Sagging rear

[Jesse]

Ok, a little update!

I reindexed the right hand side bar (again) took the car out for a spin and voila... Back where I started...

So, I would like to donate my RHS bar to science, any takers?

Thus im also in need of a good RHS 26mm torsion bar or a good, used set, anyone?

Regards
Jesse

[fetuhoe]

Ok, a little update!

I reindexed the right hand side bar (again) took the car out for a spin and voila... Back where I started...

So, I would like to donate my RHS bar to science, any takers?

Thus im also in need of a good RHS 26mm torsion bar or a good, used set, anyone?

Regards
Jesse

Yes please - let me know where it is and I can arrange a collection.

We can carry out a hardness test which will correlate to the approximate tensile strength of the steel as we have a Rockewell Hardness Tester and I recently bought a Clandon Metascop Spectrometer so we can check the basic analysis of the steel.

When I first started work in a Metallurgy Lad I used on of these instruments on a daily basis for several years and they are quite useful. We won the auction at £25.00 and it is actually if good working order and we have checked against 2 steels that we know the analysis of because when we make flywheels we buy material with a 'Release Certificate'.



With a little effort we can probably have the torque versus deflection measured as well but I will have to ask a favour from some people I used to work with.

[Jesse]

Chris, I have tried to PM you on here before but no response. Tried email also!might have got caught in some spam filter?

Where should I contact you?

Regards
Jesse

[Jesse]

Interesting..... New from Porsche before installation. Just 10 test miles or so.

I assume that the cracking paint is due to over stressed material but is has not broken into two pieces!

[fetuhoe]

Jesse,

I think that all you can conclude from this picture is that it hasn't been painted very well and that as the bar has twisted in service the paint has cracked due to lack of adhesion.

Before FEA methods allowed accurate computer modelling of stress/strain distribution within components it was fairly common to test components that had been coated with a brittle lacquer and the manner in which fine cracks developed in the film correlated to the level of stress.

The issue with a car losing ride height is not concerned with the absolute stiffness of the bar about the yield strength of the steel being used.

To explain in a little more detail:

If you make 2 x 26mm bars - one from Mild Steel and one from a High Strength Spring Steel then up to the yield point of the material both bars will behave in an identical manner.

The 'Stiffness' of the two materials will be identical up to this point.

If the bar had yielded I expect to have seen some evidence of a permanent deformation along its entire length.

Due to the work hardening behaviour of steels it is unusual to see localised plastic deformation for any other reason than a geometrically driven stress concentration which would not occur on a long straight shaft loaded in 'pure' torsion.

[Jesse]

Thank you once again Chris!

I really don't know what to believe anymore. It´s probably the human factor playing tricks over here.....

Quick update on my car.

Have been messing around with lots of other stuff but got time to install another set of original used 26mm torsion bars. Have been driving the car for 100 miles and no more sagging.

I will try to get the bar shipped to you by the end of this week!

Regards
Jesse

[fetuhoe]

The only real answer is to measure some of the properties of the bar and compare this to bars of known quality.

I have around 40 used bars so making some basic checks will be quite straightforward.

I studied Engineering Material Behavior for more years than I care to admit and if there is an issue with the material it won't be too difficult to find the problem.