Generative Designed Crankshaft

[vorticism]

At a guess I'd say the R10 V12 was able to eschew counterweights due to low operating speed and the good first order balance offered by two banks of I-6s. ..

[sosic2121]

Where are the piston rings?

[saviour stivala]

That V12 parts picture shows 12 piston rings one next to eaxh piston.

[Greg Locock]

The only crankshaft I was ever involved in designing was for an I6. It was made of cast steel. We wanted it to rev to 6000 rpm, and it had to be a plug'n'play replacement for the previous design, and had to be more refined.

So the designer decided that the best way to achieve all that was to treat it like 6 separate single cylinder engines, so far as balancing goes. That is each piston was directly counterweighted by its own crank webs. Hence the moniker the 12 counterweight crank.

This significantly reduced the dynamic force into each main bearing, and it sounded better. It did however weigh 2 kg more and so 2 years later the old design was reinstated, since one of the crazy kids in the Engine Labs had demonstrated that in fact it could handle 6000 rpm.

One of the more dispiriting things about working in noise and vibration in a large car company is that when the wish list comes round for the next model, the first items are to put back in all the stuff that has been cost reduced out.

[J.A.W.]

The only crankshaft I was ever involved in designing was for an I6. It was made of cast steel. We wanted it to rev to 6000 rpm, and it had to be a plug'n'play replacement for the previous design, and had to be more refined.

So the designer decided that the best way to achieve all that was to treat it like 6 separate single cylinder engines, so far as balancing goes. That is each piston was directly counterweighted by its own crank webs. Hence the moniker the 12 counterweight crank.

This significantly reduced the dynamic force into each main bearing, and it sounded better. It did however weigh 2 kg more and so 2 years later the old design was reinstated, since one of the crazy kids in the Engine Labs had demonstrated that in fact it could handle 6000 rpm.

One of the more dispiriting things about working in noise and vibration in a large car company is that when the wish list comes round for the next model, the first items are to put back in all the stuff that has been cost reduced out.

Hit the link below to see a couple of interesting crankshafts that also feature minimal counterweights.
(Click on the pic to enlarge the view).

On the right are the 4-throw 5-main 180 degree 'W12' triple-bank Lion cranks - with the 120 degree
angle of the banks allowing for smooth running - right up to 4,000rpm in Cobb's Railton LSR car
extending out on the Bonneville salt flats at ~400mph.

Those on the left are for H24 four-banks of six cylinders Sabre - which oddly enough relate to Greg's
post above - since the Sabre started out with fully counterweighted cranks, but these were deleted
as tests showed they were needless - due to running as a geared pair, & being dynamically balanced.
(Note also the 'organically' oval-shaped crank-webs, for aero/hydro-dynamic windage/oil-shedding).

https://archives.imeche.org/archive/175 ... ing-napier?

[Tommy Cookers]

On the right are the 4-throw 5-main 180 degree 'W12' triple-bank Lion cranks - with the 120 degree
angle of the banks allowing for smooth running .....

H24 four-banks of six cylinders Sabre - ... started out with fully counterweighted cranks, but these were deleted ....

well ....
'crankshaft counterweights are nothing to do with vibration'
(unless in a single or twin that moves like one)

the deletion of Sabre counterweights proved that it had too much bearing area
because it had diesel origins and/or because it was too long so the crankshaft needed help

the 120 deg W12 Lion has ......
compared to a 90 deg flat crank V8 of same piston size etc (say 300hp Hispano-Suiza) .....
at twice crankshaft frequency 29% less horizontal vibration .....
plus a constant rotating force of half that amount - WHICH (UNUSUALLY) IS CANCELLABLE BY COUNTERWEIGHTING
says Charles Fayette Taylor - The Internal Combustion Engine in Theory and Practice

EDIT
CFT shows the broad arrow single row 3 (Anzani- a known vibrator)) and twin row 6 are fractions of the Lion
but the Napier Cub has no vibration at either twice engine frequency or engine frequency

[vorticism]

On the right are the 4-throw 5-main 180 degree 'W12' triple-bank Lion cranks - with the 120 degree
angle of the banks allowing for smooth running .....

H24 four-banks of six cylinders Sabre - ... started out with fully counterweighted cranks, but these were deleted ....

well ....
crankshaft counterweights are nothing to do with vibration
(unless in a single or twin that moves like one)

Peering through FEA eyes here from my armchair I say that the counterweights will help smooth out second order imbalance from the top end of the piston stroke as well as other inertia variance at the bottom of the stroke, a sort of flywheel effect, and it will help with any longitudinal wobble stemming from asymmetrical piston arrangements (L2, 3, 5).

[Tommy Cookers]

Peering through FEA eyes here from my armchair I say that the counterweights will help smooth out second order imbalance from the top end of the piston stroke as well as other inertia variance at the bottom of the stroke, a sort of flywheel effect, and it will help with any longitudinal wobble stemming from asymmetrical piston arrangements (L2, 3, 5).

counterweights reduce loads at points along the crankshaft .... but the sum of these loads is anyway zero
ie without counterweights these loads will be cancelled within the block .....
that's how counterweights don't reduce vibration
(I was of course responding to advocacy of Napier engines with the conventional symmetry)

'longitudinal wobble' (imbalance of inertial moments) - have you patented this ?
crankshaft counterweighting is conventional at a level that minimises loads - and so the moment envelope & vibration
any other amount will increase the load peak - ie reshape the envelope ie in some way polarise or 'enlarge' it
crankshaft counterweighting wont cancel 2nd order inertial moments ...
eg in the inline 3 these are as big as the 1st order inertial moments - and more troublesome

[vorticism]

'longitudinal wobble' (imbalance of inertial moments) - have you patented this ?

