No, but I am willing to scan selected parts if that is of any use.

Thank you Schneiderman, I will try and put a brief list together, mainly strip steel construction details. I have the index from Vol V 1934 that I am working from, but if there is anything do do with strip steel aircraft construction I would welcome it. Scanning excerpts from such a thick volume is a pain, so I owe you one. I have struggled to find 1931, my theory was the publisher was close to giving up on it as the industry and world at large struggled with the Depression, so not many volumes made it out there. When you are carted off please leave a note in the book so your loved ones can send it on to me!!!

Off topic, but you sound like the man to answer this : what happened to the Schneider Trophy ? Was it melted down or is it sitting somewhere gathering dust? Two birds kissing, very racy trophy indeed!

Thank you

Thanks Dogsbody for that link to the pictures of the various processes on enginehistory.org; pretty much explains it. Thank you everybody else for the great links to current manufacturers of composite props, certainly not a lost art and surprising to realize that Spitfires, Hurricanes and LH tractor Ansons are all well covered. It appears that the 1930’s German technology never disappeared and is well represented in Germany and Italy today. Go Axis. I would have always assumed that these warbirds were running down stocks of original blades – the future for warbird and classic prop maintenance seems far more optimistic to me than when I first thought about it.

The replacement of original aluminium blades with modern, lighter, composite blades offers less engine wear as there is less to suspend off the crankshaft. Less destructive resonance than aluminium. These modern manufacturers claim to be able to handle up to 5,000 HP through the blades. Nothing wrong here. Struggling to find anything to complain about. Is there anything wrong or to complain about this approach ? Apart from not using historically original seventy year old aluminium blades subject to intragranular corrosion dug out of a swamp.

Modern warbird repro props are made by Hoffmann of Germany to original profiles using the composite method of construction. Anon.

Thanks Anon for some great answers. I had no idea Hoffmann is making warbird blades. What profiles do they do ? Who else is making old profiles ? I understand Avia in the Czech Republic is making Hamilton Standard aluminium blade profiles for Mustangs. It seems like an area with a growing need in future years.

Your sample is part of the engine bearer assembly – starboard side, rear, engine support point. Typical of the longer nosed Merlin XX fit. The inspection stamp on the stainless plate is not clear (might be clearer on the other plate?) but the bolts look Canadian, so maybe Canadian MkXII. Please see PM.

Foray, thank you for the quick ID and PM answered, cheers, Ed

XRF makes a living out of positive metal identification : PMI. It keeps the sons of the east, quick buck merchants and metallurgical pond scum honest. It does this instantly and cheaply, without requiring the destruction of the test piece. It is probably a good tool to stick on the standard shadow board in a restoration facility.

Material identification and quarantine has always been obviously important in aerospace. The following sample of verified Hawker Australian Demon aileron T50 spar below shows that even with all the care assumed in the sepia past, mistakes are made.

[ATTACH=CONFIG]238704[/ATTACH]

The original specifications for the tube in the aileron are 3% Nickel T50 tube. Both port and starboard aileron remnants were recovered from the same location in Australia, being 1935 manufactured items from the OEM dataplate attached. Surprisingly the values for the port remnant showed up as plain carbon steel, the same as an old clothes line or bicycle. This material could never perform like a T50 3% Nickel alloy steel or even T45 Manganese alloy steel : it had to be a mistake. Either the Reynolds tube company supplied Hawkers with the wrong tube in 1935, Hawkers made a manufacturing mistake or the aileron was repaired later by an indifferent RAAF fitter.

In any case the use of this remnant in a modern structure would be attended with the assumption that it was 3% Nickel T50, and perhaps an 80 year old mistake would finally manifest decades after it should have been found. The lesson for me is to be equally suspicious about both the old and the new. We didn’t invent stuff ups.

And so finally I could spend some time alone with the handheld XRF and do some instant chemical assays of various samples collected. As usual with a session with XRF it creates more questions than it answers. Not in the way of climbing the mountain and slipping backwards, but climbing and seeing new things from higher up. New and splendid things.

