Curious Crankshaft Configurations, Whys & Wherefores.

[johnny comelately]

I thought you may be interested in this Yamaha crank, any speculations on why

[Tommy Cookers]

...... ok I'll bite - on this cold rainy UK holiday

otoh and fwiw
there was a lot of argument over this about a year ago

the crossplane straight 4 (as invented in Japan decades after the sidecar WC-winning German URS engine)
small differences are possible within this category

iirc what I said last time was that the crank can be designed to smaller diameter saving eg bearing losses etc
as the reciprocation inertial impulses are evenly spaced (by unevenly spacing the combustion impulses) ....
the crankshaft output inertia sum is zero
(remember at very high rpm with NA the inertia force/energy is greater than the combustion-related force/energy)
ok the crankshaft exports no reciprocational inertia-related torque ripple .....but ....
the crankshaft exports increased combustion-related torque ripple and design-inherent torsion-related torque ripple

there is/was a Yamaha advert claiming the crossplane crank gives technomagic 'feel' effects at the rear tyre
which I have said is false because the tyre is so isolated from crankshaft torque ripple at eg 10000 rpm
isolated by the elastic etc behaviour of the long load path between crank and road
these crossplane technomagic effects seem imo to contradict the earlier fashion of alleged 'big bang' technomagic

[johnny comelately]

...... ok I'll bite - on this cold rainy UK holiday

otoh and fwiw
there was a lot of argument over this about a year ago

the crossplane straight 4 (as invented in Japan decades after the sidecar WC-winning German URS engine)
small differences are possible within this category

iirc what I said last time was that the crank can be smaller diameter and lighter saving eg bearing losses
because the inertia forces are evenly spaced (at the expense of unevenly spaced combustion forces)
and at very high rpm with NA the inertia-related energy is greater than the combustion-related energy

there is/was a Yamaha advert claiming of it giving technomagic effects at the rear tyre
which I have said is false because the tyre is isolated from crankshaft torque perturbations at 10000 rpm
isolated by the elastic etc behaviour of the long load path between crank and road
these technomagic effects seem imo to contradict the earlier fashion of 'big bang' technomagic

10:30pm @ 297 degrees K, fly Qantas
Advertising...misleading...NO way
Anyway my view is that regarding traction the torque/combustion pulse peaks are progressively shorter reducing breakaway effect, and that forms a larger wave (complete 4 cylinder sequence) which seems to work when riding. Sort of (emphasise only sort of ) a compromise big bang
I take your point re isolation but when everything is hooked up (mapping right too) it seems to work, and then double checked in the rain
Then there is the question of direction of rotation, gyro etc etc but that's a story for another day

[J.A.W.]

Irving suggested his 'magic' 76 deg crankshaft to the UK makers of 0 deg crankshaft parallel twins - without success
and it would have given little relief from primary frequency vibration

more recently historic race UK machines have had eg 90 deg or 180 deg made from (3 piece bolt-up) Norton crankshaft bits
I suggested here that 135 - 150 deg would be better

50ish years ago BSA/Triumph started making 3 cylinder 750cc machines with 120 deg 1 piece crankshafts
while still making 'old hat' and very vibratory 0 deg 500cc and 650cc twin cylinder machines
the 3s boosted credibility, seeming new and exciting and performing well and with much reduced vibration


they could have used the 3 cylinder as a basis for simple and cheap improved twin
this could be confirmed now ie by cutting down a 3
the 3 has a 3 piece 'salami- style' crankcase (the twin would use 2 of these)
the 3's crankshaft and camshafts etc would be cut down
(the crankshaft could have 3 mains/4 crankcase pieces or 2 mains/2 pieces stiffening added to redundant journal)

a relevant exercise in industrial archaeology- and easier than alternatives

with the 120 deg crank the primary and secondary vibration would be half (the then-existing 500cc twin's)
it would have slung less oil
the machine's sound would have been new and related to the 3 and so better imagewise

a better proposition than Irving's

If I might suggest a more practicable alternative as a 'proof of concept' exercise T-C,
perhaps a pair of cylinders sliced from a junkyard M104 (DOHC 4V) Mercedes-Benz inline six?

That would provide a 1 litre twin, and likely - it could prove it better than the Norton-Cosworth..

& on the Norton 'bolt-up' cranks, poor old Norton didn't have the metallurgical-working facilities to make them
in one piece ( BSA had a long history of gun making, the triple cyl cranks were forged, then twisted to 120 degrees).

