Talk:Parallelogram steering linkage

Inaccuracies

There are two problems with this description, and the basic concept described:

Parallelogram linkage

It's a fundamental principle of Ackermann steering that the linkage is not a parallelogram.

This is explained with diagrams at that article, but the broad principle is that all wheels (front and back) attempt to maintain orientation so that they're all on radii of a circle with the same centre, and can thus rotate around a curve without needing any tyre slip. As the rear wheels are fixed, this centre is on a line extended from the rear axle. This requires the inside front wheel to be turned further by the steering mechanism than the outside front. If the track rod is behind the axle, this is achieved by the steering arms from each hub pointing inwards to the rear, i.e. this is not a parallelogram.

It's possible that some careless reference is made to this as a "parallelogram linkage". However if that's the case, that's far from being WP:RS. Nor is it an excuse to create an article that perpetuates this myth. The linkage can be covered perfectly well under Ackermann steering, where it belongs. We don't need this article. Andy Dingley (talk) 11:09, 26 July 2010 (UTC)

Please Google "Parallelogram steering linkage". There do appear to be reliable sources that mention the term. If they do so in error, then it is a common error and it would be useful to explain this in the article. --Kvng (talk) 14:08, 28 July 2010 (UTC)

I'm glad that Google hits are now established as WP:RS.

Of course the term is "in use" - it was in the article as one of KVDP's first refs. The problem is that the term has an extremely narrow valid use (really only for older trucks and four-wheel drives), it is vastly mis-understood and it is a very minor aspect of steering linkages in general. It warrants a footnote in an article on steering linkages, it probably doesn't warrant its own article, it certainly doesn't warrant this one.

The problem is "What is a parallelogram linkage?" It is not the linkage between the two hubs or their drop arms. That just isn't a parallelogram. This article, in the absence of any clarification otherwise, presents it as such.

There's only one case when steering uses a parallelogram linkage with any claim to the name, and that's the now rare (if not obsolete) case where there's a steering box on one side and an idler box on the other side. This isn't the case for rack & pinion steering, or even the case for a steering box without a second idler (idlers are now indeed getting rare). The linkage between these two boxes forms a parallelogram. Except when it doesn't, because even here, not all of them use a parallel geometry. This linkage does not extend out to the wheel hubs (again, that's not a parallel linkage). If an article stated that much, with clarity, with a decent diagram, it would be correct. Even then it wouldn't justify a stand-alone article, no more than a footnote in an article on steering linkages in general.

Why not be WP:BOLD and make these changes to the article then - merge the content into another article even? I think that would be more productive and less confrontational and less red tape than working to have the article deleted. I assume you'll say that there's nothing salvageable here. That may turn out to be true but the system is set up to encourage editors to try. Who knows, you might be surprised. --Kvng (talk) 19:38, 28 July 2010 (UTC)

There is nothing here worth salvaging - a couple of sentences with no viable content in them.

What I'd really like to be doing is editing something useful, rather than continually sweeping up after KVDP's stream-of-consciousness editing, both here and at Commons. Andy Dingley (talk) 19:43, 28 July 2010 (UTC)

I also note that KVDP has now removed the correct and relevant diagrams of Ackermann geometry from the Ackermann article, in favour of his copyvio book scan that shows more about suspension travel than it does about steering. Way to go. Andy Dingley (talk) 17:41, 28 July 2010 (UTC)

Pitman arm and steering box

Amazingly, the exact same go-kart

When I was a child, I had a pedal-powered go-cart that used steering as described here, where the steering column operates the Pitman arm directly. That's about the biggest vehicle that can work in this way - any bigger needs a steering box of some form, which has a geared mechanical advantage and often also makes the steering action non-reversible (i.e. bumps aren't transmitted back to the wheel). Steering, in road vehicles with Ackermann steering, hasn't used this direct form since before 1900. Andy Dingley (talk) 11:09, 26 July 2010 (UTC)

How to correct

As I understand from your explaination, the image I made is correct, but the text/article isn't. So obviously the image needs to be placed at Ackermann steering (yet perhaps the name needs changing too to Ackermann steering linkage).

You also hint that parallellogram steering does exist, but the explaination doesn't match what it exactly is. So can you simply correct the text so that we also have an article about this (not sure where it's used for, but given that several on-line sources seem to give misdirections, it would nonetheless be useful to have a correct article at wikipedia (so people don't get misguided).

KVDP (talk) 11:36, 26 July 2010 (UTC)

We already have a competent article at Ackermann steering. We have no need of an incompetent article, no need of incompetent additions to it and certainly not the suggestion that power steering should be replaced by an emissions-free Stirling engine.

I don't want to make useless articles, I just thought that parallellogram steering linkages existed (since they have been mentioned in some articles on the web), and wished to make a stub explaining just what it is. If it doesn't exist though, then delete the article by all means. I'm not sure where you had the idea I would suggest somthing like using a stirling engine for power steering, that was something I never intented to do.

KVDP (talk) 12:06, 28 July 2010 (UTC)

Secondly this article and your diagram is less about steering geometry and more about practical linkages built to achieve it. There is scope for a wiki article on this, I've no idea if it's already there. Most of which history would be centred on the effects of developments in steering box designs, and the impact that independent front suspension has had. If you insist on contributing to this field, that would be a better place for this image. I would however state (at risk of being blocked for WP:NPA or not), that I have no faith in your approach to editing being competent to achieve this: It is a long and complicated history, and your track-record of refusing to do any research before editing shows no sign of abating.

OK, maybe it is more about the practical side of the steering mechanism, but that is also still very useful I think. You didn't quite answered on whether my image is correct or not, if it is considered an Ackermann steering mechanism. From your remarks, I'm guessing it is; the only thing that's needed is a name change, it doesn't need to be removed.

KVDP (talk) 12:05, 28 July 2010 (UTC)

"You also hint that parallellogram steering does exist" I don't know how you've interpreted "This is not a parallelogram" to mean that. Andy Dingley (talk) 11:45, 26 July 2010 (UTC)