BS T50 tube is a 3% Nickel steel alloy tube used in Hawker Hind, Hurricane and Typhoon and Tempest fuselages, spar liners and aileron spars. It is unobtainable. BS T2 tube is a Nickel Chromium steel tube used in the axle cross members of British biplanes. It is also unobtainable.
A new approach is required to make these materials available.
Chromium – Molybdenum Steel SAE4130 (and BS T45/Reynolds 531, for simplicity grouped as the generic SAE4130) tube is obtainable, but is different to T50 (Nickel Steel SAE 2330) & T2 (Nickel Chromium Steel SAE3140, SAE3250) for the following reasons :
a) It is generally thicker walled, to allow weld purchase, therefore increasing aircraft weight in comparison to an equivalent T50 structure.
b) Its alloying characteristics are driven by strength, weldability and elasticity. In comparison 3% Nickel T50 and NiCr T2 alloying characteristics are driven by strength and elasticity. T50 and T2 are not weldable. In forgoing this attribute they are able to discriminate in favour of elasticity. T50 and T2 tubes may therefore be thin walled, low weight, high strength and highly resilient to deformation under load. They were used in pin jointed structures, most readily recognizable in Hawker construction technique, but also in general prewar British use.
c) Viewed from the singular prism of strength, 4130, via heat treatment, may obtain similar strength values to T50 and T2, but at the cost of brittleness. In other words the key attribute of T50 and T2, aeroelasticity, may not be obtained through only satisfying the question of strength.
d) SAE 4130 materials have evolved from profound differences of opinion in the post WW1 period about sound aero structure technique. One school, developed and promoted by Anthony Fokker, viewed welded structures as a sound approach and stimulated the development of 4130 materials. The other school, which for the purposes of abbreviation and practical effect may be called the British Air Ministry, banned the use of welded tube structures in aircraft until the 1930’s. Thus to use weldable 4130 material in pin jointed tube structures is in antithesis to the engineering mindset of the original designers of pin jointed aircraft structures. Today, the practical affect of seeking to utilize 4130 in pin jointed structures requires a large investment in re-engineering these structures and invariably limiting aircraft performance characteristics. In the defensible task of risk avoidance, certifying authorities see the most appropriate response as avoiding decision making on material substitution or pushing the question away. Either nothing progresses or substitution decisions are made under experimental categories that in the absence of confronting the ‘why’ about T50 might not lead to the most optimum engineering result.
It would be very much easier for everybody to replace old T50 and T2 with new T50 and T2. But they are commercially unobtainable and this factor severely limits the prospect of restoring or maintaining aeroplanes dependent on this material. Today, ongoing supply of birch and spruce can allow the most obscure WW1 type to be restored and ongoing supply of aluminium sheet can allow the most obscure WW2 monocoque structure to be addressed. Whatever your position on the restoration of remnants into an identifiable, flying aeroplane are, it is obvious that many potential and exciting projects based on T50 structures can never be addressed until the material availability question is resolved. This is a great loss.
T50 tube production lapsed in the 1950’s. Once the last Hawker designs, the Typhoon and Tempest, using this material were obsolete it was no longer required. T2 production was already unnecessary once pin jointed steel biplanes with fixed undercarriages became obsolete. The Gloster Gladiator and later Westland Lysander had already by the mid thirties adopted sprung Dowty wheels, making T2 tube unnecessary.
A compromise material, SAE 8630 tube, incorporated some Nickel but still allowed welding. It was pioneered in US aircraft production in 1940, where performance in Wartime Emergency triumphed over cost. The addition of Nickel added cost in comparison to standard 4130. As aluminium monocoque structures soon became the basis of greater performance the cost premium argument faded. Tube was still required, but for low performance aircraft such as Taylorcraft/Austers for which standard 4130 sufficed. SAE 8630 seems to persist in engineering literature until the 60’s, but is today obsolete.
SAE 4130 persists due largely to ongoing demand in automotive manufacturing and racing and experimental welded fuselage aircraft types.
T50 and T2 tube are cold drawn tube materials, as is 4130. Cold drawn tubes are still made today for a large range of applications. It is perfectly possible to contact a large number of tube mills and commission a run of this material. The only obstacle is cost. An individual restoration may only require several feet of tube of a particular diameter and wall thickness or gauge. Within a typical aeroplane structure there may be ten or more permutations of diameter and gauge. A typical cold drawing tube mill must demand, as a commercial concern, a minimum order of 2,000 pounds or thousands of feet of a tube in a particular diameter and gauge. So the individual restorer cannot conceivably remedy the material question by engaging with a modern tube mill. In practice, scarce remnants of tube are sought like dinosaur bones and more and more restorers are placed at a table with a grim and threadbare meal before them. It is unpleasant.
Fixing this is straightforward. A rich person must form an appreciation of aggregate global demand for this material for the next 25 years and commission commercial runs of tube in a range of diameters and gauges and distribute this material in neat little packages over time. They must shrug off the opportunity cost of the cash trapped in stock on the shelf and bear the costs of safe storage until somebody wants a crust. They must remain impassive in the face of criticism over the cost of the crust when it is offered to the ragged restorer and the prudent advice of their lawyer on the liability wedge introduced into their lives by involving themselves in aerospace materials supply. It only takes one idiot to weld some T50 tube and it will consume five years of life in attending a court to prove their innocence in a chain of events leading to catastrophe. Far better if you are rich to dissipate your funds floating in a beanbag on a pool, with giggling youth paddling over to refill your Martini glass. It works for Silvio Berlusconi.
Or, perhaps like minded restorers could group together under the protection of a Non Profit Incorporated Association, aggregate their needs and issue a tender to the mills of the world to run the required material. Aggregate demand will exceed 2000 pounds in terms of a dedicated cast of 3% Nickel steel to aerospace standard. Within many mills, already producing 4130 aerospace tube, already exist the dies to produce the external diameters of tube required. So the guts of the commercial parley relate to the cost of producing the internal mandrels for cold drawing finished T50 and T2 tube, perhaps 20 mandrels. Spread over 20 people, that becomes one mandrel per person. I can’t fund 20 mandrels, but I can fund one. So where are you, Magnificent Nineteen ? Got a Hind, Demon, Hurricane, Typhoon or Tempest in your garage ? Want T50 or T2 tube? It’s in your fuselage, your spar liners, your ailerons, your tailplanes and axles. Do you want to fly?