I am grateful for all forumites who kindly submitted samples for testing. This art of ‘forensic metallurgy’ will become increasingly important as spare parts dry up and new things need to be made to keep historic aeroplanes in the sky. The topic is utterly devoid of charm for most folk but most important. It is polluted with the worst form of technical jargon : the metallurgical codes of long dead technicians; hieroglyphics and incantations held in the bony fingers of ghost metallurgists spinning in the night mist. It is hard enough prying this knowledge from deep, forgotten dungeons of British engineering thought, and I dare not contemplate digging in the cemetery of French, German and US engineering thought for simple lack of lifetime. But I have a hunch the metallurgy was common under whatever flag it came and as loose, independent little explorations into material compositions are made the jigsaw pieces may come together into a rational whole. So I would encourage you to keep contributing chunks of metal or discovery which I will gladly test and share here or anywhere.

And so some facts, understanding that these are handheld XRF results, not traditional spectroscopy, and the thoughts that develop from them may be relied upon for conversation and dispute, but not for engineering.

CCF Hurricane.

Canadian Car & Foundry operated two steel works and a rolling mill. Being contracted to manufacture the Hurricane design it is self evident that production plans and material specifications were provided by Hawker Aircraft. The logic depended in part on the sourcing of Canadian raw materials rather than supply of metals and tubes from the UK, impossible in wartime conditions. So the obvious starting point is to assume that the Canadians used the same materials as the British, constituting these within their own steel mills. Now it seems that they did not.

Below is a verified section of CCF Hurricane X centre section spar. It is composed of four layers : two roll formed ‘octagonal’ booms with two telescoping cold drawn steel tube liners. I am not overly familiar with the UK Hurricane design, but my understanding is that in the UK the roll formed boom would be made from Nickel Chromium alloy (BS S88c) and the telescoping tube from 3% Nickel alloy (T50) tube.

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The CCF section was unfortunately cut with oxy acetylene, allowing an uncontrolled heat treatment process that would make the grain structure and hardness values of the sample unreliable for testing, but the chemical assay would not change. I wondered why oxy was used to cut it. To prepare the sample I waited until the engineering workshop supervisor had left work and crept down to his beloved Brobo saw. The keen, liquid cooled blade made no impression on the Hurricane spar, so I proceeded to hang off the Brobo handle to make it bite. I like hamburgers, so the Brobo started to work. But it wouldn’t cut. Maybe the thin, rusty, ancient Hurricane steel was harder than the blade? I crept out of the workshop. The next morning the workshop supervisor reported that he had to buy a new $230 cutting blade, because the old one had become blunt, and I had to shake my head in sympathy and make clucking noises about “poor quality blades these days” while the expense form was approved. So here’s my tip : don’t use a Brobo saw on CCF Hurricane spars. I eventually used a thin stainless steel rated cutting disc with an angle grinder to cut out my chunks, all the time wondering about the spar alloy composition.

In the CCF section the roll formed octagonal booms are Manganese alloy steel, the same type of alloy used to line wear teeth on excavator buckets. I hypothesise that this strip material is DTD 138, 65 Ton carbon steel strip, based on the literature of the day describing it’s use in 1930’s aeroplane spars. I have not come across an application of DTD 138 before, but it seems that CCF chose to use this Manganese material as a substitution for Nickel Chromium BS S88c. I wonder if the gauge of CCF Manganese centre section spars is different to the gauge of UK Nickel Chromium centre section spars ? I wonder if the gauge or number of telescoping tubes are different? The fascinating thought remains that here is an original substitution that was eminently fit for purpose, that opens the possibility for an alternative approach to Hurricane spar replacement. It needs more work to directly compare the same UK and CCF section, and I wonder if any of the CCF engineering work remains to refer back to ?

In respect of DTD 138 it is an obsolete standard, substituted postwar by BS S517, also now obsolete. This composition was common to the contemporary Manganese alloy T45 tube composition used in the welded tube fuselage of the Avro Anson and deHavilland Tiger Moth. These compositions don’t disappear, they just come in different forms. But there is no shop stocking DTD 138 sheet today. But we can use this knowledge to carefully build cases for substitution using the materials available to us, as it seems the Canadians did in 1939.

