Talk:Adhesion railway

talk page for rail adhesion.

Physics question

Adhesion is directly proportional to weight isn't it? So heavy is good for mechanical engineers but civil engineers get worried. Dunc|☺ 23:00, 29 October 2005 (UTC)

Response

Correct. I have expanded your point somewhat in the article. Gordon Vigurs 09:42, 29 April 2006 (UTC)

...

1 lift to drag ratio a strange and misleading use of this term which is clearly defined and has nothing to do with the present topic.

2 Distributed Effort using brakes on all the wheels of a train and using multiple drive motors along the length of a train avoids many adhesion limitations. This should be explained (in simple terms please) in the article.

3 Limiting Gradient I was taught that roller bearing vehicles would run freely on about 1 in 180 and those with plain bearings on about 1 in 60. But nobody ever told me what is the steepest gradient that can be found in practice being worked by conventional trains.

4 "Traction or friction can be reduced when the rails are greasy..." not "can be" "is" Keep it simple for easy comprehension please.

77.97.161.230 08:26, 27 August 2007 (UTC)mikeL Good points, please update the article. Gordon Vigurs (talk) 08:37, 20 May 2008 (UTC)

TopplingLimit.png

This graphic really needs to be cropped. RobertM525 (talk) 08:56, 6 March 2008 (UTC)

I could redraw this, in due course, but should the image it be here at all? This page is about adhesion, but this section is about the effect of centrifugal force. Shouldn't the topic be in superelevation or curve of adjustment? The point is actually acknowledged in the article: "Since railway wheels usually have flanges for safety, the radius of turn is not directly determined by the coefficient of friction"--Old Moonraker (talk) 11:30, 6 March 2008 (UTC)

I don't even understand the diagram, so I couldn't say whether it belongs here or not. :) RobertM525 (talk) 07:00, 15 March 2008 (UTC)

I feel a spot of pruning coming on. The bit about Herzian Stress is also wrong: the reason C19 express locomotives had large driving wheels was to reduce the linear speed of the reciprocating components: such bits as the crank webs would break otherwise. Any salvage should be moved into superelevation. --Old Moonraker (talk) 08:45, 15 March 2008 (UTC)

Lift to drag ratio

The topic about lift to drag ratio seems to have many errors. At least, descriptions about locomotive tractive force in a level section have a calculation error. 100-tonne locomotive in a section whose friction coefficient is 0.25 can generate 25 tonnes tractive force, and it needs 2 tonnes force to move itself, then 23 tonnes force is left. 60-tonne coach needs 1.2 tonne force to move, then 100-tonne locomotive can pull 19 coaches, not 21 coaches. (23 / 1.2 = 19.166..) This is an apparent error.

Explantions about a gradient section are also strange. 12% gradient? Adhesion railway cannot overcome such steep gradient. I think it is better to rewrite this topic on the basis that the section is 12 permil gradient.

Finally, I think the lift to drag ratio "50:1" is very high. Many Japanese documents note that rolling resistance of railcars is about 2 kg/t. Current value is 10 times higher than values in these documents.

I welcome any comments about these topics.--Tam0031 (talk) 16:11, 10 March 2009 (UTC)

The original figures are in error, and if you have references which indicate the weight/rolling resistance is closer to 500:1, please include them.Gordon Vigurs (talk) 16:04, 15 June 2009 (UTC)

Cleanup

• References please

Specifically where is the info derived from (if not self written)

• "Rail Adhesion"

That's the title - it would be good if the article could stick to that topic.

• Steam engines

Why is/was there such an emphasis on steam engines?

• Copyright violation - can people please ensure that they are not violating copyright - some of the material appears "textbook" like - and is inreferenced - hopefully it has not been copied.

• Wikipedia is not a textbook.

The encyclopedia is not a textbook - it should not be written with textbook like explanations - there are other wikipedia projects for textbook like material. FengRail (talk) 21:05, 11 April 2009 (UTC)

There are articles Hunting (engineering), banked turn and others to link to.FengRail (talk) 21:19, 11 April 2009 (UTC)

Feel free to edit as much as you wish. There are no copyright violations, merely a summary of the material in the references given, of which I count five, not zero. I know we must accommodate all levels of education, but had not appreciated that we cannot assume an ability to count.Gordon Vigurs (talk) 08:37, 15 June 2009 (UTC)

Rail Squeal

Another aspect of the wheel-rail interface that needs an article of its own, is Rail Squeal, which is the screaching (squeeling) noise that can happen especially on sharp curves. Tabletop (talk) 01:56, 10 November 2013 (UTC)

Project quality ratings

Which part(s) of the specific quality rating scale for C class are you claiming that this article fails? It is not helpful to simply state "it fails", without saying why. Andy Dingley (talk) 13:04, 29 September 2016 (UTC)

The Criteria for C Class is as follows:

(1) The article is substantial, but is still missing important content or contains much irrelevant material.

(2) The article should have some references to reliable sources, but may still have significant problems or require substantial cleanup.

(3) The article cites more than one reliable source and is better developed in style, structure, and quality than Start-Class, but it fails one or more of the criteria for B-Class.

(4) It may have some gaps or missing elements; need editing for clarity, balance, or flow; or contain policy violations, such as bias or original research.

(5) Articles on fictional topics are likely to be marked as C-Class if they are written from an in-universe perspective.

