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Crossplane Crank Explained

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droog
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PostPosted: 18:59 - 20 Sep 2021    Post subject: Crossplane Crank Explained Reply with quote

Good explanation/visualisation of the physics, mechanics and advantages of the crossplane crank engine design as per Yamaha R1

(Also historical focus on the application of 'Big Bang' firing order in 90's MotoGP).

https://www.youtube.com/watch?v=uM-ycHS9uvw
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A100man
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PostPosted: 11:46 - 21 Sep 2021    Post subject: Re: Crossplane Crank Explained Reply with quote

droog wrote:
Good explanation/visualisation of the physics, mechanics and advantages of the crossplane crank engine design as per Yamaha R1

(Also historical focus on the application of 'Big Bang' firing order in 90's MotoGP).

https://www.youtube.com/watch?v=uM-ycHS9uvw


Indeed - I sure learned something - more staggering is the fact it's had 1.2 m views in 2 weeks.
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droog
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PostPosted: 13:42 - 21 Sep 2021    Post subject: Re: Crossplane Crank Explained Reply with quote

A100man wrote:
Indeed - I sure learned something - more staggering is the fact it's had 1.2 m views in 2 weeks.


Yeah, I didn't realise the crossplane crank was such a celebrity!
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grr666
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PostPosted: 16:50 - 21 Sep 2021    Post subject: Reply with quote

I was going to post this myself but couldn't be bothered, I watched it a week or so ago during a you tube surfing
session of MT10 related stuff as I'm seriously considering ordering one. All clever stuff. Thumbs Up
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droog
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PostPosted: 19:04 - 21 Sep 2021    Post subject: Reply with quote

grr666 wrote:
I was going to post this myself but couldn't be bothered, I watched it a week or so ago during a you tube surfing
session of MT10 related stuff as I'm seriously considering ordering one. All clever stuff. Thumbs Up


Yeah, I was walking down the street the other day and this guy on one of the original (2009-2011) Yamaha 'Big Bang' R1's cruised past me and I really liked the unusual noise it made - from what I already knew of the bike I realised that the interesting acoustics was due to the crossplane crank - so when this video popped up coincidentally a few days later I was already primed to watch it. Very Happy
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Zen Dog
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PostPosted: 14:21 - 22 Sep 2021    Post subject: Reply with quote

Where he's talking about the R1's use of a balancer shaft (approx 8 mins in), he says they do so as a better solution than adding mass to the crankshaft to counter the rocking couple of the outer cylinders. And he says they do this because adding mass to the crankshaft would effect the rev happy nature of the engine. That seems fair enough, but why wouldn't the additional balancer shaft also have this effect? If it's being driven directly by the crankshaft, then isn't that additional mass that also needs to be spun up as revs increase? What am I missing?
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rpsmith79
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PostPosted: 15:08 - 22 Sep 2021    Post subject: Reply with quote

grr666 wrote:
............. All clever stuff. Thumbs Up


It is all clever stuff, but i cant help thinking that unless you are trying to shave milliseconds off your laptime by being able to pin the throttle on corner exit, what (other than the unique sound) is the advatange to us mere mortals on the street

What is see is an overly complex, heavier engine, with one small advantage which only the very top percentile of riders will ever got the benefit of, on track

Though I may be completely missing the mark.......
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droog
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PostPosted: 20:31 - 22 Sep 2021    Post subject: Reply with quote

Zen Dog wrote:
adding mass to the crankshaft would effect the rev happy nature of the engine. That seems fair enough, but why wouldn't the additional balancer shaft also have this effect? If it's being driven directly by the crankshaft, then isn't that additional mass that also needs to be spun up as revs increase? What am I missing?


I'm probably the last person on BCF that should be commenting on (let alone trying to explain) complex engineering questions which is why I had to go to secondary sources - so if anyone can do better it would be welcome ;

The balancer shaft achieves the same effect as a weighted crankshaft (cancelling vibration) but employs much less weight and mass than a weighted crankshaft would need to achieve the same effect - consequently the balancer shaft has significantly less effect on engine RPM than a weighted crankshaft would have.

It does this by employing 'identical eccentric weights rotating in opposite directions at 'twice crankshaft' rpm*

* https://en.wikipedia.org/wiki/Balance_shaft
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Last edited by droog on 20:39 - 22 Sep 2021; edited 1 time in total
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droog
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PostPosted: 20:32 - 22 Sep 2021    Post subject: Reply with quote

rpsmith79 wrote:
grr666 wrote:
............. All clever stuff. Thumbs Up


It is all clever stuff, but i cant help thinking that unless you are trying to shave milliseconds off your laptime by being able to pin the throttle on corner exit, what (other than the unique sound) is the advatange to us mere mortals on the street

What is see is an overly complex, heavier engine, with one small advantage which only the very top percentile of riders will ever got the benefit of, on track


Yeah. I agree - although the advantages of this engine design will only exist at the theoretical level for the majority of riders it's a way for Yamaha to distinguish itself from rival manufacturers in the highly competitive (superbike) market where the customers are often very interested in engineering performance advantages.
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rpsmith79
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PostPosted: 07:20 - 23 Sep 2021    Post subject: Reply with quote

droog wrote:

Yeah. I agree - although the advantages of this engine design will only exist at the theoretical level for the majority of riders it's a way for Yamaha to distinguish itself from rival manufacturers in the highly competitive (superbike) market where the customers are often very interested in engineering performance advantages.


Yes, you make a good point

I suppose a similar thing happened with cars in the 90's/00's with the BTCC touring cars & WRC rally cars becoming super saloons (Volvo T5, Mondeo ST, Imprezza WRX etc), though the rules changed considerably in the 10's meaing car manufacturers didn't have to homologate 500 road going versions, and were allowed to innovate without making them road legal, also the cost of these cars put them out of reach of most of the fans

Superbikes are (by comparrison) much more affordable, and i guess much more obtainable to the fans of that genre of racing
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droog
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PostPosted: 09:09 - 23 Sep 2021    Post subject: Reply with quote

rpsmith79 wrote:
I suppose a similar thing happened with cars in the 90's/00's with the BTCC touring cars & WRC rally cars becoming super saloons (Volvo T5, Mondeo ST, Imprezza WRX etc), though the rules changed considerably in the 10's meaing car manufacturers didn't have to homologate 500 road going versions, and were allowed to innovate without making them road legal, also the cost of these cars put them out of reach of most of the fans

Superbikes are (by comparrison) much more affordable, and i guess much more obtainable to the fans of that genre of racing


Yeah, I would say most of the customers for this type of bike are fans of MotoGP and the R1’s cross-plane crank is the same technology that powered Valentino Rossi’s YZR-M1 MotoGP bike. Due to the irregular firing intervals the CPC R1 also makes the same distinctive sound as Rossi's bike - so the bike was always going to have a strong appeal to Yamaha's target market.
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