Publications: F1 Race Technology Report

Every year High Power Media, who publish ‘Race Engine Technology’ (RET) Magazine, produce a number of magazine format Race Technology Reports. Covering F1, Moto-GP, Nascar, Drag racing and 24-hour racing.

Just out is the current F1 Race Technology issue, covering Technical subjects from 2011 and 2012.

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McLaren: Adjustable Rear Brake Ducts

With the switch to Pirelli tyres, their rear tyre construction has needed a lot of care in managing degradation. This drop in tyre performance happens when the tyres drop out of their operating temperature window, and this can come from the tyres running too hot or too cold. As the preceding RenaultSport article explains managing rear temperature takes a lot of effort and understanding. McLaren have been active in understanding this problem and over the past year have developed an innovative method of controlling tyre temperature via its relationship with Brake temperatures. It’s come to light in the past two races McLaren have an adjustable brake duct set up and this can have an impact on tyre temperature.

Brake discs (red) visible inside the Brake Duct

F1 carbon brake disk temperatures can peak at over 1000-degrees centigrade. The discs being 278mm diameter inside a 305mm wheel means that there is little space between the two and heat inevitably passes from the disc into the magnesium alloy wheel. In previously years this was avoided to try to reduce heat conducting into the tyre, but McLaren have found a way to harness this.

By altering the flow of heated air coming from the periphery of the brake disc, the amount of heat passed into the wheel and tyre and can be altered. Already teams tune brake cooling with different inlets scoops, but these tend to stay fixed from qualifying onwards (wet races excepted). If the team want to alter brake and thus tyre temperatures during the race then normally there’s no path open to them. However McLaren have fitted an adjustable window in the rear brake ducts. A mechanic can adjust this in the pits to tune the brake and tyre temperature to suit conditions. Depending on the wording of the Parc Fermé rule, this could also be altered on the grid as one of the areas allowed to be changed is brake cooling blankings.

The heated flow from the brakes (arrowed) exits around the brake duct

To do this McLaren have altered their brake cooling design from most other teams. More typically the round brake drum cooling ducts exit the brake flow through the rounded outer face of the duct; this passes out through the wheel spokes. McLaren’s brake discs vent their through openings in the outside of the brake drum, with its outer face closed off from the disc. So all the heated brake flow passes between the duct and the wheel before exiting through the wheel. To accommodate this flow, McLaren’s wheel spoke arrangement has been altered. The Enkei wheel features 29 drillings around the face of the rim, with the more conventional spokes positioned inside these drillings. Brake flow is directed through these drillings and relatively little passes through ten holes between the main spokes. With this set up the heated brake flow has far more contact with the wheel, both as it passes to wards the spokes and even the spokes themselves have more surface area to absorb heat from the brake flow.

The heated brake flow passes through the outer drillings (red)

Normally teams tune the brake cooling via the inlet, taping it over or changing to a different sized inlet scoop. With the McLaren system the inlet scoop remains largely the same, but brake cooling is tuned via a threaded adjuster (Yellow in the following diagrams) moving a flap to either open or close the openings in the brake drum. This is analogous to the cars engine cooling, the inlet tends to remain the same and the outlet area is tuned for optimum cooling. A larger than required duct will create extra drag, but I suspect the operating window the adjustable duct is within quite a small range. Probably smaller range than switching to the next size brake duct inlet.

The flap (grey) is closed to cover up the cooling outlets

When the flap closes the opening, more heat is retained within the duct for hotter brakes, but cooler tyres.

The duct is open to expose more of the cooling outlet (red)

Conversely opening the flap to expose more duct exit area, brakes run cooler and more heat is passed into the tyre.

Also, see these images comparing the adjustable brake ducts of Hamiltons car (right) and the unadjustable ones on Buttons (left). via Russell Batchelor XPB.cc.  The silver coated section inside the brake duct on the right, is the adjustable part.  This semi cylindrical panel winds in to open up more cooling outlet area.

We have seen the adjusters fitted to the rear brakes in Bahrain, but they’ve reportedly been on the car since China and F1 insiders tell me they were used even last year. I’m also told the front brakes are adjustable too, but I’ve seen no evidence for this. One thing is clear, these are quoted as secret devices, but most rival F1 engineers know about them!

