Flat crank V-12...

[Cliff Beer]

I'm sure I've seen a flat crank V-12 somewhere...perhaps it was a F1 engine. Does anyone know of a production car or racing V-12 with a flat crank?

There's a recent review of the new f-car GTO having a flat crank V-12 here: 2011 Ferrari 599GTO - First Drive Review - Auto Reviews - Car and Driver

I also heard that the most recent iteration of the Aston Martin V-12 utilized a flat crank.

Apologies in advance if this post is in the wrong section - probably not much chance of a flat crank V-12 being used in a GT40 due to packaging issues....

 

[Doug S.]

I've always been a bit intrigued by the flat crank issue.....but have a general question, here.....are all horizontally opposed engines flat-crank equipped? It would seem so to me, but to say I am not an automotive engineer would be an understatement at the very least!

Doug

 

[Cliff Beer]

I've always been a bit intrigued by the flat crank issue.....but have a general question, here.....are all horizontally opposed engines flat-crank equipped? It would seem so to me, but to say I am not an automotive engineer would be an understatement at the very least!

Doug

Hi Doug,

Nope, there's plenty of both (flat crank and multi-crank) versions in a horizontally opposed configuration. Same for V designs - the basic f-car 3.0ltr V8 is a flat crank while the Lancia Thema version of the very same engine differs only in that it has a conventional multi-plane crank, just for example.

 

[Mike Huddart]

If by the term flat crank you mean single plane crank then I think you you will find that all V12 cranks are single plane. Put it this way, we have balanced dozens of V12 cranks,Ferrari, Jaguar etc and none needed bob weights like a conventional dual plane V8. Maybe I just havn't found one yet!
Mike

 

[Seymour Snerd]

....all v12 cranks are single plane. ...

 

[Mark]

I must admit to having insufficient knowledge on the subject. I don't know what I'm looking at. Take the photo above from Alan and this diagram of the crank in my 456 motor.

Are these cranks flat plane? What does a non-flat plane crank look like?

 

[Cliff Beer]

I must admit to having insufficient knowledge on the subject. I don't know what I'm looking at. Take the photo above from Alan and this diagram of the crank in my 456 motor.

Are these cranks flat plane? What does a non-flat plane crank look like?

Here's a good link to an explanation (with some pretty diagrams) of the basics: http://www.projectm71.com/Cross_FlatPlane.htm

Alan's pic (thanks Alan) is obviously of a multi-plane crank. Here's a good video representation: http://www.youtube.com/watch?v=zAG6e0O9qoM&feature=related

I'm unsure of what Mike is indicating as there are obviously many multi-plane V12 cranks being used in production cars - ferrari, jaguar, etc., these historically have been multi-plane cranks.

My question is really derived from announcements that I see being made by various manufacturers (ferrari, aston martin, etc.) of utilizing a flat plane crank in a V-12, which is quite unique and without a lot of historical precedence.

Any thoughts or examples of flat plane V-12s are appreciated!

Incidentally, here's a review of Aston's latest flat crank V-12 creation: http://www.motortrend.com/features/c...in_one_77.html

 

[colin artus]

I think the Ferrari F1 3 ltr 12 cyl of the pre turbo era was a flat plane crank in a 180degree V12 configuration. Not to be confused with the BB512 engine which was a flat 12 in boxer layout (but still a flat plane crank?).

 

[Jac Mac]

I think the Ferrari F1 3 ltr 12 cyl of the pre turbo era was a flat plane crank in a 180degree V12 configuration. Not to be confused with the BB512 engine which was a flat 12 in boxer layout (but still a flat plane crank?).

If 'It is' a flat crank with 12 individual rod journals then it must fire three cyls at a time . The intervals between these groups of three being determined by the Vee angle used.

It could also be designed with six rod journals, but my heads going nuts trying to visualise the firing order & of course what would you set the Vee angle at?.