So here’s how it might work :
A Non Profit Incorporated Association is established, at my cost, in Victoria, Australia. It offers its members the protection of a separate entity, that, in the worst case, means the entity is sued rather than a member, and the assets of the entity are at risk, rather than the assets of a member. The sole purpose of the entity is to aggregate global demand for T50 and T2 tube, issue a tender for supply, engage a certifying engineer, coordinate funding and payment for supply and distribution of tube and upon completion of this exercise be wound up. It will exist for perhaps two years, as long as it takes to coordinate a once off supply of tube, then, having achieved its aims, be shut down.
Under the precedent of the Roman Senate acting in time of war, I will submit my Presidency to the vote. The Presidency, though moderated by the Model Rules of an Incorporated Association, provides for dictatorial powers. I will be also Secretary and Treasurer, unless there is a brisk and businesslike person in Melbourne, Australia who wants to chop this wood. This is not a gabfest, we just want to make some tube then move our separate ways. I submit that I will be unpaid in this role. I will try and be fair and if I can’t be I will try and be humorous. If you don’t vote for me then I can’t do this. The way to vote is to actually join as a member. If no one joins, then nothing will happen anyway. Within the Model Rules, all members agree to never to sue each other.
All this organization will not cost a lot of money. Most of it can be done over the telephone. There will only be one initial video meeting and one formal report per year and one monthly dot point group email not exceeding 100 words on progress. I will pay for this. Members will not be asked to fund any of this organization unless they want to make a donation. There will be direct material costs which will be amortized over members, eg, payments to certifying engineer, payments to the tube mill. In all cases members will be required to pay these suppliers directly, but upfront, when requested. There will be no opportunity for me to take your funds and abscond. If you fail to pay the mill or the engineer the scheme is at risk. If there are 5 members the costs will be greater per member than if there are 50 members. Therefore the first point in answering the question “how much will T50 and T2 tube cost?” is to find out how many people are interested in participating. In basic terms it will only be the cost of the alloy and the cost of transforming this into a certifiable tube product provided to you at the door of the mill. It will never be cheaper.
Some restorers that will require T50 tube are still in nappies. It would be a good thing to provide for their needs in 25 years time. I will personally subscribe to more material than I need in order to gift or sell at profit tube to somebody I don’t yet know. It would be a nice thing to do to enable the next generation. This can work with a smaller group of people with an intergenerational mindset mixed with a larger body of folk who can only fund their own immediate needs. You may not even want to do a restoration or become a Member but enjoy the idea of a modest donation to see more unique aircraft take to the sky. You might like to donate to your local Museum if a Museum becomes a Member and this allows a Museum project to proceed. Members can be an individual, a company, anything with an address. You may be an aerospace company willing to stock enough tube for five Hurricanes on your shelf to sell later. All are welcome. No Member should be criticized for reselling material in the future at profit, for they have taken the risk and financing cost to allow this to happen. One Member may wish to construct a Handley Page Heyford, requiring a small quantity of T50 tube of uncommon diameter, causing a disproportionate cost influence per aggregate yard of tube. My attitude on this is that this opportunity is construed for just this purpose, as I also want T2 tube, which cannot be found on a Hurricane or Tempest. In commonweal, comrades.
Each Member is ultimately responsible for costs of collection of their tube from the mill door and the acceptance of material for use within their national certifying structure. It is most likely that the tube material may be made in the United Kingdom, EU or USA. It is not likely to be made in the Ukraine, even though the Soviet space program has proven to be fit for purpose. I am in Australia, so I have to do whatever is necessary for tube made in, say, the USA, to be acceptable for legal use in Australia and I have to pay for it to be transported here. The Association’s singular role is to act as a commercial broker aggregating supply. The tube can only be made in a facility certified to make aerospace materials, with all product tested and certified to modern aerospace Good Manufacturing Practice and the original British Standards T50 and T2.
I do understand that all this process eventually devolves to one mill worker who is paid a humble amount of money to supervise the casting of a billet or the drawing of a tube. Within GMP up to 30% of cold drawn aerospace tubes may be rejected for quality reasons. I do understand that close supervision of the casting of a billet may provide increased performance factors, and standing over the console as Homer Simpson presses buttons may avoid performance problems down the track. I do therefore intend to be present during production because I am excited by it, as much the worker will be more responsible to a client who has made the effort to come and see. I would welcome any Member to do the same, and if it happens to end up happening in your neighborhood, make sure your President gets a beer.
This is a model of cooperative manufacturing that might be applied to other obscurata like aggregating demand for left hand tractor blade forgings to support CNC finishing of replacement propellors for British radial engines, but that is another limited life Association and another story. I would be grateful if you would consider this concept, and even happier if you would express an interest in becoming a Member.
The next chore for me is constructing an excel spreadsheet quantity survey of T50 and T2 tube requirements across a range of tube schedules for types such as Hind, Hurricane, Typhoon, Tempest. I have all these schedules (thanks Dave and Australian National Aviation Museum Library), but there are days of work in transcribing this all into one spreadsheet to construct a quantity survey. This basic survey is then informed by how many of each aeroplane type require material. There won’t be any Hawker Henley projects, some Hind, some Demon, a bell curve peak on Hurricane and a downward slope on Typhoon. So tell me what you need. Even better, take the spreadsheet and update it with more accurate lengths for particular tubes, because I don’t have this information, nor do I know all the nooks and crannies in your aircraft where T50 and T2 hides. If you chose not to participate and there is no interest, I can’t do it alone.
Then this quantity survey can be sent out as a tender to tube mills and then after a few months you will know the price of the tube you need. Until that point you will not be asked to spend any money or even actually join as a Member of the Association, just express an interest to give me some hope this is going to work.
What have you got to lose? It’s a T50errific idea!
