Baku gamble: Set up and standing waves

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Video simulations or not, there are always unknowns when travelling to a new circuit and Baku is a brand new track that will host this weekend’s European Grand Prix. How much downforce will a car need, when and where will it need it? That long, long straight betrays the concept of a Monaco Street circuit and yet there is a tightened section that would be akin to the streets of the Monte Carlo track.

A new tarmac in some places with differing abrasion leaves and this place Pirelli in much the same position as the teams with a new circuit. One of the concerns is the same issue that, according to Motorsport, left Sebastian Vettel with a blown tire at Spa—tire standing waves.

Pirelli boss, Paul Hembery, said:

“Long straights can create standing wave issues,” Hembery said. “It seems to be a circuit that shouldn’t be too dramatic, but it has that straight, so we have to be very careful on that in terms of what’s going on with the standing wave management.

“If you go to a new circuit, it can throw up some surprises. The tendency to new circuits in recent years is smooth surfaces with very low levels of wear, but there is quite an aggressive straight and standing wave is something we have to manage, so there is an aspect of tyre integrity that we have to monitor well.”

The article is certainly interesting as, to be completely honest, I had not heard that a tire standing wave was Vettel’s issue and the article doesn’t explain much about what this condition is.

If a vehicle’s speed exceeds a certain ‘critical velocity’, intensive flexural waves travelling around the circumference of the tire can emerge from the trailing edge of the contact patch. To the observer these waves in the tire appear to be stationary. Here is a quick video that shows a similar, if not dramatic, version of it:

The long straight is certainly a concern in Baku for this type of issue but if the teams dial in a lot of downforce tactically believing that more speed can be gained through the twisty bits rather than the long straight, the critical speed may not be achieved. I guess all that depends on how the cars are set up.

Hat Tip: Motorsport

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7 Comments on "Baku gamble: Set up and standing waves"

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J. Doug Patterson
Editor

Harmonic resonance is a bad thing. Just ask the residents of Tacoma, WA about that beautiful suspension bridge they used to have. The problem with trying to solve a resonance problem is that when you eliminate one specific frequency, you may create issues at other frequencies. They’ll have to find some way to increase the internal damping characteristics of the tire, but that could also lead to unintended thermal issues.

MIE
Editor

With the gear ratios fixed for the season, aee teams really going to be going any faster than they did in China? Therefore haven’t they already addressed this issue.

J. Doug Patterson
Editor

There’s more to it than speed, although that’s a significant factor. Also at play are the damper settings, spring rates, and wing angles as they affect the magnitude and, more importantly, the frequency of the forces being applied to the tire. Mechanical resonances such as this are complex things, and frequently you cannot isolate it to a singular input.

Joe Mama
Guest
Joe Mama
I don’t know that this is necessarily a harmonic resonance issue. The standing wave itself is just an elastic response to the loading of the wheel against the ground, it travels up the back of the tire because the speed of rotation pulls the tire around faster than the rubber (simplified) can respond. Multiple waves that get smaller indicate damped oscillation. Harmonic resonance is indicated by growing wave amplitude due to insufficient damping and an input that adds energy to each wave, usually resulting in a rapid, dramatic ending. I’m guessing here, but I suspect the basic issue with the… Read more »
Peter Riva
Member
Peter Riva

Great video, drag racers know this phenomenon. Someone should ask those experts.

mini696
Member

Thats scary.

longshot
Guest
longshot

I thought Pirelli were adamant that Vettel’s blowout was caused by debris, and not any kind of flaw with their tyres?