Is the Subaru 1235 F1 engine an actual boxer engine?

[coaster]

I could imagine main journals 2 and 4 being completely milled away on a cnc 3 axis, it sure would be nice to find some photos of that motors inner modifications.

[vorticism]

So it became a 180* V4 then? That's a rare one.

[coaster]

It would have a yaw rocking motion, but still balanced as a opposed mass still travels in the opposite direction.
The 12 cylinder would 3 sets of that crank configuration spaced at 120 degrees.
To keep forces in line with each other as much as possible.
1+2@0
3+4@180

5+6@120
7+8@300

9+10@240
11+12@60

[Tommy Cookers]

It would have a yaw rocking motion, but still balanced as a opposed mass still travels in the opposite direction.
The 12 cylinder would 3 sets of that crank configuration spaced at 120 degrees.
To keep forces in line with each other as much as possible.
1+2@0
3+4@180
5+6@120
7+8@300
9+10@240
11+12@60

IMO there is no merit in this case above ....

opposite crankpins aren't better (though yes they are in the Prodrive engine of course)
because eg 6 equispaced pins cover the good effects that the opposite-spaced pin approach has

all flat 12s (and flat 6s) ever made are 'mirrored' ie symmetrical end-to-end - and so have notionally perfect balance
but at best a flat 12 as above isn't symmetrical end-to-end and so has some moment imbalance aka rocking couple(s)
(moment imbalance meaning here that the inertia forces are balanced in magnitude but not balanced in position)
plus it has 2nd order force imbalance as these on the first 4 and last 4 crankpins don't cancel ...
plus the pin 5 & 6 cancels neither the 2nd order forces nor their moments ....
(plus the firing intervals aren't even and the inlet and exhaust layouts might not seem attractive)

btw Tecno 4 throw flat 8 '180 deg V' engine has nominally zero vibration but only fires every 180 degrees (as 4 stroke)
of course Porsche's flat 8s had 8 throws - this giving quite a large moment imbalance at engine frequency

[mzso]

In my german speaking country we don't have the term "flat-engine", we would call a "flat-12" a V-12, and a "horizontally-opposed" engine a boxer engine. But as you and the colleague already said, using a crankshaft with 12 crank pins would not make any sense, maybe the amount of buzzwords and terms being thrown around the internet was just confusing me.

Why is it such a big issue having 12 pins instead of 6?

[Tommy Cookers]

... But as you and the colleague already said, using a crankshaft with 12 crank pins would not make any sense, maybe the amount of buzzwords and terms being thrown around the internet was just confusing me.

Why is it such a big issue having 12 pins instead of 6?

for the same reasons it would be a big issue having 6 crankpins in current F1 rather than the 3 that they have

[coaster]

Flange thickness disapears creating a fragile motor.

[mzso]

Why is it such a big issue having 12 pins instead of 6?

for the same reasons it would be a big issue having 6 crankpins in current F1 rather than the 3 that they have

You were pretty careful not to actually answer the question.

Flange thickness disapears creating a fragile motor.

Hm. So I guess that's not worth it for the decrease of vibration and such.

[coaster]

Yes and no, long stroke and a thin flange will be weak, but a short stroke with pin overlap wont mind so much.
But we have qualified engineers on the forum who can chime in citing other reasons also.

[Tommy Cookers]

Why is it such a big issue having 12 pins instead of 6?

for the same reasons it would be a big issue having 6 crankpins in current F1 rather than the 3 that they have

You were pretty careful not to actually answer the question.

(TC @mzso ....)
that's because you usually ignore my answers ....
(not that I'm complaining - it keeps a bit of decorum)
12 pins would degrade crankshaft torsional frequency to a critical level - load path (compliance) being so extended ....


mzso ('12 pins') .... I guess that's not worth it for the decrease of vibration and such.

TC (with apologies for the editing mess) ....
since there is no vibration with '6 pins' (6 throws) there can be no benefit with 12 ....
that's why no-one has ever made a 12 pin engine
Porsche and Coventry Climax made flat 16s (with of course 8 pins/throws)

[saviour stivala]

The Coventry Climax FWMW flat-16 was effectively four four-cylinderengines joined together, four cylinder heads, with four exhaust systems. The two flat crankshafts were phased at 90 degrees, and joined end-to-end by the Swedish SKF hydraulic pressure coupling. Dispite the double the number of cylinders, the flat-16 was only one inch longer than the V-8, and only 15 lbs heaver.

[mzso]

TC (with apologies for the editing mess) ....
since there is no vibration with '6 pins' (6 throws) there can be no benefit with 12 ....
that's why no-one has ever made a 12 pin engine
Porsche and Coventry Climax made flat 16s (with of course 8 pins/throws)

On the advantage side I was thinking about the opposed pistons cancelling out each other's forces. I guess it would be a waste of effort with a high number of cylinders to begin with.

[mzso]

The Coventry Climax FWMW flat-16 was effectively four four-cylinderengines joined together, four cylinder heads, with four exhaust systems. The two flat crankshafts were phased at 90 degrees, and joined end-to-end by the Swedish SKF hydraulic pressure coupling. Dispite the double the number of cylinders, the flat-16 was only one inch longer than the V-8, and only 15 lbs heaver.

Was it successful?

[saviour stivala]

The Coventry Climax FWMW flat-16 was effectively four four-cylinderengines joined together, four cylinder heads, with four exhaust systems. The two flat crankshafts were phased at 90 degrees, and joined end-to-end by the Swedish SKF hydraulic pressure coupling. Dispite the double the number of cylinders, the flat-16 was only one inch longer than the V-8, and only 15 lbs heaver.

Was it successful?

The FWMW flat-16 project was aborted while still on the dyno development stage.

[Tommy Cookers]

https://www.enginelabs.com/engine-tech/ ... have-made/
shows the Porsche flat-12 and flat-16