A Cartazzi axle is a design of leading or trailing wheel support[1][2][3] used worldwide.[4][5][6][7][8] The design was used extensively on the former LNER's Pacific steam locomotives and named after its inventor F.J. Cartazzi,[9] formerly of the Great Northern Railway. It should not be confused with a pony truck as it does not pivot at all.[8] The axle does, however, have sideways play built in to accommodate tight curves. Cartazzi's design causes the weight of the locomotive to exert a self-centring action on the trailing wheels.[10]
The Cartazzi design was also sometimes applied to driving wheel axles on longer wheelbase locomotives.[11]
Modelling
On small scale models the trailing wheels of Cartazzi-axled locomotives are often flangeless to allow negotiation of tighter, non-prototypical curves, or the Cartazzi axle has been replaced with a pony truck for the same reason.
^Ellis, Cuthbert Hamilton (1949). Some Classic Locomotives. Allen & Unwin. p. 156 – via Google Books. The leading and trailing carrying axles had sideplay through Cartazzi sliding axleboxes
^Nock, Oswald Stevens (1967). Steam Railways of Britain in Colour. Blandford P. p. 144. The leading pair of wheels had the Cartazzi form of axle box...
^"Modern British Practice in Tank Locomotives - II". The Mechanical World. XLIV (1139). Manchester, England: 212. October 30, 1908 – via Google Books. ... the coupled wheelbase, which is 16ft. 6in., is not rigid, the leading axle boxes having 1¼in. side play. This is compensated for in the leading length of the coupling rods and controlled by sliding caps on the axle boxes on the Cartazzi principle.