Rotary suspension (Dampers)

[mzivtins]

Hello all!

My name is Mark, i'm a long-time lurker here, love everything i read and wondered if you guys could help me out a bit...

I'm interested in the rotary suspension that a few f1 cars have used with, urm... 'limited(?)' success.
It seems the idea on paper is all good, but in reality the idea never really lived up to expectation, especially suffering from 'stiction' in its behaviour as a few F1 engineers have 'complained' about.

What sort of experience have you all got in using rotary dampers on real life? i have read the article on SCARBS site and its fantastic and the best write up i have ever found!
http://scarbsf1.wordpress.com/2011/11/2 ... y-dampers/
However the secrets of setup still elude me... what properties should the linkage, oil and oil vanes have to provide the most consistent damping force throughout all heat ranges?

Sorry if this sounds like a complete brain-fart, but im wrestling daily life with my beloved Suzuki TL1000r, which of course suffers greatly from the awful/cheap rotary damper

Cheers

[DaveW]

An interesting, if slightly contractory, article by Scarbs.

Certainly rotary dampers are very light, but that comes with obvious downsides. They operate at very high pressures, which (as Scarbs admits) bring with it high friction from preloaded seals and high hystersis (the fluid compliance introduces a significant in-series spring element). It is also true to say, I think, that seal lengths are greater than in the equivalent cylinder damper, heat capacity is reduced, and sealing between the blade and the shaft can create problems.

That leads to the contradiction. Scarbs quotes Jorg Zander: “the good side of the Rotary damper is that because of the rocker integration, the system is very stiff and direct, so there is little losses due to backlash in linkages, ball joints, etc. which meant it had a good high frequency response”. Elsewhere, Scarbs notes Zander as stating: "Initial developments started with Aluminium, then Ti and steel options to gain stiffness to reduce the issues caused due to deformation."

No doubt both of those statements has a basis in fact. However, when rig testing race vehicles I regularly estimate "installation stiffness" of a suspension. For a reasonable design, I frequently obtain greater than 1 KN/mm for a conventional design. I estimated 350 N/mm for an equivalent a rotary installation. My best guess for a cylindrical damper in isolation would be a stiffness of between 3 to 4 KN/mm (depending on CSA), the rotary damper in isolation yielded an estimate of 500 N/mm. Is that important? Some years ago we assessed the impact of installation stiffness on a FRenault "buck" & decided that overall values below 1 KN/mm had an increasingly measurable impact on performance.

I think that the best quote in Scarbs' article is: "McQuilliam goes to on to highlight its packaging and resultant aero benefits...." Says it all, really.

[hardingfv32]

impact of installation stiffness on a FRenault "buck"

What is a 'buck'?

Brian

[DaveW]

A reasonably well understood vehicle that was used for a time in an attempt to understand mechanical set-up issues. e.g. friction, compliance, rising rate rockers, mono shocks, damping styles, etc.

[Caito]

Could someone define installation stiffness please? Found nothing on google (besides some F1t threads).

Thank you very much!

[mzivtins]

Could someone define installation stiffness please? Found nothing on google (besides some F1t threads).

Thank you very much!

DaveW, some awesome info there! I'm with Caito on this one, in terms of my application of Rotary Dampers i guess the stiffness could be less of a concern? Although laterally, the linkages have almost 1mm of play within them... (Although this won't be a consideration for 'stiffness') i've long thought that this has to be intended to compensate a bending/twisting swingarm??

So could a lack of 'Stiffness' help create the 'stiction' when the damper is first moved? You can actually feel this when stationary and bouncing your a*se on the seat, its a very unique and feels completely disjointed compared to the normal cylindrical design on pretty much every other motorcylce around.

So the impossible question, how can someone improve a rotary damper?

[mzivtins]

Sorry for the double post.

For reference, this is the rotary damper unit i have, fully adjustable as you would expect, on face value it doesn't look too bad considering it was designed in 1998 and attached as standard to a bike costing around £9000 new... i guess you get what you pay for

http://www.venold.com/tl1000s/articles/ ... damper.htm

[gato azul]

Dave is the better person, to explain this more in detail, and what he specifically means with it, but one issue here is, that you end up with a spring
at "end of the chain", over which you may don't have any control in terms of damping. Now if you manage to get this spring into resonanz, you can face a complete loss of control over contact patch loadings, leading to a massive, sometimes sudden reduction in grip, under certain condition ( for example in a certain (car/bike) speed range through corners).