Cut and Paste, PM or reply :
Yes ! I am interested in becoming a Member of the
T50 & T2 Aeroplane Tube Association.
I have (insert number) ____________ project/s requiring T50 or T2 tube.
All the best,
Name_______________________________
Country_____________________________
NB – This is only posted on Key, so repost or email elsewhere if you see fit.
Thank you,
Edward Meysztowicz
President Elect Maybe and There for a Short Time Only
T50 & T2 Aeroplane Tube Maybe Association
Melbourne, Australia
By: powerandpassion - 4th June 2018 at 09:29
RE Hamilcar glider, the material would most likely be DTD166, used in Hawker fishplates and most aero engine exhausts, as it could be work hardened, as well as cut into shape in any old shed. By avoiding the need to heat treat to develop strength, it was cheaper to make a fitting from this than from a ‘cheaper’ carbon steel that needed heat treatment.
Using a thicker carbon steel that would not require heat treatment would introduce weight penalties.
There were many, many firms stamping out Hawker Hurricane fishplates in DTD 166.
The fascinating journey would be to compare Hamilcar plates to Hurricane plates, to see if there are any matches….
By: powerandpassion - 4th June 2018 at 09:23
I am still here in this padded room. I do sessions with handheld XRF on various remains and as more questions are answered, more new ones appear.
The Mond Nickel company of Canada had 90% of the world’s supply in 1939, and as Re-Armament and the US Military machine expanded, Nickel became a scarce material indeed. Even the US was forced to create National Emergency low nickel compositions, like NE8630. Just the need for stainless steel exhausts on aero engines was a critical application that drew on limited supply. Strangely enough wartime Allied examination of Japanese aero engines showed no under salting of nickel alloys. Probably the only other source of Nickel in the world at that time was New Caledonia, where the French administration chose to go with the Free French after 1940, and the US occupied as a priority of after 1941, on the way to Guadalcanal, ultimately giving us the musical ‘South Pacific’.
All this time I have been staring at Nickel as the key alloy focus, but now my eyes drift down to the more humble manganese. The problem is that NO 1930’s Hawker biplane T50 tube remains seem to have enough Manganese in them to meet the chemistry laid out in the original historical material standards. This is a scandal ! The mills were under salting the manganese in 1935 ! I can’t believe it ! In the 1930’s there should be 1.7% Mn but I am consistently getting 0.4% Mn from known Hind and Australian Demon remains. This is a big difference in specification. In other words, these tubes would fail the T50 standard of the day. They would also fail the later 2T50 standard, which has a later concession to go down to 1.2% Mn.
I have to go back and re-test later UK and Canadian Hurricane T50 tube remains check the Mn. In 1935, alloys were generally over salted and the pressures of later wartime scarcity where not in force – what could be going on ? Less alloy would make a tube material cheaper to constitute. Less Mn would make a softer tube, in other words more cold drawing with less annealing – cheaper and faster to make. I can understand why a tube mill would be attracted.
Now I am starting to realize that all the pin jointed tube structures I have been looking at are Hawker designs – Hart biplanes, Hurricanes etc. This is not so much a T50 issue as a Hawker Tube issue. Surely Hawker QC would pick up a significant difference in chemistry, even with the time consuming chemical testing methods of the day. Surely no mill would dare to pull the wool over the eyes over it’s major customer ? Surely there would have had to be a conversation about ‘making tube cheaper to buy’. But this must have been balanced with either no compromise on performance, or better performance….
Much of this relates to the function of manganese within an alloy. It has a role in purifying iron, ‘allowing’ more mechanical performance. But if you were using the finest Swedish ore, would you need all the manganese? Now if you had less manganese you would have more ductility, more capacity to work harden if you wished to manipulate the tube. This is what brings me back to Hawkers. ALL the business ends of Hawker tubes were squared. The pin jointed structure is constructed around a work hardened square portion of a round tube. This portion is mechanically different to the unmolested round portion. So maybe Hawkers REQUESTED low Mn T50, to accomodate tube end squaring, where excessive hardening around the pin joint could lead to premature failure…The issue of work hardening had an initial focus around streamline tube, as a known phenomenon around shaping round tube.
After the War, “Reynolds 531”, basically manganese alloy T45, became the bees knees for bicycle racing frames. The big trick was to stretch tube so that the middle section became thinner than the ends, but work harden to develop a desired mechanical strength. I have talked to an old racer who saw many frames badly bent, but never cracked. I wonder how much aeronautical knowledge from the 1930’s passed into the working of Reynolds 531. I will have to put the XRF onto this material to see if it was low Mn.
Another 1935 Hawkers works method was oven baking in black enamel, at 170 degrees C, for a number of hours, square ended tubes, to stress relieve. There was a lot of thought put into the material and the design method.
Things orbit around my mind like loose electrons : Hawker Australian Demons were crashed and repaired time after time after time – surely a testament to a carefully resolved and applied materials technique. Were low Mn, higher ductility T50 tubes part of the magic?
The problem is that modern T50 tubes, made to the approved recipe of T50 or 2T50 would have ‘too much’ Mn, in comparison to known Hawker remains.
The ideal thing to find is a bit of original ‘Hawkers’ T50 that is not corroded, has never been stressed within an airframe, and MEASURE what it’s actual mechanical attributes are, as distinct from the published mechanical attributes of ‘Standard T50.’
For clarification, commercially available modern 4T50 or T45 is chrome -moly, a different material.
Probably the only way any scientific conclusion could be arrived at is to cast a test rod of “Hawker Low Mn T50” and “Standard T50” and do some real life mechanical testing.
Why bother ? I understand that later on, during WW2, material performance was compromised due to scarcity and the reality of a ‘short and brutish’ aircraft life. XRF reveals some great material selection crimes in WW2 aircraft structures. Who knows how much was flak or an in flight structural failure ? I guess today we may want a restored aero structure to last 100 years, so the most highly resolved material selections can facilitate this.
By: powerandpassion - 2nd August 2015 at 12:22
Does anybody know anything about the use of BS T78 or T79 tubes in current aerospace?
