25 Pounder info needed.

[David Dunlop]

Is it possible that cast sight carrier frame is magnesium, Tony? Were the flames you noticed a bluish white and throwing white smoke?

Cast magnesium parts were not uncommon in the aviation industry during the 1930's and 1940's when the danger of using it was not fully understood. Douglas built a number of DC-3/C-47's with cast magnesium bits in the wing root areas and it was one of those aircraft that caught fire and crashed after the war killing either Buddy Holly or Ricky Nelson. The tip off to investigators were the eye witness reports of the plane giving off a whitish flame when it flew past in the night sky, and it being described as 'flare like'. If memory serves, the crash was the result of a gas leak in a Southwind Heater igniting next to a large cast magnesium component that in turn lit up. The investigators were surprised that magnesium had been used in some of the Douglas production run.

David

[Private_collector]

I considered that, and you may be right David , but I REALLY hope it isnt magnesium.
If it is, that will completely ruin my plan to have a new section welded onto the bottom.

I'm sure Rob Nixon will be able to tell us what these parts are composed of. I'll email him soon. I do know the assembly was made in Canada, as it carries their Defence Dept. markings on two parts. They were very thorough with applying part numbers to everything sufficiently big enough to take a stamp.

[David Dunlop]

A possible simple test for you, Tony.

If there is a surface, or edge, you can access which will be concealed following reassembly, take a sharp knife and cut away a small wafer. With a pair of tweezers, or small needle nose pliers, insert the wafer in an open candle flame. If it puffs into a bright white light, you have magnesium. If it just turns to white oxide, its aluminium.

David

[david moore]

David is right - it's almost certainly magnesium - aluminum would not flame - despite the misinformation put about by the steel industry after the Falklands war that Brit aluminum ships burned because of aluminum use!
Aircraft wheels were almost always magnesium in the war - a lot made in the Alcan plant in Kingston, Ontario. That could be exciting if a tire burst. Magnesium casts very nicely but is extremely difficult to make into sheet. There was a lot of magnesium capacity in the war and it was used wherever possible to replace valuable aluminum.
If it does set alight, do not use water on a magnesium fire - it makes it worse! Have to use sand as per the ARP instructions re (magnesium) incendiary bombs!

[Private_collector]

That's really beginning to worry me, guys. Magnesium would mean I could do a far lesser quality repair to the corroded bit. I will snap off a small piece of corrosion and take it across the road to my welders place for testing. I tried a small chunk myself, using my propane torch, and it didn't react in any way, but I know from experience that it would probably need more heat than i could subject it to, before 'flame on'. Anyone ever throw an old VW gearbox case into a bonfire? Wear sunglasses if you ever plan to, and be prepared to wait a while for the reaction to start.

When there was still decent hope it MIGHT have been aluminium, I was doing some mental planning on exactly HOW the repair could be fashioned best, and decided I would require purchase of some plain sheet aluminium to craft the new sections. The only place I know of in town that could easily supply me a small piece, has now closed down, and i was lamenting their passing and cursing my lack of luck with regards to the effort now needed to scunge just a small bit of aluminium plate. While puzzling over where to start looking, I suddenly realised that while I was sitting there cleaning parts, I was in fact directly facing a far larger piece of plain 6mm aluminium plate than I could ever expect to need. It was leftover from making my shield, and I had resisted throwing it out some time ago. With any luck, my metalworker/welder neighbour can bend 6mm on his enormous metal folder, and I will use that to fill the area left vacant by the corrosion. If the original item IS magnesium, I have a plan that should see a nice piece of aluminium grafted into place without requiring any welding.

[David Dunlop]

Tony. It is hard to tell from your photos, but is the corrosion damage on your potentially magnesium part on a load bearing surface for the part or other fittings?

If the piece in question just 'sits there', could you perhaps build up the missing bit with body filler, epoxy paste, or similar, and then carve/sand to the correct profile for painting?

David

[Private_collector]

No David, not load bearing, but whatever I graft on will need to be 100% fixed permanently in place, or cracks will eventually show around the edges. I did consider doing that, but using fibreglass. This morning I made all the sections to repair the hole once and for all.......hopefully!

I'm almost sure this thing isn't aluminium now. Seems lighter than aluminium, and it files differently. My welder friend isn't home today, so I never got the definitive diagnosis. Will watch for him tomorrow.
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I didn't set anything on fire while cutting the rot away, and was VERY careful I did not put too much heat in one place. When all corrosion was cut away, I was left with quite a hole.
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There are 6 separate pieces making the repair patch.
I taped them all together to see what the profile will look like. While it's not exactly original, it will do.
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More details in the next posting....