Does somebody know if the prewar and postwar frame lugs where made of whiteheart or blackheart malleable iron castings? Has someone had some lugs casted and could advise me on what material to be used.
I was under the impression that frame lugs were forgings, but then I am no expert. What are you trying to achieve? Details might help. Usually the frame lugs can be re-used with new tubing if undamaged. If you have lugs that are beyond repair you might wish to consider buying a spare frame and taking the lugs you need from that. If the frame is too rare for that then I can pass you on to a frame specialist.
mike Member #: 147 1960 T120 Bonneville 1999 H*%^a VFR 800 FI V4 Triton Project (still keeping me sane (Ha-Ha!))
As far as prewar frames are concerned I know for sure that they were castings.
I'm asking because I'm in the process of making the patterns for some lug castings for a prewar replica project.
Here is a guy in the chech republic who says the original castings where blackheart malleable castings, which contradicts everything I've heard and read about the material used. Blackheart malleable iron being unsuitable for soldering in contrast to whiteheart malleable iron. The same problem concerns the spherical graphite iron castings he's using now:
Isn't soldering a description which is also used -besides from electric components with tin- for the use with silver-solder?
I've heard that the manufacturers used brass solder instead of silver solder just for economical reasons.
The whole point is that the lug material will be heated at around 650-750 degrees celsius and even more with brass solder and that under certain circumstances the carbon ferrite bindings can change to a lesser strenght or even brittle material, if a non correct casting material has been chosen.
Dunno if i could sleep comfortably after contributing to a cast lug frame.The style of construction of a lugged frame is called forged lug construction .Steel forgings are tough and relatively flexible making it ideal for a motor or pedal bicycle frame in contrast to a casting of iron which are rigid and brittle even if heat treated to a "malleable" state.That not to say cast lugs may have been used but even in the early days of m/cycling, the blacksmithying and drop forging industry specialised in frame lugs and the manufacturers chose whatever lug kit off the shelf that suited their needs and added their own tubes. Once the manufacturer has made the decision to mass produce a lugged frame and spends the money on sets of dies many thousands can be banged out ,literally, for very low cost. By the time motorcycles came along the business of supplying forged lugs for bicycle frames was well established and easily adapted for motorcycle use. The frame tubes are a reasonably tight fit in the lugs aligned on a jig or surface plate, drilled and pinned to then go on the hearth to be brazed together with bronze spelter.There is a great old triumph factor publicity video on utube showing the process. A well skilled blacksmith could bang out lugs of a suitable steel if you can find one.Many blacksmiths turn to farriering for their bread and butter work but will ,if you can convince one to,take on odd jobs that will give them a bit of work satisfaction that doesn,t involve horses.
The driver footrests on the 50's and 60's BSA are made from malleable cast iron, when in a crash they bend but do not break and can be straightened again after localised heating. I have straightened them several times and they bend easily with the right heat. Can't see any reason why the frame lugs need to be made from a forging instead of this malleable cast iron unless the brazing operation does not work. What I can't find is any reference to them being white or black malleable cast iron.
I have found a reference to white and black malleable cast iron, page 93 of Motorcycle Engineering by Phil Irving.
White malleable cast iron is the raw casting out of the mould, it has the same properties as normal cast iron and is brittle and cannot be used for frame lugs. To convert a white malleable cast part to black malleable you subject the part to a lengthy annealing process which removes the carbon or converts it into flakes, the properties are changed and you end up with a casting with similar properties to mild steel, not as strong but more resistant to fatigue cracks and is ideal for frame lugs.
Phil goes on to say the annealing process is too onerous for one offs and suggests the speacial builder instead using Monel instead, Monel is an alloy of nickel & copper. It brazes as easily as black malleable cast iron and is easily machined.
It's possible that some manufacturers used forged lugs but it was the opposite as your describing. The majority of the prewar motorcycle frames had cast lugs. The two sorts of malleable iron castings are ductile similar to mild steel and absolutely not brittle as you state. The malleable iron castings where ideal, specially for thin walled lugs. As a perfect example the thin walled lugs for bycicle frames could be precision cast without or very little need of machining. You can not forge such thin walled lugs. You would have to forge them as a plain block and then drill out the bores for the tubes.
The malleable irons where replaced in the 70's by spherical graphite (SG) iron only because it doesn't need the costly tempering for 2-3 days in an high temperature oven. They are widely used as components in vital frame and chassis parts in the automobile industry. As an example the brake caliper body on your car is SG iron.
Yes indeed, the description is not correct as such.
White iron is the starting point. If the parts are then tempered in an oxidizing atmosphere the result will be whiteheart malleable iron. If they are tempered in an inert atmosphere they become blackheart malleable iron.