BS T78 (1997) was amended in 2013 and is a current standard. The basic specification is a 2 1/2% Nickel-Chromium-Molybdenum steel tube of 1390 Mpa, which is a pretty close match in terms of chemistry and performance to prewar T2 at 1300 Mpa.
This avenue might cover off DTD254 for Tempest and Typhoon as T79 (1997) has the same chemistry as T78, while rated at 1160Mpa.
What helicopter-jet-missile-thing in 1997 to today needs high performance steel structural tube? It would be something like undercarriage, non weldable frame. Refueling probe? High strength steel structures subject to cyclical loadings. Helicopter blade roots?
What are fast helicopter frames made out of today?
Who supplies T78 and T79 today?
Thank you, Ed
By: powerandpassion - 30th May 2015 at 23:48
More information required
Sorry mate but you have completely lost me!!!!
Ahh! I thought I was in the room all by myself! Where did I lose you?
a) It is not possible to get a cheap and tasty red from Aldi?
b) Carbon offsets are not necessary if you burn a cardboard battleship?
c) There is no difference in the flow, or Young’s Modulus of T45/4130 treated to 180KSI and T50 at the same ultimate strength?
d) This is not a forum to discuss Young’s Modulus, unless its the name of a mascot dog belonging to Flt Sgt Young in 1943?
By: Stormin' - 30th May 2015 at 18:46
Sorry mate but you have completely lost me!!!!
By: powerandpassion - 30th May 2015 at 12:59
75% more
So here courtesy of a bottle of cheap but surprisingly tasty Aldi red is the Hind chart with T50 fuselage members in yellow and other T50 members in orange.
These other members include Accles and Pollack streamline T50 used in interplane and raking struts, spar liners, aileron spar, elevator and tailplane tubes, support tube for ballast weights, mainplane drag struts. In total these additional members increase the T50 quantity by 76%, a significant requirement. When I reflect on this Hawker design, it is really a tube based aircraft, with a little strip steel in the spars.
I haven’t worked out what the base diameter for the A&P streamline T50 are, but they appear to fall within the centre right of the bell curve of all sections, with a thicker wall.
I would wager that increased T50 requirements for Gladiator may be 75%, Hurricane with fabric wing 50%, Hurricane with aluminium wing 30%, Typhoon 10%.
In rough estimate if the existing tube run quantity was maintained, the absorption of stock in these additional members will cut down the potential projects that can be helped in half.
I am only a tragic for the biplanes, so have no deep detail on new fangled things like Hurricanes and Typhoons, and can’t look into whether there may be unique sizes scattered through the design. Unless you provide this information, I will only tender out the information at hand.
[ATTACH=CONFIG]237781[/ATTACH]
By: powerandpassion - 30th May 2015 at 06:40
Bonus 50% More!
So I have sat in the corner and started to sniff through the Hind design to look for all the T50 within it. There are tailplane spar boom liners, mainplane spar boom liners, aileron spars, elevator torque tubes, mainplane bracing struts. I haven’t finished it all and there is 50% as much material in all of these as in the total fuselage tube requirement. The tailplane raking struts and interplane struts are also T50 but formed into streamline section, and these quantities haven’t been added in yet. So, on the back of the envelope T50 requirements for this biplane design may be 75% more than the previous quantities worked out for just the fuselage, meaning the tube run will be bigger.
I figure that in the monoplane designs there will be a lesser additional requirement the later the design goes, but it is surprising where T50 is found. The gut feel is that real requirements are 50% more than the original total. That’s OK, unless the size required is not already identified. I figure I will go to aerospace tube manufacturers in July 2015 with a definitive list of required dimensions, so if you are interested in a particular aeroplane design, let me know the sizes and gauges you might want, if they are not already on the list.
Last night I read ‘Daedalus’, the Halton Magazine, Christmas 1934,the rag put together for RAF Halton apprentices. It has the article, including “A Visit to Messrs. Hawker Aircraft Ltd” and out of this a a glistening pearl rolls out :
“On our second afternoon we had an hour’s quiet talk with a ‘stress merchant’, who informed us regarding more recent Air Ministry requirements in loading and strength calculations.
[I reckon this may be AP970 May 1935 ‘Design Requirements for Aeroplanes for the RAF’, based on verbatim extracts of the Handbook of Aeronautics published in 1934 by the Society of British Aircraft Constructors]
In his opinion the firm have a general reserve factor of safety of 1.1, that is to say, for example, where a front spar must be capable of standing 7.5 times normal loading, the firm makes it to stand 7.5 x 1.1 or 8.25 times normal loading.”
In AP970 May 1935 ‘Design Requirements for Aeroplanes for the RAF’ there are tube schedules which lay out performance factors for different lengths of tube at different gauges and outside dimensions. So within the Hind design the original manufacturer has incorporated an additional load reserve factor within the structure of 10%. So here is a little nugget to assist in the interpretation of the structural design, whichever tube path you follow.
My gut feel is that T45 metallurgy is at 110% of capacity if tested for T50 values and replaced like for like with the original T50 dimension, while T50 is, if the stress merchant from 1934 is believed, at 90% of its design capacity. Using T45 may not be a conservative position, viewed through the lens of historical Hawker practice. I ruminate on original aircraft still operating with original steel, that are, in good sense, operated conservatively. Without munitions, and with the original reserve factors incorporated in the design, all these factors add up to structures being only used at a fraction of their potential. All this good sense is subject to the opposing factors of corrosion, past, unknown loadings and heavy landings. I wonder if there is a more scientific way to maintain these structures as non destructive testing becomes increasingly sophisticated, faster and cheaper, like hand held ultrasonics that instantly output graphical displays that can show up cracking.
Today recreational fishers use side scan sonar which shows the eyeballs of fishes deep underwater- this digital technology becomes more and more sophisticated and cheaper every year. To an extent the use of original material in antique structures may be the conservative position for a number of decades in initial use, but in structures that may be seventy years old it may be a form of fanaticism. Anyone interested in historic aerostructures is a fanatic, so this is not a negative, but there are interesting tools out there to help defend the position. The truly conservative position is to use new metal. And cheaper. And more relaxing at 20,000 feet. To me it’s about learning how the designers thought, preserving this knowledge and using it to celebrate their achievements by keeping their products safely in the air.
