[ImperfectSense]

I'm restoring a 1941 de Havilland Tiger Moth, which is a WWII biplane trainer used all around the world. This particular one was built in Australia but the engine was constructed in 1939 in England. The lower crankcase is made of an alloy with the following composition:

Zinc 14%
Copper 3.5%
Magnesium 1.0%
Titanium 0.5%
Iron 0.25%
Remainder aluminum

First off: Has anyone here ever personally welded an alloy similar to this before?

Secondly: does anyone know of any trade names or other designations for this alloy? According to the metallurgist who tested it, it does not match any known aluminum alloy; t's not a 7000 series, it's not anything. In fact, I have a 1950s Materials Handbook from the UK and I went through all of the almost 1,500 alloys of aluminum it lists and couldn't find anything even close.

I'm not even sure yet if my crankcase needs to have any welding done, but, I wasn't expecting the alloy to come back as such a mystery, so I'd really like to know all I can about it now that I've opened this can of worms.

Thank you!

[kiwi2wheels]

In the event of no other options, these outfits may be worth contacting ;

http://www.deltair-aerospace.co.uk/engi ... sy-engines

http://www.formhalls.com/801.html

http://www.retrotec-ltd.co.uk/services/

Or the engineering dept here ; http://www.shuttleworth.org/

[Poland308]

I’m guessing you may need to talk with a welding metal metallurgist. Your filler doesn’t always have to be a perfect match ch to the base metal. In some cases it’s desirable to have a different filler because of the way the base metal will react to the welding process. Welding cast iron with a high nickle rod would be a good example.

[Coldman]

1939 predates any tig process (especially ac) and therefore not built with tig repair in mind. The alloy was most likely the manufacturer's own special alloy of the day and probably allowed them to say my motor is stronger and better than yours kind of thing.
Talk to a metallurgist by all means, but I think all that zinc is probably going to make it unweldable for all electric arc processes.
I think your best bet is to investigate oxy/fuel gas welding or brazing processes. I remember seeing on youtube years ago a Dutchman (from memory) beating the snot out of an aluminium joint he just gas welded and he couldn't break it. He was using a round head wooden mallet to deform the joint. That was impressive.

[weldin mike 27]

Tin Man tech did a video on aluminium gas welding on you tube

[robtg]

Tin Man tech did a video on aluminium gas welding on you tube

http://www.tinmantech.com/ https://www.youtube.com/watch?v=aF1Srs_e1Aw&t=360s

[ImperfectSense]

Damn, that guy's welding AND metal-beating skills are impressive!

Thanks for all the input guys, really appreciate it! It's a relief to hear feedback along the lines of what I was already thinking...

Just FYI, there's a lot of these crankcases out there that are cracked, and if you ask the engine experts, every single one of them will give you a different answer... some say throw out the crankcase, some say the cracks have been there for 70 years don't mess with them, and others say weld it up. Of course of those who say weld, each one uses a different welder who uses a different process and different fillers. Mostly these airplanes don't get flown a whole lot, and I think the crankcases are overbuilt to a ridiculous degree to start with, so I guess it doesn't seem to matter what you do. But it does make me wonder about the guys who had their crankcases TIG-welded, thinking it was just a normal 7000-series aluminum.