Has a structure of pearlite in a cementite matrix making it hard, brittle and difficult if not impossible to machine. It has limited applications in industry, it is used for wear resisting components such as extrusion dies and cement mixer liners. Fracture surfaces have light-coloured appearance.
Malleable Cast Iron..
Standard..BS EN 1562:1997: Founding. Malleable cast irons
Heat treated forms of white CI to improve ductility while maintaining the benefits of of high tensile strength ; The greatest use of white cast iron is for the manufacture of malleable cast iron. This is produced by heating white cast iron at a temperature of 870oC for an extended time period and then cooling at a slow controlled rate. The cementite loses carbon which forms into free nodules. The final product is a ferrite matrix with include free nodules of carbon. Malleable cast iron has superior mechanical properties compared to grey cast iron apart from wear.
Increased strength and wear resistance with reduced ductility are obtained by converting the structure to carbon nodules in a pearlitic matrix (or tempered martensitic). This involves heating the malleable cast iron to a temperature of 970oC for over 12 hours and then air cooling it. The faster cooling in air produces less ferrite and a finer pearlic structure. A martensitic matrix structure results if the cast iron is heated to a slightly lower temperature (about 940oC) and then quenching it in oil.
Malleable iron castings are produced in section thicknesses ranging from about 1,5 to 100 mm and in weights from less than 0,03 to 180 kg or more
The three principle types of malleable cast iron available are ;
Whiteheart..UTS 250-400 MPa, Elongation 4-10%... This is heat treated white iron compound producing an outer ferrite layer and a ferrite/pearlite core Easy to cast in thin sections, which have a tough core....
Blackheart...UTS 290-340 MPa, Elongation 6-12%... Soaked at high temperature to cause the cementite to break down, then slowly cooled to give ferrite and graphite
Pearlite... UTS=450-550 MPa, Elongation 6-12%... Similar to blackheart but faster cooling to produce a pearlite structure with higher strength
Malleable iron is preferred over ductile iron for thin-section castings and for components as listed below:
Components that are to be pierced, coined, or cold formed Components parts requiring maximum machinability Components that must retain good impact resistance at low temperatures Components requiring wear resistance (martensitic malleable iron )
As a fact, your recommended foundry and an other one, also in the midlands, are on my list to be contacted.
Here some information about the risks when heating up the different types of ductile irons. Whiteheart malleable iron (mainly the specially good weldable type EN-GJMW-360-12) seems not to have this problem.
Structural changes due to brazing
The matrix of a grey iron, pearlitic S.G. or pearlitic malleable iron will change to austenite if the material is heated to above its transformation temperature. The exact transformation temperature varies depending upon the analysis of the iron, but is about 700°C. The form taken by the austenite on cooling will depend on the rate at which this cooling takes place. Extremely fast cooling from temperatures in excess of 700°C could result in the formation of martensite, although this would be most unlikely to occur in brazing. It is quite possible however, that cooling rates significantly faster than those seen during casting could be achieved, with the danger that an unacceptably fine pearlite structure could be produced. Alternatively, prolonged cooling as might result from furnace brazing, could result in a significantly softer structure due to increased ferrite in the matrix. The use of a brazing alloy with a flow point below the transformation temperature ensures that the structure of the iron is not altered. Where the use of a filler metal with a brazing temperature in excess of the transformation temperature is envisaged, it is advisable to conduct brazing trials involving checks on the structure of the cast iron. On the basis of these trials it should then be possible to adopt a closely controlled brazing procedure which will ensure a consistently satisfactory brazed joint and cast iron structure. The production procedure employed to produce ferritic S.G. iron requires that cooling be arrested at approximately the transformation temperature for a period of several hours. Normal air cooling through this temperature will result in the formation of a largely pearlitic structure. Consequently if a ferritic S.G. iron is brazed above the transformation temperature a serious loss in ductility and impact resistance will result. Blackheart malleable iron is similarly affected and the use of low temperature silver brazing alloys is recommended. The cementite present in white iron does not begin to break down until it reaches approximately 900°C. Consequently brazing alloys with liquidus temperatures up to 850°C can be used with confidence.
Since cast steel is commonly available these days (and was rare and expensive back then), someone locally who made up some frame lugs for a Triumph simply did them in cast steel, and drilled the bores to fit the frame tubes. This ensured a nice fit, and angles could be drilled in to suit without some extremely accurate pattern making and core making. Quite inexpensive, although needed a heavy duty drill press and suitable large drills.
Some of Nortons more complicated frame parts are definitely forgings - the letters/numbers are so crisp and sharp they can't be anything else. And forgings are far stronger than castings - forging was a huge industry back then, which has largely died out. I've seen an 80 ton steam hammer thwack out steel parts into a die in just 2 or 3 skillful hits, or pound out a bar of iron into a railway axle, impressive stuff....