But staying with a cast FE centre/flywheel proved too much in racing duty, when the 2 mainbearing cranks got 'ropy',
with the resultant flex fracturing the brittle 'stove material', & ejecting the frangible remains through the cases..

Laverda too, had limited crank making facilities, so as an expedient, made their triples in 180 degree form,
(which made them sound like a 4 with a 'dead pot', to my ear), until the later series went to a regular 120..

[johnny comelately]

NSR500
And all this from re-timing the crankshaft. In 1989 Lawson’s NSR ran a 90-degree crankshaft, firing one cylinder every 90 degrees. In 1990 and 1991 the NSR used a 180-degree crank, firing two cylinders every 180 degrees. In 1992 all four cylinders fired within 70 degrees.

(Changing the combustion timing didn’t merely change power delivery, it transformed the way the motorcycle handled, steered and everything else.)

From - https://www.motorsportmagazine.com/opin ... gger-bucks
where you might enjoy Jack Miller's quote

[johnny comelately]

Irving suggested his 'magic' 76 deg crankshaft to the UK makers of 0 deg crankshaft parallel twins - without success
and it would have given little relief from primary frequency vibration

more recently historic race UK machines have had eg 90 deg or 180 deg made from (3 piece bolt-up) Norton crankshaft bits
I suggested here that 135 - 150 deg would be better

50ish years ago BSA/Triumph started making 3 cylinder 750cc machines with 120 deg 1 piece crankshafts
while still making 'old hat' and very vibratory 0 deg 500cc and 650cc twin cylinder machines
the 3s boosted credibility, seeming new and exciting and performing well and with much reduced vibration


they could have used the 3 cylinder as a basis for simple and cheap improved twin
this could be confirmed now ie by cutting down a 3
the 3 has a 3 piece 'salami- style' crankcase (the twin would use 2 of these)
the 3's crankshaft and camshafts etc would be cut down
(the crankshaft could have 3 mains/4 crankcase pieces or 2 mains/2 pieces stiffening added to redundant journal)

a relevant exercise in industrial archaeology- and easier than alternatives

with the 120 deg crank the primary and secondary vibration would be half (the then-existing 500cc twin's)
it would have slung less oil
the machine's sound would have been new and related to the 3 and so better imagewise

a better proposition than Irving's

If I might suggest a more practicable alternative as a 'proof of concept' exercise T-C,
perhaps a pair of cylinders sliced from a junkyard M104 (DOHC 4V) Mercedes-Benz inline six?

That would provide a 1 litre twin, and likely - it could prove it better than the Norton-Cosworth..

& on the Norton 'bolt-up' cranks, poor old Norton didn't have the metallurgical-working facilities to make them
in one piece ( BSA had a long history of gun making, the triple cyl cranks were forged, then twisted to 120 degrees).

But staying with a cast FE centre/flywheel proved too much in racing duty, when the 2 mainbearing cranks got 'ropy',
with the resultant flex fracturing the brittle 'stove material', & ejecting the frangible remains through the cases..

Laverda too, had limited crank making facilities, so as an expedient, made their triples in 180 degree form,
(which made them sound like a 4 with a 'dead pot', to my ear), until the later series went to a regular 120..

At the risk of being racially something or other, I would comment that the German cast iron alloys seemed to be much better, from machining and testing (piston, rod etc) for, of all things, a Lanz Bulldog motor!
EDIT:
Forgot to mention the important part, the crankshaft.
they only "rev" to 750 i think, but if you have ever seen the crankshafts with a huge pulley on the end, you wonder how they last, but they do. even when bent.
Piston is 9 inches diameter nominally in this photo

[J.A.W.]

Yes, & some moreso than others - such as M-B M104 engine transplants into BMWs..

https://www.youtube.com/watch?v=6WKBoMLzP4w

[Tommy Cookers]

[quote="johnny comelately"]
NSR500
And all this from re-timing the crankshaft. In 1989 Lawson’s NSR ran a 90-degree crankshaft, firing one cylinder every 90 degrees. In 1990 and 1991 the NSR used a 180-degree crank, firing two cylinders every 180 degrees. In 1992 all four cylinders fired within 70 degrees.
(Changing the combustion timing didn’t merely change power delivery, it transformed the way the motorcycle handled, steered and everything else.)
From - https://www.motorsportmagazine.com/opin ... gger-bucks
where you might enjoy Jack Miller's quote[/quote]


utter rubbish !!!!! written by Matt 'the Pratt' Oxley

it was a V4 with a substantial V angle
what the Pratt has written above would only happen if it was a straight 4

btw
Prof. Gordon Blair said that BB effects were due to effects in airbox (of different firing intervals) on up and down response
he did consultancy on this for the Ducati factory Moto GP

and eg the BB NSR gave too much engine braking ie Doohan preferred the non-BB machine

[johnny comelately]

I may have posted this elsewhere
https://www.facebook.com/MotoGP/videos/ ... 525615769/

[johnny comelately]

re Firing order
https://www.gtisoft.com/renault-firingorder-pdf/

[J.A.W.]

