Guest Blog: Mat Oxley - Why MotoGP is going backwards

MotoMatters.com is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.


Why MotoGP is going backwards

There’s very little all the factories agree on, but engine rotation is one of them

After sunshine, rain and fresh air, my favourite natural phenomenon is gyroscopic effect. This is because we wouldn’t be able to ride motorcycles without it. If you don’t believe me, try this next time you’re out riding: when you stop at a traffic light, don’t put your feet down. (And don’t send me the bill.)

A motorcycle’s spinning wheels create gyroscopic effect that keeps the machine going straight. The more speed, the more gyro and the more stability. This is all good, unless you are racing. Most racers don’t give a hoot about straight-line stability: they’re happy to hold on like gorillas on the straights, just so long as the bike will turn left or right in the blink of an eye.

And this is why all premier-class Grand Prix manufacturers – possibly for the first time in history – now run their engines backwards. It may also explain why Marc Márquez’s COTA and Argentina victories were so huge – bigger than any dry-track wins from last year.

When an engine runs forward (like most streetbikes) its crankshaft rotates the same way as the wheels, thus adding to the gyro effect, which makes it more difficult to turn into a corner or change direction.

The obvious way to reduce gyro effect is to reverse the direction of engine rotation, so the reverse-rotating crank reduces the total gyro effect created by the fast-spinning wheels.

Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.

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Total votes: 112
Total votes: 131

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Comments

F'n Awesome run down and straight up facts with History!

:)

Total votes: 126

Shh dont tell the BTsport comentators this, they are sure its the reason that the Hondas are having issues this year while all the otherbikes are great, because only the Hondas have a rearwards pinning crank! (i kid you not, they actually said it live on tv)

Total votes: 108

Have known about the reverse crank rotation on the likes of the M1 since it was introduced, but didn't know Honda had done it for 2016.

I'll be interested to read the comments here - the ones on the Motor Sport site indicate a fairly low understanding of engine tech.

Total votes: 129

Not MotoGP, but worth noting that the MV 675 and 800 triples have a reverse-rotating crankshaft for the same reasons espoused in Matt's article, and they steer magnificently.  In fact, the 675 is the best steering road bike I have ridden in my 46 years riding on the road.

Total votes: 117

Beat me to it, 

I think it's quite interesting that a stable bicycle or motorcycle can be produced without using the gyroscopic effect of the wheels and trail in the steering geometry. 

It sure helps a lot to improve stability but it appears to be not the main reason they stay upright.
To my knowledge, the conclusion of that research was that they still couldn't find the main reason for stability. 

Total votes: 99

According to the article, mass distribution and the center of gravity are factors, but the neccessary condition for stability of a two-wheeled vehicle is apparently unstable steering, they conclude, which is more logical than it sounds at first. When a bike starts to fall over, the front wheel has to turn in to save the situation, because then it will result in the bike standing up again. Remember that you throw a bike into a corner by turning the front wheel in the opposite direction very briefly. Give a pull on the handlebars to the left, the front of the bike goes left, the rest of the bike will push on straight and it wil result in the bike falling to the right. You then turn the handlebars quickly to the right to catch the falling bike and subsequently find the new balance. Lifting the bike up again can be done by turning briefly further to the right, into the corner. (And/or by sending power to the rear wheel).

So when a bike starts to fall over to the right and the front wheel will by itself turn to the right quicker than the bike falls, it will catch the falling bike and lift it up again. If that happens in very small amounts the whole time, the bike will stabilize itself around the straight line.

I still have to think about how negative trail can be okay. Maybe it only becomes a problem when the steering angle of the front wheel becomes bigger than a certain amount, so that it is something like walking on a wire. Too far from the balance point and you're in trouble. So you would not want to ride with negative trail, but the trail itself is not what is keeping the bike upright, nor is the gyroscopic effect of the wheels. These factors will help to make the bike less sensitive to disturbances, though, I'd say.

Interesting stuff.

Total votes: 104