Toro Rosso have released a youtube video of a complete factory tour. Both informative and in depth, the video shows us some detail of the car we do not usually get to see.
Whenever an F1 car runs on track, the team will have planned what parts are fitted and the set up of every facet of the car. Now over a year and a half old and with an even older car, this set up sheet appeared on the Lotus Media site. It was from Kimi Raikkonen’s debut test at Jerez for the team in a R30 (from 2011). It shows some of the set up detail that the teams go into. This also gives us some insight into the spring\damper configuration modern F1 cars run.
With far reaching regulation changes coming onto the sport in 2014, the 2013 season is likely to be a year of consolidation, as few changes have been are written into this year’s rule book. So teams will be expected to optimise their designs from last year, correcting mistakes and adopting some of the better ideas of their rivals.
Some rules will have a small effect of car design and some trends from last year will be more common place. Unusually there have been few leaks or well-founded rumours circulating in the off season. This is probably as teams are expending a huge amount of resources in finding big gains for just one year’s competition, instead focussing on plans for 2014.
With the shift toward pull rod rear suspension, the teams’ mechanics are faced with a maintenance issue. As the pull rod reaches down into the gearbox casing, access to the transmission is hindered by the inboard suspension inside the gear casing. Most teams maintain their transmission by first having to remove parts of the inboard suspension. However the Ferrari engined teams have each found a neater solution to this problem. Sauber use the Ferrari gearbox and also follow a similar practice of using a separate module to mount the entire inboard suspension in between the engine and gearbox.
For 2012 we will have a raft of rules changes that will alter the look and performance of the car. For most of the new cars, we will immediately see the impact of the lower nose regulations. Then the big story of 2010-2011 of exhaust blown diffusers (EBDs) comes to an end with stringent exhaust placement rules and a further restriction on blown engine mappings.
Even without rule changes the pace of development marches on, as teams converge of a similar set of ideas to get the most from the car. This year, Rake, Front wings and clever suspensions will be the emerging trends. Sidepods will also be a big differentiator, as teams move the sidepod around to gain the best airflow to the rear of the car. There will also be the adoption of new structural solutions aimed to save weight and improve aero.
Last of all there might be the unexpected technical development, the ‘silver bullet’, the one idea we didn’t see coming. We’ve had the double diffuser and F-Duct in recent years, while exhaust blown diffusers have thrown up some new development directions. What idea it will be this year, is hard, if not impossible to predict. If not something completely new, then most likely an aggressive variation of the exhaust, sidepod or suspension ideas discussed below.
The most obvious rule change for 2012 is the lowering of the front of the nose cone. In recent years teams have tried to raise the entire front of the car in order to drive more airflow over the vanes and bargeboards below the nose. The cross section of the front bulkhead is defined by the FIA (275mm high & 300mm wide), but teams have exploited the radiuses that are allowed to be applied to the chassis edges, in order to make the entire cross section smaller. Both of these aims are obviously to drive better aero performance, despite the higher centre of Gravity (CofG) being a small a handicap, the better aero overcomes this to improve lap times.
A safety issue around these higher noses is that they were becoming higher than the mandatory head protection around the cockpit, in some areas this is as low as 55cm. It was possible that a high nose tip could easily pass over this area and strike the driver.
So now the area ahead of the front bulkhead must be lower than 55cm. However the monocoque behind this area can remain as high as 62.5cm. Thus in order to strive to retain the aero gains teams will keep a high chassis and then have the nose cone flattened up against this 55cm maximum height. Thus we will see these platypus noses, wide and flat in order to keep the area beneath deformable structure clear for better airflow. The radiussed chassis sides are still allowed so we will also see this 7.5cm step merged into the humps a top of the chassis.
Areas below and behind the nose are not allowed to have bodywork (shown yellow in the diagram), so small but aggressive vanes will have to be used, or a McLaren style snowplough. Both these devices drive airflow towards the leading edge of the underfloor for better diffuser performance.
Having used the engine via the exhausts to drive aerodynamic performance for the past two years, exhaust blown diffusers will be effectively banned in 2012. The exhausts must now sit in small allowable area, too high and far forward to direct the exhausts towards the diffuser. The exhausts must feature just two exits and no other openings in or out are allowed. The final 10cm of the exhaust must point rearwards and slightly up (between 10-30 degrees). Allied to the exhaust position, the system of using the engine to continue driving exhaust when the driver is off the throttle pedal has also been outlawed. Last year teams kept the engine throttles opened even when the driver lifted off the throttle for a corner. Then either allowing air to pass through the engine (cold blowing) or igniting some fuel along the way (hot blowing). The exhaust flow would remain a large proportion of the flow used when on the throttle, thus the engine was driving the aero, even when the driver wasn’t needing engine power. Now the throttle pedal position must map more closely the actual engine throttle position, thus if the driver is off the throttle pedal, then the engine throttles must be correspondingly closed.
