v12 or v10

[saviour stivala]

On my part saying a ‘’boxer – opposed piston’’ should have really read ‘’ boxer – opposed cylinder’’ or better still a ‘’boxer – horizontally opposed cylinder’’. In any case all three means all pistons will have their own crankpin. While all ‘’180 degree flat engines’’ each pair of pistons share one crankpin.

[Stu]

The FERRARI produced 'flat' 12 engines as well as the Subaru 'flat 12 engine were not a 'boxer - opposed piston' engines but a 180 degree flat 12.

And the early/mid-nineties 3.5l Group C Mercedes was a 180 degree V12.
A ‘flat-12’ has a different firing order to a V12.

IMO and all that ....
180 degree V12 is just a name for a flat 12 - because every flat 12 every made had 6 crank throws (like a V12)
people started calling it a 180 degree V12 when Lauda won everything

a flat twin has 2 crank throws
a flat 4 has 4 crank throws
a flat 6 has 6 crank throws
a flat 8 has 8 crank throws (unless it's a Tecno)
the above if having respectively 1, 2, 3 or 4 throws would have eg a vibration issue
a flat 12 with 6 throws doesn't

a fellow worker said that horizontally-opposed meant 2 crankshafts and 2 pistons h-o in each cylinder
he having driven such (a 32000 hp Doxford)

hey - how to get on with the new mod !!


I was about to say that a heat-dilution NA engine seems unwise ... but ....
a heat-dilution NA V10 seems less unwise that a heat-dilution NA V12
(h-d meaning design around running always on extreme lean mixture)

I’m not sure (I will check), but I think Mercedes didn’t use a flat-plane crank in their 180 degree V12, which affected the firing order (for some reason I remember this from the build-up to the season that year - I didn’t ‘waste’ my evening’s reading Motoring News, Autosportivo, Motorsport and the like, it seems!!). However, I do get your point. The ‘flat’ engines that you describe (a separate throw per cylinder) are classical ‘boxers’ and shake like worried dog when running. A flat-plane crank (Ferrari) cures this by operating the banks as 2x cylinder engines with a common crank, but Mercedes we’re doing something different. If I could only remember the engine ‘type’ that the used as a name.

[Tommy Cookers]

a flat crank in a 12 cyl 180 deg engine ?

if one wanted paired firing 120 deg would do it - with the 'usual' 3 planes

all the 180 deg Ferraris have 3 plane cranks - the same 3 planes as in any other 6 or 12
(& eg the 512 'BB' road car has 6 crank throws as the F1 etc 312 )

there's the Alfa Romeo tipo 160 engine (chassisless F1 car with mid-front engine) to look at
remarkably the engine is now up and running
the 160 car was never made and is NOT the 159 muletta that was driven and photographed (this I have told this site)
the 160 crankshaft appears here - it seems somehow odd
https://forums.autosport.com/topic/1983 ... ver-thread
AR also had flat 12s c.1980 and for the 1938 etc GP formula

[Stu]

a flat crank in a 12 cyl 180 deg engine ?

if one wanted paired firing 120 deg would do it - with the 'usual' 3 planes

all the 180 deg Ferraris have 3 plane cranks - as in any other 6 or 12
(& eg the 512 BB has 6 crank throws)

Apologies, bit of a faux-pas.
For some reason I had it in my head that Ferrari used flat-plane cranks, no idea why.

Cannot find anything on the crank architecture for the Merc unit (engine is termed as M291), plenty of information as to how unreliable they were, but not much on the detail.

[echedey]

ok, I will have to design my engine at 60º and not at 75º as ferrari did, another thing the v10 and v8 engines in f1 had crankshafts that were flat or crossed.

[Tommy Cookers]

.... another thing the v10 and v8 engines in f1 had crankshafts that were flat or crossed.

all the V10s had 5-plane cranks
all the modern V8s had flat cranks

the flat crank was ......
the first type ever used in V8s c.1900s
replaced by crossplane - those at first not all the same
re-invented for the early c.1957 GP V8 Moto Guzzi 500cc - but soon replaced with a crossplane
re-invented again for the Coventry-Climax 1.5 litre F1 engine c.1962 - then became universal in F1 etc
(anyway prior to this the only V8 in F1 was the Lancia-Ferrari 1954-6)

[J.A.W.]

The FERRARI produced 'flat' 12 engines as well as the Subaru 'flat 12 engine were not a 'boxer - opposed piston' engines but a 180 degree flat 12.

