Editing Bogie (section)

== Radial steering truck ==
Radial-steering trucks, also known as radial bogies, allow the individual axles to align with curves in addition to the bogie frame as a whole pivoting. For non-radial bogies, the more axles in the assembly, the more difficulty it has negotiating curves, due to [[flange|wheel flange to rail]] friction.  For radial bogies, the wheel sets actively steer through curves, thus reducing wear at the [[flange|wheel's flange-to-rail]] interface and improving adhesion.

In the US, radial steering has been implemented in [[Electro-Motive Diesel|EMD]] and [[GE Transportation|GE]] locomotives. The EMD version, designated HTCR, was made standard equipment for the [[EMD SD70 series|SD70 series]], first sold in 1993. The HTCR in operation had mixed results and relatively high purchase and maintenance costs.  EMD subsequently introduced the HTSC truck, essentially the HTCR stripped of radial components. GE introduced their version in 1995 as a buyer option for the [[GE AC4400CW|AC4400CW]] and later [[GE Evolution Series|Evolution Series]] locomotives. However, it also met with limited acceptance because of its relatively high purchase and maintenance costs, and customers have generally chosen GE Hi-Ad standard trucks for newer and rebuilt locomotives.
<gallery mode="packed" heights="150">
File:CP9112 SD90MAC.jpg|EMD HTCR radial steering trucks on an [[EMD SD90MAC|EMD SD9043MAC]]
File:FSRR 01.jpg|GE radial steering trucks on a [[GE AC4400CW]]
</gallery>

[[File:Glenelg Railway Company clerestory-roofed, 30-window passenger car with Cleminson underframe.jpg|thumb|350px|An [[w:Gilbert Car Company|American-built]] [[5 ft 3 in gauge railways#Installations|broad-gauge]] passenger car in [[South Australia]], one of six fitted with Cleminson self-steering axles; pictured in 1890, ten years after their purchase]]
A 19th century configuration of self-steering axles on [[rolling stock]] established the principle of radial steering. The Cleminson system<ref>{{cite web|url=https://patents.google.com/patent/US511685A/en |title=US511685A |date=26 December 1893 |website=[[Google Patents]] |access-date=29 October 2024}}</ref> involved three axles, each mounted on a frame that had a central pivot; the central axle could slide transversely. The three axles were connected by linkages that kept them parallel on the straight and moved the end ones radially on a curve, so that all three axles were continually at right angles to the rails.<ref>{{cite book|title=Little coastal railways of the Adelaide Plains 1873–1929 |first=David |last=Mack |date=1986 |location=Adelaide |publisher=self-published |page=29 |isbn=0 85904 041 0}}</ref> The configuration, invented by British engineer John James Davidge Cleminson, was first granted a patent in the [[UK]] in 1883.<ref>{{Cite journal|url=https://www.icevirtuallibrary.com/doi/pdf/10.1680/imotp.1897.19461|publisher=ICE Virtual Library| doi=10.1680/imotp.1897.19461 |accessdate=2022-01-28| title=Obituary. James Lyons-Cleminson, 1840-1896 | journal=Minutes of the Proceedings of the Institution of Civil Engineers | year=1897 | volume=127 | issue=1897 | pages=379–380 }}</ref> The system was widely used on British narrow-gauge rolling stock, such as on the [[Isle of Man Railway rolling stock|Isle of Man]] and [[Manx Northern Railway]]s.<ref>{{cite web|url=http://www.festipedia.org.uk/wiki/Cleminson_Flexible_Six-Wheeled_Waggon|title=Cleminson flexible six-wheeled waggon - Festipedia|website=www.festipedia.org.uk|access-date=27 October 2024|url-status=live|archive-url=https://web.archive.org/web/20160317160428/https://www.festipedia.org.uk/wiki/Cleminson_Flexible_Six-Wheeled_Waggon|archive-date=17 March 2016}}</ref> The [[Holdfast Bay railway line|Holdfast Bay Railway Company]] in [[South Australia]], which later became the Glenelg Railway Company, purchased Cleminson-configured carriages in 1880 from the American [[Gilbert Car Company|Gilbert & Bush Company]] for its {{Track gauge|1600mm|comma=off}} broad-gauge line.