Talk:Car suspension

Put the "rear suspension" page in here...

"are more compliant. "

I don't agree with this change. David R. Ingham 07:06, 27 February 2006 (UTC)[reply]

Well, I wouldn't have changed it in the first place if you'd spelled rigid correctly! But to be honest there's no point in messing about with weasel words like 'perhaps more ridged' (quoting from memory) - the quarter elliptics will be more compliant than anything but the most grotesque of suspension arms. Anyway, by all means, have another go. Greglocock 23:07, 27 February 2006 (UTC)[reply]

What about...

What about the unique Ford twin I-beam independent front suspension? This system doesn't seem to be mentioned anywhere.

careful reading of names

Please note that the edit at 07:27, 27 February 2006 by David R. Ingharn was not by myself but someone who chose a name that resembled mine. David R. Ingham 06:58, 2 March 2006 (UTC)[reply]

Confusion regarding semi-active suspensions

This article mentions Hydragas and Kinetic systems as examples of semi-active suspensions; yet neither of these systems is inherently semi-active. In their base form, both systems (Kinetic actually have a number of systems) are passive interconnected schemes, whose advantages lie not in their ability to vary springing and damping parameters, but rather in their capacity to provide different springing and damping depending on the suspension mode in operation. Wade Smith 07:53, 9 March 2006 (UTC)[reply]

I think the confusion really comes about because semi-active may once have meant something but has been diluted into meaninglessness by the marketing boys. Hydragas in particular is just another passive suspension. Do you know of a formal definition for semi-active, or for that matter, active? It used to be whether external power was required, yet that seems a useless definition.Greglocock 09:29, 9 March 2006 (UTC)[reply]

I would take "active" to mean that the suspension uses external power to move the car. However, the active component article includes things that depend on the direction of the current, which would suggest including shock absorbers with valves as active. David R. Ingham 17:06, 9 March 2006 (UTC)[reply]

There are a number of definitions available, some better than others. I think the definitions given by Sharp & Crolla will suffice here, with some minor clarifications based on Gillespie’s work.

Passive Suspensions: consist of spring and damping properties which are time-invariant, or, at least, quasi-time-invariant. Thus most self-levelling systems could be categorised under this heading, since their capacity to fulfil their dynamic requirements is not affected by any adaptive capacity.

Active Suspensions: describe the replacement of springs and dampers with actuators that act as force producers according to some control law. The control bandwidth is usually sufficient to handle the natural frequencies of both the sprung (1-3 Hz) and unsprung masses (10-15 Hz).

Semi-Active Suspensions: contain spring and damping elements, the properties of which may be changed by external control. Most commonly, only the damper has adjustable parameters, but Gillespie makes the point that the springing may also be adjustable. The parameters may be varied either continuously or between a number of discrete settings. Perhaps a clear distinction between these and active suspensions is that semi-active systems lack the capacity to supply work. That is, the parameters that control the system’s reaction to an input (specifically, relative displacement or velocity) can be adjusted, but a more general ability to produce an arbitrary force is not apparent.

Slow-Active Suspensions: behave like active or semi-active suspensions, but only over a limited bandwidth. Sharp and Gillespie give different definitions here: Sharp sees slow-active suspensions as a sub-group of fully active systems, whereas Gillespie claims they’re included in the semi-active family (with the distinction of having discrete parameter settings, in which a switch in one direction is almost instantaneous, but the reverse switch is much slower). I think a definition which loosely encompasses both these views is possible. So, we might say that slow-active systems (or, more precisely, limited bandwidth suspensions) are simply active or semi-active systems, in which the capacity to fulfil dynamic requirements is limited to a certain bandwidth. But even fully active systems have limited bandwidths, so a further distinction is necessary. I think the most convenient one would be to say that these systems have the capacity to handle the sprung mass motions (1-3 Hz), but not the unsprung mass motions (10–15 Hz).

Interconnected Suspensions: are defined, by Smith & Walker, as suspension systems in which a displacement at one wheel station can produce forces at other wheel stations. Well-known examples include anti-roll bars, the Hydragas system, Kinetic systems etc. The advantage of these schemes is that one can achieve more control over the stiffness and damping of each suspension mode, instead of being entirely reliant upon single-wheel parameters to implicitly define modal characteristics. I can’t see why these systems couldn’t fit into any of the aforementioned categories, but a fully active interconnected scheme is probably not a meaningful concept, seeing as an active controller inherently has the capacity to adjust the actuator force in accordance with modal operation anyway.

So, in summary: active, semi-active and slow-active systems generally require external power which influences their dynamic operation; whereas passive systems generally do not require external power, or, if they do, it does not influence their dynamic operation. Active systems can supply work and handle sprung and unsprung mass motions; semi-active systems can’t supply work, but can cover sprung and unsprung mass frequencies; and slow-active systems can belong to either the active or semi-active group, but have limited bandwidths. Interconnected schemes can belong to any of those categories, but are more meaningfully conceptualised in either a passive or semi-active context.

