Impurities or alloys that complicate case or headset welding?

[Davidsquaredson]

Doing a resto. Case stud needs to be refilled and tapped. Then headset bottom needs welding. My welder asked about magnesium or impurities in the cast.

Thx
David


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[Warkton Tornado No.1]

Die casting of alloys usually includes metals that will improve the finished result from the aspect of appearance & performance.

It's not an easy process for the foundry to get spot on. As a youth, struggling to earn money in a summer holiday job, I inspected (keg) beer barrel handles, one of the checks being weighing of them in an attempt to ascertain any porosity. They would break & leave jagged edges if there was any amount........

Lambretta castings tend to have zinc as a constituent of the alloy. This tends to boil during welding, causing porous welds, as if the oil contamination were not enough

Oversize hole, or even the 'movement' of holes in conversions, can normally be achieved with the manufacture of inserts, though many types are available on the market these days.

Dependent upon the headset damage, they can be welded, but I would not personally vouch for the strength of the result if it was in the area of the control bars. They tend to break again all too easily......

[warts]

Welding die cast alloys in general is a dirty and messy job. I found a very light pass, perhaps skipping - after a good grind - then keep all the garbage away repeating light pass and grinding back until the amount of porosity is acceptable. This takes time which usually is not worth the cost if realistically priced, but OK for doing in your own time.
As WTNo1 says, its the additives that burn or boil off that are added to improve the flow of molten metal into the moulds that causes the major problem. Oil usually gets burnt off at the first pass.

[Davidsquaredson]

Welding die cast alloys in general is a dirty and messy job. I found a very light pass, perhaps skipping - after a good grind - then keep all the garbage away repeating light pass and grinding back until the amount of porosity is acceptable. This takes time which usually is not worth the cost if realistically priced, but OK for doing in your own time.
As WTNo1 says, its the additives that burn or boil off that are added to improve the flow of molten metal into the moulds that causes the major problem. Oil usually gets burnt off at the first pass.

Thanks very much for all the replies. I won’t bother with the headset weld. I have a spare headset bottom somewhere in my parts bin and will recycle that.

Cheers
David


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[hendy]

All i can say is that Shaun burns welded loads of lambretta alloy for me: headsets, cases, horncasts, gear change etc. And it was spot on.

Unfortunately, I have no idea what technique(s) he used, but all I'm saying is that a competent chap with the right gear can do it, and it was cheap too.

[Davidsquaredson]

All i can say is that Shaun burns welded loads of lambretta alloy for me: headsets, cases, horncasts, gear change etc. And it was spot on.

Unfortunately, I have no idea what technique(s) he used, but all I'm saying is that a competent chap with the right gear can do it, and it was cheap too.

The headset looks challenging. There are two metals reacting over time (metal tubes and fast Alu headset body) and about 1/3 of the broken area can’t be reached. Then there is the impurities bubbling up.

I’ve got a scooter friend who is a welder by trade who lives a few hours away. I’ll see what he can do with the cracked headset and use my spare. I got lucky, it’s off a servetta but had the chrome ring so is a perfect fit.


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