TIGHAR
Project Midnight Ghost => General Discussion => Topic started by: Ric Gillespie on November 14, 2023, 01:58:25 PM
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Subscribers to TIGHARNews emails will have seen the following notice sent out yesterday:
ARTIFACT IDENTIFIED
Subscriber responses to the October issue of TIGHAR Tracks and recent TIGHARNews emails inspired new research that has identified an artifact recovered during TIGHAR’s first visit to Gull Pond thirty-one years ago.
TIGHAR Artifact 1-21-P-1 was found with a metal detector and pulled from the mud just off the southern tip of the rocky island in
Gull Pond in October 1992.
TIGHAR Artifact 1-28-P-2, the small steel disk found
in 2021, remains unidentified.
Now preserved at The Rooms cultural and historical center in St. John’s, Newfoundland, TIGHAR Artifact 1-21-P-1 can now be reliably identified as a segment of a cylinder wall from a liquid-cooled internal combustion engine that pre-dated the first use of machines of any kind on the Cape Shore barrens.
The materials, properties, and dimensions of the artifact match a specific section of a cylinder from a 450 hp Lorraine Dietrich W12 engine like the one that powered l’Oiseau Blanc.
Exciting as these findings are, a word of caution is in order. Until the rest of the engine is found, the identification of the artifact must remain tentative.
The November issue of TIGHAR Tracks will detail the case for 1-21-P-1 being from l’Oiseau Blanc and how the new findings affect TIGHAR’s hypothesis and plans for the 2024 search.
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I'm currently writing the paper to be published in the upcoming TIGHAR Tracks and there's an historical question I'm hoping someone will be able to help answer.
XRF (X-Ray Fluorescence) analysis shows the artifact to be made of "12L14" steel. It's easy to find the properties of 12L14 steel but, so far, I haven't been able to find out when that alloy was first produced.
in testing hypotheses, we're always looking for disqualifiers. If 12L14 steel wasn't used until after 1927, either the XRF analysis is wrong (unlikely) or the artifact is disqualified as as being from l'Oiseau Blanc.
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Have you tried contacting the American Iron and Steel Institute?
https://www.steel.org/
Karen Hoy #2610
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Looking forward to seeing how the research on that came about.
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I've connected with the Steel Institute. The guy I talked to was fascinated by our project. He'll try to find out when 12L14 steel was first used and call me back.
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I've always felt the metal in that artifact is too thin to be a cylinder wall. Could it be from the water cooling jacket around the cylinder wall? (Assuming it had such a thing.)
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I've always felt the metal in that artifact is too thin to be a cylinder wall. Could it be from the water cooling jacket around the cylinder wall? (Assuming it had such a thing.)
Yes, there were water jackets around the cylinders, but they're still too thick and a fragment of a water jacket shouldn't have oil on it.
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It's always seemed more like part of an oil sump or some such to me.
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It's always seemed more like part of an oil sump or some such to me.
My earliest idea when we first found it was that it might be part of the oil tank. There was a 60 gallon oil tank immediately behind the engine, as shown in this photo of the aircraft under construction. We don't know whether the tank was aluminum or steel, but the photo looks like either unpainted aluminum or painted steel.
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I thought it looked a bit like a cylinder wall, but i could not come up with a very convincing theory of how it would blow up like that. It's just not a common kind of failure. This was a proven design and engineers knew how to build engines that would resist pressure. I came up with two rather weak ideas: 1) that the engine was forcibly stopped at the exact moment of ignition, so the full force of combustion had nowhere to go but through the cylinder wall; 2) that the overheated engine hit the cold water with enough temperature differential to cause the metal to crack (why you don't add cold water to a hot cast iron engine, or put your hot cast iron pans in cold water).
Has anyone tried taking this bit to the actual engine on display to see if it matches anyplace?
As for the type of metal, 12L14 appears to be the current American designation for a very old kind of steel, which has had other names in other times and places. In England it is classed as Bright Mild Steel, which is a common variety for machining. Knowing when it started to be called 12L14 may not answer when it was first made.
Don W.
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I think that if the artifact is indeed an internal component of the engine then this changes the search in a meaningful way. How? There is likely no large chunk of metal lying around on the bottom of the pond to be identified by magnetometer (i.e., the engine came apart in a catastrophic way). Instead, there may be several smaller bits widely distributed that each need to be investigated. Although having a single large chunk of metal is likely easier to find in the broad sense, having multiple smaller bits (any one of which would possibly confirm the crash) actually raises the odds.
