yeah, that was going to be my next attack strategy.

Actually, I don't think I want to fill it with CS. Perhaps suspend it
upside down in a deep tray of CS might be better, then I don't have to
worry about finding a way of sealing the BB.

Should be good for a laugh, anyway.

 

Eddie says...

Coca Cola, seriously. It used to work well for me at getting corroded
pistons out of iron bores on old bikes.

 

Due to the disimilar nature of the metals welding will probably be
impossible you will need to braze them together.

Look at:
http://www.jwharris.com/jwref/chart/

 

Hmmm... perhaps. It's that funny textured stuff that Marin did umpteen
years ago. The blowtorch didn't knacker it too much. Anyway, it's my
"old" bike, so I'm not too bothered - the Hammerite factory's just round
the corner, wonder if they've got a factory shop?

Absolutely. You should have seem me and Andy trying to remove it using a
combination of brute force, hacksaw, pliers, mole grips, hammer and
chisel. Oh, and ignorance, of course.