Ferrari's flat 12 engines were not actually "boxer" (as explained),
that was just hype, but the Subaru/Motori-Moderni F1 12cyl really was.

As Subaru representative Tadoshi Sazaki was duly quoted:

"The engine was planned for research into boxer configuration only, initially."

https://subaruidiots.com/formula-1-subaru-flat-12/

Subaru had obviously discovered the limitations of the "boxer" format as a 12cyl,
since the crankshaft dynamics of a V12 were not improved upon, & bulky with a
longer crankshaft yet, the true-boxer appeared to only present disadvantages
over it, even in flat/horizontally opposed* application.

Funnily enough, Koenigsegg considered a variant of this engine, but for whatever
reason (Subaru said no?) it never made it past prototype/pre-production status..

*Horizontally opposed & "opposed piston" are different things too, as it happens:

[J.A.W.]

On my part saying a ‘’boxer – opposed piston’’ should have really read ‘’ boxer – opposed cylinder’’ or better still a ‘’boxer – horizontally opposed cylinder’’. In any case all three means all pistons will have their own crankpin. While all ‘’180 degree flat engines’’ each pair of pistons share one crankpin.

Another technical issue is that boxer engines must run offset cylinders due to design,
whereas common crank-throw horizontally opposed cylinder designs need not do so:

[Greg Locock]

Couldn't you use fork and blade conrods to give a boxer with axially aligned bores?

[saviour stivala]

There is no known racing ‘flat 12’ engine ever made in true ‘boxer’ configuration (12 pin crankshaft), and the motori moderni designed 3.5l flat 12 engine made for Subaru was one of them. A fork-and-blade con-rod design serving a pair of cylinders in opposed ‘flat’ or in V-configuration will be sharing the same crank-pin, which in a 12 cylinder engine the crankshaft will be a six-pin crank, this design chose will eliminate the opposed pair of cylinder offset necessitated by a set of two opposed cylinder con-rods sharing the same crank-pin side-by-side,

[J.A.W.]

There is no known racing ‘flat 12’ engine ever made in true ‘boxer’ configuration (12 pin crankshaft), and the motori moderni designed 3.5l flat 12 engine made for Subaru was one of them. A fork-and-blade con-rod design serving a pair of cylinders in opposed ‘flat’ or in V-configuration will be sharing the same crank-pin, which in a 12 cylinder engine the crankshaft will be a six-pin crank, this design chose will eliminate the opposed pair of cylinder offset necessitated by a set of two opposed cylinder con-rods sharing the same crank-pin side-by-side,

Really, so you know more about it than Subaru?

By all means post a pic of the Subaru M-M F1 crankshaft as evidence...

You are certainly incorrect to assume the cylinder block offset that side-by-side conrods
on the same crankpin necessitates is nearly as large as that which a "boxer" engine requires
(& nor are the dynamics, yaw oscillation-wise & whatnot), either..

[J.A.W.]

Couldn't you use fork and blade conrods to give a boxer with axially aligned bores?

Hmmm...

Well, Greg, I'm tempted, but I might just leave that one to Manolis..
(Unless Feliks/Andrewski wants to chime in, too).

[saviour stivala]

The cylinder block offset of a ‘V’ or ‘FLAT’ engine configuration having a pair cylinders con-rods sharing the same crank-pin side-by-side will have a block offset as the width of one con-rod big-end. The cylinders/cylinder block offset of a ‘boxer’ configuration engine will be much bigger (plus the width of the crank web, if no main bearing in-between of the two crank-pins is used, if a mean bearing in between is used, then it is also plus the width of said main bearing and another crank-web.

[saviour stivala]

ok, I will have to design my engine at 60º and not at 75º as ferrari did, another thing the v10 and v8 engines in f1 had crankshafts that were flat or crossed.

Flat on the V8'S and crossed on the V10's.

[Tommy Cookers]

Couldn't you use fork and blade conrods to give a boxer with axially aligned bores?

one might think that ....
the potential reduction in engine and crankshaft length etc depends on the bore:stroke ratio
with a high bore:stroke ratio the reduction is only 1 rod width - so not worthwhile
with a low bore:stroke ratio the reduction is multiple rod widths - so worthwhile

Ted Martin's 3 litre V8 'axially aligned' etc was smaller and lighter than a DFV so made an F3 car into a F1 car