2 replies to this topic

[NeilR]

I curious as to the use and advantages of linear and digressive pistons in road and track use and how they could compare to the magnetorheological shocks found on some high end cars. The reason I ask is that a mechanic from a local Porsche team running a GT3RSR said that Porsche recommended a linear damper, whereas they were running a digressive damper given their drivers propensity to kerb-hop (I think I can see a road advantage in the digressive). I assume that you would run linear on totally smooth surfaces such as oval track, with no kerbs (or a driver that did not use them) and Digressive (edit - blast) when there could be bumps/kerbs/potholes etc...but would there be a time when magnetorheological shocks would have an advantage or are they more of a comfort thing?

Edited by NeilR, 21 July 2013 - 05:10.

[Greg Locock]

John Miles wrote a thought provoking article in Vehicle Dynamics International where he pointed out that the compressive/rebound ratio for dampers in 4 similar production cars with reasonable rides were different by a factor of either 2 or 4. So his conclusion was that we still don't really know what we are doing. It's also interesting to see how the guys retune the shocks after two years in production.

MRD shocks are a complex field. If you just run them at one current then you basically have a friction damper. So in order to approximate the behaviour of a traditional shock you have to adjust the current many times per cycle. http://www.dtic.mil/...oc=GetTRDoc.pdf

[NeilR]

Thanks for the link Greg, it looks very interesting...I'll get the next mag done and then give it a proper read (I stopped in the mid 20's pages). I think complex is far from an overstating things! I do know that a current GT3 F458 (at least the local one I have seen) does not have the mag dampers, but the road car apparently does. I have not seen if driver adjustable (on the move) dampers are against the GT3 rules or whether for motorsport traditional dampers are better.

Edited by NeilR, 21 July 2013 - 05:46.