Teams will be faced with the obvious choice of blowing the exhausts upwards towards the rear wing, to gain a small aerodynamic advantage, when the driver is on the throttle. These Blown Rear Wings (BRWs) will be the conservative solution and certainly will be the first solution used in testing.
However, it’s possible to be aggressive with these exhaust designs too. One idea is blowing the rear wing with a much higher exhaust outlet; this would blow tangentially athte wing profile, which is more effective at increasing the flow under the wing for more downforce. Packaging these high exhausts may cause more problems than gains. But last year’s exhausts passing low and wide across the floor suffered a similar issue, but proved to be the optimum solution.
Even more aggressive solution would be directing the exhausts onto the vanes allowed around the rear brake ducts. If avoiding the brake cooling inlet snorkel, the fast moving exhaust gas would produce downforce directly at the wheel, which is more efficient than wings mounted to the sprung part of the chassis. However the issue here would be the solution is likely to be so effective, that it will be sensitive to throttle position and rear ride height. If these issues can be engineered out, then this is an attractive solution.
Wing ride height and Rake
With rules setting a high front wing ride height and small diffusers, aero performance is limited. So teams have worked out how to work around these rules by angling the entire car into a nose down attitude. This is known as ‘Rake’, teams will run several degrees of rake to get the front wing lower and increase the effective height of the diffuser exit. Thus the front wing will sit closer to the track, than the 75mm when the car is parallel to the ground. While at the rear, the 12.5cm tall diffuser sits an additional 10cm clear of the track, making its expansion ratio greater. Teams were using the EBD, to seal this larger gap between the diffuser and the floor. Without the EBD teams will have to find alternative way to drive airflow into the gap to create a virtual skirt between the diffuser and track.
Furthermore teams have also allowed the front wing to flex downwards at speed to allow it to get closer to the ground, further improving its performance. Although meeting the FIA deflection tests, teams are allowing the wing bend and twist to position the endplate into a better orientation, either for sealing the wing to the ground or directing airflow towards the front tyres wake. Both creating downforce benefits at the front or rear of the car, respectively.
One issue with allowing the wing to ride closer to the ground through rake or flexing, is that at high speed or under braking (when the nose of the car dives), the front wing can be touching the ground. This is bad for both aero and for creating sparks, which will alert the authorities that the wing is not its normal position relative to the chassis. So teams are creating ways to manage front ride height. Traditionally front bump rubbers or heave springs will prevent excessively low ride heights. Also the front suspension geometry runs a degree of geometric anti-dive, to prevent the nose diving under braking.
Last year we saw two additional solutions, interlinked suspension, where hydraulic suspension elements prevent nose dive under braking by displacing fluid in a hydraulic circuit one end of the car to the other end, creating a stiffer front suspension set up. This prevents dive under braking, while keeping a normally soft suspension for better grip.
We have also seen Lotus (nee LRGP) use torque reaction from the front brake callipers to extend the pushrod under braking, creating an anti-dive effect and prevent the nose dipping under braking.
These and probably other solutions will be seen in 2012 to maintain the ideal ride height under all conditions.
Towards the end of last year, front end aero design was converging into a set of similar ideas. Aside from the flexible wing option, already discussed above. The main direction was the use of a delta shaped threefour element wing, sporting no obvious endplate. The delta shape means that most of the wings downforce is created at the wing tip; this means less energy is taken from the airflow towards the inner span of the wing, which improves airflow at the rear of the car. Also the higher loading near the wing tip creates a stronger vortex, which drives airflow around the front tyre to reduce drag. Three wing elements are used, each being similar in chord length, rather than one large main plane and much smaller flaps. This spaces the slots between the elements out more equally, helping reduce airflow separation under the wing. More slots mean a more aggressive wing angle can be used without stalling. At the steepest outer section of wing, teams will mould a fourth slot in the flap to further manage airflow separation.
First introduced by Brawn in 2009, the endplate-less design is used as it’s more important to drive airflow out wide around the front tyre, than to purely maintain pressure difference above and below the wing. Rules demand a minimum amount of bodywork in this area, so vanes are used to both divert the airflow and meet the surface area regulations. This philosophy has now morphed into the concept, where the wing elements curl down to form the lower part of the endplate. Making the wing a homogenous 3D design, rather than flat wing elements and a separate vertical endplate.