Don....
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Early on in discussions of this artifact, I suggested it was part of the engine oiling system, which was largely external. That still doesn't seem to explain explosive damage. If I had my druthers, I'd take it to Paris and hold it up next to the engine on display looking for a match to some part there.
Were the cylinders cast with water jackets, or were the water jackets made separately and added around the cylinders? It appears the engine had individual cylinders rather than a cylinder block. The cylinders might not even be castings.
Don W.
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I share with you my reasoning on the subject. That said, it's just a non-expert's point of view...
For what follows, I'm going to refer to 2 documents:
the booklet “Information on the Lorraine 12 Eb 450 hp engine” published by the Centre d'Instruction des Spécialistes de l'Aviation - Ministère de l'Air. (School for training Air Force mechanics between 1916 and 1928.)
The article published in the July-August 1921 issue of “La Houille Blanche ‘1 , ’LES PRINPAUX ACIERS DE CONSTRUCTION”, by P. Dejean.
Today, standards for the quality and nature of steels (alloyed, non-alloyed, hard and non-hard, ductile and non-ductile, etc.) comply with standardized industrial quality norms. For example, US standard 12L14 is similar to French standard S300pb (European designation: 11SMnPb37 or 1.0737).
S' refers to 'Structure', designating steel for the construction of structures or objects; ;
300 refers to the strength of the material (yield strength expressed in megapascals);
pb' refers to lead.
I'm no specialist, but all this is harmonized via a unified system: the UNS. In the 1920s, I doubt that such international equivalents existed.
From the “Houille Blanche” article, we can see that in France, steels in the 1920s were mostly classified according to their ductility: extra mild, mild (Adx), semi-soft, semi-hard...
Subsequently, they were classified according to their mechanical properties, since this was the main concern in industrial applications. As time went by, the composition of the steel, the alloy, became increasingly important, particularly for the application of heat treatments. Nowadays, the content of various chemical elements is also indicated.
The interest of the “Houille Blanche” article is that it proves the classification in use in France in the early 1920s for the 14 “grades” of steel, for predetermined uses. However, these « grades » are only basic, not comprehensive.
Each forge had its own classification with steels of similar grades...
This document tells us that a steel called “semi-soft carbon” (class B) corresponds to a chemical composition mostly close to that of S300pb or 12L14. The phosphorus content is identical (.35), the sulfur content is very similar (.35), as is the carbon content (.15).
Track the others components is not an easy task since no standard classification from chimical composition didn't exist at that time.
To my great regret, for our Lorraine 450hp, I was unable to find any open-source details on the composition of this perticular engine's cylinders.
The manufacturer's service manual is fairly brief on the subject (page 17): “The cylinders, made of special steel, are machined separately and worked as a whole."
In France, at the time, the term 'special steel' meant steel generally alloyed with elements other than carbon and for a specific use...
We can only deduce that each cylinder is machined, milled directly, in the Lorraine workshop, from a steel 'ingot'. These 'ingots' must have been specially ordered directly from a French foundry (St Chamont, Le Creusot, Holtzer, Châtillon, for the best known...). I will try to find out which one was commonly used by Lorraine.
On the other hand, the leaflet “Information on the Lorraine 12 Eb 450 hp engine” gives a rather interesting piece of information (page 9):
“In semi-hard, forged steel, taken from the mass and machined separately.”
Now, according to the “Houille Blanche” article, a standard semi-hard steel had the following characteristics in 1920:
generally between 0.28 and 0.34% carbon content;
Phosphorus: 0.035%;
Sulfur: 0.035%;
silicium (between 0.10 and 0.60%).
Lead is not indicated.
Regarding french 'acier spécial' ratings, according to the “Houille Blanche”, there was another 'grade' : The 'F' or, « Mangano-silicieux' (Manganese – Silicious ally Steel ?) which was a typical spécial steel used for aircraft engine's cylinder :
« It is worth noting that this steel, which has been used for a very long time, received a new application during the war, a new application which has given it a new lease of life. This was its use in aircraft engine cylinders engines. In practice, it was recognized that cylinders made in this way were better able to withstand the high temperatures than carbon steels of corresponding hardness. »
I found others writings that supports that statement.