Your right. Cast steel would be the ideal replacement for malleable iron lugs. But people told me over here that it's expensive. And since steel is cast at significantly higher temperatures the shrinking factor in the patterns should be bigger.
I have now a foundry in england who will do the small number of castings in the correct whiteheart malleable iron. If I wouldn't have found someone doing it I would definitely go for steel casting
About forgings at Nortons: Can you tell me which model your talking about? Pre- or postwar?
From the top. Specific to BSA"S ( cause that is all I know ) 1) BSA lugs were forged, BSA bragged about this in its advertising & sales literature 2) On the latter welded frames could be either a forging or casting. 3) BSA Frames were all furnace braized till welding came in in the 60's.
Frame joining lugs are generally in compression. Engine mounting lugs are either in tension or shear ( some times both ) Castings of any persuasion should always be in compression.
You can not arbitarily change either the material nor manufacturing method of any part and expect it to perform as per the original without redesigning the part. Now I expect you want the new part to look as close to the old one as possible yet to perform as well if not better.
In that case this rules out using iron of any description. grey , black , white or noduled. Most malleable iron now days is made by adding tin to the melt. The term "malleable" is a bit of a red herring a better way of thinking about it is " not quite as brittle" iron rather than Malleable iron. The old way of Black heart to White heart was necessary because white heart does not machine particularly well with old HSS or high Carbon tooling but now days you can get a reasonable finish particularly with water jetting or titanium high speed machining.
Getting back to the problem at hand which is difficult as you just stated "lugs"and did not specify which lugs. never the less, in general I would go for steel over iron every time. By prefference get a hand forging done. Second best forged blank then machined. Third best, fine grained ( inoculated ) steel casting.
Please, please, please be very careful when using old material for references . A lot of the metallurgy of Phil Irvine's day was more myth than science. A lot of process were done because they knew it worked, but not why it worked. SG irons were discovered by accident when foundries added just a little too much tin plate to the melt then noticed that the castings did not break as readily. Please use modern up to date sources such as the ASM ( American Society for Metals ) or ASTM or current standards for your data as these are the bodies that have defined the alloys that you will be using today.
When you fabricate your frame remember that most were furnace braized where both the temperatures and chemistry were closely controlled and that is a lot different to hitting the joint with a big oxy torch where you could either burn out carbon or add carbon or both to different parts of the joint let alone burning the filler alloy.
Just a final note as there seems to be a lot of confusion about terms.
Soldering could be considered as a high temperature glue. The filler has almost no chemical combination with the parent metal and the joint can be separated by adding the same amount of heat as used to make it. Solder can be made from a wide variety of metals but will always melt substantially lower than the parent metals.
Braising is similar to soldering except that the filler actually alloys with the parent metals to a limited extent . The joint can still be broken by heating but oft it will have to be higher than used to make the joint. The "alloying" is why you can not weld a previously braised joint . Brass ( welding ) Bronzing, silver soldering are all examples of this method.
Welding is essentially the joining of the metals by casting a lump of very similar metal on to the parent metals which melt together to form a ( hopefully ) homogenious weld and it can not be broken by reheating.
The definitions can get a lot more complex than this but it is good to keep these in mind when talking about joining metals.
Well for starters I was a non - ferrous tertiary foundry metallurgist so while I have a passing knowledge of irons & steels and expert I am not. Like malleable irons, SG irons can be ferritic or austinitic It depends upon the total alloying elements and in particular the Carbon & Phosphorous content. Common sperodizers in order of relative strengths are Cerium , Calcium, Magnesium, Sodium , Lithium , Barium , Boron, Tin, Tellurium, Selenium.
All have other properties, like sulphur will reduce the hot strength of the casting and drastically reduce the corrosion resistance so it is oft a trade off. Cerium is best for high carbons while Magnesium is a lot cheaper and is most effective around the eutectic ( 4.3% ) carbon content. The problem is getting the tin into the iron so it is usually added as as Nickle Silicide . Cerium is well bloody expensive and very strong so getting the exact amount correct is a bit tricky.
Now days with tools like x-ray diffraction , emission spectroscopy & magnetic resonance foundries have a lot more useable composition control. Back in the days of BSA all this was done by wet chemistry and by the time you finished the chemical analysis it would be totally wrong.
However processes and alloys that have become "time honoured" remain despite the fact that things could be done better. back in the 70's the successor to my Prof ( Dr Walwack ) designed a series of alloys roughly 50:50 Fe:Al that could be used to replace nearly every high temperature , high corrosion resistance Nickel alloy at a small fraction of the costs but could not get them into industrial use. A few years latter it a whole series of steels termed "micro alloys" were also invented which could replace the entire range of stainless steels but you could not convince the market that a steel containing less that 1% of alloying elements was as good as 18:8 stainless. For a start it was only 2/3 the weight so how could it be as good ?