A feature starting to emerge last year was arched sections of wing. Particularly near the mandatory neutral centre 50cm section of wing. These arched sections created elongated vortices, which are stronger and more focussed than tip vortices often used to control airflow. In 2012 many teams will create these unusual curved sections at the wings interface with the centre section.
Above this area, the pylon that mounts to the wing to the nosecone has been exploited to stretch he FIA maximum cross section to form the longest possible pylon. This forms the mounting pylon into endplates either side of the centre section of wing and along with the arched inner wing sections, help create the ideal airflow 25cm from the cars centreline (known as the Y250 axis).
In 2011 Mercedes GP used a section of the frotn wing to link up with the fins on the brake ducts, this created an extra long section of wing. Vanes on the front brake ducts are increasingly influential on front wing performance and front tyre wake.
Mercedes GP also tried an innovative F-Duct front wing last year. This was not driver controlled, but rather speed (pressure) sensitive. Stalling the wing above 250kph, this allowed the flexing wing to unload and flex back upwards at speed, to prevent the wing grounding at speed. But the effect altered the cars balance at high speed, and the drivers reportedly didn’t like the effect on the handling. I’ve heard suggestions that the solution isn’t planned for 2012.
With so much of the car fixed within the regulation, it’s becoming the sidepods that are the main area of freedom for the designers. Last year we saw four main sidepod concepts; Conventional, Red Bull lowtapered, McLaren “U” shape and Toro Rosso’s undercut.
Each design has its own merits, depending on what the designer wants to do with the sidepods volume to get the air where they want it to flow.
This year I believe teams will want to direct as much airflow to the diffuser as possible, Red Bulls tiny sidepod works well in this regard, as does the more compromised Toro Rosso set up. Mclarens “U” pod concept might be compromised with the new exhaust rules and the desire to use a tail funnel cooling exit. However the concept could be retained with either; less of top channel or perhaps a far more aggressive interpretation creating more of an undercut.
Part and parcel of sidepod design is where the designer wants the cooling air to enter and exit the sidepod. To create a narrower tail to the sidepod and to have a continuous line of bodywork from sidepod to the gearbox, the cooling exit is placed above the sidepod, in a funnel formed in the upper part of the engine cover. Most teams have augmented this cooling outlet with small outlets aside the cockpit opening or at the very front of the sidepod.
To let more air into the sidepod, without having to create overly large inlets, teams will commonly use inlets in the roll hoop to feed gearbox or KERS coolers.
Even without the exhaust blowing over the diffuser, its design will be critical in 2012.
As already mentioned the loss of the exhaust blowing will hurt the team’s ability to run high rear ride heights and thus a lot of rake. Unobstructed the EBDs exhaust plume, airflow will want to pass from the high pressure above the floor to the lower pressure beneath it. Equally the airflow blown sideways by the rear tyres (known as tyre squirt) will also interfere with the diffuser flow.
Before EBDs teams used a coved section of floor to pickup and accelerate some airflow from above the floor into the critical area between the diffuser and rear tyre. I predict we will see these shapes and similar devices to be used to keep the diffuser sealed at the sides.
Last year we saw teams aid the diffusers use of pulling air from beneath the car, by adding large flap around its trailing edge. So a high rear impact structure raised clear of the diffusers trailing edge will help teams fit these flaps around its entire periphery. Red Bull came up with a novel ideal by creating a duct feeding airflow to the starter motor hole; this improves airflow in the difficult centre section of the diffuser. Many teams will have this starter motor hole exposed by the raised crash structure, allowing airflow to naturally pass into the hole. However I expect some vanes or ducts to aid the flow in reaching this hole tucked down at the back of the car.
DRS was a new technology last year. We soon saw teams start to converge on a short chord flap and a high mounted hydraulic actuator pod. DRS allows the rear wing flap to open a gap of upto 50mm from the main plane below it. A smaller flap flattens out more completely with this 50mm gap, reducing drag more effectively than a larger flap.
As drag is created largely at the wing tips, I would not be surprised to see tapered flaps that flatten out at the wing tip and retain some downforce in the centre section. Teams may use the Pod for housing the actuators, although Mercedes succeeded with actuators hidden in the endplates. Having the pod above the wing clears the harder working lower surface, thus we will probably not see many support struts obstructing the wing.