Typical 'F' grade alloy steel composition was as follow (according the “Houille Blanche ») :
Carbon : 0,40/0,60 %
Silicium : 1,6/2%
Manganese : 0,30/0,50%
However, according to other sources ( “Métaux et leurs conditions d'emploi dans l'industrie moderne, caractéristiques, essais” - Jean Oertlé, 1918), the more frequent use of this special steel used more manganese and less silicium, for reasons of brittleness:
Carbon : 0,30/0,60 %
Silicium : 1,00/2%
Manganese : 0,30/1%
If I understand correctly, in France in 1920, the combined use of silicium and manganese made it possible to use much softer steels for similar applications requiring strength, ductility and good deformation and temperature behavior. This brings us closer to 12L14.
So it's not at all impossible that French forges and manufacturers were using special steels with chemical characteristics were very close to those of 12L14 as early as 1920.
For Lorraine, it's just a question of finding out which one...
Hoping this personnal guess could help a little.
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Here is the booklet “Information on the Lorraine 12 Eb 450 hp engine” excerpt i was reffering to.
LTM
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Renaud, WOW! Lots of great information there. I'll start working up comparisons to the XRF data we have on the artifacts.
I have my doubts that the cylindrical artifact is 12L14. The XRF software on some of the readings indicated "LA-C steel". None specifically said 12L14 steel. 12L14 is just one of several LA-C steels. All LA-C steels have sulphur and phosphorous and I don't see that in the XRF data.
It's remarkable that the booklet “Information on the Lorraine 12 Eb 450 hp engine” published by the Centre d'Instruction des Spécialistes de l'Aviation - Ministère de l'Air. (School for training Air Force mechanics between 1916 and 1928.) is handwritten. The date is perfect, as is the July-August 1921 issue of “La Houille Blanche ‘1 , ’LES PRINPAUX ACIERS DE CONSTRUCTION.
The "special steel" question goes further than the engine cylinders. We have a Spare Parts Manual for the Levasseur PL4 and many components were made of "acier special". Now we have data on what kinds of "special steel" were available at the time the engine and airframe of the PL8 were under construction. If our artifacts match those data it will be a huge step forward toward proving we have debris from l'Oiseau Blanc.
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Hello Ric, it's a pleasure to talk to you again.
All in all, I'm quite relieved that you've clarified that the artifact in question may not be 12L14. Indeed, I didn't dare say it, but I felt that this alloy steel would have been a little too 'soft' to make good cylinders inner walls, especially of this size and with these constraints. It is indeed possible that this type of alloy would not have had the desired endurance.
I think so (but I'm not a specialist. I like mechanics, but I'm more of a 'book man') that the hypothesis of medium-hard 'manganosilicium' alloy steel is an interesting trail to follow.
From the XRF data you evoked, do you have the exact chemical composition of the artifact? (i.e. carbon, lead, manganese, silicon, phosphorus, other...) and the type of treatment it has undergone (quenching...). This could be useful for making comparisons with the different families of French special steels of the time.
Yes, I've seen that the PL4 parts catalog often mentions special steels. It's not surprising, since this generic term in France is a bit of a 'catch-all' (not sure for the translation...) for a wide variety of steels alloyed with other components and with specific properties.
I was lucky enough to come across this copy of the 12Eb mechanics' manual. I propose to copy it for you, page by page. It's going to take some time, as it's a vintage document. It gathers some indepth technical data about the engine.
Furthermore, I came across a reprint of a reference manual on the industrial use of metals in France (1918): “Métaux et leurs conditions d'emploi dans l'industrie moderne, caractéristiques, essais” - Jean Oertlé, 1918. It has been republished by the Bibliothéque Nationale de France.
And do you know what? You can buy it on Amazon!
For a complete oicture, here's a link to all the “Houille Blanche” bulletins:
https://www.shf-lhb.org/
Houille Blanche - Revue internationale de l'eau” is a French scientific journal published since the early 20th century by the Société Hydrotechnique de France. It's a scientific engineering journal focusing on the use of water as a source of energy and a natural resource. We're very fortunate in that its editions are now available entirely online!
LTM
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Hello Ric, it's a pleasure to talk to you again.
It's a pleasure and privilege to have your help in conducting research in France.
