Ask MO: How Are Mass Dampers Used on a Motorcycle?

John Burns
by John Burns

Dear MOby,

I was reading an article on Ducati’s recent success in Moto GP, and it mentioned that Duc was the first manufacturer to use mass dampers. How are mass dampers used in motorcycles?

Kenneth Moore

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Dear Kenneth,

We had to interrupt MV Agusta Technical Director Brian Gillen’s holiday in Malta to answer this one. He says:

“Mass Dampers appeared for the first time in racing in Formula 1 at the Monza GP in 2005, with Renault, and went for the most part completely overlooked by the rest of the paddock. That soon changed as it became clear that this system was an integral part of Renault’s dominance, and as a result mass dampers were subsequently banned by the FIA after the French GP in 2006.

“What is a mass damper? An often overlooked part of the suspension system is the tire, which acts as an “underdamped” component and is not part of the suspended mass of the motorcycle. When the tire encounters a bump it responds similarly to a basketball bouncing, with the final effect of reduced grip. The mass damper is a weight (disk) suspended in a cylinder between two springs with different spring constants positioned with the stroke axis parallel to the direction that the system needs to be damped.

Illustration by Rswarbrick at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=40435208

“How it works: Imagine dropping a basketball on the ground, with the result that it keeps bouncing slightly less with each bounce until it comes to a rest. That’s your tire. Now, if the basketball had a mass damper inside (calculations and tests required to tune the system), the ball when dropped would effectively remain glued to the ground with only a few small bounces.

“Why was it a major advantage in F1 cars and not currently used on motorcycles other than in some tests (Ducati…)? F1 cars primarily use aerodynamic downforce to generate grip, and the mass damper helps attenuate tire vibration, translating that aero load into grip.

“With motorcycles the dynamics are different; motorcycles use both bike and rider weight transfer to generate grip. F1 cars are tuned to have minimum amounts of pitch and roll, where motorcycles rely on pitch and roll to brake, accelerate and turn. For this reason, the application of a mass damper on a motorcycle is very complex, as its functional envelope is limited to the vertical direction of the mass axis. With current GP bikes exceeding 60 degrees of lean angle, it’s difficult to decide when and where on a racetrack you could optimize its function, where everywhere else it would simply be moving ballast. On a bike, a mass damper is an attempt at a simple solution to a very complex problem.

“There isn’t any visible evidence that they [Ducati] are currently using a mass damper system on the race bikes, and all of the photos of the test bikes are from a while ago. That said, I don’t believe the idea has been completely abandoned and I would not be surprised to see it make an appearance on the front end of the bike in the near future.

“Great race today [ British MotoGP] and another step towards the Italian holy grail of achievements… Italian bike winning the championship with an Italian rider!”

Thanks, Brian!

PS: There’s a great story here by Mat Oxley, re. pre-season Ducati “jounce damper” testing if you haven’t already seen it.

Send your moto-related questions to AskMOAnything@motorcycle.com. If we can’t answer them, we’ll at least make you feel temporarily better by thinking you’re talking to somebody who knows what they’re talking about even if we don’t. It’s the thought that counts.

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John Burns
John Burns

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  • Donnie Donnie on Aug 29, 2017

    Hmm, I wonder if they could use some sort of gyroscopically controlled mechanism to help out at varying lean angles? Gotta think on this one.

    • See 4 previous
    • Born to Ride Born to Ride on Aug 30, 2017

      Well, you had previously said a magnetically controlled counterweight that could move a significant mass to change the weight bias under acceleration and braking. Such a system would be impossible to implement for a few reasons. For one, the generation of enough electrical current to power induction coils capable of moving a large mass of ferrous alloy, presumably steel, would vastly exceed what the charging system on a motoGP bike produces. Furthermore, it would have to work doubly hard because you are trying to resist its natural kinetic energy. Let's say you have a 20lb pound chunk of steel on a rail 18-24" long, and there was magically no packaging concerns fitting that into the dimensions of a racebike. You fit an induction coil that has the juice to move said steel on that rail. Now, you want to throw it to the back of the bike while braking from 220mph to 40 mph into turn one at Mugello. That bike is decelerating way harder than 1g, maybe even as much as 2gs. Now your 20lb weight applies 40lbs against the direction of the magnetic field. So the load on the system is magnified exponentially and the required current to move the weight skyrockets. So in summary, the system would have to be massive and draw far more electrical power than is possible to produce on a motoGP Bike in order to create a quantifiable effect on the center of gravity. Plus the control system would have to be extremely sophisticated to keep moving the weight to the optimal position on its track. Cool idea though.

  • Meaty Midrange Meaty Midrange on Aug 30, 2017

    Wow...thats quite a complex system. I won't pretend to fully understand all of it, but I can see how much harder implementing the concept on a bike would be vs. a car. Thanks for the info!

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