I understand that CCF did not operate a tube mill. From where would it get its tube from in 1939 -40 ? My hunch is that it would be sourced from the United States, simply based on the proximity of scale, peacetime US tube supply and the foundries and mills of CCF being fully occupied. A further hunch relates to the use of US SAE 4130 tube and later National Emergency 8630 alloy for tube (NE 8630, later called SAE 8630). This was the familiar SAE 4130 composition with a little more Manganese and some Nickel. This created a weldable composition that could also be applied to non weldable pin jointed structures traditionally using 3% Nickel tubes.

The CCF telescoping tubes within the spar sample report values consistent with SAE 4130, lending weight to the theory of US tube supply. A further sample of Hurricane fuselage is shown below.

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This sample is unverified, as no knowledge of the Hurricane model or aircraft identification is known. It was described as a piece of wreckage from a Hurricane crash in Scotland. Certainly the piece came from the UK and is consistent with Hawker construction. The DTD 166 stainless fishplate has the part number B104964, and I hope that folk more familiar with the Hurricane design can verify this part number and the location of the remnant within the fuselage design. I understand that the Hurricane used 3% Nickel T50 tube in the fuselage, but this remnant reported tube composition results consistent with SAE 8630, about 1% Chromium and 0.4% Nickel. So the astonishing conclusion is that this piece of Hurricane crashed in Scotland is part of a CCF Hurricane built after early to mid 1942, when the US SAE 4130 standard was changed to SAE 8630 across the board. So here we may have a means for the forensic differentiation of otherwise similar UK and CCF Hurricane components that may have tube adhering to them.

Why did the US change the ubiquitous 4130 composition to 8630 in 1942, then ultimately revert to 4130 in the current day ? My theory is that higher performance factors from a superior metal composition and a country roused to war by the December 1941 attack on Pearl Harbour demanded it. Postwar, as aluminium moncoque designs carried the performance development burden, only low stress designs like the Taylorcraft – Auster depended on welded tube, where plain 4130 would suffice.

I have also had conversations with veteran engineers in Australia concerning early problems with the 4130 welded tube fuselages of US designs such as the Wirraway and Boomerang, based on the North American Harvard design. In this case weld cracking was resolved by the use of new compositions supplied from the US to the BHP operated British Tube Mills in Adelaide, South Australia. I need to do more work to follow through this topic. Was this SAE 8630 and was this composition more stable for welding?

Again, loose and separate threads can connect in serendipity. The UK deHavilland Mosquito had Managnese alloy T45 tube specified in its landing gear. I have verified Australian built Mosquito landing gear tube that I can test for 8630 and I wonder if Canadian built Mosquito landing gear tube is made from 8630 ? The Canadians also built Harvards. I can compare this with Australain built Wirraway fuselage. Anyone have a verified piece of Canadian Mosquito undercarriage or Harvard tube piece that I can test?

Again, 8630 opens the possibility of an alternative pathway to 3% Nickel T50 tube substitution, except that SAE 8630 is utterly extinct! The real value is in the demonstration of the substitution of local materials within the engineering thought of the day. If modern regulatory and engineering thought can be as fluid as the original then it may be easier to keep sub economic numbers of antique structures flying into the future based on economic supply of modern substitutions. Knowledge of historic metallurgy can allow an informed parley between regulators and engineers, keeping at all times a respectful eye on the wallet of whoever is funding a flying resolution. Stripped of metallurgical jargon, these problems are otherwise relatively simple.

The concluding tests in these series were on further unverified Hurricane fuselage tubes sourced from the UK. In this case compositions reported values consistent with the expected 3% Nickel T50 tube.

[ATTACH=CONFIG]238699[/ATTACH]

It seems the Hurricane fuselage was made from 3% Nickel steel or, in Canada, from SAE 8630 Chromium- Manganese- Nickel – Moly steel. I do not think you can readily make a modern Hurricane with original Hurricane performance out of SAE 4130. Understanding why requires a passage back to an earlier, prewar time, to the Hawker Demon and Bristol Bulldog biplanes.