Tech Highlights: Mercedes/Red Bull ‘energy recovery’ suspension

If you haven’t heard already, F1 is set to ban the hydraulic heave springs that many teams (notably Mercedes) have been playing with over the past 12-15 months. Although it is not an official ban as yet, a technical directive has been issued to the teams addressing the claims that Ferrari raised in a recent letter to the FIA. Ferrari claims that the component can be classed under the ‘moveable aerodynamics’ catch-all phrase in the regulations, and although it has been discussed in great length over the year it is only now that the Scuderia have chosen to make a formal move against the competition. In this blog post we will aim to cover what the hydraulic heave element does and why a ban at this stage of the 2017 developments could have an impact on the pecking order.

What is the heave or third element of the suspension?

An F1 car’s suspension is composed of a pair of push/pullrods connected to rockers, matched with a damper and a torsion bar that acts as a spring – a conventional spring is too large to fit into the crammed front bulkhead and gearbox case that house the front and rear suspensions respectively. An anti-roll bar is also fitted across the two rockers to prevent over-compression/extension of the damper.

The heave/third suspension element is a type of spring-damper that sits horizontally between the rockers and is used to control the vertical displacement of the car, which occurs when braking, and oscillations that would normally disturb the tyre’s contact patch.

How has its role been expanded over recent years?

Heaveelement

Since the back end of 2015 there has been increased activity in this region of the car. Normally an inerter (or J-damper) has been used in conjunction with a coil spring of some sort. However it was noted during the 2015 Brazilian GP weekend that Mercedes had changed the inerter-spring combination for a more complex hydraulic unit. This hydraulic spring has been installed on the W07 since the very beginning of 2016 and other teams, notably Red Bull, have been fairly secretive over their own suspension layout recently.

If you kept up with the technical developments in 2016, you may have noticed that there was, well, a lack of them in general across the grid. The regulations had matured in the eight years since their introduction and performance gains were getting harder to come by, particularly from a purely aerodynamic perspective. This is quite troublesome in a formula where aerodynamics are the main performance differentiator. What if there were a way to use the mechanical package to optimise the aerodynamic platform and extract more pace?

What have Mercedes been using the hydraulic element for?

Mercedes had an especially quiet year on the technical front. From memory, the only real aerodynamic developments I remember them introducing were the multi-element bargeboards at the beginning of the year and the open-ended rear wing endplate louvres around mid-season. And yet you could argue the W07 was the best car they have ever produced despite it being a clear evolution of the previous car – had it not been for Hamilton and Rosberg’s infamous collision in Spain and Hamilton’s engine failure in Malaysia it would have been a Mercedes whitewash in 2016.

FRIC

Aside from stepping up their aero performance over the past four or five years, the Silver Arrows have also been at the forefront of suspension technology. It has been well documented how advanced the W05’s FRIC (front-rear interconnected) suspension was before it was thrown out mid-2014 (which you can read about in mine and Matt Somerfield‘s detailed technical analysis of the car here) – it allowed for softer springs to comply with kerbs and improve traction whilst maintaining good stiffness at high speed to increase responsiveness and maintain ride height.

Since the loss of FRIC F1 teams have been looking for ways to replace the system. Such mechanical advantages allow the development of more complex aero packages that give the driver a perfectly balanced car for every cornering situation, which in turn helps look after the tyres during longer stints.

In early 2016 the hydraulic reservoir that was familiar with the use of FRIC was spotted in the sidepod of various cars, and it transpired to be connected to the heave element (rather than dual-chamber dampers used with FRIC) of the front suspension. The front-to-rear connection may have been broken but knowledge on using a larger reservoir to control damping had not been forgotten.

ersuspension

The illustration describes the system above: the hydraulic spring is normally found at the front of the sidepod just under the intake (unlike what my drawing is, I know!) and the green hydraulic line is plumbed into the yellow heave element between the rockers. Once this was discovered the initial conclusion was that it was a very sophisticated way of controlling dive under braking, especially in a trail-braking situation where the car is loading up on one side at the same time – this type of motion is sometimes referred to as warp.

As it turns out, and perhaps we shouldn’t be surprised because it is F1 afterall, the hydraulic reservoir supposedly acts as an energy store that can release pressure over time to expand the heave spring. This would be extremely useful for running lower front ride height as when the car compresses under downforce the spring could provide an opposing force to keep the undertray at a desired level to maximise the aerodynamics. It would also prevent the floor from striking the ground, which can stall the airflow as well as lead to excessive plank wear.

What have Red Bull been doing with it?

Rather than focusing on controlling front ride height, Red Bull have allegedly been doing the opposite. Their high rake aero concept that has brought them such success over the years increases the the car’s frontal profile as it cuts through the air and with that comes a drag penalty.

A common way to decrease drag is to reduce wing angle, but if you are Red Bull that is not what you do! Rather than compromise the rear aerodynamics the rear heave element could be ‘de-pressurised’ once a certain load is surpassed. In essence, rather than ramping up and rebounding the suspension like Mercedes have done, the back end of the car slumps down at maybe 180mph or so to reduce the effective wing angle and boost top speed. This would explain why we have seen the return of the ludicrous rake angle not seen since the RB9 of 2013.

Conclusions

This blog post might not be entirely accurate but it does have substance. This trick suspension has been used in the past (I’m told NASCAR have been doing it a while) but through simpler methods, such as high speed compression and rebound adjustment of the dampers, rather than a coupled hydraulic system. I ride mountain bikes and a similar scenario is to ramp up the suspension towards the end of its travel to support you when cornering heavily/landing a jump using volume spacers or adjusting the damper’s high speed compression and reducing rebound. However these changes present compromises in other situations where the car/bike are loaded, whereas the F1 systems are able to cope with virtually any cornering scenario thanks to precision engineering.

Is it a moveable aero device? It has been deemed so, and I think Ferrari/FIA are right. Could it affect the 2017 pecking order? Possibly not, although it could bring the cars closer together in that Mercedes, Red Bull and possibly other teams that planned to fully exploit this technology have been weakened. As ever in Formula 1, though, they will find ways to achieve the same effect ‘legally’ again in the near future…

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5 thoughts on “Tech Highlights: Mercedes/Red Bull ‘energy recovery’ suspension

  1. fidelecastor

    in few words, this third element oppose résistance to equal presure R/L applied to the front part of the chassi and do a fluid circulation in case of differenciated resistance of main choc absorbers elements R/L … the hight presure third element is resisting to vertical aero force and make free the suspension absorption on each wheel with a free of pressure hydraulic balance R/L …
    Is it really different than an anti roll bar who maintain an horizontal asset ?

    Reply
      1. fidelecastor

        Right, it act to maintain a favorable level of the chassis from the ground, and makes suspension working out of aero presure … this is realy a suspension element, not aero one … whatever it act for a stable car asset

      2. thewptformula Post author

        I think the letter Ferrari issued was aimed more towards Red Bull than Mercedes in that they are dropping the rear to decrease drag. Mercedes have exploited it in a way that it could be classed as a stability assist rather than aero assist.

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