The Drag Reduction System, DRS, was introduced to F1 in 2011. It’s a system to open the rear wing flap for reduced drag to boost top speed. Over the subsequent years DRS operating mechanisms have evolved and converged on the same set up, with a wing mounted pod containing a high pressure hydraulic actuator to pull the wing open. This is an opportunity to see the mechanism in detail and explain how the set up works.
For a few years now, teams have been extending the inner face of their brake ducts to reach forward towards the tyres forward edge. Up until recently teams placed the protruding vane as close to the tyre as possible, but latest solution offsets the vane from the tyres sidewall to allow airflow to pass in-between the tyre and vane. An inlet formed in the brake drum duct catches some of this air and redirects it towards the brakes for cooling. This year Williams went even further and removed the usual brake cooling scoop and have the brakes entirely cooled by an inlet between the tyre and vane.
Caterham have been slowly working their way clear of Marussia and HRT to close-in on Q2 sessions and the Toro Rosso’s in the race. This year the CT-01 is a clean sheet design and exploits a Renault engine with a Red Bull gearbox and KERS.
I’ve been lucky to have been given permission from Ionut Pascut to post these detail pictures taken at Monaco, to allow us to look at the detail of the 2012 Caterham.
Not everything in F1 is aggressive, extreme, radical or innovative. In fact in many areas the car’s are very close in general design terms. Some times it’s enough just to soak up the detail engineering and explain what all the little bits and pieces do on the car. In this series of short articles, we’ll do just that, thanks to these amazing photographs from MichaelD. Following on from the details of the Force India front corner, with these photos of the Caterham in Melbourne, we can now see more of the upright design.
Caterham’s upright is fairly typical of most contemporary F1 designs. By regulation all F1 cars have to use Aluminum for their uprights. This one appears to be a fully machined or perhaps a cast part. Before the restriction to aluminum, investment cast Ti or MMC were common.
In format the upright is tightly fitted between the upper and lower ball joints and the two bearing for the hub. This design has been common in the past ten years, before that the upright tended to be a larger item with a large vaned housing for the bearing that would be the route for cooling air to reach the brake disc. Now teams route the cooling around the upright rather than through it. One exception of this design practice was Honda who routed the cooling air internally through an oversize hub. This design was dropped in 2010, as the design prevented the lower wishbone mount being as high the aerodynamicists wanted.
The upright creates part of the suspension geometry, with the distance between the upper and lower ball joints and the angle between them and the steering axis.
The first observation of a current F1 upright compared to any other racecar is the distance between the upper and lower wishbone joints. The upper joint is probably as high as the 13” wheel will allow, and then the lower wishbone is raised to near the wheels centerline. Having the mounts close together creates more loads in the wishbones and restricts space for a track rod to be mounted high up, with enough of a steering arm length to be efficient. This is a compromise forced by the aerodynamicists, who require the wishbones to be placed in the most beneficial position relative to the front wing upwash.
Due to the offset of the bulk of the upright from the steering axis, the design at first appears to offer a lot of King Pin Inclination (KPI), but closer examination of the ball joints shows them to be relatively normal for an F1 car. An increased KPI angle creates more camber change through steering.
We can see the upper ball joint (UBJ) that links the upright to the wishbone is created with a clevis bolted the upright. The wishbones outer end holds the spherical bearing. Shims between the clevis and the upright adjust the static camber. The lower ball joint (LBJ) is a fixed mounting and is not adjustable. We can see in the case of the Caterham that the lower end of the pushrod is mounted to the wishbone and the not upright. It joins near the spherical bearing in order to keep the bending load in the wishbone end to a minimum.
The steering rack is mounted low down on the front bulkhead and the track rod passes in line with the lower wishbone and attached to its own clevis on the upright. Adjusting camber also adjust steering toe angle, so any change in the camber shims will require a shim altered on the track rod arm. As the clevis is formed by the upright, the track rod arm is split, with the metal end fitting bolting to the carbon fibre arm, a shim in between this joint creates the difference I track rod length.
In between the track rod and lower wishbone is one of the two tethers to hold the wheel on in an accident; there appear to be plastic clips to hold the tether in place between the two parts.