No, the dewobbleizer is still at the prototype stage. Do pistons not transfer their inertia to the block via the crank in absence of a similar counter force? Good point on crankshaft elasticity, +1.

[J.A.W.]

On the right are the 4-throw 5-main 180 degree 'W12' triple-bank Lion cranks - with the 120 degree
angle of the banks allowing for smooth running .....

H24 four-banks of six cylinders Sabre - ... started out with fully counterweighted cranks, but these were deleted ....

well ....
crankshaft counterweights are nothing to do with vibration
(unless in a single or twin that moves like one)

Peering through FEA eyes here from my armchair I say that the counterweights will help smooth out second order imbalance from the top end of the piston stroke as well as other inertia variance at the bottom of the stroke, a sort of flywheel effect, and it will help with any longitudinal wobble stemming from asymmetrical piston arrangements (L2, 3, 5).

"Longitudinal wobble"... is generally referred to as a 'rocking couple' in English, isn't it?

If of interest, member here 'Manolis' freely offers a program on his website which runs through
the parametric permutations of inertia torque/crankshaft counter-weights/flywheel effects for
a fair number of piston engine arrangements, per the link below.

http://www.pattakon.com/pattakonEduc.htm

[J.A.W.]

On the right are the 4-throw 5-main 180 degree 'W12' triple-bank Lion cranks - with the 120 degree
angle of the banks allowing for smooth running .....

H24 four-banks of six cylinders Sabre - ... started out with fully counterweighted cranks, but these were deleted ....

well ....
'crankshaft counterweights are nothing to do with vibration'
(unless in a single or twin that moves like one)

the deletion of Sabre counterweights proved that it had too much bearing area
because it had diesel origins and/or because it was too long so the crankshaft needed help

the 120 deg W12 Lion has ......
compared to a 90 deg flat crank V8 of same piston size etc (say 300hp Hispano-Suiza) .....
at twice crankshaft frequency 29% less horizontal vibration .....
plus a constant rotating force of half that amount - WHICH (UNUSUALLY) IS CANCELLABLE BY COUNTERWEIGHTING
says Charles Fayette Taylor - The Internal Combustion Engine in Theory and Practice

Well T-C, at least in the case of the Napier Lion, C.F. Taylor must've been relying a bit too much
on theory, as he came up short on empirical experience, unlike the U.S. engineers who actually
tested a Lion, (with a highly critical eye),& they remarked on its smooth running characteristics,
despite being rigidly fixed on their test stand, rather than by typical resilient airframe mounts.

As for the Napier Sabre, rather than "too much bearing area", it was likely the robust crankcase
which contributed, in marked contrast to the Allison V-1710 V12 engine, which required revision
to a fully counterweighted crank in its later increased output series, due to what a Roy Fedden
analysis described as deficiencies in design per cylinder block/crankcase fixation methodology.

Likewise, the R/R Griffon received a full suite of crankshaft vibration/harmonics palliatives...

[vorticism]

"Longitudinal wobble"... is generally referred to as a 'rocking couple' in English, isn't it?

I prefer dynamic duo.

Does anyone think the OP crankshaft would be for a flat four.

Compare to Lycoming:



Mattituck:



Volkswagen:



Maybe a reference to their Gold Wing.

[J.A.W.]

IIRC the 4cyl Honda G-W crank features a large heavy disc flywheel adjacent to the PTO gear,
with later build units also featuring a couple of heavy crank-web counterweights on journals 2/3.
Its a 3 main bearing design though, & the G-W wasn't ever a 'sporty' bike, to be fair.

Their 6cyl G-W variant has a smaller crank-end disc flywheel & substantial crank-web counterweights,
albeit still only with 5 mains.

By contrast, the Subaru boxer 4cyl runs very thin webs (fracture prone) on a 5 main crank,
& their 6cyl boxer crank has 7 mains accordingly.

Per that VW crank, of course that is for a lowly rated mill - US hi-po aftermarket crankshafts for VW
such as offered by Scat - run to more generously counterweighted webs.

[J.A.W.]

That V12 parts picture shows 12 piston rings one next to each piston.

Jeeze, 1-ring pistons you reckon? What did they do for oil control?

Or could it be - the rings are not separately delineated - in that ah, 'exploded view' pic?

[saviour stivala]

That V12 parts picture shows 12 piston rings one next to each piston.

Jeeze, 1-ring pistons you reckon? What did they do for oil control?

Or could it be - the rings are not separately delineated - in that ah, 'exploded view' pic?

Picture shows one ring next to each piston. at least that's what I can see. As to oil control and one ring piston. In the V10 era qualifying only engines, some qualifiers used no oil control rings but just one piston ring. qualifing runs only just got them by the total oil they could hold in their oil tank.