Super slim gearboxes have been in vogue for many years, Last year Williams upped the stakes with a super low gearbox. The normally empty structure above the gear cluster was removed and the rear suspension mounted to the rear wing pillar. Williams have this design again for 2012, albeit made somewhat lighter. With the mandatory rear biased weight distribution the weight penalty for this design is not a compromise, while the improved air flow the wing is especially useful in 2012. So it’s likely the new cars will follow the low gearbox and low differential mounting in some form.
A lot is said about Pull rod rear suspension being critical for success. In 2011 only a few teams retained push rod rear suspension (Ferrari and Marussia). I would say the benefits between the two systems are small; pushrod trades a higher CofG for more space and access to the increasingly complex spring and damper hardware. Whereas pull rod benefits from a more aerodynamically compact set up and a lower CofG. I still believe either system works well, if packaged correctly.
At the front it’s unlikely pull rod will be adopted. Largely because the high chassis would place a pull rod at too shallow an angle to work efficiently. Regardless the minimum cross section of the footwell area, discounts any potential aero benefits. Leaving just a small CofG benefit as a driver to adopt this format.
Most teams now use a metal structure to provide strength inside the roll hoop; this allows teams to undercut the roll hoop for better airflow to the rear wing. Even though last year two teams followed Mercedes 2009 blade type roll hoop, for Caterham at least, this isn’t expected to return this year. Leaving the question if Force India will retain this design?
Electronics and control systems
The 2012 technical regulations included a large number of quite complex and specific rules regarding systems controlling the engine, clutch and gearbox. It transpires that these are simply previous technical directives being rolled up into the main package of regulations. Only the aforementioned throttle pedal maps being a new regulation to combat hot and cold blowing.
While I still try to crack that deal to make this my full time job, I do this blog and my twitter feed as an aside to my day job. In the next few weeks I plan to attend the launches and pre-season tests. If you appreciate my work, can I kindly ask you to consider a ‘donation’ to support my travel costs.
Lotus Renault GP (LRGP) have been on one of the teams most innovative with their suspension over the past decade. As RenaultF1 They introduced the Tuned Mass Damper (TMD) back in 2006 and have since raced conventional Inerters. Inerters are a special component in the suspension to counteract spring effect of the TyresSuspension, using a spinning mass on a threaded rod to control these loads.
LRGP have also been one of the teams racing hydraulically interlinked suspension and have looked at other ways to legally alter the suspensions performance. It seems this work has lead to the discovery of a new form of Inerter, primarily using fluid for the Inerter effect. This new development has been termed by the team a “Fluid Inerter”.
The intellectual property rights to this development have been safeguarded by Patent, allowing the details to be freely accessible in the pubic domain (the source for the picture at the top of this article). My attention was drawn to this development by Italian Mechanical Engineer Rodolfo De Vita, a specialist in Torsional Dampers and Dual Mass Flywheels (DMF).
Becoming ever more complex the suspension in an F1 car has a number of devices to counter loads fed into the chassis, in order to maintain the ideal conditions at the tyre contact patch. We understand the role of springs and dampers, but there remain other spring effects within the suspension system, not least from the high profile tyres. Their spring effect goes undamped and hence is largely out of the control of the teams in setting up the car. Being able to counteract these uncontrolled forces in a suspension will allow the tyre to main better contact with the ground for more consistent grip. In 2003 Cambridge Universities, Dr Malcolm Smith proposed a mechanical method of controlling these loads via the Inerter. McLaren took up this idea and tested the idea in 2004 then went on to race an Inerter in 2005.
In size and construction the Inerter looks like any other damper. Being placed in the same position as a Heave Damper it was well hidden and unknown to most people. Until the “Spygate” saga in 2007, when the design was referenced as both the “J-Damper” and “a Damper with a Spinning Mass”. It wasn’t until May 2008 that I was able to understand and expose the details of the Inerter concept, publishing its details in Autosport.com (subscribers only http://www.autosport.com/journal/article.php/id/1554 ). Co-incidentally this article is cited in the patent documentation!
An Inerter can be configured in two ways: a linear and a rotary format. In both guises the device uses a toothed drive to spin a mass. Likened to the same effect as a bicycle bell, the load fed into the bells lever is dissipated by the spinning element. In F1 teams use a cylindrical mass screwed onto a threaded rod inside a damper body. One end of the rod is affixed to one side of the suspension and the damper body to the other side of the suspension. Reacting to the acceleration of the suspension, the Inerter absorbs the loads that would otherwise not be controlled by the velocity sensitive conventional dampers.