I understand the brake ducts can be adjusted from a single point near the fuel filler flap, so I presume cables (Grey in the preceding diagrams) run from the threaded adjuster back to the middle of the car. At a pitstop the mechanic can adjust the brakes with a tool accordingly.

See this picture from the Spanish GP (via F1talks.pl) shows the adjustment in operation.  Cables from each of the adjusters meet at the fuel flller flap and the mechanic, who is usually there to hold the car steady and clear out the airbox, can adjust the ducts with a pre-agreed number of turns on the hand tool in the adjuster.  As the adjustment is done via a mechanic it is a legal change to set up, allowed once the race starts, but not during qualifying or whilst the car is in Parc Fermé. When the car is stationery at a pitstop, the system is not considered moveable aero.

Changing the brake ducting will alter the amount of brake cooling, opening the duct will allow more heat to escape and reduce brake disc temperatures and vice versa with closing the ducts. Adjusting the rear brake temperature may be the sole reason for this season. With changing tyre balance and KERS usage the rear brakes have been prone to overheating. But the more likely benefit is the effect of the brake heat altering tyre temperature. As the brake heat passes through the smaller set of drillings in the wheel, this has a greater surface area than the more usual 8-10 spoke wheel; this allows more heat to transfer into the wheel. Heating the wheel will transfer heat into the tyre; this will be useful when the driver is struggling for tyre temperature. The contrary is reducing the heat transfer into the wheel to reduce tyre temperature when the driver is struggling with heat related degradation.

Of other teams are able with their current wheel and duct arrangement to alter tyre temperatures via heat radiated from the brakes, then this will be an easy modification to make to the car. However many other F1 Engineers suggest that they find little effect of brake temperatures altering tyre temperature, making the solution unattractive to them. So it’s not clear if this is a must have solution or other teams are able to tune tyre temperatures with more conventional means. As yet I have not seen any other team run these types of brake ducts.

Sauber: Exhaust Sidepod Development

Sauber have proven to be one of the more progressive teams with aero development this year. The team’s have played with several different approaches to aero and exhaust positioning over the opening months of the year.
Now Sauber have produced their fourth sidepod iteration and surprisingly it is a McLaren style exhaust outlet. This goes away from the path they forged with the ramped downwash sidepod. Aiding the new exhaust position is a revised vane over the top of the sidepod.
The team also ran a revised front wing. I will cover this development in a separate post.

Sauber launched their car with a simple sidepod (above); this almost looked like a Red Bull RB5 set up, with the top exit exhaust aimed generally over the rear bodywork. This simple initial attempt was probably just for the launch pictures.

As soon after, the definitive Melbourne spec exhaust was tested. This sported a distinctive ramped section, which created a downwash that drove the top exit exiting exhaust flow downwards, then the ramped tail of the diffuser encouraged the flow to follow the sidepods line down towards the rear tyre\diffuser. This mix of downwash and coanda effect all but reproduced the EBD effect used in 2011. As the exhaust flow was directed along the bodywork, it appears to be more accurate way of directing exhaust flow towards the diffuser. However the effect lacks a path for the sidepods undercut airflow to pass through. Red Bulls Melbourne spec (V2.0) exhaust attempted to cure this with the cross over tunnel.
To aid the downwash flow over the sidepod Sauber added a horizontal vane over the front section of sidepod. This front 15cm of sidepod is free of the bodywork restrictions of the main sidepod volume. The vane points the airflow downwards, to drive greater flow over the exhaust exit. In isolation this vane actually creates lift, as is common with F1 aero this counter intuitive solution creates more global downforce because of its downstream effect, than the small loss in downforce its creates on its own.
In practice for subsequent races Sauber tried a third iteration of the exhaust, still with a top exit, but the exhaust faired-in and blow out through scalloped slot, presumably to better direct the airflow. Using similar interpretations of the exhaust\bodywork rules as McLaren exploited with their side exiting exhaust. This V3 set up wasn’t raced and will probably never race, with this fourth version now seen in testing.


The V4 sidepod discards the philosophy of the firth three completely, instead the sidepod is shorter and the coke bottle area forms a much tighter waist. Protruding from the flank of the sidepod the exhaust sits inside a small bulged fairing. This fairing mimics the McLaren with the open topped channel cut in to it, to allow the downwash to redirect the exhaust flow. The channel probably also provides a small degree of coanda effect in bending the exhaust flow downwards, but far less than with the earlier sidepod designs.

