Crankshaft material and manufacturing methods

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Mudflap
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Re: Crankshaft material and manufacturing methods

Post by Mudflap » Sun Apr 01, 2018 3:44 pm

I would argue there is no sensible crank design that would reduce windage losses.
Shaping the counterweights results in a large inertia and crank centreline penalty and as such cranks of the 20k+ rpm era have always been very "bricky".
How much TQ does it make though?

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Re: Crankshaft material and manufacturing methods

Post by godlameroso » Sun Apr 01, 2018 7:57 pm

I wonder if that holds true for these lower engine speeds. Crank pins see much less load at 15,000rpm vs 20,000, let alone 12,500. I'm sure even the harmonics are different having lopped off a cylinder on each bank.
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee

Mudflap
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Re: Crankshaft material and manufacturing methods

Post by Mudflap » Sun Apr 01, 2018 11:50 pm

Well at the same time you can argue that there is not much to be gained by reducing the drag on the webs since engine speed has reduced so much and drag is proportional to the square of velocity.

One thing to think about though is the viscous force between the crank thrust shoulder and the thrust bearing. F1 engines have traditionally used piston guided rods which meant they had to run a very tight crank axial play to avoid big end bearings riding on the pin fillet. As a result the losses in the thrust bearing are somewhat higher compared to a more conventional crank guided rod.
How much TQ does it make though?

johnny comelately
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Re: Crankshaft material and manufacturing methods

Post by johnny comelately » Mon Apr 02, 2018 12:44 am

Edax wrote:
Fri Mar 30, 2018 12:24 am
johnny comelately wrote:
Thu Mar 29, 2018 11:26 pm
I'm trying to understand the merits of different crystalline structures as they apply to crankshaft applications.
for example, grain boundary crack initiated problems are reduced by single crystal steels.
Yes but you get a whole host of other problems back for single crystals.

The advantage of single crystals is that they are very strong. But since the crystal planes are running through the whole workpiece you are susceptible to cleavage along a crystal plane. sC’s are therefore inherently more brittle than their grainy counterparts.

In SC you have no grains sliding against each other, but in single crystals you can get the whole material to slip over a crystal plane so they are not immune to creep.

One advantage of singly crystals is that you do not suffer from grain growth, since you only have one grain. So for high temperatures that can be an advantage. For Polycristalline materials you have to play some tricks like putting an inert material along the grain boundaries (grain pinning). Problem is that the best materials like thorium oxide are being banned.

A real advantage can be the heat conductivity, like in turbine blades. Having no grain boundaries and secondary phases really helps here.

Of course there are single crystals which have their specialist uses, sapphire for bearrings, watches barcode scanners etc (scratch resistance). Or CaF for optical windows.

But overall I seldomly come across a large mechanical application where the advantages of single crystals outweigh the problems with brittleness. Alloys where you have the freedom of controlling microstructure are usually a lot more versatile.
Edax, I'd be interested in your thoughts about this:
Neil Glover, chief of materials, Rolls-Royce

The single-crystal structure isn’t intended to cope with temperature, however; it’s to make the blades resistant to the huge mechanical loads that result from their rotational speed. “Every single blade extracts power from the gas stream equivalent to a Formula One car engine,” Glover said. “And the centrifugal force on them is equivalent to the weight of a double-decker bus.”

Normally, metals are composed of many crystals – ordered structures of atoms arranged in a regular lattice, which form naturally as the metal cools from a molten state. These crystals are typically of the order of tens of microns in size, positioned in many orientations. At high temperatures and under strain, the crystals can slide against each other, and impurities can diffuse along the boundaries between the grains. This is known as creep, and it badly affected early turbine blades, which were forged from steel and later nickel bars.

The first stage in development was to get rid of any grain boundaries at right angles to the centrifugal loading, which led to the development of blades that were cast so the metal crystals all ran from top to bottom. Later, this was optimised further by casting single crystals, with no grain boundaries at all. It’s a highly complex process: not only must the blades be cast with the internal cooling channels already in place, but the crystals are not homogeneous. Rather, zones of different composition and crystallographic structure exist within the blade.

johnny comelately
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Re: Crankshaft material and manufacturing methods

Post by johnny comelately » Mon Apr 02, 2018 12:48 am

Another thing I've learnt is that some grains are 10 thou (whitworth :wink: ) in size! much bigger than i had imagined
Last edited by johnny comelately on Mon Apr 02, 2018 3:15 am, edited 1 time in total.