Hub & Bearings
Rotating inside the upright is the front hub, or stub axle. This is a machined titanium part and sits on two bearings. Typically two sets of bearings are used one larger set outboard and a smaller set inboard. From the diameter of the upright you can see the differential in size is quite large. Bearing design is quite secretive, but commonly angular contact ceramic bearing are used. I was told that Honda, who used NTN bearings at the time, would have the bearing last two races and cost several thousand pounds each. Albeit this was at the time they used particularly large bearings to hold the oversize hub. The bearings are located in the upright and the hub and preloaded by the large castle nut visible inboard of the upright.
The hub is hollow and will have openings and pockets machined into it to reduce weight where stiffness isn’t required. The hub also forms part of the brake disc mounting system the wire eroded splined on the flange outboard of the upright mate to matching splines on the brake disc mounting bell. There are also drive pegs to locate the wheel. At the threaded outer part of the hub, the wheel retention system is removed. This is a sprung clip that flicks inout as the wheel nut passes over it during wheel changes. The clip will retain the nut as required by the regulation, should the wheel nut not be tightened sufficiently. It will however not replace the function of the wheel nut in holding the wheel on securely. Drivers leaving the pits will seefeel the wheel wobble slightly, driving for too long will see the retention mechanism fail and the wheel fall off. Typically the hub and wheel nut threaded are handed left of right, to help keep the nut secured.
Now entering their third year what was Team Lotus and now Caterham F1 have produced their most contemporary package yet. Also in the second year of their partner ship with Red Bull and Renault for the supply of their power train, there will be inevitable comparisons of the CT-01 to the cars from its technical partners. Indeed superficially the car bears some resemblances to the RB7, but the car is indeed the work of the technical team lead by Mike Gascoyne and Mark Smith in Hingham. Where as Red Bull supply the GearboxHydraulics and Renault the EngineKERS package.
Although the rendering of the car is clearly wearing 2011 spec wings, vanes and brake ducts, its evident the car is another step forward in design terms for the team.
Three features stand out as different from the 2011 T128; the nose, the sidepods and the roll hoop.
Firstly the nose (Cutting from this months F1Racing magazine) is the first example we have seen of the revised 2012 nose regulations, limiting the front of the nose to a height of just 55cm. However the remaining raised monocoque section between that and the cockpit can be 62.5cm high, so we see the step between these two sections and this is partly softened by the ridged “V” nose. (more detail on the 2012 nose rules)
The sidepods follow the Red Bull template with slim sidepods tapering out at their base. The coke bottle shape streamlines smoothly into the gearbox fairing, there being no cooling outlet from the sidepods themselves, instead the tail funnel acts as the main outlets, while there also appears to be small outlets either side of the cockpit sides.
Amidships we see the all-carbon blade type roll structure from 2011 has disappeared, replaced by a more conventional roll hoop. With part of its structure exposed in the form of the struts supporting the roll structure. Its likely this structure has some metal in its construction. The use of heavier metal in the structure, is offset by the shape being more structurally efficient and probably of equal weight compared to the all carbon blade.
The nose cone is much wider and shallower than in 2011, this being create enough mass within the deformable structure while still meeting the “V” shaped front bulkhead. A new front wing is in development, its likely this will follow the 2011 trend for an endplate-less design with a three element wing meeting the centre section in a curled profile. The raised front section of chassis means Caterham have retained their steeply include front suspension. Interestingly, the bulges on the nose, seem to a reverse twin keel and mount the front leg of the upper wishbone. Around the cockpit opening their appear to be cooling outlets, these aiding cooling allowing much slimmer sidepods. The bodywork aft of this area bulges outwards slightly and sweeps back smoothly around the engine to the tail funnel. In meeting the 2012 regulations the exhausts are tucked in quite low and inboard. The mandatory last 100mm of exhaust being covered by fairings formed into the engine cover. From these pictures its hard to tell how steeply the exhausts are angled at. Therefore its hard to tell if the exhaust effect the flow under the rear wing.
As the sidepods are so slim and there being no low level exhausts, there is a wide expanse of exposed floor. The diffuser sweeps outwards and there is a generous cut out around the rear wheels. The centre section of the diffuser often termed the boat tail is exposed to the airflow. Suggesting the rear impact structure is raised clear fo the floor. This is in contrast to Red Bulls preferred practice of a low rear crash structure. The lowered section probably allows airflow over the floor to pass through the starter motor hole to aid airflow passing up under the diffuser.
By using the Red Bull Carbon fibre gear case, the rear suspension is also largely taken from the Red Bull. Thus it employs pull rod operation for the springs and dampers. However the KERS installation may follow either Red Bulls Pannier style battery installation or the more typical under-fuel-tank installation.