I guess the fanatic part of me wants to unwind the conservative approach to what these structures are allowed to do. New metal with a 825% reserve factor should be allowed to dive bomb a cardboard cut out battleship and sink it in flames, as long as a sufficient number of carbon offsets are purchased.:p
By: powerandpassion - 26th May 2015 at 09:51
At first I cooked my head over the question of DTD54a-BS88c wing spar material.
Then I boiled my brains over T2 tube.
Then I sizzled my synapses over T50 tube
Now I am almost afraid to raise the topic, but I have ignored,for health and safety, aluminium T4 tube….which is all kinda thin walled in pin jointed structures and scattered here and there, although Westland and Glosters seemed to like it back then.
Can anyone tell me if T4 is available today? What is the spec for modern aerospace aluminium tube ?
By: powerandpassion - 26th May 2015 at 09:13
After swinging the verniers Hawker Aust Demon and Hind aileron spars are 1 5/8 T50, so another dimension to add to the mix.
These aileron spars are close to 10 feet long, so a significant member dimensionally and for performance and for total material requirements.
The wonderful thing about these ailerons is that they have Sopwith aileron hinges that travel through from WW1. There are a number of hinges – the centre hinge adjacent to the aileron gearbox/control arm is wide and cannot move sideways, but all other hinges are sloppy. As the aileron bends in flight or use the sloppy hinges cannot jam at the extremities, preventing the ailerons from binding up or becoming heavy. Simple but effective. No doubt a few early aviators had to spiral in before the fix was learnt.
So the original double decker busload of engineers and stress calculators would have been careful to select an aileron spar that could cope with the loads placed on it that would also deflect in sympathy with the deflection of the main wing spars. If the aileron spar was too “hard” it might cause the aileron to jam or it might transmit wing loads into a concentrated zone around the aileron fixings causing a failure from excessive cyclic loadings. The aileron also had to be light for ease of control, so the aileron spar tube had to be high strength but light. So a thin wall 3% Nickel alloy T50 tube was used matched to the DTD54a-BS88c Nickel Chromium main wing spars.
So today I must look at what I might be able to do to substitute the original T50 aileron spar.
I could use T45 or 4130 with some weight penalty, but live with that by adjusting the distribution of weight in the overall aileron design to avoid flutter issues (add Engineering and design cost).
I could use T45 or 4130 and heat treat to develop the same Ultimate Strength values as the original T50, but I will affect the modulus of elasticty values. I may end up with a “harder” aileron spar that does not deflect in sympathy with my main wing spars, causing aileron binding or load concentration issues. I need to look into the relationship between the way the main wing spars and proposed aileron spar behaves and various heat treatment and material selection permutations. (add Engineering and design costs & wind back aircraft performance allowances). Once I have figured this out I have to convince somebody to sign their liability exposure to the solution ( add Engineering costs & wind back aircraft performance allowances). So just for one tube member I can buy an off the shelf piece of T45 but spend months and months and thousands on engineering costs making sure it is not wrong. To avoid exploring the issue while at 10,000 feet the aeroplane will not be certified for dive bombing, which the original design was. No Hendon displays dropping 8 1/2 lb practice smoke bombs on cut outs of battleships.:(
Or I could just use a piece of T50 to the original specification, relying on the original engineering and a demonstrated history of safe use.:)
By: powerandpassion - 17th May 2015 at 12:20
A Thesis in One Day
A Hawker Hind biplane has an all up weight of 5,217 lbs. Within its structure, it has 166 lineal feet of T50 tube. Using an ‘average’ tube member of 1 ¼-16 gauge to calculate the mass of the tube gives a weight of 135 lbs, or 2.5% of the total weight.
So if the structure used T45 with double the wall thickness of the original T50 this would only increase the weight by 2.5% or 135 lbs. Given the Hind was rated to carry a 500 lb bomb load then omitting the bomb load would assist in compensating for the additional weight in the tubular structure. The centre of gravity issues are more complex, but this argument supports the contention that it is not necessary to use the original T50, if T45 can be supplied to the same strength values as T50. Where this T45 is only commercially available in thicker walled tube, then the weight affect of being forced to use thicker walled tube is not difficult to resolve. This, in fact, is the only realistic approach today for dealing with pin jointed T50 structures.
The cost of this approach is in the engineering for material substitution. While T45 may be obtained with a mill certificate setting out adequate ultimate strength values, the substituting of a novel member for the original T50 requires an engineering analysis. Where there are many members of many different diameters and gauges, interacting within a whole design that also must accommodate centre of gravity issues, this engineering analysis must be detailed. The financial and time cost of this analysis is significant.
One budget conscious way of performing this analysis is to be overly conservative and over specify members, resulting in an airframe that is heavier than it needs to be and more restricted in the stresses it may be exposed to.
Performing this analysis in detail will result in a more elegant engineering and performance solution, but the high financial cost places this approach beyond the resources of most participants in historic aviation.
This analysis seeks to examine a path that leverages off the extensive engineering already invested in the original airframe by the original manufacturer, that was further resolved in testing and operational use to be recognized as safe. In this case the approach is based on using materials identical to those used by the original manufacturer. Specifically, to replace T50 with T50 in pin jointed structures.
A further aspect of this approach is to seek to better understand this original material choice, in terms of high strength, aeroelastic performance structures. In this case it is argued that 3% Nickel steel alloy T50 tubes demonstrate performance factors that exceed those of Chrome Moly steel alloy T45 tubes. Both tubes may be treated to the same ultimate strength, but T50 has a higher fatigue life.
So the benefits of this approach derive from lower engineering and time costs and better performance factors for a resultant T50 aerostructure. The assumption is that T50 may be provided at less net cost than the combined material and engineering costs of utilizing a T45 substitute aerostructure. This assumption needs to be tested.
In reviewing the T50 tubes used in four typical pin jointed structures, Hind, Gladiator, Hurricane and Typhoon, four tube sizes ( the 4 size group) constitute 80 -90% of each structure, in simple terms 80 – 90% of the engineering challenge.