Cold Fussion
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Re: Crankshaft material and manufacturing methods

Post by Cold Fussion » Mon Apr 02, 2018 3:10 am

Jet engine turbine blades are in a much more extreme environment than a normal ICE crankshaft. The thermal efficiency of a turbofan engine is tightly linked to how hot you can run your turbine blades at before failure, so the pressure to develop materials to increase that temperature are very high.

Edax
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Re: Crankshaft material and manufacturing methods

Post by Edax » Mon Apr 02, 2018 8:51 pm

johnny comelately wrote:
Mon Apr 02, 2018 12:44 am
Edax, I'd be interested in your thoughts about this:
Neil Glover, chief of materials, Rolls-Royce

The single-crystal structure isn’t intended to cope with temperature, however; it’s to make the blades resistant to the huge mechanical loads that result from their rotational speed. “Every single blade extracts power from the gas stream equivalent to a Formula One car engine,” Glover said. “And the centrifugal force on them is equivalent to the weight of a double-decker bus.”

Normally, metals are composed of many crystals – ordered structures of atoms arranged in a regular lattice, which form naturally as the metal cools from a molten state. These crystals are typically of the order of tens of microns in size, positioned in many orientations. At high temperatures and under strain, the crystals can slide against each other, and impurities can diffuse along the boundaries between the grains. This is known as creep, and it badly affected early turbine blades, which were forged from steel and later nickel bars.

The first stage in development was to get rid of any grain boundaries at right angles to the centrifugal loading, which led to the development of blades that were cast so the metal crystals all ran from top to bottom. Later, this was optimised further by casting single crystals, with no grain boundaries at all. It’s a highly complex process: not only must the blades be cast with the internal cooling channels already in place, but the crystals are not homogeneous. Rather, zones of different composition and crystallographic structure exist within the blade.
It is a beautiful piece of engineering.The application is also very impressive. 20 years ago I worked for a shop which coated turbine parts (they also did F1 engine parts). It is incredible how much gains they have been able to get out of these turbines since then.

The trick is to have the high pressure part of the turbine as hot and as small as possible, that allows for a high efficiency. But the reliability requirements are such that they are basically not allowed to fail. Failure of a high pressure disk will likely result in hot pieces flying through the wings and fuselage.

What we were doing was coating parts with thermal barrier coatings to protect the material below. But single crystal really fits here. High conductivity means that you need less cooling channels, and you can tailor the strenght along the principal axis of the stress. Indeed creep resistance is also big here.

That said the load case is relatively special. Yes it is hot and the loads are considerable, But the load is relatively stable as turbines are protected from spooling up and down too quickly, there are no gear changes or shocks, no changes in direction of the stress, no mechanical contact.

My guess is that that is why, even though the materials have been around for 40 years, they are almost exclusively used for turbines.

johnny comelately
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Re: Crankshaft material and manufacturing methods

Post by johnny comelately » Mon Apr 02, 2018 9:29 pm

Edax,
I see that yttrium (oxide?) is also used for grain pinning, is it a coincidence that it s also one of the thermal barrier coating materials in relation to your work (previous?)
Is there any similarity with carbon's MO when added to iron?

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Re: Crankshaft material and manufacturing methods

Post by irsq4 » Tue Apr 03, 2018 7:09 pm

Mudflap wrote:
Sat Mar 31, 2018 3:08 pm
No mystery there - chances are that no design changes were required to make the cranks last.

If we assume that engines run on average about 3 hours per race weekend it means that last season's engine life was 15 hours while this year it has gone up to 21 hours. At an average speed of 10kRPM, the cranks had to last 9E6 fatigue cycles last year and 1.26E7 cycles this year.

In fatigue theory a component loaded within its endurance limit will last indefinitely. For steel the fatigue strength is usually defined at 1E7 cycles. It is therefore very likely that last season's cranks were designed for theoretically infinite life.