(6) It is most likely that C-Class articles have a reasonable encyclopedic style.

On all six counts, The article meets this criteria. Everyone needs to be made aware that the editor reverting the change of class back to start has a long history of contentious editing [1].KirksKeyKard (talk) 14:23, 29 September 2016 (UTC)

Oh, really? What about the history of bad attitude and dummy-spitting by User:KirksKeyKard, a moron who needs to grow up? I won't trouble the article again. Old Lanky (talk) 14:27, 30 September 2016 (UTC)

Unsupported assertions

There are a few alarming unsubstantiated assertions in the section Effect of Adhesion Limits, as well as some strange rpsoe writing.

static friction, referred colloquially to as "stiction",

Is it? Wouldn't we rather use encyclopaedic language here rather than what is "referred colloquially to"?

Thus a 100-tonne locomotive could have a tractive effort of 350 kilonewtons, under the ideal conditions (assuming sufficient force can be produced by the engine), falling to a 50 kilonewtons under the worst conditions.

What is the implication of those numbers?

Steam locomotives suffer particularly badly from adhesion issues because power delivery is pulsed

Yet anyone who was around when steam locomotives were commonplace remembers slipping taking place at starting, (or near stalling on steep up gradients) when speed was close to zero and the "pulsing" is absent. Need some facts about steam engines slipping at high speed.

although some 3-cylinder locomotives, such as the SR V Schools class, operated with a factor of adhesion below 4 due to their smoother power delivery.

If this is a "such as" situation, could we name two or three others like this? Or are the Schools more or less unique, in which case we should be frank about that.

Other steam locomotive design factors significantly affecting traction include wheel size (smaller diameter wheels offer superior traction ...)'

Can you point to the technical basis for that remarkable assertion?

... and the sensitivity of the regulator.

Well I suppose so; and the skill of the driver. What about modern traction, though? Steam is not commonplace nowadays. Afterbrunel (talk) 12:08, 14 August 2017 (UTC)

Adhesion

The claim in the article that "smaller diameter wheels offer superior traction at the expense of top speed" seems to me to be confusing the issue of gearing and traction. Smaller wheels certainly provide a better gearing ratio at the expense of top speed, but I can't find any references to support the claim that they also offer better adhesion. I've added a 'citation' needed' tag for this for now, but I may come back later and delete the section if it can't be verified. MarkSG (talk) 08:33, 21 September 2017 (UTC)

I think you are right, in which case better wording would be (assuming it's referring to a steam locomotive) "...offer superior tractive effort..." I don't think it is worth correcting though, better to delete it as irrelevant to this article. The article is about adhesion and should focus on the ways wheel/rail friction results in both good and bad. Tractive effort v. wheel diameter is addressed in a different article I'm sure.

Incidently, I have a source for "the coefficient of adhesion does not vary much with the size of the wheel".Pieter1963 (talk) 02:39, 26 November 2017 (UTC)

Given the "factor of adhesion" is the weight on the driven wheels divided by the theoretical starting tractive effort, the lower the factor of adhesion the better - it is the reciprocal, or inverse, of co-efficient of friction, in which higher is better for tractive effort.

Thus the word in brackets in the quote following should replace the word immediately preceding: was generally designed to be a value of 4 or slightly higher [lower], reflecting a typical wheel-rail friction coefficient of 0.25. A locomotive with a factor of adhesion much lower [higher] than 4 would be highly prone to wheelslip, although some 3-cylinder locomotives, such as the SR V Schools class, operated with a factor of adhesion below [above] 4 because the traction force at the wheel rim do not fluctuate as much.2605:E000:A983:4B00:E9:58F9:6FD4:C270 (talk) 02:42, 20 January 2020 (UTC) — Preceding unsigned comment added by 2605:E000:A983:4B00:E9:58F9:6FD4:C270 (talk) 23:35, 19 January 2020 (UTC)

absence of flange/rail contact

"close examination of a typical railway wheel reveals that the tread is burnished but the flange is not - the flanges rarely make contact with the rail"

Does this statement apply to a particular type of railway, perhaps high speed passenger on dedicated track with gentle curves?Pieter1963 (talk) 14:24, 29 November 2017 (UTC)

You can tell when the flanges contact, they squeal. This does happen on tight curves, but it's generally avoided. If there's a tight curve and the trains can't slow down there will often be a flange lubricator: a bucket of grease with a wheel-actuated pump. Andy Dingley (talk) 14:52, 29 November 2017 (UTC)

A long wheelbase can exacerbate the problem. --Redrose64 🌹 (talk) 09:39, 30 November 2017 (UTC)

My concern is the validity of the statement (it is not sourced) i.e. that someone has had a look at a wheel and decided that it is a typical wheel, ie representative of the adhesion railway, and then personally drawn a conclusion from it, ie flange contact rare on adhesion railways (when, in fact, it is a big problem for railways).

Just looking for input before editing. Thanks.Pieter1963 (talk) 16:19, 30 November 2017 (UTC)

I've just been out to take a look. Here is my personal research statement. "Even just a cursory glance at a typical railway wheel reveals significant wear and pitting on the flange - flange contact with the rail is very common". The point being that the article has to give credit to a flanging force, not just rolling radius difference, to get round lots of curves.Pieter1963 (talk) 16:55, 3 December 2017 (UTC)