In general, a commercial tube mill will seek larger quantities of tube orders for ease of operation and to develop cost efficiencies, generally a minimum run of 2000 pounds per tube size. In order to develop a commercial model, this analysis is based on the assumption of meeting the needs of 28 aero frames in the next 25 years. Where the four principal tube types will meet up to 90% of the engineering challenge, these are pursued in the model to the exclusion of outlying dimensions required in smaller quantities or differing metallurgy.
Strategies for fulfilling the smaller dimension/differing metallurgy demand are :
In the case of T2 and DTD 254 Nickel Chrome members, machining Nickel Chrome round bar to the finished dimension
Or
Providing a billet of Nickel Chrome steel to be run in conjunction with Chrome Moly steel in a standard tube run with the closest dimension to that finally required, then machining to finish or accommodating higher weight in these members.
In the case of T50 members of smaller dimension than the 4 size group, where tube squaring in pin jointed structures allows different diameters to be incorporated into the same joint, using larger T50 members from the 4 size group to substitute smaller T50 members and accommodating higher weight
Or
In the case of T50 members of larger dimension than the 4 size group, providing a billet of 3% Nickel steel to be run in conjunction with Chrome Moly steel in a standard tube run with the closest dimension to that finally required
Or
In the case of T50 members of larger dimension than the 4 size group, using T45 tested to T50 and accommodating higher weight.
In order to resolve a commercial mill run of the 4 size group, two considerations are accommodated :
1. In full pin jointed fuselage structures, the longest and most critical members in the fuselage are the continuous lengths running from behind the cockpit to the tail, generally 11 feet in length, and it is desirable in an engineering sense that these members are included in the 4 size group.
For Hind these are 1 ¼ – 20 gauge
For Gladiator these are 1 1/8 – 22 gauge
For Hurricane these are 1 3/8 -20 gauge and 1 ¼ – 20 gauge
2. Within the 4 size group , are a range of gauges. In order to aggregate the greatest quantity of a particular OD within a single gauge, the thickest gauge is chosen for each OD, to reduce the manufacturing task from 12 tube tooling sets to 4 tube tooling sets. This approach may be reviewed in respect of what tooling may already be available to a manufacturer to use.
[ATTACH=CONFIG]237495[/ATTACH]
By aggregating this volume the following tube runs emerge in commercial quantity, an aggregate of 1,454 lineal metres or 4,772 lineal feet.
[ATTACH=CONFIG]237496[/ATTACH]
By using an “average” tube of 1 ¼ – 16 gauge at 0.811 lbs per lineal foot the value of 3,870 lbs or 1,757 kgs is obtained.
To obtain a costing for this production, certain assumptions are applied to these figures. These assumptions must be tested in a commercial tender.
Assumption 1.
Suitable billets or blooms of aerospace grade vacuum furnace 3% Nickel steel alloy or Nickel Chromium steel alloy are obtained at USD30 per kg, being USD52,715 for 1,757 kg.
Assumption 2.
The cost of transforming this material into a cold drawn tube, including the cost of 4 tooling sets, is USD60 per kg, being USD105,430 for 1,757 kg.
This cost includes the cost of material losses, where a policy is pursued of retaining full
lengths of tube where ultrasonics detects flaws. In this case flaws are cut out but short lengths of accept tube are retained, where final requirements may only be 3 feet of tube.
Assumption 3. In this case it is aimed to have 90% utilization of the original billet material.
The combined cost of transformation is USD90 per kg or a USD158,145 funding requirement for 1,757 kg.
What may this cost to an individual subscriber ?
In the case of one Hind, using 61.45 kg of T50, the pro rata cost is USD5,531
In the case of one Gladiator, using 51.41kg of T50, the pro rata cost is USD4,627
In the case of one Hurricane, using 96.44kg of T50, the pro rata cost is USD 8,679
In the case of one Typhoon, using 63kg of T50, the pro rata cost is USD5,706
These costs are indicative for 80 – 90% of the steel tube requirement. Each aeroplane design has further tube costs for undersize and oversize tube not provided from the 4 size group and members made from T2/DTD254 and T4 aluminium.
Accepting error in any of the assumptions, and additional costs of engineering perculiar to individual designs, it may be prudent to reserve the figure of USD10,000 to provide for T50 fuselage tubing for an airworthy project.
In this case, in using T45 which must be proof tested, a significant portion of this USD10,000 allowance may be absorbed in purchasing T45. In addition, an investment must be made in re engineering the aero structure which may, in itself, cost far in excess of USD10,000.
Alternatively, subscribing to a T50 production run may absorb a significant portion of this UDS10,000 allowance, but the costs of re engineering up to 90% of the aero structure for material substitution are avoided. In addition, the benefit of enjoying fuller performance from the aero structure akin to its previous demonstrated history of safe use.
This approach is only as realistic as the willingness of unrelated parties to combine temporarily together to form a buying club for T50 tube. A failure to fully subscribe to a buying project can obviously frustrate the basic object. One way to formalize a buying club that provides prudent regulation and protection for members is in an entity called a Non Profit Incorporated Association, that exists to achieve defined aims, then ceases to exist.
These aims may include :
1. Co-ordinating an accurate quantity survey of T50 & T2/DTD254 tube requirements.
2. Issuing a tender for supply of T50 tube to aerospace certified tube mills.
3. Coordinating with National Aerospace Regulators to ensure that any T50 tube supplied by a certified tube mill is acceptable for use within each jurisdiction.
4. Contracting a certified engineer to perform a body of work on the substitution of say, T50 larger diameter for T50 smaller diameter, T45 for T50, machined Nickel Chrome bar or hollow for T2 and DTD254. Submitting this work to National Aerospace Regulators to assist in the timely evolution of individual projects and reduce the work of Authorities in examining the same question over myriad individual projects.
5. Coordinating the manufacture of suitable billet and tube material and final distribution to subscribers of finished tube product.
Such a process may take two years and incorporate 5 steps :
The first step is to obtain expressions of interest from any party that may wish to subscribe to a T50 production run under the buying club Association model.