Exhaust flow exiting the duct now passes openly towards the tyre\diffuser intersection. With the coke bottle area now free of the ramped section, the undercut sidepod flow can pass towards the centre of the diffuser to use the energy in the flow to drive some downforce from the trailing edge gurney and starter motor slot.
With the change in sidepod profile and the exhaust exiting more sideways the through the top, the downwash vane has also been altered. Rather than a horizontal vane, the vanes curved around the frontal of the sidepod, to create the depression over the revised exhaust outlet position.

Force India: New Front End Aero

Sahara Force India ran a new front end in testing, with some of the distinctive features from the launch car dropped. The new set up is aimed redirecting the flow along the edges of the nose towards the floors lower leading edge. The new package consists of; a revised nose tip, front wing pylons and different turning vanes.
The team also ran a revised sidepod package with McLaren style exhaust outlets. I will cover this development in a separate post.

From the cars launch and through the first four races, the nose tip sported a hammer-head style twin camera set up. Now the cameras have relocated to further back along the nose and the nose tip now forms a more aesthetically pleasing rounded shape. Although neutral in aero section, the camera pods are placed in a position where their shape will interact with the airflow to create some aero benefit downstream on the car.
Below this the pylons mounting the front wing have been extended and form a linger vane like shape. This was something FIF1 have worked with a lot over the past few seasons. Using this shape as part of the cars aero set up for different speed\downforce circuits. Typically longer pylons for higher downforce tracks and smaller pylons for places like Monza. Although the vanes may well create some low pressure behind the neutral front wing centre section to create load at the front axle, I expect they are more for directing the airflow along the y250 axis. This is a longitudinal line along the edge of the chassis, 250mm from the cars centre line. This is effectively as far outboard aero devices are allowed and hence where teams tend to focus on vane development. Creating different flow structures along this axis, helps creates the airflow distribution at the floors lower leading edge which is critical to diffuser efficiency.


Along similar line are the new turning vanes, on the launch car these were the popular “L” shaped hanging vanes (pictured above), mounted beneath the nose cone. Now they are a pair of curved vanes under the front suspension, a similar solution to Sauber\Renault and adopted by Red Bull last year. Again similar to these teams there is a small split in the vane to induce a stronger vortex effect along the y250 axis.

McLaren: Front End Aero Development

McLaren have long since followed their own path in aero development. Certainly since 2009 the car has increasingly diverged from other team’s aero concepts and the 2012 MP4-27 is no different. However the current car has a clear lineage in some of the design solutions and the whole front end is an evolution of recent cars.

Development Chronology

2009

Their first car to the current aero regulations in 2009 sported a conventional nose, front wing and cascades.

2010

The car that was launched in 2010 had a very different front end. The drooped nosed of the MP4-24 was gone replaced by a more horizontal and shallower nose cone. Beneath this was fitted large aero device, I term a “snow plough”, Williams had run a similar solution in 2009.

From a horizontal leading edge positioned between the front wing mounting pylons, the snow ploughs surface splits into left and right sections and eventually forms a pair vertical vanes protruding below the nose. This creates a “V” section mid way along its length and the twist of the airflow along with the pressure differential between the upper\lower surfaces creates vortices trailing from the rear of the vanes. This is an aggressive solution compared to the simpler turning vanes other teams use. This device probably creates some downforce in its own right, but I suspect the primary purpose is to direct the strong vortices along the Y250 axis, to drive a better airflow towards the floors lower leading edge.

Later in 2010 after a series of different iterations of endplate and cascade design, the wing substantially changed for Singapore GP.  The main plane was effectively split into two; a section ahead of the front tyres and a section inboard of that. The intersection between the sections formed an upright for the main cascade winglet. While the less aggressive inboard wing span gains a simple “r” shaped vane.

2011

McLaren continued the 2010 design of snowplough nosecone and split front wing into 2011 with the MP4-26. Again later in the year, the wing was simplified for the Indian GP with similar endplates and cascades, but the complex split shape wing profile was changed to be straight across its width.

