powerandpassionI sense this is such a hurtful event for so many families. I sense this event affected the very fibre of the RAAF as an organisation, causing an impossible to reconcile conflict between loyalty to its officer class and its obligation to respect that the privelage of command demands honest leadership. So much is left unsaid about this event. How is it possible for a commander to lead subordinates into such a terrible doom? Maybe after half a century there is some space for honest reexamination. One thing that bugs me about this is the crash landing of Mosquito A52-303 in 1951, pilot officer AH Jones. In the court of inquiry for this event, the pilot was injured by striking his head against the rudder trim tab. To do this his body would need to be bent forward, in the same way as the crash test dummy of a car in the usual slow motion video of an air bag deploying. Prior to air bags in cars, the major, non fatal consequence of car crashes was brain injury, as the head struck parts of the car. I wonder how much this trauma may have affected the physical performance of Jones later, whether through spatial reasoning, migraines or whatever. The times called for “never complain, never explain,” in an Air Force officered by men still carrying shrapnel in their bodies. The armed forces generally are a dog once you are injured, abandoning you as a burden on the tax payer. So holding this in the back of the mind, how much did Jones brother officers protect him and push him, by an expectation to not underperform, to that fateful command over Sale ten years later? What do they mean by “condition m”? The report is full of allusions to medical conditions. What were the grumblings in Malaya? Was he fit? The RAAF does a great job in blaming dead pilots. I don’t think this was entirely the Commanders fault. He did it, but what was in the cockpit with him?
powerandpassionThe COPE
We choose the bottom left pattern on the pallet and place it on the bench.
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Like the first pattern that set up the DRAG we box around this and fill it with sand. This becomes the COPE.
The cope void establishes the other outside face of the wheel.
The Cope is placed on top of the Drag.
If you look at the void that is left, you can see what will become the wheel once metal flows in.
This is our sand casting mold.
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To allow metal to flow in the caster will also incorporate a FLUE to let metal in and a FEEDER to let metal out. For simplicity, these are not shown on the drawings. Molten metal is poured into the flue until it starts to flow out of the Feeder. As the metal solidifies within the mold, it shrinks. The excess metal in the feeder is then drawn back into the mold to ensure the casting is complete.
Making these casting patterns using 3D printing is totally useless. The speed with which an experienced pattern maker can generate the tools, using wit, hands and wood, easily outpaces the convoluted process of CAD design and printing of plastic patterns. The finish of the traditional pattern is finer that that achievable in 3D printed plastic. The problem is that the pattern maker is a vanishing breed. Casting is a very efficient process, and pattern makers will not entirely disappear, but as the manufacturing base recedes so to pattern making resources.
The wood used by the pattern maker her is Jeluton, a fine, even grained and easily worked tropical timber. It comes from Malaysia, and the pattern maker reports finding pieces of wartime shrapnel in the wood. It’s a surprise, a connection, that makes it seem appropriate to form our Mosquito wheels this way.
powerandpassionAxle core
We take the pattern to form the axle core and fill it with sand.
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We place this sand form into the middle of the Drag, to create the hollow for our axle.
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powerandpassionRing core
We choose the top left pattern on the pallet and fill it with sand.
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We lift this sand form out and place it carefully in the Drag void. This will create the void for metal to form the outside circumference of the wheel.
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powerandpassionMore spoke internals
Using the same pattern we make another, identical sand form, which we place back to back with the first one. This will give us the void to form the inside, hidden face of the second set of spokes. The spokes are offset 90 degrees to each other, so we rotate the second sand form 90 degrees.
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powerandpassionSpoke internals
We chose the top right pattern on the pallet and fill it with sand.
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This creates the sand form that gives us a void to form the inside, hidden face of the wheel spokes. We place this inside the DRAG void, facing down.
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powerandpassionThe DRAG
OK, so first we do the DRAG box, using the pattern on the bottom right of the pallet. This creates the void that, filled with metal, will become the outside face of the wheel. The pattern is placed on a bench, flat side down, a box set up around it, then filled with sand which is compressed around the pattern. A cover is put on the box and it is ‘dragged’ or tipped around and the pattern taken out, leaving a void.