The Inerter predates Renaults TMD, which aimed to achieve the same effect. With the TMD a weight is suspended on spring to offset the same forces being fed into the chassis as the Inerter. Renault first raced the TMD in 2005, its discovery by Giorgio Piola around Monaco of that year; both forced a development race and an enquiry by the FIA. It was subsequently banned on what proved to be false grounds. The FIA citing a movable aerodynamic effect as the reason for its ban.
Unaware of its effect on the contact patch, I initially saw the device as a means to prevent the front wing pitching downwards when braking. The inertia of the suspended mass keeping the nose from pitching downwards during the initial braking phase. This I thought would prevent the car from being pitch sensitive. Despite a lengthy court room case, this “aero” function was upheld as the reason for the ban of the device.
Ironically the McLaren was using the Inerter at the time, and despite it being used for the same function was not banned and remains legal and in universal use to this day.
LRGP’s Fluid Inerter Concept
Reading the detail of the LRGP patent, it’s clear this was at least partly a surprise discovery. The Patent states the discovery was “based on lab testing of another hydraulic suspension device”, when it was found that the effect of the fluid within the system “has a very significant inertia effect”.
I would suspect this discovery was made during the development of the linked suspension system. Where fluid lines are used to link the suspension in a similar manner to the Mercedes system I detailed earlier this year (http://scarbsf1.wordpress.com/2011/10/17/mercedes-innovative-linked-rear-suspension/). Perhaps the longer fluid lines to link front and rear suspension provided the discovery, rather than the very short left to right linking pipework. I understand Renault have had hydraulically linked suspension on the car since at least 2009.
With this insight LRGP have proposed a Fluid Inerter using both the inertia of the fluid and a spinning mass. By making the Inerter device more like a damper, where by a damper rod displaces fluid; this fluid is then piped into a circuit to spin the mass. There by both effects can be created. It is the inertance of the fluid that differentiates the LRGP patent to the conventional Inerter proposed by Dr Malcolm Smith.
Inertance is a new term and I’ll quote the patent for LRGP’s explanation of the effect.
“Hydraulic fluid inertance means” concerns an arrangement in which the presence of a hydraulic fluid provides an inertance, where inertance is a measure of the fluid pressure which is required to bring about a change in fluid flow rate in a system. Between the terminals this translates to an inertial force which resists acceleration.
LRGP found that the fluid used was critical to the efficiency of the design. In particular to make it effective for the lightweight and small packaging volume required to make the device work within the tight confines of an F1 footwell or gearbox. Needing to be incompressible and low viscosity, they have proposed several fluids, such as water and oil, but the preference appears to be for Mercury. Although a metal, it’s liquid at ambient temperatures and very dense. This means smaller fluid lines filled with mercury will provide the necessary inertance, compared to larger amounts of less dense fluids. Passing from one chamber in the damper body via the fluid line to the other chamber, the detail design of the length and diameter of the fluid lines are key in creating the correct tuned inertance effect. Just “1 to 50g” of fluid is required to get the desired effect. The range of inertial reaction is quoted as “10 to 500kg, which is a typical range required in Formula One racing cars”.
As a side note McLaren decouple this inertial reaction force into different measured units. Rather than Kg of Inertial force, McLaren use the term “Zog”, this allows them to hide the actual units set up on their Inerter.
Renault suggests winding the lines around the damper body as one solution for the packaging of the fluid circuit. Additionally a valve or shim stack in the damper rod would also alter the amount of fluid displaced, to further tailor the Inerters effect.
With Mercury having a high coefficient of thermal expansion, the patent suggests using a relief valve emptying into another chamber is used to ensure the system has a constant volume of fluid.
Clearly the emphasis is on the fluid to provide the inertance effect, the patent citing a minimum 50%, up to as much as 90% of the inertance coming from the fluid.
Not only does the Patent contain the conceptual information on the Inerter, but also detailed cross sections. I have simplified these to explain the Inerters construction. LRGP have been able to condense the entire solution into a single self contained component, which fits into the same volume as the conventional Inerter.
The device is made up of a main body and a damper rod. The main body split into left and right sections bolted together. The left hand casing forms the cylinder, not only contains the fluid, but also channels machined in the outer casing form the fluid lines. Such that no external pipework is required. The right hand casing allows the damper rod to pass through and also houses bump stops to prevent the device bottoming at the end of its 16mm of bump travel or 23mm of droop travel. In total the device is just 220mm long (eye to eye).
In cross section we can see the casing is a complex machined part. With the right hand chamber formed with bushes, seals and endplates to create the cylinder for the damper rods to pass through. The damper rod along with its shim stack valve pass through the cylinder like piston as the suspension compresses and rebounds. The mercury within is displaced and passes through channels into the channels machined into the wall of the body.