All in all, I'm quite relieved that you've clarified that the artifact in question may not be 12L14. Indeed, I didn't dare say it, but I felt that this alloy steel would have been a little too 'soft' to make good cylinders inner walls, especially of this size and with these constraints. It is indeed possible that this type of alloy would not have had the desired endurance.
The metal still seems too thin to be a cylinder wall and the artifact does not have the ridges that are present on the cylinder walls.
I think so (but I'm not a specialist. I like mechanics, but I'm more of a 'book man') that the hypothesis of medium-hard 'manganosilicium' alloy steel is an interesting trail to follow.
I'll pull the XRF data together and we'll see what that tells us.
From the XRF data you evoked, do you have the exact chemical composition of the artifact? (i.e. carbon, lead, manganese, silicon, phosphorus, other...) and the type of treatment it has undergone (quenching...). This could be useful for making comparisons with the different families of French special steels of the time.
The XRF data give us the percentages of elements detected but nothing about treatments. Several points on the artifact are samples and the results vary somewhat. Sometimes elements show up that are probably contaminates that adhered to the artifact during the time it was buried in the mud. I'll be looking for elements that show up consistently in roughly th same percentages.
Yes, I've seen that the PL4 parts catalog often mentions special steels. It's not surprising, since this generic term in France is a bit of a 'catch-all' (not sure for the translation...) for a wide variety of steels alloyed with other components and with specific properties.
"Catch-all" is the right term.
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The clearest definition of "special steel" I've found is at https://www.voestalpine.com/blog/en/innovation-technology/what-is-special-steel/
"When Steel Becomes Special
As so often in life, when it comes to special steel it is the intrinsic values that count. Including those which are absent. What makes these steel grades special is their purity. That means an exceptionally low sulfur and phosphorus content: no more than 0.025%, or 25 parts in a thousand. That is comparable to two tiny pinches of salt in a liter of water, which is why extreme precision is required to achieve the chemical compositions of special steel grades. It is the same level of precision as demanded in their subsequent processing.
The exceptional properties of special steel, such as resistance to corrosion and heat, strength, wear resistance, workability, and polishability, all depend on its composition and the care with which it is produced. This is where special additives, so-called alloys, come into play. The manufacturers’ “recipe books” include a variety of ingredients:
• Chrome: for resistance to corrosion and heat
• Tungsten and cobalt: increase wear resistance which is important for milling tools and drills
• Chrome and nickel: increase weld strength
• Molybdenum: increases heat resistance and makes steel rust-proof
• Titanium, niobium: creates resistance to intergranular corrosion
• Manganese: increases tensile strength"
We have 15 XRF scans of various points on the exterior surface of our cylindrical artifact, 4 done in September 2021 and 11 done in November 2021. As expected, in all scans, iron (FE) was greater than 90%.
• The cobalt, titanium, and lead detected are almost certainly attributable to the bluish-gray paint and are not almost certainly part of the steel alloy.
• The most common probably-alloyed element (found in 12 of the 15 scans) was manganese. The percentage of manganese was quite consistent, from a low of 0.262% to a high of 0.580%. The average was 0.458.
• The second most common probably-alloyed element was molybdenum (found in 7 of the 15 scans). The readings measured from a low of 0.015% to a high of 0.087% percentage, except for one reading of 0.683%. If we throw out the anomaly we get an average of 0.0325.
• In third place was chromium (found in 6 out 15 scans) from a high of 0.238% to a low of 0.096 for an average of 0.129.
• Silicon came in fourth (4 out of 15 scans) with readings of 3.507, 3.151, 3.010, and an anomalous 0.864.
• Zinc was found in 3 readings but the amounts are all over the shop: 2.425%, 1.303%, and 0.494%
• Vanadium was also present in 3 scans, more consistent: 0.118%, 0.059%, and 0.058%
• Inconsistent traces of copper and tin showed up in 2 scans and there was bit of phosphorus in 1 scan. I think those can be dismissed as environmental contaminants.
The steel in this artifact fits the above definition of "special steel". The steels shown in the “Houille Blanche” article are quite different, but neither does it fit the definition of 12L14 in https://www.eatonsteel.com/12l14-cold-rolled-steel-bar.html
"12L14 is a standard resulfurized and rephosphorized carbon steel. Lead is also added in order to increase machinability, and it also means it can be bent, riveted, or crimped. However, this extra ductility and machinability do mean that 12L14 is slightly weaker than comparable carbon steel alloys." There is no sulfur and no meaningful phosphorus in the artifact. Also, there seems to be no such thing as 12L14 sheet. It's generally used for plating.