The second step is to divide the quantity survey task amongst subscribers intimately familiar with particular designs, to fully identify tube requirements that may be hidden in spar liners, aileron spars, undercarriage members, wing drag struts etc
The third step is to issue an accurate tender from an Association to a range of mills to make tube supply cost assumptions accurate.
The fourth step is to engage with Regulators and Engineering resources to resolve certification and acceptance of tube and substitution solutions.
The fifth step is to make the tube.
🙂
By: powerandpassion - 17th May 2015 at 07:12
Back of the envelope
I am going to enter some arbitary best guesses as to volume of aeroplanes of a particular type to be restored/maintained over the next decade into the individual schedules to create a total length and mass of T50 required.
Thus I will propose the following :
Hind (Hart family including Demon) – 10 aeroplanes
Gladiator – 3 aeroplanes
Hurricane – 10 aeroplanes
Typhoon/Tempest – 5 aeroplanes
Here is the schedule with total qty for one aeroplane of each type in white, then total qty to support the number of projects given in the proposed figure. Given the commonality of the 4 principal tube types across aircraft designs then the quantity would support up to 28 projects of any type. There may be 10 that use material today, 10 that are brought into restoration by virtue of the existence of a tube supply over the next 10 years and 10 worth of material utilised piecemeal to support maintenance and repair over the next 25 years.
[ATTACH=CONFIG]237491[/ATTACH]
By: powerandpassion - 16th May 2015 at 14:36
4 T50 for most of it.
Here is the schedule with Hurricane included in blue. Some minor amendments have been made to the Typhoon schedule in green; 3″ OD has been omitted as it is not T50 but Nickel Chrome DTD254. Some other Typhoon members were aluminium T4.
[ATTACH=CONFIG]237483[/ATTACH]
What stands out are the groupings of common tubes across these aircraft designs. These groupings can be condensed to 4 different tube sizes that constitute between 80 – 90% of the aircraft fuselage structure across all the designs. In this case, the provision of only 4 T50 tube sizes would resolve 80-90% of the original tube requirement for Hart biplanes, Gladiator, Hurricane and Typhoon.
[ATTACH=CONFIG]237490[/ATTACH]
DTD254 is given as 75T Nickel Chromium steel tubes, at this stage I do not have a chemical composition, but I suspect it is identical to T2 85T Nickel Chromium steel tube, with different mechanical/heat treatment accounting for the performance difference.
In the Hurricane is one tube given as DTD 211, Non Corroding 50T steel tube. This is a set of Vee bracing engaging with the rear spar and fuselage around the pilot’s cockpit. I assume these members were open to the weather if the cockpit hood was open.
By: QldSpitty - 13th May 2015 at 02:16
There may be some resource allocation issues, which may result in an alternative reality where I am left by myself in a cold shed late at night, fitting ferrules, muttering and farting…
Been there done that 😉 Tapered Drifts of 1/4″ and 3/8″ are a most welcome addition to the toolbox.Once a routine is in place it does get easier.Cockpit side sheetmetal gussets at corner of the instrument panel,the cotton reels only go on one way.Took three days figuring that out Rocket did..
By: powerandpassion - 12th May 2015 at 07:45
Well I hope you win lotto and get some cash together for the multitude of hollow rivets needed to pin it all in place.:dev2:
Hollow rivets are T26 ! Different Association !
For complete authenticity these structures should be put together by Rosie the Rivetter. So at this stage the project plan calls for ten chicks in bikinis spin rivetting away….
There may be some resource allocation issues, which may result in an alternative reality where I am left by myself in a cold shed late at night, fitting ferrules, muttering and farting…:p
By: powerandpassion - 12th May 2015 at 07:37
In practical terms no one has signed on, no Association exists, no quantity survey has been completed and no tender has been issued to determine price.
This development phase is known as the “Kermit plays the banjo on stage while the old men in the balcony grumble”
https://www.youtube.com/watch?v=h0Hd3uWKFKY
In doing the Gladiator survey there were lots of T2 members carrying the wing stresses across the fuselage and it has been brought to my attention that the 3″ members performing a similar function in the Tiffy are DTD254, which is 75T ultimate stress material; my punt is that this is Nickel Chrome alloy akin to T2, which was 85-100T material. A quick look at the Hurricane design also shows DTD254 as the front boom liner. Postwar DTD254 was used as helicopter blade spar, a nice connection to T2 used in Cierva Autogiro spar.
The interesting thing about doing this quantity survey is getting into the detail of the designs from Hart biplanes to Typhoon monoplanes. You can almost start to see what they were thinking.
There is twice as much T4 aluminium in a Gladiator as there is in a Hart biplane. This coincides with the development of better aluminium alloys in the mid 30’s which supported the shift to moncoque aluminium structures in British design thought from 1935 onwards. When you think about it a tube is a pure monocoque structure. There seems to be a very confident use of aluminium tube in the Gladiator. Glosters was bought by Hawkers in 1935 so this IP would have transferred over. So why wasn’t the Hurricane made of aluminium tube ? Why was the Typhoon forward fuselage still substantially of steel alloy tube ?In fact, when you start to think about the aluminium extrusions coming into service for monoplane wing structures in the late thirties, it would be entirely feasible to extrude a complex octagonal aluminium tube, akin to strip steel formed wing spars, that would have lighter walls and higher strength than a plain aluminium tube. Why didn’t they do it?
I can only figure that aluminium was not only more expensive than steel as a finished ‘performance member’, but it was provided in limited supply in comparison to the demands of rearmament based on monocoque aluminium designs like the Blenheim, Battle and Spitfire. Just as deHavilland focused on timber for the Mosquito to avoid drawing on the limited aluminium resource, so Hawkers went for a design that was based on a domestic steel capacity that could support greater supply. The Sigristian spirit in Hawkers was thoroughly practical and it could be argued that the capacity to quickly turn out large numbers of steel based Hurricanes saved the world.
However, back to T2 and DTD254. Sooooo, I put the knife into the T2 chapter, maaaaybe I was a little premature. I mean, I really respect and like the T2 tube, and they were a really good chapter, the T2s, always brought along the creme biscuits.
So it’s too early to know all the answers…..
