Japanese invention of the year: Yamaha’s cross-plane crankshaft
Bang 270º bang 180º bang 90º bang 180º
If Japan has been known for one thing when it comes to cars and motorbikes, it is innovation. This year, Yamaha’s cross-plane crank engine, which appears in their R1 Superbike is sure to make some (asymmetrical) waves.
It’s going to be a good year for Japanese inventiveness. We’ve got Showa’s Big Piston Fork (fitted to the Suzuki GSX-R1000K9 and Kawasaki ZX-6R); Honda’s electronic braking for the CBR6 and Blade; and Yamaha’s ‘just like Rossi’ cross-plane crank. If you want useful, the Honda brakes are the easy winner. Trouble is, they’re so clever you don’t know they’re working. Same goes for the new Showa forks, unless you’re braking hard into a bend.
But you can’t ignore the R1’s new crank. It looks different, it feels different, and boy does it sound different. Although Yamaha patented a cross-plane crank in the 1960s, this one dates back to 2003. They’d just tempted Valentino Rossi away from Honda, and they needed something special to turn their dog of an M1 into a MotoGP winner. Of four experimental ‘growler’ engines at the Sepang winter test, one stood out.
At the time most commentators called it the ‘Big Bang’ engine. We now know that a better description might be ‘Big Grip’. That’s what Yamaha are claiming, at any rate.
So what’s so great about uneven firing pulses? They are certainly nothing new. For more than 100 years singles, V-twins and some parallel twins and triples have delivered uneven pulses to the rear wheel, while fours have stayed regular. But the last 20 years have seen a growing consensus (first in 500s, now in MotoGP) that uneven firing intervals are superior.
The traditional explanation is that an engine with an irregular beat gives the rear tyre more time to recover between pulses, so the rider can use more throttle before it spins up. But if you cluster all the pulses together, who’s to say they won’t make the tyre let go more easily? With the new R1, Yamaha offer a more credible reason. They say their system creates a more direct feel for the rider between throttle and rear tyre. And it does that by stripping out the undesirable ‘momentum effect’ of a traditional four-cylinder crankshaft.
To get your head around this idea, think about what an engine actually deals out to the rear wheel. Firstly, it transmits the combustion force. Open the throttle, the engine gulps more fuel and air, the burn does its thing, and you get a bigger ‘whomp’ acting on the tops of the pistons. Simple and controllable. But there’s also a secondary effect. As a conventional four-cylinder crankshaft rotates, it creates a stop-start signature. All four pistons (and their crank web balancing weights) reach their highest and lowest speeds at the same time. Yamaha call this ‘inertial torque’, and describe it rising and falling in a sine wave.
This fluttering, say Yamaha, gets in the way of you feeling what’s going on. And there’s nothing you can do about it. Enter the crossplane crankshaft. Viewed from one end, there’s a crankpin every 90 degrees (north, south, east and west). So as the crank spins there are always two pistons going flat out when the other two are stopped. The inherent architecture of Ducatis creates the same effect.
Is it really any use? In MotoGP, it’s contributed to three world titles in five years. On the road, the advantage isn’t so clear, unless you yearn to own a straight four that sounds like a Vee. The 2009 R1 is a peaky beast, and low-speed running is – well, lumpy. The Suzuki and Honda rivals are tough competition, too. We’ll have to wait for hot summer tarmac to know for sure.
Doh. What is a crankshaft again? A crankshaft is just a device that turns up-and-down motion into round-and-round – for example, the pedals on a bicycle. Naturally, the pedals are spaced opposite each other, so that one of your legs is pushing when the other one can’t. Most four-cylinder engines use the same principle: the pistons (the things that transmit the ‘shove’ derived from burning fuel and air in a confined space) rise and fall in pairs. Because an individual cylinder only fires once every two revolutions, the crankshaft as a whole receives a one-cylinder pulse of power once every half revolution, or 180 degrees. Yamaha’s new crossplane crankshaft is different. There’s no direct comparison with a bicycle because the bike has four pistons, and you’ve only got two legs. But imagine the angle between your pedal cranks being something like 100 degrees, rather than 180. It would feel horrible. But the R1 revs 200 times faster than your legs, so it’s not bothered.
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Great article. I didn’t know about this!
The reason for yamaha winning these world championships was not this wonderfull crank but the genious of Rossi. On the track the Ducatti is a far better package. On the road for the everyday biker I am sure no differance will be felt. So I feel its just another marketing gimmick.
Interesting article, i have bookmarked your site for future referrence 🙂
The bike magazines seem to like it. Then Rossi could probably win on my Harley….
It sounds fantastic, but it’s actually just a basic 90 degree equally-spaced crank. Triples often use a 120 degree spacing but the Italian Laverda didn’t on the Jota giving it the thump, thump, thump, gap! that made it sound cool. It made a compact powerful engine, but no one came up with the above baloney above to justify it – it was just a well tuned engine. Audi and Volvo have been producing 5 cylinder engines with crank spacing at 144 degrees for years, not rocket science.
You’re more likely to get better performance through the lack of counter balancing, smaller lighter bearings and their associated weight saving, plus the aformentioned ‘slightly mad rider’, than any of the wishful thinking mentioned in the above article.
In the 80’s Honda started to develop a plastic engine and the sadly ‘Not Ready” NR 500 featuring oval pistons. That was radical, if somewhat unsuccessful… Unlike a 90 degree spaced crank.
The Japanese are great designers, especially with bikes. But they’re also excellent at marketing. Don’t believe the hype.
i”v got one, after going from a 08 blade to this it”s out of this world, fantastic!!!