I see Cliff has been on the Ferrari Chat forum about this same subject ( Even trying to take wagers on the outcome...is there nothing this man wont do for a $$$? )

Heres a clue from a text book... Quote..'Ferrari started with their inlet ports on the outside of the Vee, then moved them to the inside for 1969, but for 1970 sidestepped the issue by adopting an engine configuration with 180° between banks. Unlike most flat 'boxer' engines, the crankshaft remains similar to that of a Vee-12 in having six throws, each shared by a pair of opposed cylinders, an arrangement shared by Porsche with their 917 Flat-12 sports car engine.... end Quote..

Now to me 180° is a flat cyl layout, with crank throws paired end to end @ 120°, Not a Vee of any description....

Added dwg of porsche motor cutaway

 

[Seymour Snerd]

Now to me 180° is a flat cyl layout, with crank throws paired end to end @ 120°, Not a Vee of any description....

I think the reason some automotive writers do that (call it a "180° V") is to be intellectually cute (or more rudely, pedantic) although at the expense of clarity for the readers.

But they also do it to distinguish that kind of flat cyl layout from the "true boxer" kind where each piston has its own journal and moves in exact opposition to the one across from it.

I guess the purpose of the cute naming comes from the idea that if you take the "true boxer 180° V" and change the "bank angle" from 180° to 60° or 65° it would not correspond to any V-x that anyone had ever built. But, I think Cliff's citation of the Aston and Ferrari flat-crank-V12's blows that distinction, so maybe people will quite talking about "180° V" engines which as you point out is an abuse of the language.

But all of that aside, I would love to know why Ferrari and/or Aston Martin chose such an arrangement. I'd also love to see a picture of the crank.

 

[Cliff Beer]

Thanks Jac Mac, thanks Alan, I'm certainly following what you're saying, and that all makes sense.

As Jac Mac wisely points out, a flat crank in a four stroke V12 of any angle results in three cylinders arriving at the top of their throws at the same time. How one times ignition firing with that happening and not ending up with horrible harmonics/vibration is unclear, but it's at least possible that the ferrari/aston skunk works have figured out a way to make it all work with acceptable levels of longevity/vibration.

To Alan's question on the why front, I would guess the reasoning is the same as for use of any flat crank - less inertia and corresponding faster wind up, although it may be that the way the harmonics/vibration is controlled is by use of some manner of counterbalancing which, of course, in itself, diminishes the advantage of a flat crank....

On the "boxer" v. 180 degree V debate, I think Alan is exactly right - some folks use the "180 degree V" descriptor just to be intellectually cute, or to try to seem somehow smarter than others. For most folks, an engine with horizontally opposed cylinders is a "boxer" configuration and also not a "V" because, well, it just looks that way from a visual and common sense standpoint, regardless of what crank configuration is being employed.

Bottom line, I'm still a bit confused.....but if the car magazine reports are correct about the use of a flat crank in a V12 configuration by ferrari and aston then I would guess some technical details will emerge over time. In the meantime it certainly makes for some interesting mental gymnastics.

Thanks gents.

 

[Seymour Snerd]

OK, not only is this delightful thread in the wrong forum, but I'm going to make it worse by changing the subject just on the theory that anyone who read this far would find the following interesting: Last years' Yamaha R1 bike made a departure from the norm by switching from a flat crank inline-4 to a cross-plane, but for really interesting reasons unlike any that we've discussed here. To get the whole picture watch the video here (it gets useful after the somewhat silly musical introduction).

Details: 2009 Yamaha R1 crossplane crankshaft - Hell For Leather

 

[Ron Earp]

OK, not only is this delightful thread in the wrong forum, but I'm going to make it worse by changing the subject just on the theory that anyone who read this far would find the following interesting: Last years' Yamaha R1 bike made a departure from the norm by switching from a flat crank inline-4 to a cross-plane, but for really interesting reasons unlike any that we've discussed here. To get the whole picture watch the video here (it gets useful after the somewhat silly musical introduction).

Details: 2009 Yamaha R1 crossplane crankshaft - Hell For Leather

Leave it to a music company to make a video on cranks...

I read about the big bang application a couple of years back in Cycle World but never saw the video on the bike application. Thanks for sharing that.

Cliff, I thought you had a flat plane crank to go into your Ford motor? Or was that someone else that had one?

