Talk:Wheel arrangement

When I first added material to the “EMD E6” page, I included 90 words about the A1A-A1A wheel arrangement. This was all right for one page, but I wanted to add the same wheel arrangement material to all the EMD E-unit pages, a total of nine pages. Text would be needlessly duplicated. So I moved the A1A-A1A wheel arrangement material to a new page, “AAR wheel arrangment”, and added material for several other wheel arrangements. That way, myself or anyone can internally link to the section within “AAR wheel arrangement” that corresponds to the desired wheel arrangement, and eliminate some text duplication. Rmeier 16:35, 24 Oct 2004 (UTC)

Steam Locomotive Wheel Arrangement

I don't see a point of adding a chapter for "Steam Locomotive Wheel Arrangement" since it is already covered in articles for Whyte notation and UIC Classification. Removed. Z220info 14:38, 22 March 2006 (UTC)

Amended whole article

I found the initial article very confusing to read, especially given that to understand anything of the differences between the three main notation systems (AAR, UIC, Whyte) one had to click on each link in turn. So I set to work rephrasing several words and passages, and reordering the run of sentences etc. There were also some inconsistencies in the article - three bullet points at the end of the article contradicted statements in previous paras, causing reader confusion about whether or not Whyte notation is used in the US. So I checked all thoroughly while reworking the whole, so as to give a proper "overview" of the subject. Lastly I tried to find any decent sources - there are loads on the web describing the various steam wheel arrangements, but almost nil about the overall nature of wheel arrangements as a subject, ie. why and how they matter. Finally found one source that defined it reputably as "the distribution of wheels under (etc)", and referenced it accordingly. The article's still not great, but at least it's now a whole lot better to read / easier to understand. Hopefully others will agree. Pete Hobbs (talk) 01:52, 2 August 2011 (UTC)

One Omission that I found, is the 4-2-4 which is a C.P. Huntington. Russ The Rail Guy 21:23, 22 December 2019 (UTC) — Preceding unsigned comment added by Railguyruss (talk • contribs)

Reason behind there being different wheel arrangements?

It's nice to know how different notations work and all, but what are the dis-/advantages of different arrangements of leading/driving/trailing wheels to begin with? An ember of hope is sparked in the introduction – quote "Especially in steam days, wheel arrangement was an important attribute …" – but it then fails to explain why it was so important – speed, efficiency, safety? Any or all (or none) of them? What role do more/fewer/taller/smaller/… individual axles and wheels play? — Preceding unsigned comment added by 2001:A62:19B4:D801:DA66:E804:CDFA:63B2 (talk) 09:01, 29 April 2023 (UTC)

The first factor to consider is the overall weight of the locomotive compared to the maximum permitted axle load for the routes that it is intended for. The more axles there are, the more that the weight is spread, and the loco's axle load will be lower and the route availability will be greater. If the anticipated weight of the loco is eighty-one tons, and the route has a max axle load of 18 tons, 80/18=4.5 and so the loco must have at least five axles to get an ideal axle load of 16.2 tons.

Next is the number of coupled axles. When starting a heavy train, a high axle load on the driving axle (high adhesion weight) reduces the likelihood of slipping, but as noted above, a route may impose a maximum axle load; coupled wheels allow the adhesion weight to be spread over two or more axles, keeping the individiual axle loads down. Assume that our five-axle loco has its weight evenly distributed. If it has two axles coupled, it has 32.4 tons adhesive weight; for three axles coupled, it has 48.6 tons adhesive weight; and for four axles coupled, it has 64.8 tons. Of these three, clearly the latter is more appropriate for hauling a heavy train such as a freight. But where there are many coupled axles, the coupled wheelbase will be long; coupled wheels typically have little side-play, so tight curves will be a problem unless traversed at low speed. So locos intended for passenger trains, which run at higher speeds than freight trains, will have fewer coupled axles. Whilst this means a lower adhesive weight, this is less of a problem because passenger trains are typically lighter than freight trains.

Non-driven (carrying) axles almost always have some degree of side-play, particularly if mounted in a bogie or pony truck, and can follow curves more easily than coupled axles. They add nothing to the adhesive weight, but do spread the total waight over more axles. So we have:

• 0-10-0 for slow heavy freight
• 2-8-0 for freight
• 4-6-0 or 2-6-2 for fast freight or heavy passenger
• 4-4-2 for express passenger

Similar choices apply to larger locomotives (more powerful but heavier) and smaller locomotives (lighter but less powerful). --Redrose64 🌹 (talk) 20:42, 29 April 2023 (UTC)

Then there is the boiler. If the loco designer wishes to incorporate a wide firebox, one that is wider than the space between two wheels on the same axle, the boiler either needs to overhang at the rear - which would be unstable due to both pitching and yawing - or be placed above a wheel; and to avoid too great a height, that wheel should be small. It is possible for this to be a coupled wheel, but a small coupled wheel would be used fo high power at low speed: a freight locomotive in other words, and this was done with the BR Standard Class 9F 2-10-0 (see this photo). When the coupled wheels are large, as with a passenger loco, a wide firebox needs to be placed over a small-diameter carrying wheel - such as with several LNER classes, like A1, A3, A4, C1, P1, P2, V2, V4 and W1. --Redrose64 🌹 (talk) 14:57, 2 May 2023 (UTC)

Table

So what happened to the quite useful and enjoyable table of all the different wheel arrangements that used to be featured on the bottom of like most or all locomotive-related pages? We just like ditched that? And this article is what we have left?

To whoever made this article, there are actual images available graphically illustrating every wheel arrangement. You don't need to do the whole "ooOOOo" thing for every single entry.

I can't believe a subject as popular as rail and this is the best we have after ten or fifteen years. Idumea47b (talk) 18:45, 11 September 2023 (UTC)

@Idumea47b: Do you mean Template:Whyte types? --Redrose64 🌹 (talk) 15:14, 12 September 2023 (UTC)