To learn and share about dampers / shock absorbers

[marcush.]

rosberg admitted he was unable to switch on the tyres after the pacecar period as the remaining rubber was too thin and he could not put the energy back in
at ohlins we had a special damper piston arrangement for ultra smooth tracks -called high frequency piston -which basically was a little slack of the connection between piston and piston rod allowing for small quick oscillation -bringing up the tyre temps quite a bit...this worked well for the amateurs I usually had to look after .

[hardingfv32]

...this worked well for the amateurs I usually had to look after .

Why, what was their weakness?

Brian

[marcush.]

...this worked well for the amateurs I usually had to look after .

Why, what was their weakness?

Brian

switch on the tyres ! waiting for the tyres to come to life is a nono for a rosejointed stiff car starting on cold rubber
you need to push .
As long as you had some slack (or misalignment ,or compliance ,flex )all was well as that did the trick for you but as soon as you removed this from the equation they seemed to be fazed by the car on "cold" tyres.

[ubrben]

rosberg admitted he was unable to switch on the tyres after the pacecar period as the remaining rubber was too thin and he could not put the energy back in
at ohlins we had a special damper piston arrangement for ultra smooth tracks -called high frequency piston -which basically was a little slack of the connection between piston and piston rod allowing for small quick oscillation -bringing up the tyre temps quite a bit...this worked well for the amateurs I usually had to look after .

Or as a well known rig engineer once said to me - "they've built a very expensive damper that doesn't cavitate and sold you a part that makes it cavitate..."



Ben

[DaveW]

...at ohlins we had a special damper piston arrangement for ultra smooth tracks -called high frequency piston -which basically was a little slack of the connection between piston and piston rod allowing for small quick oscillation -bringing up the tyre temps quite a bit...this worked well for the amateurs I usually had to look after .

I have often wondered about the logic of the HFP piston...

To my knowledge, the effect was identified (probably not for the first time) by John Miles when he was developing the Esprit to go racing in the USA - perhaps 20+ years ago. The free play, introduced by accident in otherwise closed front dampers, "transformed" the vehicle, preventing the tyres "stalling" (John's words), but also lost control of the hub modes. He then introduced controlled bleed (velocity dependent), which cured the "stalling" problem without losing control over the hub modes.

The HFP piston has the same effect as John's free play accident. What works at <2Hz. doesn't look so good at 17 Hz. The loss in hub control is very apparent on a rig.

It is quite probable that the uncontrolled hub modes would work the tyres harder, but the loss of CPL control would ultimately cause the vehicle to be behave inconsistently (at best).

[ubrben]

...at ohlins we had a special damper piston arrangement for ultra smooth tracks -called high frequency piston -which basically was a little slack of the connection between piston and piston rod allowing for small quick oscillation -bringing up the tyre temps quite a bit...this worked well for the amateurs I usually had to look after .

It is quite probable that the uncontrolled hub modes would work the tyres harder, but the loss of CPL control would ultimately cause the vehicle to be behave inconsistently (at best).

In my experience it didn't work the tyre noticeable harder, and was very inconsistent...

Generally the best way of building tyre temp in my experience is to have a stable and predictable car that the driver feels confident to push with.

Ben

[kaushik14]

Please any one update working principle and equations related to monotube dampers. As I am new to this field, it is very difficult to understand this stuff.

[DaveW]

You might try "The Shock Absorber Handbook" by John Dixon.

[kaushik14]

You might try "The Shock Absorber Handbook" by John Dixon.

Thanks for your info.. Can I find this book for free ??

[WilO]

I sincerely hope not. Authors have the right to be compensated for their work. If you are a student, you might try a university library.

[kaushik14]

I sincerely hope not. Authors have the right to be compensated for their work. If you are a student, you might try a university library.

Thanks.. I will find in my library

[Belatti]

It might help you to take a look at this thread, we have discussing many many things about monotube dampers here. Its a pity many of the 747 posts pics vanished, although there is still much to read and learn.

[JACKHOLE]

This is a great thread with alot of quality reading and links.

Thanks

[Smokes]

if I know the damper dimension and the piston dimensions and the oil vicosity can i plot a simple graph of the damper behavior or damping constant C, milliken RCVD dosen't seem to cover this or have i missed something?

Thanks

[Greg Locock]

No, unless you know a lot about the shims and bleed orifice sizes etc etc. if you do know all that stuff then it is possible to build a model of the shock absorber that apparently works well, but it is no small project. SAE has published at least one paper on it.