I'd love to see a side by side comparison of a cross and flat plane crank, in identical motors (besides necessary changes), to see what the advantage, if any, the flat plane offers to a conventional large pushrod V8. One trip to a dirt track race, drag strip, or mud truck event reveals all matter of domestic V8s that seem to spin up pretty damn fast if the owner spends a small amount of coin to lighten up the reciprocating bits. Be interesting to see how much faster it could be.

 

[Cliff Beer]

Ron, yup, that was me. Unfortunately, my all alloy flat plane 331 stroker motor project went wrong when the custom crank and cam builder I had engaged decided to retire and close up shop before I ever got my crank and cam. The builder and I had agreed upon the basic specs of the crank (mostly based on what Jac Mac had reco'd) and cam, he had apparently secured the cad file to be able to machine both from billet and was in the process of machining it all out. I had paid him about half the total estimated cost in progress payments and stopped by the machine shop (local to me in Seattle here) after not hearing anything for about six weeks. The shop was locked up and most of the contents had been removed, including all the big machine tools like the cnc milling machine and various lathes, etc. A guy at the business next door said the owner had closed shop and retired to the eastern part of Washington State, but didn't know exactly where. That's when I realized I'd been screwed... The motor was intended for an old Indy car track car project - sort of a low-tech variation on a cosworth 3.0ltr motor. In other words, a bit exotic, roughly equivalent hp/ more tq, but not nearly as rare and expensive to maintain over the course of a few seasons of non-serious racing.

Losing that money and time was discouraging, and a set back to say the least. I need to get the project back in gear now. I did bid on an old Michael Andretti Indy car roller that was on ebay but was outbid in the closing minutes of the auction. So, now I need both a motor, and a chassis....

 

[Ron Earp]

Sorry to hear that Cliff. Having been on the losing side of two of those sorts of deals in the last five years I can feel your pain. Here's to moving on.

 

[Dave Wood]

I think the Ferrari F1 3 ltr 12 cyl of the pre turbo era was a flat plane crank in a 180degree V12 configuration. Not to be confused with the BB512 engine which was a flat 12 in boxer layout (but still a flat plane crank?).

Since 180 is FLAT, how is it a V12?? If it was 179,160 or any other degree less than 180, I'll go with the V designation...but really...isn't 180 degress basically a flat/pancake/boxer style engine?

In this discussion, it seems that few grasp what a "flat crank" is. Any "flat crank", regardless of number of cylinders, has rod journals exactly opposite of each other , hence the term "flat". VW (bug) cranks are flat.

 

[Seymour Snerd]

Since 180 is FLAT, how is it a V12??.

That's the linguistic abuse I was referring to in my post; you might read it again. Everyone here gets what a flat crank is; we weren't the ones who invented the stupid terminology.

BTW the Ferrari BB has a conventional 120-degree tri-plane crank, so according to my definition it's NOT a boxer. Another abuse of the language. It was only their F1 car that had a true boxer flat 12. (and maybe some later race cars, I can't remember. Wasn't there a flat-12 Ferrari can-am car?).

 

[Seymour Snerd]

BTW I just noticed wikipedia, at

Flat-twelve engine - Wikipedia, the free encyclopedia

is one of the propagators of the "flat vee" idiocy: "Flat-12 engines are generally not true horizontally opposed engines (boxer), but rather 180° V-engines." However, if you search for the phrase you'll see it's all over the web so I think we're stuck with it.

 

[Seymour Snerd]

The motor was intended for an old Indy car track car project - sort of a low-tech variation on a cosworth 3.0ltr motor. In other words, a bit exotic, roughly equivalent hp/ more tq, but not nearly as rare and expensive to maintain over the course of a few seasons of non-serious racing./QUOTE]

At the risk of further stirring unpleasant memories, if you were to resurrect the project, couldn't you get Moldex to make you a crank? My informal understanding from a previous life is that they would make a 12-cyl Lambo crank for about $3K, so I would think a flat v8 crank would be even cheaper (if one can think of that as being "cheap").

 

[Cliff Beer]

Alan, thanks that's a good possibility - will call Joe at moldex and inquire.

And, yes, $3K would be very reasonable...very reasonable indeed. The crank and cam together that I was having made was to be about $10K - $7,500 for the crank and $2,500 for the cam.