There is nothing new about this crank design , honda used a BIG BANG 2 stroke engine on the NSR500 in the 80’s & 90’s and a long time before coventry climax used this type in a 1.5 ltr V8 in the 1960’s and that lead on the HILLMAN IMP engine which is pretty half the V8 engine , hence the reason it lays on one side as it does.
Pretty much every V8 engine since has used what they call a cross plane crank , all it does is fire all cylinders very close together and then a pause to allow the rear tyre a break for a short while to grip again giving it an easier time
Gotta be good its japanese….
You lot yanking my crank?
Just test rode 2009 R1 my last two machines were R1’s and this new one has totally re-written all the rule books. Now in process to tie up a deal on a 2009 one any colour will do dont care “JUST GOT TO HAVE IT”
Had 30+ top tackle bikes over the years still even got my 13 yr old Duc 916. But this new R1 has got to be tried power everywhere standard suspension is ace too.
Go on try and then defy yourself to buy!!!
The Bull.
Keith,
You are misled my friend. The aluminium Hillman Imp engine was designed as a water pump for the fire brigade not as half a V8. I apologise if I am wrong but I never have been before.
what a load of balony about performance , if the power drop is to great , put a heaver flywheel on it to counteract it (and before u thing but we need a lighter flywheel) , the big bang crank on a 4 stroke needs a heavier flywheel anyway to get over the gap in power and makes the engine more uneven) the dip being greater anyway for the big bang so i wish they would state facts not bs , and this big bang crank was as previously mentioned developed originally for 2 strokes as they fire every 360 degrees , so 4 cylinders required a 90 degree spacing between the cylinders for an equal power output , not mentioning the smaller gap in the revolution and fact there is a power on n 1 breath at same time allows for a much lighter flywheel , ,,,,,, the only thing the bik bang crank on a 4 stroke would do is allow a 90 degree v shape n keep the timings right , or in an inline 4 create a shed load of vibration , lumpy power at low revs and a lot of vibration , not to mention require a heavier flywheel to carry the crank round further unpowered degrees , all of which is not good , oh it would give that v type sound , but then so could a tuned exhaust , without as meny drawbacks
Wonder what it will soound like with after market silencers on?
I am not a biker, my limited automotive engineering was mostly 4 wheeled but I have listened in when this subject has recently been discussed. The conclusion arrived at was that there was a similarity with mainstream anti-lock brakes. For these the control system is not currently sophisticated enough to provide the optimum hydraulic pressure at all times so the logic is to provide enough to lock (as is usually present in a panic application) and immediately back off repeating very rapidly. As measured against “normal skill” drivers this is better than consistent over or under pressure. For propulsion it was thought that the lack of smoothness in torque with the “recovery time” previously mentioned by Keith would allow the “most skilled controllers” to get get a different form of feedback regarding grip or lack thereof at the borderline which one assumes they can exploit. It was also thought that there might be some unknown benefit at the tyre contact spot for a pulsed grip-slip system (certain railway tests have shown a benefit in traction with 3 to 5% deliberate slippage).
ah so, velly intresting!
after reading the comments that people have left here it seems to me that every one is once again battling on about a new bike that has been completly over written however what people tend to forget that in the 90s one litre bikes will out perform most of us road users and the full potential of the bikes can only be ridden by the likes of rossi ! the moral of this story is no matter how much we talk about cranks wheels and so on its the rider that will make the bike do what its caperble of also when the new blade was launch every one said wow its rides like nothing weve ever riden same thing with the r1 however the more these bikes are profiled and tamperd with the more power the bigger problems and thats exactly what happed to the 08 blade it used more oil than shell could produce and the ri in 6 months will have people back on here saying its to noisy its to thirsty and so on!! wonder what suzuki are planning for next year??????
As said, all very interesting. But R1 ain’t my kinda bike – I prefer’m naked – much more fun. ABS sounds handy though, but a fair old weight at 10kgs. Also the big piston forks sound useful for staying on the brakes a tad longer when or as required.
To all those who say it’s just a marketing ploy and the only reason Yamaha wins is because of Rossi I beg to differ! Lozenzo has been regularly beating Rossi this Season and 4 Yamahas are often in the top 5. In SBK Yamaha are winning races on a brand new bike with no data and Camier has won three race in a row in BSB with absolutely NO testing.
It’s not just a clever crank but also a brilliantly engineered bike, just as the first R1 was back in ’98
Just chopped in 2007 R1 for 2009 R1 15.05.09, after getting a demo ride last month my mind was made up. Owned too many sports bikes to type up, this latest R1 is a strange beast indeed up to 7 thou its a rapid twin with NO yes NO engine braking what so ever, after 8 thou to redline its a conventional R1.
Not easy getting into it if your not a fan of the low down instant grunt of the twins and you need to enjoy your short shifting.
Handling slightly beta than 07 model which I ended up putting an Ohlins Road Shock on which helped a lot. Still running in this 09 model so will post more in the future.
If thinking of one and cant make mind up just do it I did and have absolutely NO REGRETS ITS INSTANT FUN EVEN WHEN RUNNING IN!
I have one too, gone from a Suzuki K6 1000 which was brill, but this beast is better again, alot better. All the doubters out there go book a test ride then come tell us what you think.
I have covered 1500 miles on mine & it amazes me every time I go out on it.
Anyway bye for now, off out for a ride:)
pmkeith………..wrong
AlanMcT……….correct
Coventry Climax did build the light weight engine for portable fire pumps.
I worked with them for many many years until they were replaced with a Nissan Micra
deridative.