The BTCC’s lattest specification “NGTC” touring cars use a common standard TOCA front and rear suspension assemblies regardless of base vehicles manufacturer. In this post we will take a look at this TOCA rear subframe assembly.
Matt Neal (@mattnealracing) has kindly published this picture on http://www.twitter.com showing his teams (Team dynamics) new Honda racing 2012 Civic. So what can we see in this photo?
This photo is taken from the rear of the Civic, looking through the tailgate opening down at the rear floor of the shell.
Highlighted in point 1 is the common NGTC rear sub frame which is a fabricated suspension assembly manufactured for TOCA by GPR Motorsport (http://www.gpr-motorsport.com/). You can see that this assembly is similar to the front sub frame (discussed in this post http://btcctechnical.wordpress.com/2012/02/14/a-quick-once-over-of-a-btcc-ngtc-front-sub-frame/) And is also quite a considerable heavy duty fabrication made from of steel tube. You can see that it is mounted to the underside of the shell and is tied into the rest of the vehicle at four mountings points highlighted in point 2. These mounting points are incorporated into the cars roll cage which connects front and rear sub-frames.
The suspension provided by these sub-frame assemblies is double wishbone and as oppose to Mcphearson strut suspension found on S2000 specification cars, the dampers are laid out flat to the floor in the shell running left to right, These are shown in highlighted point 3. The NGT cars use a Penske nitrogen filled dampers (.http://www.penskeshocks.co.uk/) The resevoir for the damper is local to the damper and is highlighted in point 4. The damper can be adjusted via the adjustment nobs on this resevoir, Highlighted in point 5. The NGTC’s use coil over dampers, springs with different spring rates can be fitted over the damper depending on the car setup. The spring is not fitted in these photos, however I have highlighted the area where the spring would normally be fitted in point 6.
Access to the dampers will be via a removable cover which will normally hide this assembly from view, this cover is not fitted in this photo.
To the rear of the sub-frame assembly it is possible to see where the rear air-jack is mounted, The rear air jack, which raises the rear of the car is hidden from view by the flat steel sheets, however you can see the hard air lines leading to the cylinder , I have marked the approximate position of the air jack highlighted in point 7.
The fuel tank is fitted in this photo and its located forwards of the rear suspension highlighted in point 8 and the cars fire extinguisher can be seen to the left of the fuel tank highlighted in point 9.
Seeing the dampers laid out across the floor in the above photo it can be a little confusing to picture how the suspension all links together. To help clarify how this suspension works I have created the below illustration:
(Illustration not drawn to scale)
The top illustration shows the double wishbone suspension at rest and the lower illustration shows the suspension moving under load, perhaps when ridding over a curb.
You can see in this illustration that the damper is laid out horrizontaly as we see in team Dynamics photo and is connected to the rest of the suspension via a pivoting “rocker” and a push rod.
So how does this system work? As the wheel moves upwards under load the push rod pushes against the rocker which transfers the movement to a flat horizontal movement compressing the spring on the coil over and pushing the piston into the damper.
This suspension system used by all NGTC’s is more advanced than the Mcphearson strut systems used in other s2000 touring cars and is in fact used by most single seaters and should allow some very fast corner speeds.
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