MotoGP »

Masao Furusawa reflects on MotoGP career

Given your background in vibration analysis, did you ever consider the use of carbon fibre for the Yamaha chassis or swingarm?

Masao Furusawa:
Some of the engineers thought about using carbon fibre, but for me no. Carbon fibre is very good for keeping rigidity and it is very lightweight. But for a motorcycle I don't think it is so good.

When you lean over 45 degrees there is almost no suspension, so you need some flexibility in the frame. And with carbon fibre it is really hard to control stiffness. For carbon fibre the stiffer it is, the better, which is why it is perfect for a Formula One chassis.

So how do you find the right balance between enough chassis flex and too much flex?

Masao Furusawa:
We do analysis, simulation and also experimental tests to acquire real data, which we feed into the simulation software to help improve the accuracy. But it can be difficult to get right.

This is one of the keys to a good chassis: You must have smooth stiffness changes from the steering head to the rear.

In 2006 we made a mistake with the chassis. We designed a chassis that was much more flexible on the lateral side, but to do that we needed to make some parts with a thin cross-section [so that they would flex more] which can be pretty hard.

So instead of decreasing the stiffness of these parts, we reduced the thickness of the frame in the middle. Point-to-point the overall stiffness was the same, but now the distribution of the stiffness was not 'smooth' and not changing in a consistent way along the bike.

That makes for a pretty bad chatter problem. Chatter is not a linear problem. It is self-excited vibrations. Once it starts, more and more vibrations happen and finally you have a big problem.

One of the solutions is to keep continuous stiffness changes from the head to the rear. Even then you can still get some chatter, but not so much.

So, in the future, what we really need is a damping force for the chassis, but so far that is not so successful. Sometimes we tried a performance damper like on my Miata. Sometimes it works, sometimes not.

This chatter phenomenon is probably the last remaining problem to be cracked by motorcycle engineers.

End of interview.

Related Pictures

Click on relevant pic to enlarge
Valentino Rossi with Yamaha`s Masao Furusawa (Yamaha)
Lorenzo, Czech MotoGP race 2016
Rossi overtaking Iannone, Czech MotoGP race 2016
Lorenzo, Czech MotoGP race 2016
Smith, Lorenzo Czech MotoGP race 2016
Lorenzo, Pol Espargaro, Czech MotoGP race 2016
Pol Espargaro, Lorenzo, Czech MotoGP race 2016
Rossi, Czech MotoGP race 2016
Rossi, Crutchlow Czech MotoGP race 2016
Rossi, Crutchlow Czech MotoGP race 2016
Lorenzo, Laverty Czech MotoGP race 2016
Lorenzo, Czech MotoGP race 2016
Lorenzo, Bradl, Crutchlow Czech MotoGP race 2016
Rossi, Lorenzo Czech MotoGP race 2016
Pedrosa, Rossi Czech MotoGP race 2016
Rossi, Lorenzo Czech MotoGP race 2016
Rossi, Lorenzo Czech MotoGP race 2016
Lorenzo, Petrucci Czech MotoGP race 2016

Join the conversation - Add your comment

Please login or register before adding your comments.

Although the administrators and moderators of this website will attempt to keep all objectionable comments off these pages, it is impossible for us to review all messages. All messages express the views of the poster, and neither Crash Media Group nor Crash.Net will be held responsible for the content of any message. We do not vouch for or warrant the accuracy, completeness or usefulness of any message, and are not responsible for the contents of any message. If you find a message objectionable, please contact us and inform us of the problem or use the [report] function next to the offending post. Any message that does not conform with the policy of this service can be edited or removed with immediate effect.

© 1999 - 2016 Crash Media Group

The total or partial reproduction of text, photographs or illustrations is not permitted in any form.