By: Jag248rpa - 12th May 2015 at 00:05
How many have signed up and….
How many projects have signed on and what do you think the cost will be for each project?
By: QldSpitty - 11th May 2015 at 06:47
Well I hope you win lotto and get some cash together for the multitude of hollow rivets needed to pin it all in place.:dev2:
By: powerandpassion - 10th May 2015 at 07:33
Here is the schedule with Gladiator included in red.
[ATTACH=CONFIG]237388[/ATTACH]
Because I was eating chocolate cake instead of drinking wine while I was doing the Typhoon schedule I made the error of not doubling the quantities for the fuselage side members. Ie, I only counted one side of the fuselage. This has the affect of increasing the Typhoon values in the latest graph. Thankfully I will not be in charge of calculating oxygen requirements for a Mars mission otherwise the intrepid astronauts will be tapping the bottles half way out….
I must also admit that the Typhoon information I am working from does not also specify whether tubes are T4 (aluminium) or T50 (steel alloy), so the values may have to be revised by a concerned member of the Tiffy Brigade.
In doing the Gladiator work I did not repeat this error, firstly making sure I had opened a bottle of Argentinian Zuccardi Malbec 2012. What stands out is that three different tubes in a tight range constitute 70% of the requirement, with small quantities of outliers.
Then the beautiful thought came : We should not worry about cold drawing the outliers. The smartest thing to do would be to not worry about tooling for these micro quantities. It would be cheaper to use existing tooling that outputted a thicker wall tube then machine/bore out the ID, given the affected outlier members were all short length, approx 3 foot. In other words commission 3% Nickel blooms that run through some cold drawing internal mandrels for the big runs, then use existing tooling for the little runs. Even cheaper, but cover the whole range.
By: powerandpassion - 2nd May 2015 at 06:22
Let then eat cake
Here is the schedule with Quantity for Typhoon entered. I would like to thank Dave and my friend the chocolate cake for repeated support during this phase of data entry.
[ATTACH=CONFIG]237200[/ATTACH]
The key realization is the fairly even spread of ODs in these monoplane, half monocoque, structures and drift towards larger ODs. I assume that Tempest exhibits a similar pattern. The benefit of a collective approach is to force the production of small volumes on the outer like 5/8″ and 3″ OD within the scale provided by smaller ODs common across designs.
The extra nutrition offered by the chocolate cake has also made me reflect on the fact that up to 30% of aerospace tube may be rejected upon inspection, which is folded into the final price of retailed tube. Thus if you could reduce the reject rate then there is a conceivable reduction in price of up to 30%, which is significant and would help support the production of the smaller volumes on the outer. On top of carefully producing the bloom from which tube is ultimately made another opportunity is to make it a condition of the tender that reject tube is recovered rather than immediately scrapped. Ie – a cold drawn tube may be 30 feet or 10 metres in length in the factory, while final demand requires sections that are 2-3 foot in length only. In the usual production process, a flaw detected by ultrasonics may only occupy a few inches of a 30 foot tube, but the whole tube is rejected by Stacey from QA. In the proposed approach, the flaw area would be marked and the reject portion cut out, with the balance of the tube retained for use. In this case reject may be reduced from 30% to 5%, a very significant saving. Thank you chocolate cake, you cost $3 but the Return on Investment has been handsome.
It will take some time to input the Hurricane and Gladiator tube lengths. I only have the tube schedule and my thumb to roughly scale off. If anybody has a list of tubes and lengths in these aeroplanes or any other types using T50 I would welcome being able to borrow this to speed up the process.
The graph starts to show the boundaries of the tender proposition. I am going to enter some arbitary best guesses as to volume of aeroplanes of a particular type to be restored/maintained over the next decade into the individual schedules to create a total length and mass of T50 required.
Thus I will propose the following :
Hind (Hart family including Demon) – 10 aeroplanes
Gladiator – 3 aeroplanes
Hurricane – 10 aeroplanes
Typhoon/Tempest – 5 aeroplanes
Within the mix for biplanes may be the odd Wapiti or Wallace or Siskin.
This would be as real as whatever you volunteer or argue, publicly or confidentially, may be projects requiring T50 in the next decade or so.
Yes you can use T45/4130, but the initial tube affordability is balanced by serious hurt money incurred in the engineering costs of material substitution and structural analysis.
My gut feel is that a certified T50 production run with a 5% reject rate, well negotiated with a sympathetic aerospace tube mill, with internal mandrels (fit for purpose) and high quality blooms from an aerospace casting plant externally provided by the Association, will be affordable. Whether this intersects with a users capacity to pay or timing of projects on the day the T50 is run will determine whether you can get material at cost price on the day or at additional cost when you are ready later. I would welcome any member willing to enter into any bulk order for profitable sale later on. Anybody willing to risk investment in stock costs, storage and piecemeal sales over time deserves to make whatever profit that market will bear. Once the Association is dissolved and internal mandrels scrapped, “that’s all folks.”
It probably pays to be inter generational though. We need to support the 20 year old today that will take the baton from you in 20 years time and be required to maintain or restore pin jointed tube structures in the future. No doubt 3D printing would have made tube mills obsolete by then ! It would be a good thing to run material and carefully preserve it to be held in trust for somebody eating an ice cream on the flight line today and dreaming of the day when they could work on a Hind or Typhoon. So I would welcome any philanthropic subscription to a volume of production that could be kept wherever the contributor sees fit for later distribution in any way they see fit. I wish somebody :angel: :dev2: had greased up some Merlins and buried them in crates for me decades ago in the same way…:)
By: powerandpassion - 1st May 2015 at 12:25
the Hind most.
Here is the schedule with Quantity for Hind entered, courtesy of of Excel.
[ATTACH=CONFIG]237173[/ATTACH]
The key realization is nearly 80% of the T50 issue for Hind is sorted in one OD of tube.
Compiling and entering all this data into Excel takes forever. Since none of you are helping me only a bottle of Angove Organic Merlot, product of South Australia, has assisted.
By the time I finish the entire schedule I will be a confirmed alcoholic. :very_drunk:
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April 23, 2015 at 2:44 pm