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powerandpassionDo you have photos of the actual spar pins or bolts used to make the connection. It may be that ferrules of steel are inserted into the larger holes but the bolt sizes are the same ? If I recall the engine bearer connection to aircraft frame for many Merlin applications used a steel ferrule to prevent crushing of the member being fitted.
Spar connections always amaze me. Knuckle joints for Navy aircraft with folding wings amaze me even more. Watching a Corsair fold down its wings then take off always gets a wince going on my face. All those forces concentrated into a folding joint !
Biplane spar connections are made using chicken bones, relying on the trussed box section bi-wing assembly to demonstrate its simple soundness.
powerandpassionI happen to have a few hidminiums (AS2229 0410) and loads of the magnesiums (AS162 0410). I weighed them with my scales and came up with this:
70x AS2229 0410 = 26 grams
70x AS162 0410 = 24 grams
Robbiesmurf,
Thank you for doing this little weight test.
Given that magnesium is lighter than aluminium (really aluminium copper alloy) then there must be more metal in the magnesium rivet to come up with an almost similar weight. So the other way to develop more strength in the magnesium rivet, understanding the shank must be the same diameter, is to put more metal in the head. So you could say ‘more metal & work hardening’ is the principle behind interchangeability with duraluminium rivets.
Courtesy of a few little chats on the subject this seems to be an entirely UK issue, eg Beauforts made in UK had magnesium rivets but Beauforts made in Australia had aluminium rivets. I do not thing that ‘designed obsolesence’ was the factor behind this, rather, faster production. Also distributed production, without the need for heat treatment facilities, explaining why final assembly works incorporated some structural sections with magnesium rivets.
I do not think aircraft disintegrating in mid air due to electrolytic corrosion of magnesium rivets was ever an issue in wartime, but certainly after 10 years you would start to be nervous. I wonder how much the reluctance of postwar aviation regulators, staffed with people that truly understood the structures, to support the nascent warbird movement in the 70’s developed from this issue ?
Turning a negative into a positive, I do believe that historical aeroplane structures should be fitted with sacrificial magnesium anodes, in the same way that this practice is readily accepted in the marine world. Today, we do want aero structures to last 100 years. So a readily accessible and replaceable lump of magnesium will protect an aluminium structure. It’s the same as zinc based paint, except magnesium will more actively protect the aluminium. For a few quid, a Museum can protect static airframes exposed to the weather. For aluminium parts sitting on a shelf, I use a band of magnesium ribbon, purchased on ebay, to monitor and protect. I have seen too many steel shipping containers holding aluminium parts, subject to daily cycles of condensation, where the aluminium sacrifices to the steel. A part ‘protected’ in goodwill by a volunteer putting it in a shipping container will be swept out as dust by another volunteer in ten years time.
powerandpassionthe powder monkeys of Wellington’s battleships,
Apology and Retraction.
It came to me at night that the Duke of Wellington was an Army man, and that what I should have written was ‘Nelson’s battleships’. I apologize if I have offended anybody in the Nelson family, much as if I had said ‘Montgomery’s Bomber Command.’ Still they don’t teach us colonials this stuff anymore and none of you lot picked up on it either, so fat lot of good we all are in a pub quiz!
God Save the Queen !
powerandpassionCongratulations on the start of a wonderful project ! I have an orphan interplane strut that may be good for patterning if you need such things – send a PM with address and I will send it on, simply because you live in the most beautiful state of the Union ! I am based in Melbourne, Victoria so can fossick around to see if any VIA records remain. I suspect that VIA was a sub contractor to the RAAF for Tiger Moth work during the War so there may be something in some dusty RAAF archive. Can’t do anything tomorrow, just will keep an eye out if looking through records for other things. Enjoy you project, Ed.
powerandpassionThese thoughts were recently stimulated by work on a UK made Mosquito elevator, during which the rivets were picked off by fingernail, as per urban legend. So I can confirm, most definitely, the use of magnesium rivets in a British aluminium aero structure, that 70 odd years later can be picked off by fingernail.