As you say, "special steel" seems to have been a catch-all name. I think we have a piece of "special steel" and it should be possible to research its virtues, which may point us to where it came from.
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Hi Ric,
What carbon measurement do you have (if any)?
For Silicon, I'm a bit surprised by levels above 3%...
The Vanadium and Molybdenum content is the sign of a steel of a certain quality (of a certain price) for the 1920s standard, especially in Europe. According to Jean Oertlé, low levels of Vanadium further enhance a part's core hardness without making it more brittle. That said, the grades are modest. It is used in certain bolts, for example.
With 3% silicon and around 0.50% manganese, this is a high-grade “manganese-silicon” industrial steel, approaching the “F” category of the “Houille Blanche” article. The only difference is the silicon content (generally speaking, at the time, over 2% was a brittleness factor), but vanadium, molybdenum and chromium can perhaps mitigate this effect. I'm not a metallurgist...
The use of chromium is not surprising, given its thermal resistance and its ability to homogenize a part during the quenching process. It also makes parts less brittle (more elastic) for the same hardness, but with a lower carbon content.
The zinc content is also interesting. At the time, zinc was used in moving parts, such as bearings, for its anti-friction properties.
For all this, I'm basing myself on the Jean Oertlé manual I mentioned earlier.
So we certainly have a very special piece of steel. And quite expensive for its time. A sort of compromise between hardness, elasticity, strength, resistance to impact, heating and friction...
It would be interesting to know the carbon content. A medium-hard steel made in 1920 generally has a carbon content of between 0.40 and 0.45. For manufacturers, by using other elements, lowering this content while preserving hardness and resistance to deformation is interesting, as it makes the part less brittle and therefore less likely to break on impact.
I think we need a metallurgist's opinion on the properties of a steel alloyed with all these elements. From these properties we might be able to deduce its use.
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The metal still seems too thin to be a cylinder wall and the artifact does not have the ridges that are present on the cylinder walls.
Some others members made the hypothesis that it could a piece à the oiling system.
Leafing through my books, I found this image of an oil feeder adapted to the PL7 (the cylindrical item)
I know that this aircraft had a Hispano-Suiza very different from the Lorraine. This oil feeder was intended to allow the oil to be preheated an immediatly in use for a quicker and safer throttle-up.
We know that it's likely that the PL8 version 1 had an oil preheating system. Could it be that Levasseur adopted the same system as for its contemporary PL7? Do you have any assembly diagrams? (I do not possess any).
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Leafing through my books, I found this image of an oil feeder adapted to the PL7 (the cylindrical item)
I know that this aircraft had a Hispano-Suiza very different from the Lorraine. This oil feeder was intended to allow the oil to be preheated an immediatly in use for a quicker and safer throttle-up.
We know that it's likely that the PL8 version 1 had an oil preheating system. Could it be that Levasseur adopted the same system as for its contemporary PL7? Do you have any assembly diagrams? (I do not possess any).
No assembly diagrams, but the pictured oil preheater could be the right size to be our cylindrical artifact and the cap on the filler neck could also be right for our disk artifact. Did the PL8 have such a device? If so, where would it be located? I don't know how the preheater worked, but the detailed press accounts of the takeoff on May 8 say the engine was started at 5:15am and they started the takeoff run at 5:18am. Three minutes is not long enough to warm the oil.
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If there is an oil heater, it should be lower than the tank at the rear of the engine, not far from the pump.
I've reviewed the PL4 parts catalog: there are feeders for water (double feeder) but not for oil.
The PL8 is indeed the contemporary of the PL7 in its first version, so much so that Levasseur himself had insisted that Nungesser adopt the Hispano Suiza instead of the Lorraine.
Certainly, for a trip in fairly low-temperature conditions, this device would have been useful.
Several accounts state that the engine was tested and preheated at around 4am.
According to the testimonies, Nungesser left the engine running for between 2 and 5 minutes, probably more like 2 minutes. The take-off time is reported as 5:18 a.m., sometimes 5:21 a.m.
However, the presence of a preheater is only assumption i am afraid.
LTM
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However, the presence of a preheater is only assumption i am afraid.
