AMR Launch, Aero bits on GT Cars

I was quite lucky to attend the Aston Martin Racing Launch this Tuesday. It was great having the first look at their new car Vantage GTE for Le Mans and WEC. However the biggest surprise was meeting Bruno Senna as their new season driver there.  And it was kind of last minute boom – heard that AMR signed him just the day before launching! To be honest I was not a big follower of GT racing, but after having a close look at this beautiful GT car with some nice aero bits on it, I was quite attracted to it!

Aston Martin Vantage GTE

Aston Martin Vantage GTE

The look of car is very nice, although the colour scheme is quite similar to Force India 😛 Very distinctive features from a competitional car to a road car includes front air splitter/airdam, side skirt, rear wing, rear diffuser and some corresponding air inlets/outlets/conditioning pipes. For comparison, here is a picture of their Vantage V12:

From Aston Martin official site

V8 Vantage Roadster

A competition car is often modified from a road car. Without those aero devices, it generates lift force instead of downforce due to the shape of the car. Below is a lift and drag coefficient figure provided by Racecar Engineering for Subaru Impreza:

Cl and Cd with or without aero (Subaru Impreza)

Typical Cl and Cd values for Subaru Impreza

It can be noted that there is significant difference in downforce with/without aerodynamics devices, although drag reduction is not that noticeable. At around 60mph, these aero parts become significant. Also from Racecar Engineering figures: at 70mph, the equivalent downforce is 51.8 kg (3.6% of car weight including driver), this value reaches 105.7 (7.4%) and 178.6 (12.5%) for 100mph and 130mph respectively as downforce is proportional to velocity squared.

Vantage GTE front air splitter

Vantage GTE front air splitter

The air splitter refers to the horizontal extension at the bottom of the car. This would create a high pressure region as air accumulated above the plate, therefore increasing front downforce. The air splitter would induce some drag force, although benefit of increasing downforce is dominating.

Vantage GTE Side Skirt

Vantage GTE Side Skirt

The side skirt prevents the mixing of high pressure air from the side of the body with the low pressure one underneath the chassis. It therefore smooth the flow down to the rear end and facilitate rear downforce generation.

Vantage GTE Side View

Vantage GTE side view from rear

On picture above, you can see an exhaust pipe in the middle of the side skirt of the car – instead of mounting it at the rear. They seem to do this for better cooling at cockpit as this was their problem last year. However, I doubt whether the exhaust air at this position would cause any aero deficiency for the car. In addition, at the right top corner, you can see a big air intake which feeds the air into the rear diffuser.

Vantage GTE Rear Diffuser

Vantage GTE rear diffuser

Here is the rear diffuser of Vantage GTE. It has a wire mesh structure to smooth the air out of the diffuser. As mentioned above, the exhaust now is at the side of the car, so that the hole you can see above is not the exhaust outlet. Instead, this is an air condition outlet for cooling purpose.

Vantage GTE rear wing

Vantage GTE rear wing

Very similar to F1 cars, rear wing is one of the most important downforce device. It looks massive from a close view of the car – the span of it is actually wider than the car width. The position of rear wing can significantly influence the downforce generated. Generally speaking, as the wing goes rearwards and higher, more downforce is generated due to the explosion of the wing to cleaner air. However, most regulation would limit the height of the wing so that designers need to take careful consideration of its location.

It was overall an amazing event from AMR, which caused massive attention with the signing of Bruno Senna. I wish him best luck in Le Mans and WEC – he was a nice person as I met him.

Advertisements

McLaren MP4-28 Launch Review

With car launches nearly every day this week, we finally feel the return of F1 races. People are saying ‘It’s exactly the same as last year!’ everytime a new car reveals, even though they all know that 2013 is not a year for revolution. In McLaren’s launch, Jenson said that ‘under the skin, it’s so different’ – well we don’t really know before the Jerez test, but through bare eyes, we can see several detail changes on the new seasons car.

First of all, if you haven’t watched their launch video, you should really do it now! They have a brilliant built-up to the revealing of MP4-28:

With little change in regulations, one thing most team would do is trying to steal some good ideas from other cars last season. In terms of this, McLaren has somehow adopted Ferrari’s pull rod suspension and Red Bull’s rear suspension merging with driveshaft and track rod.

Covered Step Nose

The most obvious change is the covering of step nose with modesty panel. Step nose appeared in F1 since the 2012 season, when FIA modified the height limitation for nose cone and monocoque due to safety reasons. The 2012 regulation has a 550mm limitation for nose cone and 625mm for monocoque. As it’s beneficial to get more air flow underneath the car to feed into the diffuser, most teams are pushing to upper limit for both nose cone and monocoque. And in order to make up for the margin between them, step nose came out as the solution. The step doesn’t look good and there could be slight aero deficiency as the surface is less streamline like. So in 2013, regulation allows using of a modesty panel to cover the nose. It’s basically a thin carbon fibre panel that doesn’t have any structure function (it simply breaks down during front impact). However, the penalty of using this panel would be additonal weight at the front of the car. It’s the team’s choice to decide whether to use it or not considering its aero and aesthetic benefit and weight penalty.

McLaren MP4-28 Nose Cone

MP4-28 Nose cone with modesty panel

Original Step Nose without Modesty Panel

MP4-28 Original step nose without the cover

Front Pull-rod Suspension

This was what Ferrari used last year (this year as well). Pull-suspension is basically an upside-down version of push-rod suspension (well not exactly, but you may understand it this way..). With the chassis and nose cone lifted up for maximum aero benefit, for stability, it’s good to lower down centre of gravity with a pull-rod suspension as all those springs and dampers are mounted at the bottom side of the nose. Actually McLaren must have made a whole change in the front part design due to the change of suspension.

McLaren MP4-28 Pull-rod suspension

McLaren MP4-28 Front Pull-rod Suspension

Rear Suspension Integration with Driveshaft

This was a Red Bull idea implemented since the development of RB5!  It basically utilise one of the wishbone to cover up the rear driveshaft. The covering of this part would make it more aerodynamically desirable. It smooths out the air at the rear of the car, therefore good for the efficiency of rear diffuser. From the picture below, you can see a very thick wide structure of the wishbone, which houses the whole driveshaft.

McLaren MP4-28 Rear Suspension

McLaren MP4-28 Rear Suspension

*Pictures from AMuS