If we examine a typical woehler curve for 4140 steel (first one I could find and a common crank material) with a fatigue strength coefficient of 1745 MPa and a fatigue strength exponent of -0.07 we can calculate the maximum allowable alternating stress to be 568.85 MPa @9E6 cycles and 555.61 MPa @1.26E7 cycles.

This means that to make the crank go from 5 to 7 race weekend stress needs to be reduced by a mere 2%. For all practical purposes the cranks can be identical.
Could You explain how did You get 555,61 MPa @1.26E7 cycles? Thank You in fwd!

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Re: Crankshaft material and manufacturing methods

Post by Mudflap » Tue Apr 03, 2018 8:21 pm

The equation is sigma=Sf'*(2N)^b, where N is the number of reversals and 2N=1 cycle.
Sf' is known as the fatigue strength coefficient and b is the fatigue strength exponent (also known as the Basquin exponent - as some refer to a Woehler curve as a Basquin curve or an S-N curve).

I think the correct definition of the stress term (sigma) in this case is "equivalent fully reversed uniaxial stress". Of course, the actual stress state in a crankshaft is non-proportional and multiaxial.
How much TQ does it make though?

Edax
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Re: Crankshaft material and manufacturing methods

Post by Edax » Tue Apr 03, 2018 11:05 pm

johnny comelately wrote:
Mon Apr 02, 2018 9:29 pm
Edax,
I see that yttrium (oxide?) is also used for grain pinning, is it a coincidence that it s also one of the thermal barrier coating materials in relation to your work (previous?)
Is there any similarity with carbon's MO when added to iron?
Not really, zirconia, which is the basis for most TBC’s switches crystal structure between RT and high temperatures. This is quite violent as it goes with a big volume change. If you would sinter zirconia pure and let it cool down it would crack.

The way to prevent this is to stablize the high temperature phase during cooling. For this you add Yttria. When you buy zirconia ceramics it usually says Yttria- or Magnesium stabilized.

But you’re right lanthanides are also used for grain pinning. I know La2O3 is used in tungsten to prevent grain growth and creep, for instance in light bulb filaments to prevent sagging, or welding tips.

johnny comelately
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Re: Crankshaft material and manufacturing methods

Post by johnny comelately » Tue Apr 03, 2018 11:09 pm

Edax wrote:
Tue Apr 03, 2018 11:05 pm
johnny comelately wrote:
Mon Apr 02, 2018 9:29 pm
Edax,
I see that yttrium (oxide?) is also used for grain pinning, is it a coincidence that it s also one of the thermal barrier coating materials in relation to your work (previous?)
Is there any similarity with carbon's MO when added to iron?
Not really, zirconia, which is the basis for most TBC’s switches crystal structure between RT and high temperatures. This is quite violent as it goes with a big volume change. If you would sinter zirconia pure and let it cool down it would crack.

The way to prevent this is to stablize the high temperature phase during cooling. For this you add Yttria. When you buy zirconia ceramics it usually says Yttria- or Magnesium stabilized.

But you’re right lanthanides are also used for grain pinning. I know La2O3 is used in tungsten to prevent grain growth and creep, for instance in light bulb filaments to prevent sagging, or welding tips.
Thank you for that

coaster
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Re: Crankshaft material and manufacturing methods

Post by coaster » Sat Jan 12, 2019 2:32 am

Honda used to make hollow cranks for f1 which were friction stir welded from many peices, you can imagine why they suffered so many failures.
If only they stuck to a machined billet things could have turned out so differently for their NA kers era.
Yours truly,
Wolsy Esquire.

saviour stivala
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Re: Crankshaft material and manufacturing methods

Post by saviour stivala » Sat Jan 12, 2019 11:44 am

Wasn’t the Peugeot V10 the last formula 1 engine to had used roller bearings crankshaft? Wasn’t the crankshaft machined from the solid using split roller gauges as well as split main and big end bearing caps?

BobbyBreeze
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Re: Crankshaft material and manufacturing methods

Post by BobbyBreeze » Thu Feb 28, 2019 11:25 pm

Anyone got any photos / drawings of old built up F1 cranks using hirth joints?