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This elevator was found in Australia, most likely arriving in the country with 618 ‘highball’ Squadron. The manufacturers data plate shows an assembly serial number which is inconsistent with Australian deHavilland elevator assembly numbers, an alpha numeric code prefaced for Australian production with MEExxx. On this elevator the number is GPB DH 106. Perhaps somebody in the UK could confirm its origins. There are two dataplates, one brass, and one aluminium, more consistent with dH standards. Is this a very early elevator, refurbished and fixed to a later Mosquito ?
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Once the rivets were picked off and skin came away, a most perplexing sight ensued : ribs designed for fabric covering. I always understood the Mosquito had metal covered control surfaces, but here is an elevator showing the unmistakable sign of an original rib designed for fabric covering, and the remains of red fabric dope. The original rib has a furrow on its top and bottom edge, to allow fabric to be stitched down. Someone has later fixed an additional rib, without furrow, to allow aluminum to be riveted on. So twice as many ribs as necessary, the making of a ‘modern’ elevator out of what surely is a prototype or early fabric covered elevator.
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This kind of work would surely not pass muster today. Some of the additional ribs have not enough sheet in them to run full length, so additional tips are riveted on. It’s as if they were making ribs with off cuts, leaving nothing to waste. The thing is a patchwork that would furrow the brow of any inspector, unless desperate times called for production at some cost to quality. This is not a criticism, just a piece of old metal that speaks of terrible, fearful times. It’s almost a shame to fix it up, to make it sound, pretty, symmetrical, worthy of modern approval, unreal.
powerandpassionThe pattern maker has whittled his magic, and what you end up with for one Mosquito wheel are six pieces of tooling to go off to the casting plant. Six !
The tooling that would have been used in 1944 would have been different, made in some cases from metal, for longevity. Within the design of this production tooling were prompts for the foundry man to align the tooling correctly, left as marks or telltales in the finished castings. Our modern tooling is made from timber, for what will always be a modest production requirement. We have , however, incorporated an element that does allow telltales to be left in the finished casting, just like the original.
Some of the tooling is self evident :
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This tooling is for the cast iron brake drum, which will be a machined fit into the magnesium casting.
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This tooling is for the separate split rim, in magnesium, again a machined element. It slowly dawns on you that there is a lot of machining in a single wheel, lots of machining.
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This is the tooling for the axle core. This allows for a ‘tube’ with funnel shaped ends to be made from sand, which will be placed in the final sandbox, to leave a central hollow in the final casting. With tooling, you have to start to think in reverse. It is designed to make shapes out of sand, that then determine where metal flows and does not flow.
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This is the balance of the tooling. At this point I start to scratch my head. How does it all fit together ? I ask the pattern maker to explain. He is patient, but I slowly watch as his eyebrows arch into the realisation that he is talking to a half wit. I make noises at the right moment in the conversation but I am Goldilocks lost in the big, dark wood. I will have to go and get some CAD drawings done to understand it all. This is why we do this, to learn.
powerandpassionDo either of you gentlemen or anybody have A Stds 355- 360, 502-517, 564-567, 753-757, 771-820.
These are all rolled sections.
Thanks,
Ed
powerandpassionNick, thank you. Bristol Aeroplane, and I suspect Bristol Engines, would have had their own material specifications. These would be prefaced BACA, certainly in the 60’s; perhaps under different nomenclature in the 30’s. I cannot believe that Sir Roy Fedden would condescend to rely on British Standards or Directorate of Technical Development Standards. Rolls Royce had their proprietory metallurgical confections, the RR alloys, eg RR56, which played a big part in aero engine development. If you find ANY material standards in your peregrinations through the archives I would be incredibly grateful to be connected to the appropriate librarian; if attractive and female then this would additionally elevate my interest. Thanking you, Ed
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