True – but it's the only thing we've found so far that seems to really fit the artifact, including a film of oil on the interior surface.
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Page 35 of the PL4 Parts Manual shows the "Feuilles Metaliques" (sheet metals) used. There are two steels listed, "Sheet steel No. 12" and "Alloyed sheet L2R".
The latter is presumably the "special steel" referred to in the part descriptions. I can't find a definition for L2R steel but L2 steel is described on
https://en.wikipedia.org/wiki/Low-alloy_special_purpose_steel
In the attached screen shot, I've compared the element averages found in the XRF scans with the corresponding allowable ranges for L2 steel.
Most of the artifact element averages (shown in green) meet L2 specs. Only the averages for phosphorous and silicon (shown in red) fall outside the limits – both are too high. Phosphorus showed up in only one scan, so that anomaly can probably be dismissed. Silicon was detected in 4 scans, so there was probably really some silicon in the alloy. Our artifact appears to be L2 steel with silicon added. Maybe that's what the R stands for.
At the very least, our artifact appears to be made of steel very similar to steel known to be used in the PL4.
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Ric, really bravo, I think you're on to something here... Investigating the composition of the alloy is a good idea. Rather than finding the part, let's find the material!
The L2 standard is, nowodays, American. In France, we refer to 80CRV2 (Afnor).
Nevertheless, The L standard was already known in France in 1920, and is referred to as “Houille Blanche”. At the time, it was a hard carbon steel alloyed with nickel-chromium to prevent wear, oxidation and deformation. For the time, a standard of tooling. Quite a different acier spécial compared to L2 and the artifact.
Interestingly, the Levasseur spare parts catalog dates from 1929. It's a direct source that categorizes the steel in question according to standards for which an international standardization effort may have been made between 1920 and 1929.
Whatever, it is, possibly, a first direct step and link between the artifact and a first sourced docuement from Levasseur.
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Ric, a few thoughts.
As for the high silicon content, isn't it possible that the artifact had been contaminated by the sand at the bottom of the pond, which has aggregated with it? You mentioned that the scan was surface scan only.
I couldn't find any mention of L2R among French forges in 1918... But if Levasseur uses it in 1929, it's because it's an established standard, and probably a widespread one. I will see if i could track any classification around 1930.
The 'R' reference could be the metal treatment. Perhaps a reference to the French term 'recuit' which is a heat-tratment of the laminated steel (beteween 500 and 800 °C) to restore his original mécanical properties.
By the way, i found a source reporting that Le Creusot (Schneider) had won a contract to build parts for the Lorraine 400 hp engine. It is not specified what type, however. Il could be the V12 e 12Db around 1918-1919. So it is likely that Lorraine had established good working trends with Schneider.
But i need more sourcing for all of these.
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As for the high silicon content, isn't it possible that the artifact had been contaminated by the sand at the bottom of the pond, which has aggregated with it? You mentioned that the scan was surface scan only.
I had the same thought, but apparently not. We have a 1975 breakdown (see below) of the elements in Gull Pond (referred to by its topographic map name Goose Pond).
Interestingly, there is no naturally-occurring:
• Silicon
• Vanadium
• Titanium
• Tin
• Phosphorpus
Alll of which were detected in the XRF scans of the artifact. The titanium (like the cobalt and lead) is probably from the paint. The silicon and vanadium are apparently part of the alloy. The little bit of copper could be from a tiny pocket of sediment. There shouldn't be any phosphorous in alloyed steel so it's probably an impurity. Ditto for the trace of tin.
If I’m right, the base metal is steel alloyed with manganese, molybdenum, chromium, silicon, zinc, and vanadium. That’s a complex, very high-quality “special steel’”.
I couldn't find any mention of L2R among French forges in 1918... But if Levasseur uses it in 1929, it's because it's an established standard, and probably a widespread one.
Agreed.
The 'R' reference could be the metal treatment. Perhaps a reference to the French term 'recuit' which is a heat-tratment of the laminated steel (beteween 500 and 800 °C) to restore his original mécanical properties.
That would make sense.
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Ric, I think this hypothesis is sound. We must persevere.
'Recuit' treatment is justified for a laminated ('écrouissage'), bent and stamped part ( that needs to retain its tear strength.
For the moment, I can't go any further on the subject. I'll try to find more studies on French special steels around 1930.
If I see anything else, I'll let you know. We'll be in touch. ;)