Ok engine-tech brainiacs.. guess what crankshaft configuration was used by the Junkers Jumo 222,
a 24 cyl WW 2 German aero-engine which did get off the drawings & in to metal,(to the ~200 engine mark!),
- but never made service..

Anyhow this lump was deemed a 'radialine' being a multiple of inline 4's disposed radially in six banks..
- if you can visualise the Napier Lion, which featured 3 X 4, & double it - so its six-pointed star-like, or asterisk-wise..

Right then, are ya still with me?

Then its anti-climax time.. the Jumo 222 used a basic 180 degree/flat-plane 4-throw crank..

Now as to its bloody firing pattern.. nah.. it gets my neurones grinding, later maybe..

[Tommy Cookers]

[quote="johnny comelately"]re Firing order
https://www.gtisoft.com/renault-firingorder-pdf/[/quote]

this says .....
different firing orders give different power curves due to different acoustic coupling within the plenum
(independent of similar effects due to different acoustic coupling within the exhaust system)
this seems to agree with Blair's views re so-called 'big bang' GP motorcycles

the 360 deg aka 0 deg BB race Honda VFR crankshaft is said to have given a better power curve
the NR500 apparently always had a 360 deg aka 0 deg crankshaft
the NSR 500 was descended from a 250 V twin
fwiw iirc I said one NSR crankshaft was 180 deg N-S-N-S

[johnny comelately]

Ok engine-tech brainiacs.. guess what crankshaft configuration was used by the Junkers Jumo 222,
a 24 cyl WW 2 German aero-engine which did get off the drawings & in to metal,(to the ~200 engine mark!),
- but never made service..

Anyhow this lump was deemed a 'radialine' being a multiple of inline 4's disposed radially in six banks..
- if you can visualise the Napier Lion, which featured 3 X 4, & double it - so its six-pointed star-like, or asterisk-wise..

Right then, are ya still with me?

Then its anti-climax time.. the Jumo 222 used a basic 180 degree/flat-plane 4-throw crank..

Now as to its bloody firing pattern.. nah.. it gets my neurones grinding, later maybe..

this will cost me a day
This might be a start for firing order

[godlameroso]

Ok engine-tech brainiacs.. guess what crankshaft configuration was used by the Junkers Jumo 222,
a 24 cyl WW 2 German aero-engine which did get off the drawings & in to metal,(to the ~200 engine mark!),
- but never made service..

Anyhow this lump was deemed a 'radialine' being a multiple of inline 4's disposed radially in six banks..
- if you can visualise the Napier Lion, which featured 3 X 4, & double it - so its six-pointed star-like, or asterisk-wise..

Right then, are ya still with me?

Then its anti-climax time.. the Jumo 222 used a basic 180 degree/flat-plane 4-throw crank..

Now as to its bloody firing pattern.. nah.. it gets my neurones grinding, later maybe..

So 6 rods per crank journal? So each bank was 60 degrees apart? That would make for an interesting firing pattern. You could definitely have 3 cylinders fire simultaneously. What a nutty engine, I like it.

[johnny comelately]

Ok engine-tech brainiacs.. guess what crankshaft configuration was used by the Junkers Jumo 222,
a 24 cyl WW 2 German aero-engine which did get off the drawings & in to metal,(to the ~200 engine mark!),
- but never made service..

Anyhow this lump was deemed a 'radialine' being a multiple of inline 4's disposed radially in six banks..
- if you can visualise the Napier Lion, which featured 3 X 4, & double it - so its six-pointed star-like, or asterisk-wise..

Right then, are ya still with me?

Then its anti-climax time.. the Jumo 222 used a basic 180 degree/flat-plane 4-throw crank..

Now as to its bloody firing pattern.. nah.. it gets my neurones grinding, later maybe..

So 6 rods per crank journal? So each bank was 60 degrees apart? That would make for an interesting firing pattern. You could definitely have 3 cylinders fire simultaneously. What a nutty engine, I like it.

My first thoughts were with 6 lobes it might be firing a bank at a time, but that would have invented the rocking couple!
so, is it 4 separate radial cranks with a cylinder per row being fired at once, that would be much smoother