LRGP provide a diagram for the Inerters mounting. This being a typical position between the pushrod rockers. No doubt a similar mounting is found between the rear pull rod rockers. Externally it would be hard distinguish the Fluid Inerter from a Mechanical version. Albeit the Renault front bulkhead design shows almost nothing of the Inerter inside the footwell. The steering rack and anti roll bar getting in the way of the small aperture inside the front of the monocoque. Thus we cannot be clear if the device has raced.
One benefit is the technology is proprietary to LRGP and not used under license via Penske or Dr Malcolm Smith. Thus LRGP are free to use and develop this technology freely.
I couldn’t state whether the Fluid Inerter has any compliance benefits over a mechanical one. Perhaps it’s easier to tune via the shim stack in the damper rod, rather than the fixed specification of the mechanical Inerter. Equally it may be easier to maintain, teams needing to strip clean and re-grease their Mechanical Inerters frequently to maintain their smooth operation.
It seems one advantage to this device might be lightweight. The tiny amount of fluid required would be lighter than an equivalent spinning mass. As Inerters tend to be mounted relatively high a weight saving will aid CofG height, as well as ballast placement.
One negative issue is that Mercury is a hazardous material. Considering the unit is positioned ahead of the driver’s legs, any mercury leakage as a result of a major accident will only complicate the health issues for the Driver and Marshalls. I am not aware of Mercury being specifically restricted by the FIA approved material list. Although with just a few CC’s of the liquid contained within the cylinder, this might not be regarded as an issue by the FIA.
However the team came across this solution, it is a new direction for Inerter development. The solution is totally legal, as set by the precedent of the mechanical Inerter being allowed to race, even when the TMD wasn’t
It will be interesting other teams come forward with new Inerter or linked suspension solutions. The only problem is few teams patent their design to allow us such insight to their design.
More references on Inerters
The Rotary damper has been an innovation that has recently come and gone in F1. Typically F1 cars use Lineartelescopic dampers. However, in 2003 Sachs Race Engineering developed a Rotary version of a classic monotube damper for Ferrari. This was a tidier solution for packaging the dampers at the rear of the car. Since 2003 several teams have used Rotary dampers, Toyota, Midland and most notably Brawn GP. Who won the 2009 championship with these fitted at the rear of the car. I have recently come across a Rotary damper as fitted to the Midland car in 2006 and thus we have the chance to look into the detail of this development. I’ve also been in touch with two of the designers who have raced this device and they have given us some unique insight into its use.
Firstly John McQuilliam, who is now Designer for Marussia, but back in 2006, was the designer for Midland F1 (previously Jordan, latterly Spyker and Force India). The Midland M16 was the first of the teams’ cars to exploit Rotary dampers, as McQuilliam explains “I remember we were working with Sachs, as we had their Clutches on the car at the time. The Ferrari had Rotary dampers and it looked to be such a neat installation, we wanted to do something similar “. But this was not a total success, as their use on the Midland was short lived as they were replaced mid season with Linear dampers.
Secondly we have insight from the ex-Brawn Designer Jorg Zander, now running his own consultancy (http://jz-engineering.com/). As Honda were leaving F1 and the Brawn GP team was created, due to the Honda link the team had been using Japanese Showa dampers, but Zander was persuaded to switch to a Rotary design. As Zander recalls “Showa did a brilliant job and they would have provided us with continued support, but my boss was keen to go down the Rotary damper path with Sachs”. He adds that “the car still won the championship!”. Along with the Ferrari wins during their use of the Sachs Rotary damper, it’s clear that the technology has had a lot of success in F1. But it is still blighted by a reputation of being a troublesome technology.
A conventional Linear damper is made up from a cylindrical body in which a damper rod slides in and out of (much like a bicycle pump). A valve at the end of the damper rod passes through the inside of the cylinder which is filled damper oil and the oil passing through the vales controls the rate of movement of the damper. Being cylindrical it is easy to machine in a lathe and oil is kept in place with simple circular seals.
The Dampers are installed on the car by one end being secured to the gearbox case, the other end to a rocker which re-orientates the movement from the pushrod into the movement of the damper. The rocker can be made up of several levers splined to a single shaft and requires several bearings to make the suspension movement friction free. This amasses into quite a lot of separate components which all need space to fit in.
Rotary Damper Anatomy
Essentially the Rotary damper rotates the axial movement of the Linear damper into a Rotary movement. All the components have the same function, they just move in a different orientation. Thus the damper body is deep “keyhole” shape and the damper rod (known as the vane) rotates in the body, the vanes arm sweeping through a small angular rotation in the keystone section of damper body. The damping valves are placed in the face of the damper vane and work in exactly the same manner as a Linear damper.
