I believe they call this an axle box. Some useful spare parts stored in what appears to be a three and a half plank wagon at Threlkeld Quarry Museum.
Location: Threlkeld Quarry (former)
Original line: Threlkeld Quarry Railway
Photographer: Ken Strachan
Contact photographer: Ken Strachan
Date: 18/05/2014
Image number: 49400