2012

Again this format was brought forward to the launch and initial test version of the 2012 MP4-27. Only in the last days of Barcelona testing did the revised front end appear. Gone was the snowplough and the straight wing profile. In their place was a simpler nose cone and a pair of vanes dropping vertically from the nose. While the more complex split wing profile was reintroduced. With EBDs less powerful this year, teams are finding downforce levels are lower. We could conclude that the snowplough and straighter wing arrangement were better for downforce, so the new simpler arrangement may be a more efficient way of producing less downforce.

The other change in China was the deletion of the slots in the small cascade winglet. The slots would have reduced the strength of the vortex produced by the winglet, removing the slots will have increased them. This change will be made in order to direct a stronger airflow around the inside face of the front wheel.
As the team get to grips with the new exhaust regulations and start to develop more downforce, potentially some of these solutions could return. So any reappearance will tell us a story of development and aero load figures in 2012.

Lotus E20: Overview and Development

Compared to the other leading teams the Lotus appears to be quite conservative car. However performances in testing and the in particular at the Bahrain GP show the cars looks belie its pace.

E20 Overview


Unlike its rivals there isn’t a stand out feature or innovation that’s obvious on the E20. Development from the Renault R31 with its ill fated front exit exhausts (FEE) has been iterative and logical. Unlike its forebear the E20 features a simple exhaust set up, blowing over the tail of the engine for apparently less aero effect than other team’s downwashed sidepod\exhaust solutions.

Indeed the sidepods are largely conventional, the peak above and below the sidepod inlet are similar to the R31, only the vane atop the sidepod front is unusual. Within the sidepods the team have spent time with internal airflow management, the left sidepod houses a large single water radiator, the left sidepod has a split cooler set up, which appears to keep the coolers mounted clear of the floor with electronics houses below. Perhaps for the KERS power control hardware. This high mounted radiator set up reminiscent of the packaging for the FEE and also similar to McLarens 2012 cooler package.

The nose is a straightforward interpretation of the 2012 regs, with the rounded undernose profile similar to 2011. Only the presence of a slot under the nose is a distinctive feature, this smiley face shaped slot is created under the nosecone and passes through the front bulkhead into the chassis. Presumably for cooling the driver or the steering rack mounted low on the front bulkhead. One interesting point on the front of the car is the unusual hump arrangement on the top of the chassis. The usual bumps used to clear the rockers and other front suspension linkages are asymmetric. With a larger bulge on the left and a smaller one to the right. This suggests something is unusual about the suspension, Renault were known for the innovation in this area with front to rear interlinked suspension, the reactive ride height system and also running with a roll damper in place of side dampers. I suspect the bulge is to neatly incorporate the asymmetric rocker arms needed for a roll damper and hence the car runs without left and right dampers. However the front of the bulkhead is so heavily packaged with other hardware it’s impossible to see the spring\damping elements inside. Externally we can see that the torsion bar mounts allow for free rotation and even feature a rotary sensor to measure their movement. This shows that the torsion bars are not grounded to the chassis instead react against each other. This negates their spring effect in roll, so all roll stiffness is provided by the anti roll bar. This approach has been common on other cars for a few years.
The anti roll bar is mounted higher in relation to the front bulkhead compared to last year, equally the link between the torsions has been moved inside the chassis, rather than the external bracing strut seen on last year’s car.


At the rear, the gearbox shows no evidence of side dampers either, although these could be packaged inside the casing so also not visible externally. Its possible Lotus have made a step in suspension design, which makes the best use of the tyres or control of the aero platform better.
Lotus are another team to adopt OZ wheels with integral fairings added to the front rims.


At the rear, a lot has been made of the laterally diverging diffuser. All teams start the diffuser far narrower than the 1000mm allowed between the rear wheels, and then diverge the diffuser (in plan view) outwards towards the limit of the allowable area. This effectively limits the expansion that can be achieved within the regulatory diffuser volume. Lotus has effectively diverged the diffuser to the 1000mm limit far earlier, with the outermost channels effectively exiting out of the side of the diffuser. This potentially gains more theoretical volume for the diffuser, but also creates a far more aggressive sidewall to the diffuser, risking flow separation and the diffuser sidewall is shorter more open and hence may leak more. Other teams have followed this path in the past, so the potential benefit is there assuming the drawbacks of the geometry can be overcome.

