Goods wagon design
We were told that early brake levers were fashioned from a wrought iron taper bar usually eleven feet long. Axleguards were originally shaped from a single bar using blacksmith technology, which by the British Railways era appear to be cut from sheet material using a torch.
In general wooden wagons have 12 inch by 5 inch frames - although some of the depth is hidden by the curb rail. Early iron frame wagons were usually made from 9 inch by 3 inch channel section. To accommodate standard axle (lengths) and axleboxes wagons can have a joggle in both axleguards and "Vees" usually of 1 inch to adapt to the different size materials in use in later designs.
Generally you will find the width between solebars ranges from 6 feet 3 inches, 6 feet 1 inch on most RCH 1923 standard designs , down to 5 feet 11 inches for older wooden wagons.
Instanter Links
There are at least three types of Instanter link. One is a plain casting as used before British Railways introduced a lighter version with relief in the sides of the link. The first instanter design introduced by the GWR from c1908 using standard round bar but these tended to stretch or straighten out in use. The instanter link was introduced to allow usual coupling and uncoupling procedures, with a shunters' stick, to work, but enabling the gap between vehicles to be shortened for higher speed running and less "snatch" in a train.
The solution of auto-braked vehicles was very slow to be adopted in Britain and initially most railway companies adopted vacuum brakes, until air brakes finally replaced those during the later years of British Rail.
Below is a "modern" instanter coupling showing the relieved sides of the cast centre link.
Early photographs do not show a general use of a draw bar hook. Many locomotives had couplings of loose links terminating in a hook, the coupling being shackled to the headstocks. Because of the fragility of iron links passenger carrying stock may well have safety chains (two scaled down versions of the coupling, one either side of the main coupling). Technology improved the quality of iron/steel so the use of safety chains was reduced. Gradually it became the "norm" to fit draw bar hooks on locomotives and for passenger carrying stock to be fitted with screw couplings. The screw coupling was to eliminate a "snatch" as loose couplings were shortened/tightened and forced use of the side buffers. Movement in sprung buffers can take up changes to the distance between stock on curves used on prototype trackwork. Model railway often use curve radii much sharper than that used on the prototype which in extreme situations can result in the buffers locking together and causing derailments.
The earliest stock had "dumb" buffers - wooden solebar extensions - which were outlawed and removed from wooden wagon designs, for main line use, all stock had fitted buffers. Often these were sprung using hidden leaf springs also used to allow movement in the draw bar hook and both ends of the wagon were joined together making up a "continuous" draw bar, allowing the wagon body to oscillate around the draw bar. However some stock was fitted with "self contained" buffers which are not connected to the drawbar. It gradually became a standard that passenger carrying stock was fitted with a screw coupling attached to the coach underframe to simulate the continuous drawbar. There are a number of benefits to the continuous drawbar, a summary would be for load carrying comfort and to allow the engine driver some better control of a train. Further protection for passengers was given by the use of a continuous and automatic brake - usually vacuum - controlled from the engine or guard on a train whereas most freight or mineral trains relied on the loose coupled and separately braked wagons.
Below is seen part of a continuous drawbar on a vacuum fitted steel frame wagon - probably from a LNER brake van at the Mid-Suffolk Light Railway preservation site.
However screw couplings can be very long and officially had to be stowed away from rail height so they did not catch on any obstruction and cause an accident. Railways used different solutions to this, for example the GWR used a stowage hook on the buffer beam and this resulted in them using a "U" shape top link, other railways used a shackled to link.
Only later did the LNER and Southern Railways introduce the buckeye automatic coupling particularly for their express stock. Later still auto-couplings carrying communication equipment were adopted for use on multiple unit stock. This is the buffing fittings and couplings on a BR Mk.1 coach, the buffers are extended and the "buck-eye" coupling dropped to reveal a normal coupling hook. The vacuum brake pipe is stowed to the left and a steam heating pipe drops towards the rails. When the "buck-eye" coupler is used the buffers would be retracted by removing blocks fitted over the buffer shank.
Since the "privatisation" of British Railways the use of air brakes has replaced the vacuum brake, loose couplings have been virtually eliminated and screw couplings exist primarily as a emergency measure as passenger trains are either multiple units or use stock run in permanently coupled sets. Railways used to practice running trains of through coaches, where a passenger train was progressively divided for different destinations on the outward journey and joined together on the return journey. This practice generally declined from the 1920's until today where most passenger trains are kept as one set continuously running between two places.
