Philbax was asking about the Ivatt Class 2 2-6-2 tanks which appeared in some recent photos.
The Ivatt is an as yet unmodified Bachman body on a chassis based on the Comet kit, with some additional detail and the valvegear modelled in forward rather than mid gear. The chassis is compensated as an 0-6-0 using twin beams on the rear two axles and a central rocking support on the front. Drive is a 1616 Portescap on the (floating) centre axle. The trucks are sprung.
On this loco, the pony trucks are scratch built and sprung using hair-pin springs made from 0.33 brass wire. These are just visible through the frames of the truck, but not too obtrusive on this rather open, bar framed truck design. The two trucks are quite different in appearance as one has spring side control and the other swing link side control (the difference was to avoid the risk of hunting caused by having the same natural frequency at both ends if two identical trucks had been used). On the Ivatt, the swing link truck was usually at the front.
The BR Standard loco is a stretched DJH body on a cut-down Comet based chassis. On this loco, thetrucks are the Brassmasters etches, suitably modified to represent the swing linkat one end. On these locos, the swing link truck was always at the rear.
The two photos try to illustrate the differences in appearance. (Sorry for the slightly out-of-focus on the front shot.)