Are inerter dampers still allowed in F1?

[Xwang]

I was sure they were banned, but today I've read on Racecar Engineering (September 2020 issue) an article regarding inerters and at a point it says that "Formula 1's new rules forbid them from 2022, as do the FIA's hypercar regulations that will start in 2021".
The article explains that there are two types of inertes the mechanical ones and the ones which use the displacement of a heavy fluid to obtain the same results.
I think that at the moment only the mechanical ones have been outlawed in F1. Is it so? If yes do you know if someone uses the fluid inerters in F1 at the moment (I will bet Mercedes and Red Bull at least)?

[PhillipM]

Mass dampers are banned, inerters are not. Every single team runs them.

[Xwang]

Mass dampers are banned, inerters are not. Every single team runs them.

I thought that mass damper and inerter were the same thing.

[henry]

They’re not the same thing. The inerter is attached to the suspension and is driven actively by it. A mass damper is connected to the chassis and moves passively.

They are both intended to control,indirectly, the relatively undamped vibrations of the tyres.

Mass dampers are banned now,inerters will be banned in 2022 when, in theory, the 18” tyres will be stiffer and more intrinsically damped.

[Xwang]

They’re not the same thing. The inerter is attached to the suspension and is driven actively by it. A mass damper is connected to the chassis and moves passively.

They are both intended to control,indirectly, the relatively undamped vibrations of the tyres.

Mass dampers are banned now,inerters will be banned in 2022 when, in theory, the 18” tyres will be stuffer and more intrinsically damped.

Thank you. It's true that you never stop learning.

[Greg Locock]

mathematically, a mass damper is something like m.D^2.x1=k.(x1-x2)=F (I think) where D is the differential operator, and an inerter is F=m.D^2(x1-x2)

where x1 and x2 are the ends of the inerter

[63l8qrrfy6]

Is the implication that with an inerter there is no fixed natural frequency ?
So whenever the system would resonate, the acceleration across the inerter would increase the load adding to the effective (apparent) mass and decreasing the natural frequency ?

On a second thought no it won't, it would just increase the apparent mass of the wheel by a fixed amount and lower it's natural frequency a bit.

Is that the whole point of inerters?

[henry]

Here’s a paper by Prof Smith who developed the inerter as a solution to vibration control problems.

http://www-control.eng.cam.ac.uk/foswi ... ol_859.pdf

And a useful post on this forum by @DaveW From 2012.

https://www.f1technical.net/forum/view ... 82#p331682

In a good damper (with a correctly sized & loaded reservoir) the gas spring force of a non-through rod damper should constant, and equal to the charge pressure multiplied by the rod area. It acts exactly like preloading a spring, and has (or should have) no impact on the dynamic behaviour on the suspension.

An inerter acts (normally) directly across the damper. It generates a force proportional to its "equivalent mass" times the acceleration on one end of the damper relative to the other. In a similar way, a (coil over) spring generates a change in force proportional to the displacement of one end of the damper relative to the other, and an ideal damper generates a change in force proportional to the velocity of one end of the damper relative to the other.

Hence a suspension transfer function, comprising spring stiffness K, inerter equivalent mass M, and a damper strength C, can be written

,

where Omega is the frequency, and I is the square root of -1.

This demonstrates that an inerter acts to reduce the dynamic spring rate at low frequencies. It has a number of other characteristics, useful or otherwise, & interesting things start to happen when the dynamic spring stiffness becomes less than zero...

[Tim.Wright]

Is the implication that with an inerter there is no fixed natural frequency ?
So whenever the system would resonate, the acceleration across the inerter would increase the load adding to the effective (apparent) mass and decreasing the natural frequency ?

On a second thought no it won't, it would just increase the apparent mass of the wheel by a fixed amount and lower it's natural frequency a bit.

Is that the whole point of inerters?

There is no natural frequency for an inerter, but there is also no natural frequency for a spring until it's connected to a mass.

Correct that it simply increases the effective unsprung mass. It's a reflected inertia type problem where the additional unsprung mass is equal to the rotational inertia of the inerter rotor multiplied by the square of it's motion ratio.

[63l8qrrfy6]

I should have been more specific, I was refering to a typical configuration where the inerter connects to a mass in parallel with a spring.

Is that how it is used in practice - in parallel with the spring and the damper?

So then the advantage is that it can increase the effective inertia (flywheel inertia times motion ratio squared) for a very small increase in "real" mass?

Edit:
Must have missed henry's post which seems to answer my question - the inerter does reduce the natural frequency of a system. The post explains this as an effective reduction in spring rate while I saw it as an increase in effective mass.

The inerter force is proportional to the relative acceleration across he inerter terminals so it will be 180 degrees out of phase with the spring force hence the minus sign which DaveW interprets as an effective reduction in spring rate.

[henry]

Here’s what the 2022 regs think the teams can do without.

10.2.6 On each axle, the state of its suspension system must be uniquely defined by the rotation, and angular velocity of its two rockers. Inertial and hysteresis effects are acceptable provided they are incidental.
In addition, the following systems or configurations are not permitted:
a. Any response of the suspension elements to body accelerations and/or angular acceleration of the rockers (e.g. any inerters, mass dampers, acceleration-sensitive valves in the dampers).

I wonder if the 2022 cars will lose a lot of the ability to ride the kerbs that is such a feature of current cars?

[Cold Fussion]

What is the FIA's justification for banning inerters for 2022?

[thisisatest]

My understanding is that the use of inerters is driven mainly by the tires with tall, soft sidewalls. Their lower natural frequency (for a tire) approaches the relatively high frequency (for a car) of the suspension, kind of meeting in the middle.
With the introduction of 18in wheels and tires, the need for inerters should be greatly reduced anyway.

[Hoffman900]

My understanding is that the use of inerters is driven mainly by the tires with tall, soft sidewalls. Their lower natural frequency (for a tire) approaches the relatively high frequency (for a car) of the suspension, kind of meeting in the middle.
With the introduction of 18in wheels and tires, the need for inerters should be greatly reduced anyway.

Same.

They’re used in the rear shocks in Pro Stock and Pro Mod drag race cars... they are great in that application.

[BROW]

There is no natural frequency for an inerter, but there is also no natural frequency for a spring until it's connected to a mass.

Correct that it simply increases the effective unsprung mass. It's a reflected inertia type problem where the additional unsprung mass is equal to the rotational inertia of the inerter rotor multiplied by the square of it's motion ratio.

How does increasing the effective unsprung mass effect the whole system, what benefit does it bring? And is this a secondary effect to what DaveW mentioned, where the effective spring rate changes with frequency?