References:

Gillespie, T. D. 1992, Fundamentals of Vehicle Dynamics, SAE International, Warrendale, PA.

Sharp, R. S. and Crolla, D. A. 1987, ‘Road Vehicle Suspension System Design – a review’, Vehicle System Dynamics, vol. 16, pp. 167-192.

Smith, M. C. and Walker, G. W. 2005, ‘Interconnected Vehicle Suspension’, Journal of Automobile Engineering, vol. 219, no. 3, pp. 295-307.

These definitions might not be entirely robust, but they’re a start. Hope that helps. Wade Smith 02:52, 10 March 2006 (UTC)[reply]

Definitions?

They suck. How exactly are the term being defined here?

It looks as though the signature above should be "03:41, 26 April 2006 70.26.11.45".

Which term or terms would you like someone to define better? (I won't ask for a clear definition of "suck", which has always seemed poorly defined to me.) David R. Ingham 04:20, 26 April 2006 (UTC)[reply]

Ride comfort data

Hai friends.,

I am doing project work on "Damping force variation reduction for front fork of two wheelers using Design of experiment". can you give me the Anthropometric data for riding comfort, for two wheeler in indian road condition.

Help!

Road vehicles are not the only wheeled vehicles requiring suspension systems. Some of us are interested in railway suspension. Does anybody know anything about it? Gordon Vigurs 09:06, 3 July 2006 (UTC)[reply]

Questions

Wiki is not a place to ask for advice. For suspension related questions, I recommend the newsgroup sci.engr.mech, or, IF you are a professional engineer, not a student, www.eng-tips.com in the appropriate forum.

Greglocock 13:42, 3 July 2006 (UTC)[reply]

Thank you, but I have access to appropriate sources - my point is that suspension is not just an automotive issue. The article should have gone from general (i.e. seismic oscillations) to particular (the details of specific vehicle suspension system designs), rather than jumped into the specifics from the outset. Please excuse my naive assumption that an encyclopedia should be a source of knowledge. Gordon Vigurs 17:42, 5 July 2006 (UTC)[reply]

Oops sorry, I was referring to the Indian guy asking for help, not you. You are right, the article does need a section on other forms of suspension.

Greglocock 09:04, 9 July 2006 (UTC)[reply]

Armoured fighting vehicle vs tracked vehicle

I gather from the article that the suspensions of armoured fighting vehicles face design challenges in the form of land mines and other explosive devices. Beyond this, are there appreciable differences between the suspension of a late model tank and, say, a civilian bulldozer, which faces similar terrain and is also a heavy, tracked vehicle? If not, would the article be improved by making armoured fighting vehicles a subsection of a section on tracked vehicles? Also, I remember (perhaps falsely) hearing about wheeled (non-tracked) armoured fighting vehicles - how do they connect with this section? Thanks --Badger151 15:50, 18 September 2006 (UTC)[reply]

"Kneeling" busses, &c.

Many of the public busses I now see are equiped to lower their front ends, reducing the height of the step into the bus from the pavement (and making it easier for people with movement limitations to enter the bus). Around here (NYC area) I've seen it called "kneeling", though it may have other names in other places. I'm also familiar with some ambulances that lower their back ends to ease loading and unloading of the stretcher. Is this a function of these vehicles' suspensions? If so, does it deserve treatment in this article? Thanks --Badger151 16:05, 18 September 2006 (UTC)[reply]

Picture

Isn't kind of weird that the picture for this article that deals with suspension for the car comes from a vehicle which was designed 98 years ago? Can we get a picture of a more modern car's suspension, as that picture only shows control arms and a spring on a very very antiquated design. BMan1113VR 04:18, 5 December 2006 (UTC)[reply]

Perhaps this is a better picture:

File:Caterham CSR Rear suspension.JPG

(resized) BMan1113VR 11:25, 23 December 2006 (UTC)[reply]

Automotive suspension design merge

Automotive suspension design seems redundant (or close to it) with this. I have suggested we merge it here. (John User:Jwy talk) 15:03, 23 February 2007 (UTC)[reply]

I disagree. One is about the process, the other is about the hardware. There again, I'm biased (since I design suspensions)! Greglocock 23:19, 23 February 2007 (UTC)[reply]

I guess redundant is the wrong word. Might it make sense to include the design information in a section here. (I didn't mean to dis your profession!) The design article is rather short. (John User:Jwy talk) 00:14, 24 February 2007 (UTC)[reply]

It was a requested article, so I created it, but it obviously included just enough information to escape being a stub. I'll expand it at some point. If you can make some suggestions on its talk page I'll gladly do that. Greglocock 00:42, 24 February 2007 (UTC)[reply]