These W-irons are proportioned for 9ins solebars when used with the suspension plates. For deeper solebars, such as the standard RCH 12ins, may be used.
Buffer beams, or headstocks are the same depth as the solebars, and the standard height of the buffer heads is 3ft 5ins from rail level - of course this varies depending on whether the wagon is loaded or not. So on a 4mm scale model this might vary from 13mm for a loaded wagon to 14mm for an empty wagon. Thus the underside of the floor should be 14.5mm above track level for a loaded wagon with 9ins solebars. Whereas an empty wagon with 12in solebars may be as high as 16mm between rail height and underside of the floor.
Most mineral and general freight vehicles used 3ft 2in or 3ft 1.5in diameter wheels, although these would wear considerably and were re-profiled until the tyre was too thin. All commercial model wheels are standardised at 12mm diameter. The distance from the axle hole to the W-iron is 6.5mm so giving a height from rail to top of W-iron at 12.5mm. Thus depending on the way in which these are mounted, and the proportions of the wagon being modelled, appropriate packing should be usedÂ between them and the wagon floor..