Years When Crankshafts Were Machined From Billets?

Discussion in 'Vintage (thru 365 GTC4)' started by Lowell, Nov 20, 2017.

  1. Lowell

    Lowell Formula Junior
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    The 68/69/70 Ferrari Year Book has an eight page spread describing how
    Ferrari crankshafts were machined from solid steel billets.

    How long did this continue?

    They must have changed to forged crankshafts at some point.
     
  2. Smiles

    Smiles Moderator
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    Good question.

    Decades ago I always remember them being described as machined from solid billet.

    As a boy, I didn’t know much about machining, molding or forging and wondered how else one would make a crankshaft!

    Curious for relies because this is a nostalgic question for me.

    Matt
     
  3. Motob

    Motob Formula 3
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    I think that they are still machined from billet. Since production is so low and the performance of engines so high, billet is probably easier and cheaper than making forging dies for each different motor. I don't think that a forged crankshaft would live very long in a 458 at 9,000RPM.
     
  4. Ed Niles

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  5. Bob Zambelli

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    I'm not sure if they still do it but machined cranks were used at least up into the Daytona/Boxer models.
    308s also.
    Machining is preferred as it is quite simple to make dimensional changes in the tooling.
    Forging requires very expensive tooling and equipment and is only justified for very large quantities.

    The preferred material is Nitraloy 135, a premium grade nitriding steel used in many aircraft applications like camshafts, gears and miscellaneous shafts.
    After machining, it can be hardened (nitrided) to a case depth of .040 or more.
    In the Ferrari application, the crankshaft is then straightened after nitriding.
    As far as I know, the Nitraloy billets for the Ferrari crankshafts were imported from the United States.
     
  6. Smiles

    Smiles Moderator
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    Forged parts are usually stronger by most properties than machined, even machined and hardened.

    Matt
     
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  8. Jumprun

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    A crankshaft milled from a solid bar is usually a forged bar, not technically a billet. Not all forgings are shaped for a particular use, or need special tooling.

    The term billlet is the popular description of a solid metal plate or bar but it is actually the word for an unprocessed rough shaped mass of material ready to be final worked into shape and or heat treated, it's the dough before the bread is baked.
     
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  9. Motob

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    Show me one Formula one, MotoGP or World Superbike engine with a forged crankshaft, there aren't any. If forged cranks were stronger, then they would use them.
     
  10. Smiles

    Smiles Moderator
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    Seriously?

    That's like proving a negative.

    Or... Are you really arguing that there were little or few forged crankshafts in real life application?

    Matt
     
  11. Jumprun

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    Guy's, you are both right, I can say that a forging is always stronger than just a hot rolled bar, I think the confusion is that when people say "forging" they think of something called a "die forging" This process hammers the metal into a sort of mold with some finish features.
    I can also say with some certainty that crankshafts that are milled from a solid are indeed made from a forging that has been hammered from the billet into a basic shape that gets machined everywhere, this type of forging can be stronger than a die forging.

    I'm an Aerospace guy not a crankshaft guy but I believe ALL crankshafts are made from forgings, some from a die forging and some from solid forgings.
     
  12. MiuraP400

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    Crankshafts can be cast, machined from billet or forged. The material used plays a role in the strength of the crank so it is hard to compare absolutely. Generally billet is stronger that cast and forged is stronger than billet. Forged are typically stronger because the grain in the material is orientated so that it can take the stresses better. However, the strength is also a function of the material selected, stronger materials cost more money. Forged cranks are usually used in high volume production due to the tooling costs. Billet are used in low volume applications. Billets made from a high quality material can be extremely strong, it is possible for a billet crank to be stronger than a forged if the material is better. Of course all this assumes the design of the crank is similar. There can also be design differences that effect the strength of the crank.

    Cheers Jim
     
  13. Motob

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    Ferrari crankshafts start out life as a round cylinder of ingot of steel ( a billet), and is machined down into a crankshaft. That is the definition of a billlet crankshaft. There are is no forging of the crankshaft to get it into a rough shape, it is all cutting and grinding. They start out with a steel blank that is made of material that is much stronger than a forging.
    If the highest forms of motor racing (Formula 1, Motogp, Pro-stock, Top Fuel/Funny car, Nascar, etc.). would use something that is better and stronger than a billet crankshaft they would. A forged crankshaft is great if you are going to make thousands of them for an engine that gets moderate performance use, but it is not as strong as a billet crank.
     
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  15. Motob

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    In theory a forged crankshaft made of the same material as a billet crank will be stronger because the grain of the material follows the shape of the crank and is not cut through. In practice the material that a billet crank is made from, a vacuum remelted bar of steel (which is basically a forged cylinder of steel with no impurities or inclusions) is so much stronger than the material from which a forged crank is made from, that cutting the grain of the material still results in a crankshaft that is much stronger.
     
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  16. JCR

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    https://en.wikipedia.org/wiki/Vacuum_arc_remelting
     
  17. kare

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    Cutting grains isn't critical in this application, plus nitriding makes it much stronger. like surface treatments always do. One should also remember that certain dimensions are needed to control slip (axial distorition) under load. Engine quickly loses power if the pistons are not in the phase they are supposed to be, especially if the distribution/ignition follows one end of the shaft.

    ps. vacuum materials are difficult to use as they are usually very difficult to machine.
     
  18. Lowell

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    PING:

    The posts have been very interesting and informative. But my original question has yet to be answered.

    Does Ferrari still make crankshafts by machining round, solid steel billets? If not, when was this method discontinued?
     
  19. PAUL500

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    in the video on you tube of the 612 engine being produced, it shows a forged rough blank crankshaft being machined, and given these are related to as far back as the 456 engine then I would say at least prior to then.
     
  20. Dave rocks

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    I don't know the answer but my guess would have been that they are forged but based on these pictures, I don't believe so. If they are not forged, they certainly must be roughed, stress relieved and then finished. You cannot remove that much material without of the part springing all over the place. When I was at GM, they were all forged (yes, I know that's different). Looking at this photo - you can see the counter weights have been machined. Now, that's not a guarantee that those still did not start as a forging but it's a good indication.

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    The camshafts on the other hand, by this photo are clearly forged.

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  21. Dave rocks

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    Check this video out at around 27:20



    The video clearly shows one fully machined crank and another that is forged. The rough surface is from the forging - you can even see the parting line.
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  22. TTR

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    Check this video out ...

    ... Henry would've been sooo jealous of all that robotic automation. ;)
     
  23. johngtc

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    This thread reminds me of a tale I once read, where the US intelligence services spent millions trying to secure details of a new Soviet warship. They were then shocked to find a detailed spec and schematic drawing in the latest edition of 'Janes Book of all the Worlds Fighting Ships'. When asked, Janes simply said we asked them and they told us!

    Surely someone on here has good enough contacts with Ferrari to simply ask them? I can't see that this is a state secret and I suspect a crankshaft expert could tell us by examining the fiinished product!
     
  24. PAUL500

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  25. Dave rocks

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    Paul - good photos. So it looks like they just machine 90% of the counter weights. Where did you find those photos?
     
  26. Smiles

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    A parting line indicates a casting, not a forging.

    Matt
     
  27. Dave rocks

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    Not true. Yes, castings along with injection molded parts and forgings have parting lines. When the hot ingot of steel is slammped between two dies to form (forge) the shape, you have a parting line.

    Watch this video - you can see it clear as day.

     

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