Developments
Pre season
As one of the cars shown at the launch was a R31 rebranded and reworked to look like the E20, initial observations were hard to make. The car that commenced testing was the E20.
The first test went outwardly successfully, but problem on the first runs of the second chassis being tested at the Barcelona test showed problems with the monocoque. Subsequent checks on the first monocoque tested in Jerez, revealed the same structural problem. The tub was failing where rear leg of the top wishbone mounts. The team skipped the test to add 1kg of reinforcement to the cars.


As soon as the car recommenced testing it started to gain revisions to the floor and front wing. This included a re-profiled splitter along with its side vanes, as well as a new iteration of the front wing. The initial wing with its “R” shaped vanes and cascade winglet were nearly parallel to the cars centreline, the updated wing changed these into a more curved outswept shape. Notably the front wing pylons also house the FIA camera pods, these being mounted between the pylons and siamesed into an aerofoil shape behind the neutral centre section, to negate the lift created by this profile.

China\Bahrain update


A new aero package was prepared for China, but the team found testing inconclusive with the variable track conditions. The package was run again in practice for the Bahrain GP and adopted for both cars from qualifying onwards. The package included a revised rear wing, with new endplates sporting a squared-off lower section and mated to the diffuser with a larger vane. The floor was also revised, although the concept was largely carried over, so the changes are in the detail geometry and not the overall shape.
At the front the wing was altered for a completely new version. At first the wings appear similar aside from the vane treatment on the endplates, but the main planes leading edge dips downs more suddenly at the on with the neutral centre section, while the flaps join the same area without the coved section on the old wing. At the wing tips, the flaps fold down to form the endplate as is common in current F1, the upper flap gaining a small extra slot to aid flow through the steepest section of wing. With this endplate-less set up, the minimum surface area regulation is met by two vanes added to the footplate. These being somewhat reminiscent of Toro Rosso’s vaned set up. It’s hard to speculate on how the new package gains lap time or bring a difference in aero efficiency over the old set up.

The new package was worth a couple of tenths according to the team and the back to back tests in free practice proved its worth over the older aero package. As with the rest of the car it’s hard to pin point where the lap time comes from, For Lotus the conventional approach and iterative detail development has brought dividends over a more aggressive approach.
One wonders how much more potential there is within the car should adopt the sidepod\exhaust or DRS solutions of its rivals. If the team can successfully introduce these performance upgrades and continue to understand the tyres requirements, then there is scope for them to remain in the hunt for strong results throughout the year.

Red Bull: Bahrain Sidepod Analysis

Having been slightly off the pace in the opening three races, Red Bull clearly do not have the RB8 working as they had expected. Pole position in Bahrain doesn’t prove their issues are over, but the car sports a revised sidepod set up this weekend and this has perhaps has unlocked the potential in the car. The new sidepods are a revision of the Version2 spec sidepod/exhaust set up. The Bahrain spec simplifies the sidepod, removing the complex crossover tunnel under the exhaust ramp.

Exhaust Versions

Sidepod Version1

At the cars launch the RB8 features a simple Version1 exhaust set up, aimed at being a benign solution to get the bulk of testing out of the way, without interference from complex exhaust issues. Then later in testing the focus could switch to the greater potential performance offered by the V2 set up. The V1 set up placed the exhaust in board and rearward, blowing under the top rear wishbone. The exhaust flux blew along the tail of the bodywork and under the beam wing. Despite suggestions at the time that this set up was a novel exhaust blown suspension set up; the solution was never intended for race use.

Sidepod Version2


Then on Day11 of the 12 day preseason testing schedule, the V2 sidepod\exhaust appeared. A more complex solution than either the McLaren or Sauber set up, the sidepod aimed to both direct exhaust flow at the diffuser and route the sidepods undercut flow to the centre of the diffuser. To do this the sidepod had a more outboard and rearward exhaust position.

The exhaust blows down the tail of the sidepod, over a ramp made to try to attach the exhaust flow to the bodywork via a coanda effect to direct it in the correct gap between the rear tyre and diffuser. This is the same area the teams aimed their exhausts directly at last year. This area helps both seal the diffuser from flow blown laterally from the rear tyres and also the greater mass flow of the exhaust plume creates more flow through the diffuser, with both effects adding downforce. This solution follows the same path as the much applauded Sauber solution. Although the two systems were developed in parallel and RBR did not copy the Sauber after seeing it launch. The RB8 always was planned to run the V2 set up.