Obviously the shape is the biggest difference and manufacturing the damper is far harder due to the fact that the parts have to be CNC milled and not spun in a lathe.
We can see the damper body is a robust metal housing machined from solid. Open on one side to allow the damper vane to be installed, there is a closing plate sealed with an “O” ring and 13 small bolts. To allow the damper vane to pivot the body features two bearings and seal arrangements, one on the closing plate the other is the main housing.
As the housing also acts the suspension rocker, there are also elements machined into its outer face to accommodate this function. Firstly the housing acts as the rocker linkage, so a rocker arm is part of the machined shape. One of these eyes in the rocker will mount the heave damper and the other eye has bearing to accept the pushrod. Showing the packaging efficiency of the Rotary damper a further spherical bearing is fitted to a machined section of the cover plate. This accepts the Anti Roll Bar linkage. Thus for the Midland, no further suspension elements need to be fitted to anything but the damper housing. In the case of the all F1 Rotary dampers, the damper body rotates and the damper rod is fixed to the gearbox (via splines). As one part moves and the remains static, the vane moves through the oil filled cavity, the reaction force of these two parts creates the damping effect. To allow the damper body to rotate in the gearbox, two bearing surfaces are machined into the outer face of the housing and cover plate.
One additional external feature is machined into the damper body, a single damper valve. I believe this is a valve to compensate for the effect of heat on the volume of oil inside the casing. The valve offsets the thermal expansion of the oil to ensure there is a constant volume of oil within the damper cavity.
Inside the damper body sits the damper vane. This is a highly finished and possibly DLC coated component. Even when degreased this part had the feel of a lightly oiled component. The friction reducing coating being there to reduce the friction created by the vane moving inside the housing. Again machined (as most F1 parts are) from solid, the damper vane is formed of two shapes.
Firstly, the spindle that sits in the bearings that allows the arm to the rotate. One end of this spindle has splines machined into it.
Then secondly a flat plate shape is formed into the vane, this is the equivalent of the Linear dampers damping rod. This arm needs to be a close fit to the damper cavity in order to accurately control oil for the damping effect. It’s the edges of this arm that need to be sealed against the housing. A single square edged seal is fitted into a machined groove around the periphery of the vane. There are also four friction reducing pads (two on each side) to aid the movement of the vane against the body.
Providing the damping effect the damper valve is a simply circular shim stack arrangement fitted to hole machined into the vanes face. This valve set up is almost identical to the set up used on the end of a Linear damper. This is perhaps the only aspect of the Rotary damper that directly echoes a Linear set up.
As already alluded to, the Rotary damper is fitted to the gearbox casing and forms both the damper and the rocker. The damper vane slides into splines machined into the gearbox casing and a bearing locates on the bearing surface of the cover plate. Then another bracket fits to the rear of the gearbox to locate the rear bearing and secure the damper in place. The torsion bar passes through the damper engaging in splined in the spindle of the damper vane and also on the front face of the gearbox. Splines on the protruding section of the damper body are probably for the preload adjuster arm.
The pushrod passing up from the lower wishbone fits to the rocker, as does the heave springdamper which sits over the top of the damper to attach to the other side damper. One end of the anti roll bar attaches to each spherical bearing and then the installation is complete.
Pros and Cons of Rotary Dampers
As explained the main benefit is the packaging of these units. Typically Linear dampers are operated by rockers and the dampers are then either laid across the top of the gearbox or sit vertically (requiring a recess in the top of the gearbox case). Either option carries complications in the cars structure or aero. With a Rotary damper the unit forms both the rocker and the damper and takes up far less volume.
As the damper vane permanently sits inside the casing, as the vane sweeps through the radial movement, no oil displaced. This is described a constant volume system. Unlike a monotube damper where the damper rod displaces fluid inside the damper body. This requires a method to offset the movement of the excess fluid. Typically separate nitrogen charged cylinder is used, the gas is compressed by the displaced fluid. But this in itself creates a small spring effect inside the damper. Other methods include the though rod damper, whereby the damper rod passes through both ends of the damper body, thus displacing no fluid. However through rod dampers do require additional seals and this creates some additional friction in the design.
