Classic 2CV Racing Club Ltd

Classic 2CV Racing Club Ltd Forum => Off topic => Topic started by: Nathan Pasho on January 21, 2007, 23:06:54



Title: Question about 2CV Suspensions
Post by: Nathan Pasho on January 21, 2007, 23:06:54
Hello everyone!  Glad to see that you are preparing for another eventful year. :)  Hope you can keep your attendance numbers up. :)

I have a quick question about the design of the suspension.  I tried to make the suspension design for the computer model as well as possible.  

What I am wondering about is that the front end of my model rises during braking because of the torque of the brakes on the front arms.  Is this behavior something that real 2CVs also do?  Especially with the original soft springs?  Or should the front dive during braking the way a wishbone suspension does?


Title: Question about 2CV Suspensions
Post by: Marc Fenner on January 22, 2007, 16:53:03
Hi Nathan.

A road car dips a far bit. Aas for the race car they do dip slightly. Not alot though


Title: car suspension
Post by: pat collier on January 23, 2007, 10:25:19
I am delving back into my memory here but

the 2cv works in the opsite way to a normal supension... i.e the shock works by expansion rather than compression, and the springs are on the oposite of the cantalever although are compressed.

In geometry this could creat a neutral situation of lift rather than dip however weight transfer more than counterbalances this effect therefore you get a dip which is not as extream as it would be in a normal car...

If you are cornering a 2cv which has decent springing you should feel initial understeer created by the cantalever effect followed by oversteerish effect, on a badly balanced car or one with too hard springing/shocks especially on a greasy surface snap oversteer is a possible conclusion.

Sorry this is a bit wooley but it was a good few years ago I looked at suspension on thses things

Patrick


Title: Re: Question about 2CV Suspensions
Post by: Ken Hanna on January 24, 2007, 22:49:34
Nathan,
A 2CV's front brakes are attached directly to the gearbox, not to the radius arms, so braking torque at the front end is transmitted to the engine/gearbox unit.  
Under heavy braking, this will result in an increased downward force on the front chassis crossmember and 'possibly' an upwards force on the gearbox mounting (at the tail of the gearbox), which suggests that this torque being applied to the vehicle 'could' cause the front end of the car to dip.
However, because the backplates for the rear brakes are mounted on the radius arms, braking torque transmitted to those arms will tend to make the rear of the car dip as well.
The net effect is that 2CVs, especially race prepared versions with uprated springing, usually have little or no change in attitude even under heavy braking on dry tarmac, when there can be just a hint of smoke from burning rubber under the front tyres...

Ken

Quote from: Nathan Pasho
Hello everyone!  Glad to see that you are preparing for another eventful year. :)  Hope you can keep your attendance numbers up. :)

I have a quick question about the design of the suspension.  I tried to make the suspension design for the computer model as well as possible.  

What I am wondering about is that the front end of my model rises during braking because of the torque of the brakes on the front arms.  Is this behavior something that real 2CVs also do?  Especially with the original soft springs?  Or should the front dive during braking the way a wishbone suspension does?