V2: a tunnel is created under the Exhaust ramp bodywork (yellow)

V2: Flow from the sidepod undercut passes through the tunnel (yellow)

To keep the airflow passing over the top and centre of the diffuser, teams direct the fast moving flow from the sidepods undercut to this area. In Red Bulls case, the path of this flow is obstructed by the exhaust ramp and plume. To overcome this Red Bull have simply created a tunnel for the air to pass under the exhaust ramp and remerge towards the centre of the diffuser. This solution looks like is major aim was to direct flow to the start motor hole, an area exploited by ductwork on the 2011 RB7. Having more airflow passing into the starter motor hole, makes the hole act like a blown slot, making the airflow better up and under the middle section of diffuser for more downforce. Creating a crossover effect is somewhat like McLarens bulged exhaust fairing, that allow both the exhaust to be directed down to the diffuser edge by the downwash flow over the sidepod, but also creates a channel beneath the exhaust bulge to allow the undercut flow to reach the centre of the diffuser.
So it seems Red Bulls V2 floor make the best of the Sauber Coanda solution and the McLaren undercut solution.

What are the issues?
However this tunnel is compromised by the post-2009 area rules. Sidepod bodywork 50mm above the floor (actually 100mm above the reference plane) must meet tangential and minimum radius regulations. This means Red Bulls tunnel is limited to slightly less than 50mm in height, with a sharp top edge.


It seems it’s this crossover tunnel on the V2 sidepod that is an issue with the car. Recent flowviz tests in free practice were focussed specifically on the tunnel, as well as tests with an array of aero sensors trailing the diffuser in Bahrain. Also an insider tells me that the Red Bulls starter motor might not be creating the accelerating airflow into the steep middle section of diffuser that was envisaged. Instead the starter hole works better when blocked off. Perhaps this crossover tunnel is not flowing correctly to the centre of the diffuser and altering the accuracy of the exhaust flow towards the tyre\diffuser intersection.
If the exhaust flow cannot reach the tyre\diffuser gap accurately or perhaps more importantly consistently, then the driver will have a car that sensitive to throttle position.
Red Bull have been alleged to have clever engine mappings, cutting down to four cylinders at larger throttle openings at lower revs. This could either have the effect of a softer power delivery for better traction, of greater exhaust flow for more downforce at lower revs. Red Bull and Renault may still be finding ways to gain performance from exhaust mappings and these mapping have been investigated the FIA and shown to be within the regulations.
With several issues around the way the exhaust affects the cars handling, Red Bull said in China that the V2 sidepod was the potentially better solution, but the V1 set up gave Vettel more confidence. Horner admitted that it was possible to get the performance of the V2 with the feel of the V1. At Bahrain it appears that this is what RBR have done.

Sidepod Version 2.1

V2.1: With no tunnel the exhaust flow can pass without interference to the diffuser

These issues may explain the Bahrain sidepod upgrade. This new sidepod set up appears to be a rework of the V2 sidepod, most of the shape remains the same and the exhaust appears to be in the same position. So it looks like the moulds were altered to close off the cross over tunnel create a V2.1 sidepod.
With the tunnel closed off the issues complicating the exhaust and starter motor hole flow have been cleared up. But there still remains an issue with how the sidepod undercut flow reaches the rest of the diffuser. Sauber appear to manage this, but there still may be some potential airflow performance that is lost with this set up. Although the overall effect of an exhaust aimed accurately at the tyre\diffuser gap may be a greater gain that that loss.
However with the tunnel gone there is a less complex route for the exhaust to reach the diffuser. With the exhaust flow better managed the intended exhaust effect will more consistent resulting in a better feel for the driver at different throttle positions and car attitudes.

V2.1: Slots in the floor aid the effect in sealing the diffuser

It’s notable that Red Bull have also reintroduced the slots in the floor ahead of the rear tyres, these haven’t been seen for a couple of years, their function is to inject some higher energy airflow into the gap between the tyre and diffuse. This, like the exhaust blown diffuser, offsets the sidewash (known as ‘Squirt’) created by the rear tyres impinging into the diffuser. Again this will all result in greater rear downforce.

If this is the first solution for Red Bulls woes, then it will be interesting how the team develop from the V2.1 sidepod. Perhaps the tunnel will reappear in revised form or a McLaren style solution will be tried.