Other key benefits of the simpler Rotary design are weight reduction, with fewer parts the 950g damper with its integrated rocker is lighter than a conventional damper and separate rocker set up. John McQuilliam confirms “We did achieve a weight saving over the conventional layout when you consider the damper, its drive arm and reaction bracket.” McQuilliam goes to on to highlight its packaging and resultant aero benefits “also the packaging is easier, without finding a volume for the damper. Akio Haga who is now alternating chief designer at Force India was laying out the rear suspension back then and we had a few different lay outs, mainly to try and keep the mechanicals out of which ever area the Aero was telling us was most important”.
With there being less parts to be splined together and less bearings in the Rotary design is also stiffer and suffers much less from slop. Jorg Zander explains “the good side of the Rotary damper is that because of the rocker integration, the system is very stiff and direct, so there is little losses due to backlash in linkages, ball joints, etc. which meant it had a good high frequency response”.
So with the damper being a constant volume design, structurally stiff, lightweight and easy to package why has it not become the norm for F1 suspensions?
There is a simplistic argument bandied about that the damping effect is the reason they do not work so well. Neither designer suggested this was the case to me, although at the time McQuilliam did suggest to me it was a factor, but corrected himself with hindsight “I think the damping was actually reasonable”. McQuilliam continues to highlight a more specific deficiency in the Rotary design, “there is a much more complicated sealing arrangement in the damper, adding stiction”. Stiction is one of the enemies of the suspension designer, a mix of terms meaning “sticky” “friction”. This is seen as initial friction, then smoother running. This non Linearity of response is hard to design out. Where as the inherent spring rate added by a gas charged damper can be considered in the overall suspension spring rate, stiction cannot. Zander also echoes this issue “However, the downside is that due to the high internal pressure, the hydraulic seals had to have reasonable preload, which induced a large amount of friction and hysteresis”. This internal pressure also lead to structural issues, the Ex Brawn designer tells me “the high internal pressures caused local deformation of the housing, as well as the vane, this lead to increased friction and pretty inconsistent damping characteristics. Initial developments started with Aluminium, then Ti and steel options to gain stiffness to reduce the issues caused due to deformation. The Midland Damper that I have appears to be titanium. This was an earlier design compared to the Sachs dampers run on the Brawn in 2009. It is possible to see the ribs machined in to the casing to reinforce the device from deformation.
Another argument quoted in the press is the small size of the damper, which results in a lack of oil or radial movement. I removed some 75cc of fluid from the damper and the damping chamber was quite large. The limited radial movement was not seen to be a major problem, being taken into account in the rocker sizing, although both designers point out it still had to be factored in. Zander explains “The angular displacement wasn’t so much of an issue in 2009 and in previous years, but with the heavier fuel loads from 2010 that should be something to be considered.” Seeing as the 2009 Brawn BGP001 was succeeded by the Mercedes W01, it’s interesting to note the latter went back to Linear dampers.
Away from the technical argument of Rotary over Linear there was one other factor which perhaps underlines the less publicised aspect of the designers’ role, budgets! But when we recall that Midland and Brawn were both teams managing a tight budget, this last issue makes sense. Both designers highlighted price as one of the major issues of the Rotary damper. McQuilliam starting by saying “They were mighty expensive, so not good value for money for the weight saving”. Zanders more recent recollection of the Brawn days provides this insight “I think a bigger argument against it for some teams, were the cost of such a Rotary damper. Depending on the specification, it was in the region of about €15.000 per piece”. With these being sealed dampers for each set up, a pair of dampers (€30,000) would be on the car and a multitude of other dampers pairs in the pits, each set up for different damping characteristics.
Clearly the stiction and internal stiffness issues need to be addressed with the design. Evolution via detail design has overcome similar issues with Linear dampers, so presumably the same could be resolved for Rotary dampers too.
The cost issue still remains; inherently they are a complex and high precision part. Where as turning on a lathe produces the correct finish for a Linear damper, careful milling operations are required for the damper body of the Rotary damper, which will inevitably make this an expensive part to produce. No doubt more teams using the damper would drive the price down.
It’s interesting to note that the Sachs Race Engineering website no longer details Rotary dampers as part of their range. Instead conventional Linear dampers and a Through-Rod version of the same, form the basis of their product range and their current Formula1 teams use these Linear format dampers.
Given the choice between Rotary and Linear, Zander sums up the decision well “I would at the current stage of damper technology development prefer Linear dampers over Rotary ones. The friction can be controlled in a better way and problems like cavitation are well understood and do not cause any issues in contemporary Linear damper designs. Also the flexibility with Linear damper designs is much wider, considering systems like: frequency depending damping, high & low speed damping, drop off characteristics (blow by valves, pressure relief valves)”.
Perhaps the Rotary damper will be explored in F1 again at some point, but for now the Linear damper is the sole solution in F1.