Another issue here, is that with a spring element you always induce some lap/delay in your overal system response, and this may shifts with exitation frequencies.
In simple terms the difference in time (lag or lead) between the peak of your spring force and the peak of your damping force, in a simple mass, spring, damper system.

something along the lines of this:



Some of the challenges in a rotary damper arises from the shape of the working chamber.
In a conventional damper (cylindrical)this is normally radial symetric, and expansion/distortion due to pressure is more or less symetric as well.

In a rotation damper this, is not always/necessary the case, and giving high internal working pressures (especially in the F1 case), it is difficult to control
distortions of the body under all conditions (pressure/heat etc.).
Distortions in the housing in turn will/can lead to friction/stiction and sealing issues around the piston/vane. Whhile the damper may performs satisfying under some
conditions (load/temperature) he may don't under others, and consictency and predictability may is becoming a challenge.

[DaveW]

Installation stiffness is a generic term usually used to collect all compliances acting in series with a damper that will interfere with the way a damper does its job. Typically the compliances are introduced by damper, damper mounts, rockers, push/pull rods & uprights, including the upright mounts. In a road car they also include "top mounts" - bushes that deliberately exchange performance for comfort. Damper compliance specifically includes fluid compliance and damper structure. Both of the latter are functions of internal damper pressure.

I'm not sure about your damper, mzivting, I'm afraid. My results were obtained from the damper described by Scarbs. In a conventional damper, compliance is normally under good control, but that is not the case for Scarbs' rotary damper, where the damper contribution more than offset any benefits of a better layout.

The effect on the operation of a damper in the presence of the compliance (incidentally, every car I have tested has some compliance) is to reduce the effectiveness of the damper, increasingly so as the frequency increases (much as gato azul pointed out). In a well controlled vehicle damper effectiveness is maintained adequately over the frequency range of the rigid body modes (sprung mass & unpsrung mass modes). However, modal control is reduced when the compliance becomes significant. The first modes to suffer would be the unsprung masses (this, despite Zander's claim), & I guess that gato's reference to a "sudden reduction in grip" would be an example of this loss in control. It is not long since I was informed by an engineer "we can't increase damping, we would control over the hubs" - and he was right.

[Andi76]

Hello all!

My name is Mark, i'm a long-time lurker here, love everything i read and wondered if you guys could help me out a bit...

I'm interested in the rotary suspension that a few f1 cars have used with, urm... 'limited(?)' success.
It seems the idea on paper is all good, but in reality the idea never really lived up to expectation, especially suffering from 'stiction' in its behaviour as a few F1 engineers have 'complained' about.

What sort of experience have you all got in using rotary dampers on real life? i have read the article on SCARBS site and its fantastic and the best write up i have ever found!
http://scarbsf1.wordpress.com/2011/11/2 ... y-dampers/
However the secrets of setup still elude me... what properties should the linkage, oil and oil vanes have to provide the most consistent damping force throughout all heat ranges?

Sorry if this sounds like a complete brain-fart, but im wrestling daily life with my beloved Suzuki TL1000r, which of course suffers greatly from the awful/cheap rotary damper

Cheers

Again reviving an old topic to correct a few things - rotary dampers were not used with limited sucess in F1. Indeed rotary dampers were used with massive sucess by some teams. Sachs in 2002 developed and produced rotary dampers in close cooperation and with design specifications by Rory Byrne, Ferraris Chief Designer. These dampers, made out of Titanium were called revolutionary back then and were an innovation in F1. They were used on the Championship Winning F2003 and F2004 and Ferrari used them for many years. I am not sure about it, but i think the Championship Winning F2007 and F2008 used rotary dampers, too. Other teams like Sauber and Toyota "copied" Byrnes idea and used the Sachs rotary dampers, too, for some years. Brawns Championship Winning Car of 2009 also used rotary dampers. Rotary dampers had big advantages in terms of packaging what resulted in a much smaller coke-bottle area of the car with obvious benefits for aerodynamics. They also saved weight and stiffness was another advantage and less moveable parts were the other advantage, what was also why they had less friction than a conventional set-up. "Stiction", even if i do not remember that really being a problem, but as Zander tells that, it probably was one disadvantage. But with all the other benefits rotary dampers were definetely an advantage in comparison to a conventional set-uo and the reason for rotary dampers to disappear was mainly because they were extremely expensive. With Cost Reduction being agreed in the early 2010's, the 30 000+ dollars for one pair of rotary dampers was just too much money, so they disappeared. But they were used with massive sucess in F1 between 2003 and 2010, winning nine F1-Championships in 2003, 2004, 2007, 2008 and 2009.

[johnny comelately]

The Ferrari F2004 at the 2:40 mark