These Tony, the small 4 wheeled bogies behind this Janus at Appleby Frodingham are casting cars. The buffer to which Dave refers is that central 'block' on the locos buffer beam. A few works, Port Talbot had longer, bogie, casting cars.
Simple but heavy flat topped cars, ingot moulds are stood on them and then the liquid steel is teemed into them from teeming ladles. They steel is allowed to solidly sufficiently for the moulds to be withdrawn and then the ingots either go to storage or into the soaking pits prior to rolling. These cars can be seen moving empty ingot moulds, full moulds or the solidified ingots.
They have simple couplings between them, often just a bar and link pins, but tend to operate in fixed rakes. Having said that, they were often involved in accidents with shunters getting caught between cars whilst coupling/uncoupling. The only fatality during my time at Irlam steelworks was such an incident. As a consequence automatic couplings were introduced at some works.
Being lower than conventional wagons, locomotives cannot buffer up to them. Either a modified spacer car with a raised buffer beam at one end is used or, more commonly, a casting car buffer is fitted. A single heavy buffing block fitted on the locos buffer beam below the three link coupling. This enables the loco to buffer up against the casting car and it incorporates a bracket to enable the car to be linked to it.
They're very much a steelworks only fitting and as traditional ingot casting has long since been superseded by continuous casting, the cars, and the need for such buffers, has gone.
Edited by Arthur, 17 September 2017 - 18:49 .